An Analysis of Variable-Speed Wind Turbine Power-Control Methods with Fluctuating Wind Speed

Directory of Open Access Journals (Sweden)

Seung-Il Moon

2013-07-01

Full Text Available Variable-speed wind turbines (VSWTs typically use a maximum power-point tracking (MPPT method to optimize wind-energy acquisition. MPPT can be implemented by regulating the rotor speed or by adjusting the active power. The former, termed speed-control mode (SCM, employs a speed controller to regulate the rotor, while the latter, termed power-control mode (PCM, uses an active power controller to optimize the power. They are fundamentally equivalent; however, since they use a different controller at the outer control loop of the machine-side converter (MSC controller, the time dependence of the control system differs depending on whether SCM or PCM is used. We have compared and analyzed the power quality and the power coefficient when these two different control modes were used in fluctuating wind speeds through computer simulations. The contrast between the two methods was larger when the wind-speed fluctuations were greater. Furthermore, we found that SCM was preferable to PCM in terms of the power coefficient, but PCM was superior in terms of power quality and system stability.

An analytical investigation on the valve and centrifugal pump speed control with a constant differential pressure across the valve

International Nuclear Information System (INIS)

Jung, B. R.; Joo, K. I.; Lee, B. J.; Baek, S. J.; Noh, T. S.

2003-01-01

A valve opening and centrifugal pump speed control was investigated analytically in a simple pumping system where the differential pressure across the control valve is maintained constant over the required flow range. The valve control program was derived analytically only as a function of the required flow rate to maintain the constant differential pressure across the valve. The centrifugal pump speed control program was also derived analytically for the required flow rate for the constant differential pressure across the control valve. These derivations theoretically show that the independent control is possible between the valve and pump speed in a system with a constant valve pressure drop. In addition, it was shown that a linear pump speed control is impossible in maintaining the constant valve pressure drop

Speed control at low wind speeds for a variable speed fixed pitch wind turbine

Energy Technology Data Exchange (ETDEWEB)

Rosmin, N.; Watson, S.J.; Tompson, M. [Loughborough Univ., Loughborough, Leicestershire (United Kingdom)

2010-03-09

The maximum power regulation below rated wind speed is regulated by changing the rotor/generator speed at large frequency range in a fixed pitch, variable speed, stall-regulated wind turbine. In order to capture the power at a maximum value the power coefficient is kept at maximum peak point by maintaining the tip speed ratio at its optimum value. The wind industry is moving from stall regulated fixed speed wind turbines to newer improved innovative versions with better reliability. While a stall regulated fixed pitch wind turbine is among the most cost-effective wind turbine on the market, its problems include noise, severe vibrations, high thrust loads and low power efficiency. Therefore, in order to improve such drawbacks, the rotation of the generator speed is made flexible where the rotation can be controlled in variable speed. This paper discussed the development of a simulation model which represented the behaviour of a stall regulated variable speed wind turbine at low wind speed control region by using the closed loop scalar control with adjustable speed drive. The paper provided a description of each sub-model in the wind turbine system and described the scalar control of the induction machine. It was concluded that by using a constant voltage/frequency ratio of the generator's stator side control, the generator speed could be regulated and the generator torque could be controlled to ensure the power coefficient could be maintained close to its maximum value. 38 refs., 1 tab., 10 figs.

Constant speed control of four-stroke micro internal combustion swing engine

Science.gov (United States)

Gao, Dedong; Lei, Yong; Zhu, Honghai; Ni, Jun

2015-09-01

The increasing demands on safety, emission and fuel consumption require more accurate control models of micro internal combustion swing engine (MICSE). The objective of this paper is to investigate the constant speed control models of four-stroke MICSE. The operation principle of the four-stroke MICSE is presented based on the description of MICSE prototype. A two-level Petri net based hybrid model is proposed to model the four-stroke MICSE engine cycle. The Petri net subsystem at the upper level controls and synchronizes the four Petri net subsystems at the lower level. The continuous sub-models, including breathing dynamics of intake manifold, thermodynamics of the chamber and dynamics of the torque generation, are investigated and integrated with the discrete model in MATLAB Simulink. Through the comparison of experimental data and simulated DC voltage output, it is demonstrated that the hybrid model is valid for the four-stroke MICSE system. A nonlinear model is obtained from the cycle average data via the regression method, and it is linearized around a given nominal equilibrium point for the controller design. The feedback controller of the spark timing and valve duration timing is designed with a sequential loop closing design approach. The simulation of the sequential loop closure control design applied to the hybrid model is implemented in MATLAB. The simulation results show that the system is able to reach its desired operating point within 0.2 s, and the designed controller shows good MICSE engine performance with a constant speed. This paper presents the constant speed control models of four-stroke MICSE and carries out the simulation tests, the models and the simulation results can be used for further study on the precision control of four-stroke MICSE.

Direct battery-driven solar LED lighting using constant-power control

KAUST Repository

Huang, Bin-Juine

2012-11-01

A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result has shown that the power of 18. W and 100. W LED luminaires can be controlled accurately with error at 2-5%. A solar LED street lighting system using constant-power and dimming control was designed and built for field test in a remote area. The long-term performance was satisfactory and no any failure since the installation. Since no high-power capacitor is used in the present constant-power control circuit, a longer lifetime is expected. © 2012 Elsevier Ltd.

On the Profitability of Variable Speed Pump-Storage-Power in Frequency Restoration Reserve

Science.gov (United States)

Filipe, Jorge; Bessa, Ricardo; Moreira, Carlos; Silva, Bernardo

2017-04-01

The increase penetration of renewable energy sources (RES) into the European power system has introduced a significant amount of variability and uncertainty in the generation profiles raising the needs for ancillary services as well as other tools like demand response, improved generation forecasting techniques and changes to the market design. While RES is able to replace energy produced by the traditional centralized generation, it cannot displace its capacity in terms of ancillary services provided. Therefore, centralized generation capacity must be retained to perform this function leading to over-capacity issues and underutilisation of the assets. Large-scale reversible hydro power plants represent the majority of the storage solution installed in the power system. This technology comes with high investments costs, hence the constant search for methods to increase and diversify the sources of revenue. Traditional fixed speed pump storage units typically operate in the day-ahead market to perform price arbitrage and, in some specific cases, provide downward replacement reserve (RR). Variable speed pump storage can not only participate in RR but also contribute to FRR, given their ability to control its operating point in pumping mode. This work does an extended analysis of a complete bidding strategy for Pumped Storage Power, enhancing the economic advantages of variable speed pump units in comparison with fixed ones.

THE FUZZY LOGIC BASED POWER INJECTION INTO ROTOR CIRCUIT FOR INSTANTANEOUS HIGH TORQUE AND SPEED CONTROL IN INDUCTION MACHINES

Directory of Open Access Journals (Sweden)

Selami KESLER

2009-01-01

Full Text Available The power flow of the rotor circuit is controlled by different methods in induction machines used for producing high torque in applications involved great power and constant output power with constant frequency in wind turbines. The voltage with slip frequency can be applied on rotor windings to produce controlled high torque and obtain optimal power factor and speed control. In this study, firstly, the dynamic effects of the voltage applying on rotor windings through the rings in slip-ring induction machines are researched and undesirable aspects of the method are exposed with simulations supported by experiments. Afterwards, a fuzzy logic based inverter model on rotor side is proposed with a view to improving the dynamic effects, controlling high torque producing and adjusting machine speed in instantaneous forced conditions. For the simulation model of the system in which the stator side is directly connected to the grid in steady state operation, a C/C++ algorithm is developed and the results obtained for different load conditions are discussed.

Effects of vehicle power on passenger vehicle speeds.

Science.gov (United States)

McCartt, Anne T; Hu, Wen

2017-07-04

During the past 2 decades, there have been large increases in mean horsepower and the mean horsepower-to-vehicle weight ratio for all types of new passenger vehicles in the United States. This study examined the relationship between travel speeds and vehicle power, defined as horsepower per 100 pounds of vehicle weight. Speed cameras measured travel speeds and photographed license plates and drivers of passenger vehicles traveling on roadways in Northern Virginia during daytime off-peak hours in spring 2013. The driver licensing agencies in the District of Columbia, Maryland, and Virginia provided vehicle information numbers (VINs) by matching license plate numbers with vehicle registration records and provided the age, gender, and ZIP code of the registered owner(s). VINs were decoded to obtain the curb weight and horsepower of vehicles. The study focused on 26,659 observed vehicles for which information on horsepower was available and the observed age and gender of drivers matched vehicle registration records. Log-linear regression estimated the effects of vehicle power on mean travel speeds, and logistic regression estimated the effects of vehicle power on the likelihood of a vehicle traveling over the speed limit and more than 10 mph over the limit. After controlling for driver characteristics, speed limit, vehicle type, and traffic volume, a 1-unit increase in vehicle power was associated with a 0.7% increase in mean speed, a 2.7% increase in the likelihood of a vehicle exceeding the speed limit by any amount, and an 11.6% increase in the likelihood of a vehicle exceeding the limit by 10 mph. All of these increases were highly significant. Speeding persists as a major factor in crashes in the United States. There are indications that travel speeds have increased in recent years. The current findings suggest the trend toward substantially more powerful vehicles may be contributing to higher speeds. Given the strong association between travel speed and crash

High speed analysis of high pressure combustion in a constant volume cell

NARCIS (Netherlands)

Frijters, P.J.M.; Klein-Douwel, R.J.H.; Manski, S.S.; Somers, L.M.T.; Baert, R.S.G.; Dias, V.

2005-01-01

A combustion process with N2, O2 and C2H4 as fuel used in an opticallyaccessible, high pressure, high temperature, constant volume cell forresearch on diesel fuel spray formation, is studied. The flame frontspeed Vf,HS is determined using high speed imaging. The pressure traceof the combustion

Effect of Laser Power and Scan Speed on Melt Pool Characteristics of Commercially Pure Titanium (CP-Ti)

Science.gov (United States)

Kusuma, Chandrakanth; Ahmed, Sazzad H.; Mian, Ahsan; Srinivasan, Raghavan

2017-07-01

Selective laser melting (SLM) is an additive manufacturing technique that creates complex parts by selectively melting metal powder layer-by-layer using a laser. In SLM, the process parameters decide the quality of the fabricated component. In this study, single beads of commercially pure titanium (CP-Ti) were melted on a substrate of the same material using an in-house built SLM machine. Multiple combinations of laser power and scan speed were used for single bead fabrication, while the laser beam diameter and powder layer thickness were kept constant. This experimental study investigated the influence of laser power, scan speed, and laser energy density on the melt pool formation, surface morphology, geometry (width and height), and hardness of solidified beads. In addition, the observed unfavorable effect such as inconsistency in melt pool width formation is discussed. The results show that the quality, geometry, and hardness of solidified melt pool are significantly affected by laser power, scanning speed, and laser energy density.

The independent effects of speed and propulsive force on joint power generation in walking.

Science.gov (United States)

Browne, Michael G; Franz, Jason R

2017-04-11

Walking speed is modulated using propulsive forces (F P ) during push-off and both preferred speed and F P decrease with aging. However, even prior to walking slower, reduced F P may be accompanied by potentially unfavorable changes in joint power generation. For example, compared to young adults, older adults exhibit a redistribution of mechanical power generation from the propulsive plantarflexor muscles to more proximal muscles acting across the knee and hip. Here, we used visual biofeedback based on real-time F P measurements to decouple and investigate the interaction between joint-level coordination, whole-body F P , and walking speed. 12 healthy young subjects walked on a dual-belt instrumented treadmill at a range of speeds (0.9-1.3m/s). We immediately calculated the average F P from each speed. Subjects then walked at 1.3m/s while completing a series of biofeedback trials with instructions to match their instantaneous F P to their averaged F P from slower speeds. Walking slower decreased F P and total positive joint work with little effect on relative joint-level contributions. Conversely, subjects walked at a constant speed with reduced F P , not by reducing total positive joint work, but by redistributing the mechanical demands of each step from the plantarflexor muscles during push-off to more proximal leg muscles during single support. Interestingly, these naturally emergent joint- and limb-level biomechanical changes, in the absence of neuromuscular constraints, resemble those due to aging. Our findings provide important reference data to understand the presumably complex interactions between joint power generation, whole-body F P , and walking speed in our aging population. Copyright © 2017 Elsevier Ltd. All rights reserved.

Planck Constant Determination from Power Equivalence

Science.gov (United States)

Newell, David B.

2000-04-01

Equating mechanical to electrical power links the kilogram, the meter, and the second to the practical realizations of the ohm and the volt derived from the quantum Hall and the Josephson effects, yielding an SI determination of the Planck constant. The NIST watt balance uses this power equivalence principle, and in 1998 measured the Planck constant with a combined relative standard uncertainty of 8.7 x 10-8, the most accurate determination to date. The next generation of the NIST watt balance is now being assembled. Modification to the experimental facilities have been made to reduce the uncertainty components from vibrations and electromagnetic interference. A vacuum chamber has been installed to reduce the uncertainty components associated with performing the experiment in air. Most of the apparatus is in place and diagnostic testing of the balance should begin this year. Once a combined relative standard uncertainty of one part in 10-8 has been reached, the power equivalence principle can be used to monitor the possible drift in the artifact mass standard, the kilogram, and provide an accurate alternative definition of mass in terms of fundamental constants. *Electricity Division, Electronics and Electrical Engineering Laboratory, Technology Administration, U.S. Department of Commerce. Contribution of the National Institute of Standards and Technology, not subject to copyright in the U.S.

Direct battery-driven solar LED lighting using constant-power control

KAUST Repository

Huang, Bin-Juine; Chen, Chun-Wei; Hsu, Po-Chien; Tseng, Wei-Min; Wu, Min-Sheng

2012-01-01

A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result

Development of constant-power driving control for light-emitting-diode (LED) luminaire

KAUST Repository

Huang, Bin-Juine; Chen, Chun-Wei; Ong, Chin-Dian; Du, Bo-Han; Hsu, Po-Chien

2013-01-01

changes from 0 to 40 °C, the LED illumination varies slightly (-1.7%) for constant-power driving, as compared to that of constant-current driving (-12%) and constant-voltage driving (+50%). The constant-power driving has revealed advantage in stabilizing

The speed-curvature power law of movements: a reappraisal.

Science.gov (United States)

Zago, Myrka; Matic, Adam; Flash, Tamar; Gomez-Marin, Alex; Lacquaniti, Francesco

2018-01-01

Several types of curvilinear movements obey approximately the so called 2/3 power law, according to which the angular speed varies proportionally to the 2/3 power of the curvature. The origin of the law is debated but it is generally thought to depend on physiological mechanisms. However, a recent paper (Marken and Shaffer, Exp Brain Res 88:685-690, 2017) claims that this power law is simply a statistical artifact, being a mathematical consequence of the way speed and curvature are calculated. Here we reject this hypothesis by showing that the speed-curvature power law of biological movements is non-trivial. First, we confirm that the power exponent varies with the shape of human drawing movements and with environmental factors. Second, we report experimental data from Drosophila larvae demonstrating that the power law does not depend on how curvature is calculated. Third, we prove that the law can be violated by means of several mathematical and physical examples. Finally, we discuss biological constraints that may underlie speed-curvature power laws discovered in empirical studies.

Accounting for the speed shear in wind turbine power performance measurement

Energy Technology Data Exchange (ETDEWEB)

Wagner, R.

2010-04-15

The power curve of a wind turbine is the primary characteristic of the machine as it is the basis of the warranty for it power production. The current IEC standard for power performance measurement only requires the measurement of the wind speed at hub height and the air density to characterise the wind field in front of the turbine. However, with the growing size of the turbine rotors during the last years, the effect of the variations of the wind speed within the swept rotor area, and therefore of the power output, cannot be ignored any longer. Primary effects on the power performance are from the vertical wind shear and the turbulence intensity. The work presented in this thesis consists of the description and the investigation of a simple method to account for the wind speed shear in the power performance measurement. Ignoring this effect was shown to result in a power curve dependant on the shear condition, therefore on the season and the site. It was then proposed to use an equivalent wind speed accounting for the whole speed profile in front of the turbine. The method was first tested with aerodynamic simulations of a multi-megawatt wind turbine which demonstrated the decrease of the scatter in the power curve. A power curve defined in terms of this equivalent wind speed would be less dependant on the shear than the standard power curve. The equivalent wind speed method was then experimentally validated with lidar measurements. Two equivalent wind speed definitions were considered both resulting in the reduction of the scatter in the power curve. As a lidar wind profiler can measure the wind speed at several heights within the rotor span, the wind speed profile is described with more accuracy than with the power law model. The equivalent wind speed derived from measurements, including at least one measurement above hub height, resulted in a smaller scatter in the power curve than the equivalent wind speed derived from profiles extrapolated from measurements

Tip Speed Ratio Based Maximum Power Tracking Control of Variable Speed Wind Turbines; A Comprehensive Design

Directory of Open Access Journals (Sweden)

Murat Karabacak

2017-08-01

Full Text Available The most primitive control method of wind turbines used to generate electric energy from wind is the fixed speed control method. With this method, it is not possible that turbine input power is transferred to grid at maximum rate. For this reason, Maximum Power Tracking (MPT schemes are proposed. In order to implement MPT, the propeller has to rotate at a different speed for every different wind speed. This situation has led MPT based systems to be called Variable Speed Wind Turbine (VSWT systems. In VSWT systems, turbine input power can be transferred to grid at rates close to maximum power. When MPT based control of VSWT systems is the case, two important processes come into prominence. These are instantaneously determination and tracking of MPT point. In this study, using a Maximum Power Point Tracking (MPPT method based on tip speed ratio, power available in wind is transferred into grid over a back to back converter at maximum rate via a VSWT system with permanent magnet synchronous generator (PMSG. Besides a physical wind turbine simulator is modelled and simulated. Results show that a time varying MPPT point is tracked with a high performance.

Control of cooling of an oil-immersed power transformer by varying speed of fans

OpenAIRE

Đorđević, Nikola Z.; Žakula, Dane M.; Jevtić, Milica M.; Tomašević, Radojica Ž.; Radaković, Zoran R.

2016-01-01

The paper presents a prototype system for speed control of cooling fans for a small oil-immersed 6.6 kVA transformer, implemented on a standard PLC. Generally, the potential for optimization of the cooling process depends on the accessible cooling modes and construction of the transformer; basically the aim of the cooling system control is reduction in power consumption of the fans / pumps and keeping the top-oil temperature at constant value (to reduce transformer 'breathing' and infiltratio...

Development of constant-power driving control for light-emitting-diode (LED) luminaire

International Nuclear Information System (INIS)

Huang, Bin-Juine; Chen, Chun-Wei; Ong, Chin-Dian; Du, Bo-Han; Hsu, Po-Chien

2013-01-01

The illumination of an LED may be affected by operating temperature even under constant-current condition. A constant-power driving technique is proposed in the present study for LED luminaire. A linear system dynamics model of LED luminaire is first derived and used in the design of the feedback control system. The PI controller was designed and tuned taking into account the control accuracy and robust properties with respect to plant uncertainty and variation of operating conditions. The control system was implemented on a microprocessor and used to control a 150W LED luminaire. The test result shows that the feedback system accurately controls the input power of LED luminaire to within 1.3 per cent error. As the ambient temperature changes from 0 to 40 °C, the LED illumination varies slightly (−1.7%) for constant-power driving, as compared to that of constant-current driving (−12%) and constant-voltage driving (+50%). The constant-power driving has revealed advantage in stabilizing the illumination of LED under large temperature variation. - Highlights: ► A constant-power driving technique is proposed for LED luminaire. ► A linear system dynamics model of LED luminaire is used in the control system design. ► The test shows that the feedback system accurately controls the input power. ► The LED illumination varies slightly (−1.7%) for constant-power driving.

A General Constant Power Generation Algorithm for Photovoltaic Systems

DEFF Research Database (Denmark)

Tafti, Hossein Dehghani; Maswood, Ali Iftekhar; Konstantinou, Georgios

2018-01-01

Photovoltaic power plants (PVPPs) typically operate by tracking the maximum power point in order to maximize conversion efficiency. However, with the continuous increase of installed grid-connected PVPPs, power system operators have been experiencing new challenges, like overloading, overvoltages...... on a hysteresis band controller in order to obtain fast dynamic response under transients and low power oscillation during steady-state operation. The performance of the proposed algorithm for both single- and two-stage PVPPs is examined on a 50-kVA simulation setup of these topologies. Moreover, experimental...... and operation during grid voltage disturbances. Consequently, constant power generation (CPG) is imposed by grid codes. An algorithm for the calculation of the photovoltaic panel voltage reference, which generates a constant power from the PVPP, is introduced in this paper. The key novelty of the proposed...

Supplementary speed control for wind power smoothing

NARCIS (Netherlands)

Haan, de J.E.S.; Frunt, J.; Kechroud, A.; Kling, W.L.

2010-01-01

Wind fluctuations result in even larger wind power fluctuations because the power of wind is proportional to the cube of the wind speed. This report analyzes wind power fluctuations to investigate inertial power smoothing, in particular for the frequency range of 0.08 - 0.5 Hz. Due to the growing

Study on a constant-tip-speed-ratio operation of wind power generation system. Effect of load control system on dynamic behavior; Furyoku hatsuden system no hensoku seigyo unten ni kansuru kenkyu. Fuka seigyokei ga system no rikigakuteki kyodo ni oyobosu eikyo

Energy Technology Data Exchange (ETDEWEB)

Wakui, T.; Yamaguchi, K. [Waseda University, Tokyo (Japan); Tanzawa, Y. [Nippon Institute of Technology, Saitama (Japan); Hashizume, T.; Ota, E. [Waseda University, Tokyo (Japan). School of Science and Engineering

1998-06-01

The effect that the set data of the load control system in a wind power generation system exerts on the dynamic behavior of a system was investigated. The wind power generation system consists of a hybrid wind turbine with combined Darrieus and Savonius rotors, load with a generator and battery in the center, and a controller. A constant-tip-speed ratio operation that holds the circumferential speed ratio in which the power coefficient is maximized irrespective of the change in wind velocity was used to extract and convert the wind energy more effectively. In a high-wind velocity area, the system is operated at a fixed speed, and the increase in rotation is suppressed to protect the wing strength. In a large system, the response characteristics are only slightly improved by the limited load operation range and influenced rotor inertial. Power cannot be fully extracted even if the control system is changed in setting, and the applicability to the wind situation remains low. During the actual operation, the adjustment value of the control system should be set so that the output operation is satisfactorily possible in the specified load operation range, that is, the change in the instantaneous value of an effective power coefficient indicates almost flat gain characteristics in frequency characteristics. 14 refs., 10 figs., 2 tabs.

Evaluation of single tracks of 17-4PH steel manufactured at different power densities and scanning speeds by selective laser melting

Directory of Open Access Journals (Sweden)

Makoana, N. W.

2016-11-01

Full Text Available In Selective Laser Melting, the initial units produced are single tracks that overlap to create a single layer; from the sequence of layers, a 3D object is manufactured. The properties of the parts produced by SLM depend heavily on the properties of each single track and each layer formed by these tracks. This study evaluates the effect of processing parameters on the geometrical characteristics of single tracks manufactured from 17-4PH stainless steel powder. A single-mode continuous-wave ytterbium fibre laser was used to manufacture single tracks at laser powers in the range of 100-300 W with a constant spot size of ∼80μm. The single tracks produced were subjected to standard metallographic preparation techniques for further analysis with an optical microscope. Deep molten pool shapes were observed at low scan speeds, while shallow molten pool shapes were observed at high scan speeds. At higher laser power densities, under-cutting and humping effects were also observed. The dimensions of single tracks processed without powder generally decrease with increasing scan speed at constant laser power. However, the geometrical features of the single tracks processed with powder revealed pronounced irregularities believed to be caused by non-homogeneity in the deposited powder layer.

Overview of Variable-Speed Power-Turbine Research

Science.gov (United States)

Welch, Gerard E.

2011-01-01

The vertical take-off and landing (VTOL) and high-speed cruise capability of the NASA Large Civil Tilt-Rotor (LCTR) notional vehicle is envisaged to enable increased throughput in the national airspace. A key challenge of the LCTR is the requirement to vary the main rotor speeds from 100% at take-off to near 50% at cruise as required to minimize mission fuel burn. The variable-speed power-turbine (VSPT), driving a fixed gear-ratio transmission, provides one approach for effecting this wide speed variation. The key aerodynamic and rotordynamic challenges of the VSPT were described in the FAP Conference presentation. The challenges include maintaining high turbine efficiency at high work factor, wide (60 deg.) of incidence variation in all blade rows due to the speed variation, and operation at low Reynolds numbers (with transitional flow). The PT -shaft of the VSPT must be designed for safe operation in the wide speed range required, and therefore poses challenges associated with rotordynamics. The technical challenges drive research activities underway at NASA. An overview of the NASA SRW VSPT research activities was provided. These activities included conceptual and preliminary aero and mechanical (rotordynamics) design of the VSPT for the LCTR application, experimental and computational research supporting the development of incidence tolerant blading, and steps toward component-level testing of a variable-speed power-turbine of relevance to the LCTR application.

Dynamic Influences of Wind Power on The Power System

DEFF Research Database (Denmark)

Rosas, Pedro Andrè Carvalho

2004-01-01

between different wind turbines.Here the wind speed model is applied to a constant rotational speed wind turbine/farm, but the model is suit-able to variable speed wind turbine/farm as well. The cases presented here illustrate the influences of the wind power on the power systemquality and stability...... integration due to the low spatial correlation of the wind speed. The voltage quality analysed in a Brazilian power system and in the Nordel power system from connecting largeamount of wind power showed very small voltage variations. The frequency variations analysed from the Nordel showed also small varia...

Wind speed power spectrum analysis for Bushland, Texas

Energy Technology Data Exchange (ETDEWEB)

Eggleston, E.D. [USDA-Agricultural Research Service, Bushland, TX (United States)

1996-12-31

Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.

Modeling a constant power load for nickel-hydrogen battery testing using SPICE

Science.gov (United States)

Bearden, Douglas B.; Lollar, Louis F.; Nelms, R. M.

1990-01-01

The effort to design and model a constant power load for the HST (Hubble Space Telescope) nickel-hydrogen battery tests is described. The constant power load was designed for three different simulations on the batteries: life cycling, reconditioning, and capacity testing. A dc-dc boost converter was designed to act as this constant power load. A boost converter design was chosen because of the low test battery voltage (4 to 6 VDC) generated and the relatively high power requirement of 60 to 70 W. The SPICE model was shown to consistently predict variations in the actual circuit as various designs were attempted. It is concluded that the confidence established in the SPICE model of the constant power load ensures its extensive utilization in future efforts to improve performance in the actual load circuit.

BEGA Starter/Alternator - Vector Control Implementation and Performance for Wide Speed Range at Unity Power Factor Operation

DEFF Research Database (Denmark)

Blaabjerg, Frede; Boldea, Ion; Coroban-Schramel, Vasile

2008-01-01

Biaxial Excitation Generator for Automobile (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles (HEVs). This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range (CPSR), theoretically...... to infinite. A vector control structure is proposed for BEGA operation during motoring and generating, at unity power factor with zero d-axis current (id) and zero q-axis flux (Ψq) control. In such conditions BEGA behaves like a truly dc. brush machine (with zero reactance in steady state !). A high iq...

BEGA Starter/Alternator—Vector Control Implementation and Performance for Wide Speed Range at Unity Power Factor Operation

DEFF Research Database (Denmark)

Boldea, Ion; Coroban-Schramel, Vasile; Andreescu, Gheorghe-Daniel

2010-01-01

The Biaxial Excitation Generator for Automobiles (BEGA) is proposed as a solution for integrated starter/alternator systems used in hybrid electric vehicles. This paper demonstrates through experiments and simulations that BEGA has a very large constant power speed range. A vector control structure...... is proposed for BEGA operation during motoring and generating, at unity power factor with zero d-axis current (id) and zero q-axis flux (Ψq) control. In such conditions, BEGA behaves like a separately excited dc brush(commutator) machine, in the sense that no stator inductance voltage drop occurs...

Effect of operating methods of wind turbine-generator system on net power extraction under wind speed fluctuations in fields; Hendo fukyoka deno doryoku chushutsu kara mita furyoku hatsuden system no unten seigyoho ni kansuru kosatsu

Energy Technology Data Exchange (ETDEWEB)

Wakui, T. [Japan Society for the Promotion of Science, Tokyo (Japan); Hashizume, T.; Ota, E. [Waseda University, Tokyo (Japan). School of Science and Engineering

2000-01-25

The effect of operating methods of wind turbine-generator system on net power extraction under wind speed fluctuations is discussed in relation to the dynamic behavior of the system. The system is composed of a Darrieus-Savonius hybrid wind turbine and a load generator. In this paper, two types of operating method are examined; constant tip speed ratio operation for stand-alone power systems (Scheme 1) and synchronous operation for utility power systems (Scheme 2). The computed results of the net extracting power using our dynamic simulation model show that the dominant factor of power extraction in Scheme 1 is the dynamic characteristics of rotational components and that it is important to select the appropriate rated wind speed in Scheme 2. Thus, it is concluded that a conformable operating method and rated power output of the system exist for each wind condition. In particular, small-scale systems, which are smaller than approximately 10 kW-system range, are desirable to be operated under a constant tip speed ratio as stand-alone power systems. (author)

Transport equivalent diffusion constants for reflector region in PWRs

International Nuclear Information System (INIS)

Tahara, Yoshihisa; Sekimoto, Hiroshi

2002-01-01

The diffusion-theory-based nodal method is widely used in PWR core designs for reason of its high computing speed in three-dimensional calculations. The baffle/reflector (B/R) constants used in nodal calculations are usually calculated based on a one-dimensional transport calculation. However, to achieve high accuracy of assembly power prediction, two-dimensional model is needed. For this reason, the method for calculating transport equivalent diffusion constants of reflector material was developed so that the neutron currents on the material boundaries could be calculated exactly in diffusion calculations. Two-dimensional B/R constants were calculated using the transport equivalent diffusion constants in the two-dimensional diffusion calculation whose geometry reflected the actual material configuration in the reflector region. The two-dimensional B/R constants enabled us to predict assembly power within an error of 1.5% at hot full power conditions. (author)

Control of cooling of an oil-immersed power transformer by varying speed of fans

Directory of Open Access Journals (Sweden)

Đorđević Nikola Z.

2016-01-01

Full Text Available The paper presents a prototype system for speed control of cooling fans for a small oil-immersed 6.6 kVA transformer, implemented on a standard PLC. Generally, the potential for optimization of the cooling process depends on the accessible cooling modes and construction of the transformer; basically the aim of the cooling system control is reduction in power consumption of the fans / pumps and keeping the top-oil temperature at constant value (to reduce transformer 'breathing' and infiltration of moisture. The following constraints should be taken into account: hot-spot temperature, its current value and the one which would appear for planned overloads must not exceed the allowed limit. Based on the results in steady state, the paper offers the quantitative determination of transformer thermal characteristics depending on the fan speed.

SPEED POWER AFTER DIFFERENT TRAINING METHODS

Directory of Open Access Journals (Sweden)

Milan Gužvica

2011-09-01

Full Text Available As the strength is a very important capability, with which are more or less, related and all other motor skills relevant to the successful conduct of sports fight in karate, we were interested in what extent the ability of the speed of force development changes under the influence of different types of loads. For this purpose we used two different methods: the development of speed power with weights and plyometric method. Research is organized on a sample of 20 subjects (first year students of the College of Internal Affairs in Banja Luka, divided into two groups, of which only 12 students responded to the demands of research. The program was implemented during the period of six weeks for two hours per week. Before beginning and three days after the training process, we also tested levels of speed power using eight specific motor tests. After completion of the initial and final measurements, data were analyzed by appropriate statistical procedures, where all respondents, across the various tests, achieved better results. However, statistically significant differences were not obtained in both groups. Specifically, statistically significant differences were obtained in the group T across the various tests, while in group P, statistically significant differences were not obtained in three tests conducted. Given results allowed us that, with caution, we conclude that the method of working with weights, in a limited period of time, when it comes to beginners, is still more efficient than the plyometric method of work. Therefore recommendation for increasing the speed power, in a limited period of time, is to use a method of working with weights.

Development of constant-power driving control for light-emitting-diode (LED) luminaire

KAUST Repository

Huang, Bin-Juine

2013-01-01

The illumination of an LED may be affected by operating temperature even under constant-current condition. A constant-power driving technique is proposed in the present study for LED luminaire. A linear system dynamics model of LED luminaire is first derived and used in the design of the feedback control system. The PI controller was designed and tuned taking into account the control accuracy and robust properties with respect to plant uncertainty and variation of operating conditions. The control system was implemented on a microprocessor and used to control a 150W LED luminaire. The test result shows that the feedback system accurately controls the input power of LED luminaire to within 1.3 per cent error. As the ambient temperature changes from 0 to 40 °C, the LED illumination varies slightly (-1.7%) for constant-power driving, as compared to that of constant-current driving (-12%) and constant-voltage driving (+50%). The constant-power driving has revealed advantage in stabilizing the illumination of LED under large temperature variation. © 2012 Elsevier Ltd. All rights reserved.

Hour-Ahead Wind Speed and Power Forecasting Using Empirical Mode Decomposition

Directory of Open Access Journals (Sweden)

Ying-Yi Hong

2013-11-01

Full Text Available Operation of wind power generation in a large farm is quite challenging in a smart grid owing to uncertain weather conditions. Consequently, operators must accurately forecast wind speed/power in the dispatch center to carry out unit commitment, real power scheduling and economic dispatch. This work presents a novel method based on the integration of empirical mode decomposition (EMD with artificial neural networks (ANN to forecast the short-term (1 h ahead wind speed/power. First, significant parameters for training the ANN are identified using the correlation coefficients. These significant parameters serve as inputs of the ANN. Owing to the volatile and intermittent wind speed/power, the historical time series of wind speed/power is decomposed into several intrinsic mode functions (IMFs and a residual function through EMD. Each IMF becomes less volatile and therefore increases the accuracy of the neural network. The final forecasting results are achieved by aggregating all individual forecasting results from all IMFs and their corresponding residual functions. Real data related to the wind speed and wind power measured at a wind-turbine generator in Taiwan are used for simulation. The wind speed forecasting and wind power forecasting for the four seasons are studied. Comparative studies between the proposed method and traditional methods (i.e., artificial neural network without EMD, autoregressive integrated moving average (ARIMA, and persistence method are also introduced.

Improving transition between power optimization and power limitation of variable speed/variable pitch wind turbines

Energy Technology Data Exchange (ETDEWEB)

Hansen, A D; Bindner, H [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark); Rebsdorf, A [Vestas Wind Systems A/S, Lem (Denmark)

1999-03-01

The paper summarises and describes the main results of a recently performed study of improving the transition between power optimization and power limitation for variable speed/variable pitch wind turbines. The results show that the capability of varying the generator speed also can be exploited in the transition stage to improve the quality of the generated power. (au)

Comparison of performances of full-speed turbine and half-speed turbine for nuclear power plants

International Nuclear Information System (INIS)

Wang Hu; Zhang Weihong; Zhang Qiang; Li Shaohua

2010-01-01

The steam turbines of nuclear power plants can be divided into the full-speed turbine and half-speed turbine. Different speed leads to differences in many aspects. Therefore, the rational speed is the key point in the selection of steam turbines. This paper contrasts the economy between the half-speed turbine and full-speed turbine, by calculating the relative internal efficiency of half-speed and full-speed steam turbines with the typical level of 1000 megawatt. At the same time, this paper also calculate the relative speed of high speed water drops in the last stage blade of half-speed turbine and full-speed turbine, to contrast the water erosion between the half-speed turbine and full-speed turbine. The results show that the relative internal efficiency of half-speed turbine is higher than that of the full-speed turbine, and that the security especially the ability of preventing water erosion of half-speed turbine is better than that of the full-speed turbine. (authors)

Auto type-selection of constant supporting in nuclear power stations

International Nuclear Information System (INIS)

Liu Hu; Wang Fujun; Liu Wei; Li Zhaoqing

2013-01-01

To solve the type-selection of constant supporting in nuclear power stations, combining the characteristics of constant supporting which can adjust in the certain scope and the rules of load-displacement, the requirements and process for the type-selection of constant supporting is proposed, and the process of type-selection is optimized by Visual Basic. After inputting of the known parameters, the process can automatically select the most economical and reasonable constant supporting by array and function. (authors)

Power, speed & automation with Adobe Photoshop

CERN Document Server

Scott, Geoff

2012-01-01

This is a must for the serious Photoshop user! Power, Speed & Automation explores how to customize and automate Photoshop to increase your speed and productivity.  With numerous step-by-step instructions, the authors-two of Adobe's own software developers!- walk you through the steps to best tailor Photoshop's interface to your personal workflow; write and apply Actions; and use batching and scripts to process large numbers of images quickly and automatically.  You will learn how to build your own dialogs and panels to improve your production workflows in Photoshop, the secrets of changing

Experimental evaluation of the power balance model of speed skating.

Science.gov (United States)

de Koning, Jos J; Foster, Carl; Lampen, Joanne; Hettinga, Floor; Bobbert, Maarten F

2005-01-01

Prediction of speed skating performance with a power balance model requires assumptions about the kinetics of energy production, skating efficiency, and skating technique. The purpose of this study was to evaluate these parameters during competitive imitations for the purpose of improving model predictions. Elite speed skaters (n = 8) performed races and submaximal efficiency tests. External power output (P(o)) was calculated from movement analysis and aerodynamic models and ice friction measurements. Aerobic kinetics was calculated from breath-by-breath oxygen uptake (Vo(2)). Aerobic power (P(aer)) was calculated from measured skating efficiency. Anaerobic power (P(an)) kinetics was determined by subtracting P(aer) from P(o). We found gross skating efficiency to be 15.8% (1.8%). In the 1,500-m event, the kinetics of P(an) was characterized by a first-order system as P(an) = 88 + 556e(-0.0494t) (in W, where t is time). The rate constant for the increase in P(aer) was -0.153 s(-1), the time delay was 8.7 s, and the peak P(aer) was 234 W; P(aer) was equal to 234[1 - e(-0.153(t-8.7))] (in W). Skating position changed with preextension knee angle increasing and trunk angle decreasing throughout the event. We concluded the pattern of P(aer) to be quite similar to that reported during other competitive imitations, with the exception that the increase in P(aer) was more rapid. The pattern of P(an) does not appear to fit an "all-out" pattern, with near zero values during the last portion of the event, as assumed in our previous model (De Koning JJ, de Groot G, and van Ingen Schenau GJ. J Biomech 25: 573-580, 1992). Skating position changed in ways different from those assumed in our previous model. In addition to allowing improved predictions, the results demonstrate the importance of observations in unique subjects to the process of model construction.

Resonant Vibrations Resulting from the Re-Engineering of a Constant-Speed 2-Bladed Turbine to a Variable-Speed 3-Bladed Turbine

Energy Technology Data Exchange (ETDEWEB)

Fleming, P.; Wright, A. D.; Finersh, L. J.

2010-12-01

The CART3 (Controls Advanced Research Turbine, 3-bladed) at the National Wind Technology Center has recently been converted from a 2-bladed constant speed machine to a 3-bladed variable speed machine designed specically for controls research. The purpose of this conversion was to develop an advanced controls field-testing platform which has the more typical 3-bladed configuration. A result of this conversion was the emergence of several resonant vibrations, some of which initially prevented operation of the turbine until they could be explained and resolved. In this paper, the investigations into these vibrations are presented as 'lessons-learned'. Additionally, a frequency-domain technique called waterfall plotting is discussed and its usefulness in this research is illustrated.

Accounting for the speed shear in wind turbine power performance measurement

DEFF Research Database (Denmark)

Wagner, Rozenn

the vertical wind shear and the turbulence intensity. The work presented in this thesis consists of the description and the investigation of a simple method to account for the wind speed shear in the power performance measurement. Ignoring this effect was shown to result in a power curve dependant on the shear...... for turbulence intensity suggested by Albers. The second method was found to be more suitable for normalising the power curve for the turbulence intensity. Using the equivalent wind speed accounting for the wind shear in the power performance measurement was shown to result in a more repeatable power curve than......The power curve of a wind turbine is the primary characteristic of the machine as it is the basis of the warranty for it power production. The current IEC standard for power performance measurement only requires the measurement of the wind speed at hub height and the air density to characterise...

Effect of material constants on power output in piezoelectric vibration-based generators.

Science.gov (United States)

Takeda, Hiroaki; Mihara, Kensuke; Yoshimura, Tomohiro; Hoshina, Takuya; Tsurumi, Takaaki

2011-09-01

A possible power output estimation based on material constants in piezoelectric vibration-based generators is proposed. A modified equivalent circuit model of the generator was built and was validated by the measurement results in the generator fabricated using potassium sodium niobate-based and lead zirconate titanate (PZT) ceramics. Subsequently, generators with the same structure using other PZT-based and bismuth-layered structure ferroelectrics ceramics were fabricated and tested. The power outputs of these generators were expressed as a linear functions of the term composed of electromechanical coupling coefficients k(sys)(2) and mechanical quality factors Q*(m) of the generator. The relationship between device constants (k(sys)(2) and Q*(m)) and material constants (k(31)(2) and Q(m)) was clarified. Estimation of the power output using material constants is demonstrated and the appropriate piezoelectric material for the generator is suggested.

Accounting for the speed shear in wind turbine power performance measurement

DEFF Research Database (Denmark)

Wagner, Rozenn; Courtney, Michael; Gottschall, Julia

2011-01-01

The current IEC standard for wind turbine power performance measurement only requires measurement of the wind speed at hub height assuming this wind speed to be representative for the whole rotor swept area. However, the power output of a wind turbine depends on the kinetic energy flux, which...... itself depends on the wind speed profile, especially for large turbines. Therefore, it is important to characterize the wind profile in front of the turbine, and this should be preferably achieved by measuring the wind speed over the vertical range between lower and higher rotor tips. In this paper, we...... describe an experiment in which wind speed profiles were measured in front of a multimegawatt turbine using a ground–based pulsed lidar. Ignoring the vertical shear was shown to overestimate the kinetic energy flux of these profiles, in particular for those deviating significantly from a power law profile...

DC Motor Parameter Identification Using Speed Step Responses

Directory of Open Access Journals (Sweden)

Wei Wu

2012-01-01

Full Text Available Based on the DC motor speed response measurement under a step voltage input, important motor parameters such as the electrical time constant, the mechanical time constant, and the friction can be estimated. A power series expansion of the motor speed response is presented, whose coefficients are related to the motor parameters. These coefficients can be easily computed using existing curve fitting methods. Experimental results are presented to demonstrate the application of this approach. In these experiments, the approach was readily implemented and gave more accurate estimates than conventional methods.

Modelling and control of variable speed wind turbines for power system studies

DEFF Research Database (Denmark)

Michalke, Gabriele; Hansen, Anca Daniela

2010-01-01

and implemented in the power system simulation tool DIgSILENT. Important issues like the fault ride-through and grid support capabilities of these wind turbine concepts are addressed. The paper reveals that advanced control of variable speed wind turbines can improve power system stability. Finally......, it will be shown in the paper that wind parks consisting of variable speed wind turbines can help nearby connected fixed speed wind turbines to ride-through grid faults. Copyright © 2009 John Wiley & Sons, Ltd.......Modern wind turbines are predominantly variable speed wind turbines with power electronic interface. Emphasis in this paper is therefore on the modelling and control issues of these wind turbine concepts and especially on their impact on the power system. The models and control are developed...

Changes of indicators of high-speed and high-speed and power preparedness at volleyball players of 12–13 years old

Directory of Open Access Journals (Sweden)

Oleg Shevchenko

2016-04-01

Full Text Available Purpose: to define changes of indicators of high-speed and high-speed and power preparedness of volleyball players of 12–13 years old. Material & Methods: the test exercises, which are recommended by the training program of CYSS on volleyball, were used for the definition of the level of development of high-speed and high-speed and power abilities of volleyball players. 25 young volleyball players from the group of the previous basic preparation took part in the experiment. Sports experience of sportsmen is 3–4 years. The analysis of scientifically-methodical literature, pedagogical testing, pedagogical experiment, methods of mathematical statistics were carried out. Results: the analyzed level of high-speed and high-speed and power abilities of volleyball players. Conclusions: the results had reliable changes (t=2,2–2,4 at р<0,05 of the level of high-speed and high-speed and power abilities of volleyball players of 12–13years old in the experimental group at the end of the experiment, except run on 30 m that demonstrates a positive influence of application of special exercises in the educational-training process.

Stand-alone excitation synchronous wind power generators with power flow management strategy

Directory of Open Access Journals (Sweden)

Tzuen-Lih Chern

2014-09-01

Full Text Available This study presents a stand-alone excitation synchronous wind power generator (SESWPG with power flow management strategy (PFMS. The rotor speed of the excitation synchronous generator tracks the utility grid frequency by using servo motor tracking technologies. The automatic voltage regulator governs the exciting current of generator to achieve the control goals of stable voltage. When wind power is less than the needs of the consumptive loading, the proposed PFMS increases motor torque to provide a positive power output for the loads, while keeping the generator speed constant. Conversely, during the periods of wind power greater than output loads, the redundant power of generator production is charged to the battery pack and the motor speed remains constant with very low power consumption. The advantage of the proposed SESWPG is that the generator can directly output stable alternating current (AC electricity without using additional DC–AC converters. The operation principles with software simulation for the system are described in detail. Experimental results of a laboratory prototype are shown to verify the feasibility of the system.

Power Control of Permanent Magnet Generator Based Variable Speed Wind Turbines

DEFF Research Database (Denmark)

Deng, Fujin; Chen, Zhe

2009-01-01

When the wind power accounts for a large portion of the grid, it will be required to regulate the active power and reactive power. This paper investigates a MWlevel variable speed wind turbine with a permanent magnet synchronous generator (PMSG). The power control capabilities of two kinds...... of control schemes conducted respectively on this wind turbine under two conditions, including rapid wind speed change and grids faults, are compared. The simulation study of the wind turbine system is conducted using PSCAD/EMTDC, and the results show the different power control capabilities of the two...

Fixed-speed and Variable-speed Pumped Storage Dispatch Model in Power Systems with High Renewable Penetration

Science.gov (United States)

Yuan, Bo; Zong, Jin; Xu, Zhicheng

2018-06-01

According to different operating characteristics of pumped storage fixed speed unit and variable speed unit, a joint dispatching model of pumped storage unit and other types of units based on mixed integer linear optimization is constructed. The model takes into account the operating conditions, reservoir capacity, cycle type and other pumped storage unit constraints, but also consider the frequent start and stop and the stability of the operation of the unit caused by the loss. Using the Cplex solver to solve the model, the empirical example of the provincial power grid shows that the model can effectively arrange the pumping storage speed and the dispatching operation of the variable speed unit under the precondition of economic life of the unit, and give full play to the function of peak shaving and accommodating new energy. Because of its more flexible regulation characteristics of power generation and pumping conditions, the variable speed unit can better improve the operating conditions of other units in the system and promote the new energy dissipation.

Fixed-speed and Variable-speed Pumped Storage Dispatch Model in Power Systems with High Renewable Penetration

Directory of Open Access Journals (Sweden)

Yuan Bo

2018-01-01

Full Text Available According to different operating characteristics of pumped storage fixed speed unit and variable speed unit, a joint dispatching model of pumped storage unit and other types of units based on mixed integer linear optimization is constructed. The model takes into account the operating conditions, reservoir capacity, cycle type and other pumped storage unit constraints, but also consider the frequent start and stop and the stability of the operation of the unit caused by the loss. Using the Cplex solver to solve the model, the empirical example of the provincial power grid shows that the model can effectively arrange the pumping storage speed and the dispatching operation of the variable speed unit under the precondition of economic life of the unit, and give full play to the function of peak shaving and accommodating new energy. Because of its more flexible regulation characteristics of power generation and pumping conditions, the variable speed unit can better improve the operating conditions of other units in the system and promote the new energy dissipation.

Variable current speed controller for eddy current motors

Science.gov (United States)

Gerth, H.L.; Bailey, J.M.; Casstevens, J.M.; Dixon, J.H.; Griffith, B.O.; Igou, R.E.

1982-03-12

A speed control system for eddy current motors is provided in which the current to the motor from a constant frequency power source is varied by comparing the actual motor speed signal with a setpoint speed signal to control the motor speed according to the selected setpoint speed. A three-phase variable voltage autotransformer is provided for controlling the voltage from a three-phase power supply. A corresponding plurality of current control resistors is provided in series with each phase of the autotransformer output connected to inputs of a three-phase motor. Each resistor is connected in parallel with a set of normally closed contacts of plurality of relays which are operated by control logic. A logic circuit compares the selected speed with the actual motor speed obtained from a digital tachometer monitoring the motor spindle speed and operated the relays to add or substract resistance equally in each phase of the motor input to vary the motor current to control the motor at the selected speed.

Effects of endurance training on reduction of plasma glucose during high intensity constant and incremental speed tests in Wistar rats

Directory of Open Access Journals (Sweden)

P. Abreu

Full Text Available The aim of this research was to investigate the effects of endurance training on reduction of plasma glucose during high intensity constant and incremental speed tests in Wistar rats. We hypothesized that plasma glucose might be decreased in the exercised group during heavy (more intense exercise. Twenty-four 10-week-old male Wistar rats were randomly assigned to sedentary and exercised groups. The prescription of endurance exercise training intensity was determined as 60% of the maximum intensity reached at the incremental speed test. The animals were trained by running on a motorized treadmill, five days/week for a total period of 67 weeks. Plasma glucose during the constant speed test in the exercised group at 20 m/min was reduced at the 14th, 21st and 28th min compared to the sedentary group, as well at 25 m/min at the 21st and 28th min. Plasma glucose during the incremental speed test was decreased in the exercised group at the moment of exhaustion (48th min compared to the sedentary group (27th min. Endurance training positively modulates the mitochondrial activity and capacity of substrate oxidation in muscle and liver. Thus, in contrast to other studies on high load of exercise, the effects of endurance training on the decrease of plasma glucose during constant and incremental speed tests was significantly higher in exercised than in sedentary rats and associated with improved muscle and hepatic oxidative capacity, constituting an important non-pharmacological intervention tool for the prevention of insulin resistance, including type 2 diabetes mellitus.

Constant versus variable response signal delays in speed accuracy trade-offs : Effects of advance preparation for processing time

OpenAIRE

Miller, Jeff; Sproesser, Gudrun; Ulrich, Rolf

2008-01-01

In two experiments, we used response signals (RSs) to control processing time and trace out speed accuracy trade-off (SAT) functions in a difficult perceptual discrimination task. Each experiment compared performance in blocks of trials with constant and, hence, temporally predictable RS lags against performance in blocks with variable, unpredictable RS lags. In both experiments, essentially equivalent SAT functions were observed with constant and variable RS lags. We conclude that there is l...

Structural integrity of power generating speed bumps made of concrete foam composite

Science.gov (United States)

Syam, B.; Muttaqin, M.; Hastrino, D.; Sebayang, A.; Basuki, W. S.; Sabri, M.; Abda, S.

2018-02-01

In this paper concrete foam composite speed bumps were designed to generate electrical power by utilizing the movements of commuting vehicles on highways, streets, parking gates, and drive-thru station of fast food restaurants. The speed bumps were subjected to loadings generated by vehicles pass over the power generating mechanical system. In this paper, we mainly focus our discussion on the structural integrity of the speed bumps and discuss the electrical power generating speed bumps in another paper. One aspect of structural integrity is its ability to support designed loads without breaking and includes the study of past structural failures in order to prevent failures in future designs. The concrete foam composites were used for the speed bumps; the reinforcement materials are selected from empty fruit bunch of oil palm. In this study, the speed bump materials and structure were subjected to various tests to obtain its physical and mechanical properties. To analyze the structure stability of the speed bumps some models were produced and tested in our speed bump test station. We also conduct a FEM-based computer simulation to analyze stress responses of the speed bump structures. It was found that speed bump type 1 significantly reduced the radial voltage. In addition, the speed bump is equipped with a steel casing is also suitable for use as a component component in generating electrical energy.

Trend on High-speed Power Line Communication Technology

Science.gov (United States)

Ogawa, Osamu

High-speed power line communication (PLC) is useful technology to easily build the communication networks, because construction of new infrastructure is not necessary. In Europe and America, PLC has been used for broadband networks since the beginning of 21th century. In Japan, high-speed PLC was deregulated only indoor usage in 2006. Afterward it has been widely used for home area network, LAN in hotels and school buildings and so on. And recently, PLC is greatly concerned as communication technology for smart grid network. In this paper, the author surveys the high-speed PLC technology and its current status.

Research on H2 speed governor for diesel engine of marine power station

Science.gov (United States)

Huang, Man-Lei

2007-09-01

The frequency stability of a marine power system is determined by the dynamic characteristic of the diesel engine speed regulation system in a marine power station. In order to reduce the effect of load disturbances and improve the dynamic precision of a diesel engine speed governor, a controller was designed for a diesel engine speed regulation system using H2 control theory. This transforms the specifications of the system into a standard H2 control problem. Firstly, the mathematical model of a diesel engine speed regulation system using an H2 speed governor is presented. To counter external disturbances and model uncertainty, the design of an H2 speed governor rests on the problem of mixed sensitivity. Computer simulation verified that the H2 speed governor improves the dynamic precision of a system and the ability to adapt to load disturbances, thus enhancing the frequency stability of marine power systems.

A Meteorological Information Mining-Based Wind Speed Model for Adequacy Assessment of Power Systems With Wind Power

DEFF Research Database (Denmark)

Guo, Yifei; Gao, Houlei; Wu, Qiuwei

2017-01-01

Accurate wind speed simulation is an essential prerequisite to analyze the power systems with wind power. A wind speed model considering meteorological conditions and seasonal variations is proposed in this paper. Firstly, using the path analysis method, the influence weights of meteorological...... systems with wind power. The assessment results of the modified IEEE-RTS79 and IEEE-RTS96 demonstrated the effectiveness and accuracy of the proposed model....

CMOS analog integrated circuits high-speed and power-efficient design

CERN Document Server

Ndjountche, Tertulien

2011-01-01

High-speed, power-efficient analog integrated circuits can be used as standalone devices or to interface modern digital signal processors and micro-controllers in various applications, including multimedia, communication, instrumentation, and control systems. New architectures and low device geometry of complementary metaloxidesemiconductor (CMOS) technologies have accelerated the movement toward system on a chip design, which merges analog circuits with digital, and radio-frequency components. CMOS: Analog Integrated Circuits: High-Speed and Power-Efficient Design describes the important tren

Short-Term Wind Speed Forecasting for Power System Operations

KAUST Repository

Zhu, Xinxin

2012-04-01

The emphasis on renewable energy and concerns about the environment have led to large-scale wind energy penetration worldwide. However, there are also significant challenges associated with the use of wind energy due to the intermittent and unstable nature of wind. High-quality short-term wind speed forecasting is critical to reliable and secure power system operations. This article begins with an overview of the current status of worldwide wind power developments and future trends. It then reviews some statistical short-term wind speed forecasting models, including traditional time series approaches and more advanced space-time statistical models. It also discusses the evaluation of forecast accuracy, in particular, the need for realistic loss functions. New challenges in wind speed forecasting regarding ramp events and offshore wind farms are also presented. © 2012 The Authors. International Statistical Review © 2012 International Statistical Institute.

Reactive power control methods for improved reliability of wind power inverters under wind speed variations

DEFF Research Database (Denmark)

Ma, Ke; Liserre, Marco; Blaabjerg, Frede

2012-01-01

method to relieve the thermal cycling of power switching devices under severe wind speed variations, by circulating reactive power among the parallel power converters in a WTS or among the WTS's in a wind park. The amount of reactive power is adjusted to limit the junction temperature fluctuation...

High-Performance Constant Power Generation in Grid-Connected PV Systems

DEFF Research Database (Denmark)

Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede

2016-01-01

An advanced power control strategy by limiting the maximum feed-in power of PV systems has been proposed, which can ensure a fast and smooth transition between maximum power point tracking and Constant Power Generation (CPG). Regardless of the solar irradiance levels, high-performance and stable...... operation are always achieved by the proposed control strategy. It can regulate the PV output power according to any set-point, and force the PV systems to operate at the left side of the maximum power point without stability problems. Experimental results have verified the effectiveness of the proposed CPG...

Optimal determination of the elastic constants of composite materials from ultrasonic wave-speed measurements

Science.gov (United States)

Castagnède, Bernard; Jenkins, James T.; Sachse, Wolfgang; Baste, Stéphane

1990-03-01

A method is described to optimally determine the elastic constants of anisotropic solids from wave-speeds measurements in arbitrary nonprincipal planes. For such a problem, the characteristic equation is a degree-three polynomial which generally does not factorize. By developing and rearranging this polynomial, a nonlinear system of equations is obtained. The elastic constants are then recovered by minimizing a functional derived from this overdetermined system of equations. Calculations of the functional are given for two specific cases, i.e., the orthorhombic and the hexagonal symmetries. Some numerical results showing the efficiency of the algorithm are presented. A numerical method is also described for the recovery of the orientation of the principal acoustical axes. This problem is solved through a double-iterative numerical scheme. Numerical as well as experimental results are presented for a unidirectional composite material.

Thermal loading of wind power converter considering dynamics of wind speed

DEFF Research Database (Denmark)

Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

2013-01-01

The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...... turbines. In this paper, the junction temperatures in the wind power converter are studied under not only steady state, but also turbulent wind speed conditions. The study is based on a 1.5 MW direct-driven turbine system with aerodynamic model described by Unsteady Blade Element Momentum Method (BEMM......), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low...

Distance constant of the Risø cup anemometer

DEFF Research Database (Denmark)

Kristensen, L.; Frost Hansen, O.

2002-01-01

The theory for cup-anemometer dynamics is presented in some detail and two methods of obtaining the distance constant lo are discussed. The first method is based on wind tunnel measurements: with a constant wind speed the cup anemometer is released from alocked position of the rotor...... and the increasing rotation rate recorded. It is concluded that the rapid increase in rotation rate makes the method very inaccurate. The second method consists of an analysis of turbulent, atmospheric of wind speed asmeasured by the cup anemometer and a fast-responding sonic anemometer with a spatial eddy...... resolution which is significantly better than that which can be obtained by a cup anemometer. The ratio between the measured power spectra of the horizontal windspeed by the two instruments contains the necessary information for determining the response characteristics of the cup anemometer and thereby lo...

Factors affecting speed in human-powered vehicles.

Science.gov (United States)

White, A P

1994-10-01

It is shown how to derive the appropriate cubic equation relating power and the effects of friction, gradient and wind resistance on the speed of a human-powered vehicle (HPV). The effects of gradient and wind resistance are explored for parameters representing a typical racing cyclist. The principal conclusion may be summarized as follows: for optimum performance in a time trial, there should be no wind and the course should be level. Any deviation from these conditions will produce a decrement in performance.

Critical parameters and decay constants for one-speed neutrons in slabs and spheres with anisotropic scattering

International Nuclear Information System (INIS)

Yildiz, C.

2001-01-01

Time-dependent, one-speed neutron transport equations with strong forward and backward scattering together with isotropic scattering are studied in homogeneous slabs and spheres. First, a simple formal equivalence between the transport equations for a critical and for a time-decaying system is established. Then, the transport equation is converted into a more conventional one. The F N method of solving the resulting transport equation is applied to the calculation of the critical parameters and decay constants for the fundamental mode of the flux distribution and one-speed neutrons in spheres and infinite slabs. Numerical results are given for a number of significant figures and compared with those already available in the literature. (orig.) [de

Post-error action control is neurobehaviorally modulated under conditions of constant speeded response.

Science.gov (United States)

Soshi, Takahiro; Ando, Kumiko; Noda, Takamasa; Nakazawa, Kanako; Tsumura, Hideki; Okada, Takayuki

2014-01-01

Post-error slowing (PES) is an error recovery strategy that contributes to action control, and occurs after errors in order to prevent future behavioral flaws. Error recovery often malfunctions in clinical populations, but the relationship between behavioral traits and recovery from error is unclear in healthy populations. The present study investigated the relationship between impulsivity and error recovery by simulating a speeded response situation using a Go/No-go paradigm that forced the participants to constantly make accelerated responses prior to stimuli disappearance (stimulus duration: 250 ms). Neural correlates of post-error processing were examined using event-related potentials (ERPs). Impulsivity traits were measured with self-report questionnaires (BIS-11, BIS/BAS). Behavioral results demonstrated that the commission error for No-go trials was 15%, but PES did not take place immediately. Delayed PES was negatively correlated with error rates and impulsivity traits, showing that response slowing was associated with reduced error rates and changed with impulsivity. Response-locked error ERPs were clearly observed for the error trials. Contrary to previous studies, error ERPs were not significantly related to PES. Stimulus-locked N2 was negatively correlated with PES and positively correlated with impulsivity traits at the second post-error Go trial: larger N2 activity was associated with greater PES and less impulsivity. In summary, under constant speeded conditions, error monitoring was dissociated from post-error action control, and PES did not occur quickly. Furthermore, PES and its neural correlate (N2) were modulated by impulsivity traits. These findings suggest that there may be clinical and practical efficacy of maintaining cognitive control of actions during error recovery under common daily environments that frequently evoke impulsive behaviors.

Modeling and performance improvement of the constant power regulator systems in variable displacement axial piston pump.

Science.gov (United States)

Park, Sung Hwan; Lee, Ji Min; Kim, Jong Shik

2013-01-01

An irregular performance of a mechanical-type constant power regulator is considered. In order to find the cause of an irregular discharge flow at the cut-off pressure area, modeling and numerical simulations are performed to observe dynamic behavior of internal parts of the constant power regulator system for a swashplate-type axial piston pump. The commercial numerical simulation software AMESim is applied to model the mechanical-type regulator with hydraulic pump and simulate the performance of it. The validity of the simulation model of the constant power regulator system is verified by comparing simulation results with experiments. In order to find the cause of the irregular performance of the mechanical-type constant power regulator system, the behavior of main components such as the spool, sleeve, and counterbalance piston is investigated using computer simulation. The shape modification of the counterbalance piston is proposed to improve the undesirable performance of the mechanical-type constant power regulator. The performance improvement is verified by computer simulation using AMESim software.

The economics of a variable speed wind-diesel

International Nuclear Information System (INIS)

Moll, W.

1992-01-01

A remote community power supply system generating over 1,000 kWH/d will have at least one diesel generator running all the time. If one or more wind turbine generators are added to such a system, the diesel generator will produce less power when wind speeds are adequate, but its fuel efficiency will gradually decrease as load decreases. In the variable speed wind/diesel concept, the diesel rpm is reduced with decreasing load and a high fuel efficiency is maintained over virtually the full power range. The outputs of the diesel and wind turbine generators are fed into an inverter which synthesizes a desired voltage wave-shape with controlled magnitude and frequency. The variable speed wind/diesel concept may make vertical axis wind turbines suitable for remote community power supply because the inverter effectively isolates the power ripple of the wind turbine. A possible wind/diesel system configuration using the variable speed concept is illustrated. The economics of a 50-kW variable speed diesel and a 80-kW variable speed wind turbine generator was analyzed. Going from a constant speed diesel generator to a variable speed generator operating at 55% capacity factor, a 6% fuel saving was achieved. Adding one 80-kW wind turbine increased fuel savings to 32% at 5 m/s wind speed, but the unit energy cost rose 8.5%. At 7 m/s wind speed, fuel savings were 59% and energy savings were 7.8%. Economics are better for a peaking variable speed 50-kW wind/diesel system added to an existing diesel system to extend the installed capacity. At 7 m/s wind speed the fuel savings translate into ca $40,000 over 10 y and purchase of a $150,000 diesel generator is postponed. 7 figs., 1 tab

Topography of Slow Sigma Power during Sleep is Associated with Processing Speed in Preschool Children.

Science.gov (United States)

Doucette, Margaret R; Kurth, Salome; Chevalier, Nicolas; Munakata, Yuko; LeBourgeois, Monique K

2015-11-04

Cognitive development is influenced by maturational changes in processing speed, a construct reflecting the rapidity of executing cognitive operations. Although cognitive ability and processing speed are linked to spindles and sigma power in the sleep electroencephalogram (EEG), little is known about such associations in early childhood, a time of major neuronal refinement. We calculated EEG power for slow (10-13 Hz) and fast (13.25-17 Hz) sigma power from all-night high-density electroencephalography (EEG) in a cross-sectional sample of healthy preschool children (n = 10, 4.3 ± 1.0 years). Processing speed was assessed as simple reaction time. On average, reaction time was 1409 ± 251 ms; slow sigma power was 4.0 ± 1.5 μV²; and fast sigma power was 0.9 ± 0.2 μV². Both slow and fast sigma power predominated over central areas. Only slow sigma power was correlated with processing speed in a large parietal electrode cluster (p power predicted faster reaction time. Our findings indicate regional correlates between sigma power and processing speed that are specific to early childhood and provide novel insights into the neurobiological features of the EEG that may underlie developing cognitive abilities.

Modeling the Power Variability of Core Speed Scaling on Homogeneous Multicore Systems

Directory of Open Access Journals (Sweden)

Zhihui Du

2017-01-01

Full Text Available We describe a family of power models that can capture the nonuniform power effects of speed scaling among homogeneous cores on multicore processors. These models depart from traditional ones, which assume that individual cores contribute to power consumption as independent entities. In our approach, we remove this independence assumption and employ statistical variables of core speed (average speed and the dispersion of the core speeds to capture the comprehensive heterogeneous impact of subtle interactions among the underlying hardware. We systematically explore the model family, deriving basic and refined models that give progressively better fits, and analyze them in detail. The proposed methodology provides an easy way to build power models to reflect the realistic workings of current multicore processors more accurately. Moreover, unlike the existing lower-level power models that require knowledge of microarchitectural details of the CPU cores and the last level cache to capture core interdependency, ours are easier to use and scalable to emerging and future multicore architectures with more cores. These attributes make the models particularly useful to system users or algorithm designers who need a quick way to estimate power consumption. We evaluate the family of models on contemporary x86 multicore processors using the SPEC2006 benchmarks. Our best model yields an average predicted error as low as 5%.

Speed of sound in biodiesel produced by low power ultrasound

Science.gov (United States)

Oliveira, P. A.; Silva, R. M. B.; Morais, G. C.; Alvarenga, A. V.; Costa-Felix, R. P. B.

2018-03-01

The quality control of the biodiesel produced is an important issue to be addressed for every manufacturer or retailer. The speed of sound is a property that has an influence on the quality of the produced fuel. This work presents the evaluation about the speed of sound in biodiesel produced with the aid of low power ultrasound in the frequencies of 1 MHz and 3 MHz. The speed of sound was measured by pulse-echo technique. The ultrasonic frequency used during reaction affects the speed of sound in biodiesel. The larger expanded uncertainty for adjusted curve was 4.9 m.s-1.

Evaluation of the power consumption of a high-speed parallel robot

Science.gov (United States)

Han, Gang; Xie, Fugui; Liu, Xin-Jun

2018-06-01

An inverse dynamic model of a high-speed parallel robot is established based on the virtual work principle. With this dynamic model, a new evaluation method is proposed to measure the power consumption of the robot during pick-and-place tasks. The power vector is extended in this method and used to represent the collinear velocity and acceleration of the moving platform. Afterward, several dynamic performance indices, which are homogenous and possess obvious physical meanings, are proposed. These indices can evaluate the power input and output transmissibility of the robot in a workspace. The distributions of the power input and output transmissibility of the high-speed parallel robot are derived with these indices and clearly illustrated in atlases. Furtherly, a low-power-consumption workspace is selected for the robot.

Modeling and Performance Improvement of the Constant Power Regulator Systems in Variable Displacement Axial Piston Pump

Science.gov (United States)

Park, Sung Hwan; Lee, Ji Min; Kim, Jong Shik

2013-01-01

An irregular performance of a mechanical-type constant power regulator is considered. In order to find the cause of an irregular discharge flow at the cut-off pressure area, modeling and numerical simulations are performed to observe dynamic behavior of internal parts of the constant power regulator system for a swashplate-type axial piston pump. The commercial numerical simulation software AMESim is applied to model the mechanical-type regulator with hydraulic pump and simulate the performance of it. The validity of the simulation model of the constant power regulator system is verified by comparing simulation results with experiments. In order to find the cause of the irregular performance of the mechanical-type constant power regulator system, the behavior of main components such as the spool, sleeve, and counterbalance piston is investigated using computer simulation. The shape modification of the counterbalance piston is proposed to improve the undesirable performance of the mechanical-type constant power regulator. The performance improvement is verified by computer simulation using AMESim software. PMID:24282389

Modeling and Performance Improvement of the Constant Power Regulator Systems in Variable Displacement Axial Piston Pump

Directory of Open Access Journals (Sweden)

Sung Hwan Park

2013-01-01

Full Text Available An irregular performance of a mechanical-type constant power regulator is considered. In order to find the cause of an irregular discharge flow at the cut-off pressure area, modeling and numerical simulations are performed to observe dynamic behavior of internal parts of the constant power regulator system for a swashplate-type axial piston pump. The commercial numerical simulation software AMESim is applied to model the mechanical-type regulator with hydraulic pump and simulate the performance of it. The validity of the simulation model of the constant power regulator system is verified by comparing simulation results with experiments. In order to find the cause of the irregular performance of the mechanical-type constant power regulator system, the behavior of main components such as the spool, sleeve, and counterbalance piston is investigated using computer simulation. The shape modification of the counterbalance piston is proposed to improve the undesirable performance of the mechanical-type constant power regulator. The performance improvement is verified by computer simulation using AMESim software.

Post-error action control is neurobehaviorally modulated under conditions of constant speeded response

Directory of Open Access Journals (Sweden)

Takahiro eSoshi

2015-01-01

Full Text Available Post-error slowing is an error recovery strategy that contributes to action control, and occurs after errors in order to prevent future behavioral flaws. Error recovery often malfunctions in clinical populations, but the relationship between behavioral traits and recovery from error is unclear in healthy populations. The present study investigated the relationship between impulsivity and error recovery by simulating a speeded response situation using a Go/No-go paradigm that forced the participants to constantly make accelerated responses prior to stimuli disappearance (stimulus duration: 250 ms. Neural correlates of post-error processing were examined using event-related potentials (ERPs. Impulsivity traits were measured with self-report questionnaires (BIS-11, BIS/BAS. Behavioral results demonstrated that the commission error for No-go trials was 15%, but post-error slowing did not take place immediately. Delayed post-error slowing was negatively correlated with error rates and impulsivity traits, showing that response slowing was associated with reduced error rates and changed with impulsivity. Response-locked error ERPs were clearly observed for the error trials. Contrary to previous studies, error ERPs were not significantly related to post-error slowing. Stimulus-locked N2 was negatively correlated with post-error slowing and positively correlated with impulsivity traits at the second post-error Go trial: larger N2 activity was associated with greater post-error slowing and less impulsivity. In summary, under constant speeded conditions, error monitoring was dissociated from post-error action control, and post-error slowing did not occur quickly. Furthermore, post-error slowing and its neural correlate (N2 were modulated by impulsivity traits. These findings suggest that there may be clinical and practical efficacy of maintaining cognitive control of actions during error recovery under common daily environments that frequently evoke

Constant versus variable response signal delays in speed--accuracy trade-offs: effects of advance preparation for processing time.

Science.gov (United States)

Miller, Jeff; Sproesser, Gudrun; Ulrich, Rolf

2008-07-01

In two experiments, we used response signals (RSs) to control processing time and trace out speed--accuracy trade-off(SAT) functions in a difficult perceptual discrimination task. Each experiment compared performance in blocks of trials with constant and, hence, temporally predictable RS lags against performance in blocks with variable, unpredictable RS lags. In both experiments, essentially equivalent SAT functions were observed with constant and variable RS lags. We conclude that there is little effect of advance preparation for a given processing time, suggesting that the discrimination mechanisms underlying SAT functions are driven solely by bottom-up information processing in perceptual discrimination tasks.

Dynamic Modeling of Adjustable-Speed Pumped Storage Hydropower Plant: Preprint

Energy Technology Data Exchange (ETDEWEB)

Muljadi, E.; Singh, M.; Gevorgian, V.; Mohanpurkar, M.; Havsapian, R.; Koritarov, V.

2015-04-06

Hydropower is the largest producer of renewable energy in the U.S. More than 60% of the total renewable generation comes from hydropower. There is also approximately 22 GW of pumped storage hydropower (PSH). Conventional PSH uses a synchronous generator, and thus the rotational speed is constant at synchronous speed. This work details a hydrodynamic model and generator/power converter dynamic model. The optimization of the hydrodynamic model is executed by the hydro-turbine controller, and the electrical output real/reactive power is controlled by the power converter. All essential controllers to perform grid-interface functions and provide ancillary services are included in the model.

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Science.gov (United States)

2010-07-01

... cylinders having an internal diameter of 13.0 cm and a 15.5 cm stroke length, the rounded displacement would... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Maximum engine power, displacement... Maximum engine power, displacement, power density, and maximum in-use engine speed. This section describes...

Modeling of the dynamics of wind to power conversion including high wind speed behavior

DEFF Research Database (Denmark)

Litong-Palima, Marisciel; Bjerge, Martin Huus; Cutululis, Nicolaos Antonio

2016-01-01

This paper proposes and validates an efficient, generic and computationally simple dynamic model for the conversion of the wind speed at hub height into the electrical power by a wind turbine. This proposed wind turbine model was developed as a first step to simulate wind power time series...... for power system studies. This paper focuses on describing and validating the single wind turbine model, and is therefore neither describing wind speed modeling nor aggregation of contributions from a whole wind farm or a power system area. The state-of-the-art is to use static power curves for the purpose...... of power system studies, but the idea of the proposed wind turbine model is to include the main dynamic effects in order to have a better representation of the fluctuations in the output power and of the fast power ramping especially because of high wind speed shutdowns of the wind turbine. The high wind...

Topography of Slow Sigma Power during Sleep is Associated with Processing Speed in Preschool Children

Directory of Open Access Journals (Sweden)

Margaret R. Doucette

2015-11-01

Full Text Available Cognitive development is influenced by maturational changes in processing speed, a construct reflecting the rapidity of executing cognitive operations. Although cognitive ability and processing speed are linked to spindles and sigma power in the sleep electroencephalogram (EEG, little is known about such associations in early childhood, a time of major neuronal refinement. We calculated EEG power for slow (10–13 Hz and fast (13.25–17 Hz sigma power from all-night high-density electroencephalography (EEG in a cross-sectional sample of healthy preschool children (n = 10, 4.3 ± 1.0 years. Processing speed was assessed as simple reaction time. On average, reaction time was 1409 ± 251 ms; slow sigma power was 4.0 ± 1.5 μV2; and fast sigma power was 0.9 ± 0.2 μV2. Both slow and fast sigma power predominated over central areas. Only slow sigma power was correlated with processing speed in a large parietal electrode cluster (p < 0.05, r ranging from −0.6 to −0.8, such that greater power predicted faster reaction time. Our findings indicate regional correlates between sigma power and processing speed that are specific to early childhood and provide novel insights into the neurobiological features of the EEG that may underlie developing cognitive abilities.

In-process tool rotational speed variation with constant heat input in friction stir welding of AZ31 sheets with variable thickness

Science.gov (United States)

Buffa, Gianluca; Campanella, Davide; Forcellese, Archimede; Fratini, Livan; Simoncini, Michela

2017-10-01

In the present work, friction stir welding experiments on AZ31 magnesium alloy sheets, characterized by a variable thickness along the welding line, were carried out. The approach adapted during welding consisted in maintaining constant the heat input to the joint. To this purpose, the rotational speed of the pin tool was increased with decreasing thickness and decreased with increasing thickness in order to obtain the same temperatures during welding. The amount by which the rotational speed was changed as a function of the sheet thickness was defined on the basis of the results given by FEM simulations of the FSW process. Finally, the effect of the in-process variation of the tool rotational speed on the mechanical and microstructural properties of FSWed joints was analysed by comparing both the nominal stress vs. nominal strain curves and microstructure of FSWed joints obtained in different process conditions. It was observed that FSW performed by keeping constant the heat input to the joint leads to almost coincident results both in terms of the curve shape, ultimate tensile strength and ultimate elongation values, and microstructure.

Gender-specific influences of balance, speed, and power on agility performance.

Science.gov (United States)

Sekulic, Damir; Spasic, Miodrag; Mirkov, Dragan; Cavar, Mile; Sattler, Tine

2013-03-01

The quick change of direction (i.e., agility) is an important athletic ability in numerous sports. Because of the diverse and therefore hardly predictable manifestations of agility in sports, studies noted that the improvement in speed, power, and balance should result in an improvement of agility. However, there is evident lack of data regarding the influence of potential predictors on different agility manifestations. The aim of this study was to determine the gender-specific influence of speed, power, and balance on different agility tests. A total of 32 college-aged male athletes and 31 college-aged female athletes (age 20.02 ± 1.89 years) participated in this study. The subjects were mostly involved in team sports (soccer, team handball, basketball, and volleyball; 80% of men, and 75% of women), martial arts, gymnastics, and dance. Anthropometric variables consisted of body height, body weight, and the body mass index. Five agility tests were used: a t-test (T-TEST), zig-zag test, 20-yard shuttle test, agility test with a 180-degree turn, and forward-backward running agility test (FWDBWD). Other tests included 1 jumping ability power test (squat jump, SQJ), 2 balance tests to determine the overall stability index and an overall limit of stability score (both measured by Biodex Balance System), and 2 running speed tests using a straight sprint for 10 and 20 m (S10 and S20, respectively). A reliability analysis showed that all the agility tests were reliable. Multiple regression and correlation analysis found speed and power (among women), and balance (among men), as most significant predictors of agility. The highest Pearson's correlation in both genders is found between the results of the FWDBWD and S10M tests (0.77 and 0.81 for men and women, respectively; p Power, measured using the SQJ, is significantly (p balance measures were significantly related to the agility performance for men but not for women. In addition to demonstrating a known relationship

Adjustable Speed Drives and Power Quality

DEFF Research Database (Denmark)

Davari, Pooya; Yang, Yongheng; Zare, Firuz

2016-01-01

This paper provides an overview and proposes cost-effective and efficient opportunities in improving power quality in Adjustable Speed Drive (ASD) systems. In particular, an Electronic Inductor (EI) technique has been used in single drives to overcome the existing challenges in conventional...... frontend rectifiers even at partial loading conditions. Moreover, the effectiveness of the EI technique along with a phase-shifted current control in terms of improved grid current quality in multi-drive configurations is addressed. Furthermore, a novel DC-link current modulation scheme for multi...

Speed-dependent emission of air pollutants from gasoline-powered passenger cars.

Science.gov (United States)

Jung, Sungwoon; Lee, Meehye; Kim, Jongchoon; Lyu, Youngsook; Park, Junhong

2011-01-01

In Korea emissions from motor vehicles are a major source of air pollution in metropolitan cities, and in Seoul a large proportion of the vehicle fleet is made up of gasoline-powered passenger cars. The carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and carbon dioxide (CO2) contained in the exhaust emissions from 76 gasoline-powered passenger cars equipped with three-way catalysts has been assessed by vehicle speed, vehicle mileage and model year. The results show that CO, HC, NOx and CO2 emissions remained almost unchanged at higher speeds but decreased rapidly at lower speeds. While a reduction in CO, HC and NOx emissions was noticeable in vehicles of recent manufacture and lower mileage, CO2 emissions were found to be insensitive to vehicle mileage, but strongly dependent on gross vehicle weight. Lower emissions from more recent gasoline-powered vehicles arose mainly from improvements in three-way catalytic converter technology following strengthened emission regulations. The correlation between CO2 emission and fuel consumption has been investigated with a view to establishing national CO2 emission standards for Korea.

Power system integration and control of variable speed wind turbines

Energy Technology Data Exchange (ETDEWEB)

Eek, Jarle

2009-12-15

A wind power plant is a highly dynamic system that dependent on the type of technology requires a number of automatic control loops. This research deals with modelling, control and analysis related to power system integration of variable speed, pitch controlled wind turbines. All turbine components have been modelled and implemented in the power system simulation program SIMPOW, and a description of the modelling approach for each component is given. The level of model detail relates to the classical modelling of power system components for power system stability studies, where low frequency oscillations are of special importance. The wind turbine model includes a simplified representation of the developed rotor torque and the thrust force based on C{sub p-} and C{sub t} characteristic curves. The mechanical system model represents the fundamental torsional mode and the first mode of blades and tower movements. Two generator technologies have been investigated. The doubly fed induction generator (DFIG) and the stator converter interfaced permanent magnet synchronous generator (PMSG). A simplified model of a 2 level voltage source converter is used for both machine types. The generator converter controllers have been given special attention. All model components are linearized for the purpose of control system design and power system interaction related to small signal stability analysis. Different control strategies discussed in the literature have been investigated with regard to power system interaction aspects. All control parameters are identified using the internal model control approach. The analysis is focused on three main areas: 1. Identification of low damped oscillatory modes. This is carried out by the establishment and discussion of wind turbine modelling. 2. Interaction between control loops. A systematic approach is presented in order to analyse the influence of control loops used in variable speed wind turbines. 3.Impact on power system performance

Solid-state fast voltage compensator for pulsed power applications requiring constant AC power consumption

CERN Document Server

Magallanes, Francisco Cabaleiro; Viarouge, Philippe; Cros, Jérôme

2015-01-01

This paper proposes a novel topological solution for pulsed power converters based on capacitor-discharge topologies, integrating a Fast Voltage Compensator which allows an operation at constant power consumption from the utility grid. This solution has been retained as a possible candidate for the CLIC project under study at CERN, which requires more than a thousand synchronously-operated klystron modulators producing a total pulsed power of almost 40 GW. The proposed Fast Voltage Compensator is integrated in the modulator such that it only has to treat the capacitor charger current and a fraction of the charging voltage, meaning that its dimensioning power and cost are minimized. This topology can be used to improve the AC power quality of any pulsed converters based on capacitor-discharge concept. A prototype has been built and exploited to validate the operating principle and demonstrate the benefits of the proposed solution.

Prompt neutron decay constant estimation of RSG-GAS at high power noise experiment

International Nuclear Information System (INIS)

Jujuratisbela, U.; Kristedjo; Tukiran; Pinem, S.; Iman, J.; Puryono; Sanjaya, A.; Suwarno

1998-01-01

The determination of prompt neutron decay constant (α) of RGS-GAS by using low power noise experiment method at the equilibrium core indicated that the result is not good. The bad result was due to the small ratio of the noise signal to background which was caused by low detector efficiency or contaminated core after long time operation. To solve the problem is tried by using noise experiment technique at high power. The voltage output of neutron detectors at power of 5, 12, and 23 MW were connected to preamplifier and filter then to the Dynamic Signal Analyzer Version-2 and then the power spectral density of each channel of JKT04 and JKT03, the cut off frequency of each channel can be determined by using linear regression technique such that the prompt neutron decay constant can be estimated

Experimental research of variable rotation speed ICE-based electric power station

Directory of Open Access Journals (Sweden)

Dar’enkov Andrey

2017-01-01

Full Text Available Developing variable rotation speed ICE-based stand-alone electric power stations which can supply distant regions and autonomous objects with electricity are of scientific interest due to the insufficient study. The relevance of developing such electric power stations is determined by their usage is to provide a significant fuel saving as well as increase ICE motor service life. The article describes the electric station of autonomous objects with improved fuel economy. The article describes multivariate characteristic. Multivariate characteristic shows the optimal frequency of rotation of the internal combustion engine. At this rotational speed there is the greatest fuel economy.

Speed controller for an alternating - current motor

International Nuclear Information System (INIS)

Bolie, V.W.

1984-01-01

A controller for a multi-phase ac motor that is subject to a large inertial load, e.g. an induction motor driving a heavy spinning rotor of a neutron chopper that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal Esub(L) having a meandering line frequency, includes a sensor which provides a feedback pulse train representative of the actual speed of the motor which is compared (by counting clock pulses between feedback pulses) with a reference clock signal in a computing unit to provide a motor control signal Esub(c). The motor control signal is a weighted linear sum of a speed error signal, a phase error signal, and a drift error signal, the magnitudes of which are recalculated and updated with each revolution of the motor shaft. The speed error signal is constant for large speed errors but highly sensitive to small speed errors. The stator windings of the motor are driven by variable-frequency power amplifiers which are controlled by the motor control signal Esub(c) via PROMs which store digital representations of sine and cosine waveforms in quadrature. (author)

Control design for a pitch-regulated, variable speed wind turbine

Energy Technology Data Exchange (ETDEWEB)

Hansen, M.H.; Hansen, A.; Larsen, T.J.; Oeye, S.; Soerensen, P.; Fuglsang, P.

2005-01-01

The three different controller designs presented herein are similar and all based on PI-regulation of rotor speed and power through the collective blade pitch angle and generator moment. The aeroelastic and electrical modelling used for the time-domain analysis of these controllers are however different, which makes a directly quantitative comparison difficult. But there are some observations of similar behaviours should be mentioned: 1) Very similar step responses in rotor speed, pitch angle, and power are seen for simulations with steps in wind speed. 2) All controllers show a peak in power for wind speed step-up over rated wind speed, which can be almost removed by changing the parameters of the frequency converter. 3) Responses of rotor speed, pitch angle, and power for different simulations with turbulent inflow are similar for all three controllers. Again, there seems to be an advantage of tuning the parameters of the frequency converter to obtain a more constant power output. The dynamic modelling of the power controller is an important result for the inclusion of generator dynamics in the aeroelastic modelling of wind turbines. A reduced dynamic model of the relation between generator torque and generator speed variations is presented; where the integral term of the inner PI-regulator of rotor current is removed be-cause the time constant is very small compared to the important aeroelastic frequencies. It is shown how the parameters of the transfer function for the remaining control system with the outer PI-regulator of power can be derived from the generator data sheet. The main results of the numerical optimisation of the control parameters in the pitch PI-regulator performed in Chapter 6 are the following: 1) Numerical optimization can be used to tune controller parameters, especially when the optimization is used as refinement of a qualified initial guess. 2) The design model used to calculate the initial value parameters, as described in Chapter 3

Mathematically modelling the power requirement for a vertical shaft mowing machine

Directory of Open Access Journals (Sweden)

Jorge Simón Pérez de Corcho Fuentes

2008-09-01

Full Text Available This work describes a mathematical model for determining the power demand for a vertical shaft mowing machine, particularly taking into account the influence of speed on cutting power, which is different from that of other models of mowers. The influence of the apparatus’ rotation and translation speeds was simulated in determining power demand. The results showed that no chan-ges in cutting power were produced by varying the knives’ angular speed (if translation speed was constant, while cutting power became increased if translation speed was increased. Variations in angular speed, however, influenced other parameters deter-mining total power demand. Determining this vertical shaft mower’s cutting pattern led to obtaining good crop stubble quality at the mower’s lower rotation speed, hence reducing total energy requirements.

Path integration of head direction: updating a packet of neural activity at the correct speed using neuronal time constants.

Science.gov (United States)

Walters, D M; Stringer, S M

2010-07-01

A key question in understanding the neural basis of path integration is how individual, spatially responsive, neurons may self-organize into networks that can, through learning, integrate velocity signals to update a continuous representation of location within an environment. It is of vital importance that this internal representation of position is updated at the correct speed, and in real time, to accurately reflect the motion of the animal. In this article, we present a biologically plausible model of velocity path integration of head direction that can solve this problem using neuronal time constants to effect natural time delays, over which associations can be learned through associative Hebbian learning rules. The model comprises a linked continuous attractor network and competitive network. In simulation, we show that the same model is able to learn two different speeds of rotation when implemented with two different values for the time constant, and without the need to alter any other model parameters. The proposed model could be extended to path integration of place in the environment, and path integration of spatial view.

Power Maximization Control of Variable Speed Wind Generation System Using Permanent Magnet Synchronous Generator

Science.gov (United States)

Morimoto, Shigeo; Nakamura, Tomohiko; Takeda, Yoji

This paper proposes the sensorless output power maximization control of the wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information of wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as a wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method.

Variable-Speed Power-Turbine Research at Glenn Research Center

Science.gov (United States)

Welch, Gerard E.; McVetta, Ashlie B.; Stevens, Mark A.; Howard, Samuel A.; Giel, Paul W.; Ameri, Ali, A.; To, Waiming; Skoch, Gary J.; Thurman, Douglas R.

2012-01-01

The main rotors of the NASA Large Civil Tilt-Rotor (LCTR) notional vehicle operate over a wide speed-range, from 100 percent at takeoff to 54 percent at cruise. The variable-speed power turbine (VSPT) offers one approach by which to effect this speed variation. VSPT aerodynamics challenges include high work factors at cruise, wide (40 to 60 ) incidence-angle variations in blade and vane rows over the speed range, and operation at low Reynolds numbers. Rotordynamics challenges include potential responsiveness to shaft modes within the 50 percent VSPT speed-range. A research effort underway at NASA Glenn Research Center, intended to address these key aerodynamic and rotordynamic challenges, is described. Conceptual design and 3-D multistage RANS and URANS analyses, conducted internally and under contract, provide expected VSPT sizing, stage-count, performance and operability information, and maps for system studies. Initial steps toward experimental testing of incidence-tolerant blading in a transonic linear cascade are described, and progress toward development/improvement of a simulation capability for multistage turbines with low Reynolds number transitional flow is summarized. Preliminary rotordynamics analyses indicate that viable concept engines with 50 percent VSPT shaft-speed range. Assessments of potential paths toward VSPT component-level testing are summarized.

Empirical investigation on using wind speed volatility to estimate the operation probability and power output of wind turbines

International Nuclear Information System (INIS)

Liu, Heping; Shi, Jing; Qu, Xiuli

2013-01-01

Highlights: ► Ten-minute wind speed and power generation data of an offshore wind turbine are used. ► An ARMA–GARCH-M model is built to simultaneously forecast wind speed mean and volatility. ► The operation probability and expected power output of the wind turbine are predicted. ► The integrated approach produces more accurate wind power forecasting than other conventional methods. - Abstract: In this paper, we introduce a quantitative methodology that performs the interval estimation of wind speed, calculates the operation probability of wind turbine, and forecasts the wind power output. The technological advantage of this methodology stems from the empowered capability of mean and volatility forecasting of wind speed. Based on the real wind speed and corresponding wind power output data from an offshore wind turbine, this methodology is applied to build an ARMA–GARCH-M model for wind speed forecasting, and then to compute the operation probability and the expected power output of the wind turbine. The results show that the developed methodology is effective, the obtained interval estimation of wind speed is reliable, and the forecasted operation probability and expected wind power output of the wind turbine are accurate

Variable Ratio Hydrostatic Transmission Simulator for Optimal Wind Power Drivetrains

Directory of Open Access Journals (Sweden)

Jose M. Garcia-Bravo

2017-01-01

Full Text Available This work presents a hydromechanical transmission coupled to an electric AC motor and DC generator to simulate a wind power turbine drive train. The goal of this project was to demonstrate and simulate the ability of a hydrostatic variable ratio system to produce constant electric power at varying wind speeds. The experimental results show that the system can maintain a constant voltage when a 40% variation in input speed is produced. An accompanying computer simulation of the system was built and experimentally validated showing a discrete error no larger than 12%. Both the simulation and the experimental results show that the electrical power output can be regulated further if an energy storage device is used to absorb voltage spikes produced by abrupt changes in wind speed or wind direction.

Perfection of badminton players’ speed-power fitness with the help of training means’ variable modules

Directory of Open Access Journals (Sweden)

I.V. Karatnyk

2016-06-01

Full Text Available Purpose: to determine effectiveness of badminton players’ speed power fitness program’s perfection at stage of specialized basic training with different variants of training means modules’ combination. Material: in experiment badminton players of 15-17 years’ age (from 1st sports grade to master of sports participated. The sportsmen were divided into three experimental groups (10 persons in each. The trainings were being conducted during 24 weeks by different variants of program. Results: we created different complexes of exercises, combined in three modules (every of each lasted eight week micro-cycles. Every module has more expressed meaningful parts (1 – speed, 2 – power, 3 – jumping. All modules were combined in program of badminton players’ speed power fitness perfection. For every experimental group we worked out distinguishing variant of modules’ combination in program (first variant – 1-2-3 modules; second – 2-3-1; third – 3-1-2. General duration of program was 24 week micro-cycles. Conclusions: we recommended some variants of variable modules’ combination for badminton players’ speed-power fitness perfection. With it, we can regard total influence on the following: speed-power endurance, work with support on own body, quick movements of different body links.

Deepening structural reform, and speeding up self-reliant nuclear power development

International Nuclear Information System (INIS)

Wang Binghua

2010-01-01

Combining the implementation practices of the strategy on self-reliant development of the third generation nuclear power plant, the paper set forth that speeding up self-reliant nuclear power development has strategic significance to the national economy and the people's livelihood, which need further deepening structural reform and nuclear power structural reform with an aim to enhance the international competitiveness of China's nuclear industry. (author)

Influence of wind speed on free space optical communication performance for Gaussian beam propagation through non Kolmogorov strong turbulence

International Nuclear Information System (INIS)

Deng Peng; Yuan Xiuhua; Zeng Yanan; Zhao Ming; Luo Hanjun

2011-01-01

In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received signal, affecting link performance. Most theoretical treatments have been described by Kolmogorov's power spectral density model through weak turbulence with constant wind speed. However, several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly, especially through the strong turbulence with variable wind speed, which is known to contribute significantly to the turbulence in the atmosphere. We present an optical turbulence model that incorporates into variable wind speed instead of constant value, a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized amplitude factor instead of constant value 0.033. The free space optical communication performance for a Gaussian beam wave of scintillation index, mean signal-to-noise ratio , and mean bit error rate , have been derived by extended Rytov theory in non-Kolmogorov strong turbulence. And then the influence of wind speed variations on free space optical communication performance has been analyzed under different atmospheric turbulence intensities. The results suggest that the effects of wind speed variation through non-Kolmogorov turbulence on communication performance are more severe in many situations and need to be taken into account in free space optical communication. It is anticipated that this work is helpful to the investigations of free space optical communication performance considering wind speed under severe weather condition in the strong atmospheric turbulence.

Arrangement for adapting a wind wheel to an electric power generator

Energy Technology Data Exchange (ETDEWEB)

Beusse, H

1977-08-11

The invention is concerned with a device for adapting a wind wheel to an electric power generator in such a way that the wind wheel will always be operated with a maximum performance coefficient, that another source of energy, e.g. a prime mover, can supply the power deficit if the wind power is not sufficient, and that the generator at the output of the facility is kept mains-synchronous of constant speed and constant voltage. According to the invention, the shaft power of the wind power engine is transmitted to a first generator driving an electromotor. The motor is coupled to a second generator feeding into a consumer grid. By means of an anemometer the excitation output of the motor is controled in such manner that the speed of the generator is practically constant-provided a sufficient supply of wind is available. On the shaft of the output generator a prinse mover, e.g. a Diesel engine, is mounted being controllable for contant speed by means of a controll device in such a way that the prime mover takes over the missing amount of power if the wind supply falls short of the power taken off at the generator output.

Understanding mismatches in body size, speed and power among adolescent rugby union players.

Science.gov (United States)

Krause, Lyndon M; Naughton, Geraldine A; Denny, Greg; Patton, Declan; Hartwig, Tim; Gabbett, Tim J

2015-05-01

With adolescent sport increasingly challenged by mismatches in size, new strategies are important to maximize participation. The objectives were to (1) improve the understanding of mismatches in physical size, speed and power in adolescent rugby union players, (2) explore associations between size and performance with demographic, playing-history, and injury profiles, and (3) explore the applicability of existing criteria for age/body mass-based dispensation (playing-down) strategies. Cross-sectional study. Four hundred and eighty-five male community rugby union players were recruited from three Australian states selected to represent community-based U12, U13, U14 and U15 players. Body mass, stature, speed (10, 30, and 40 m sprints) and lower-leg power (relative peak power and relative peak force) were measured. Independent student t-tests, linear regressions and Chi square analyses were undertaken. Mean values in age groups for size, speed and power masked considerable overlap in the ranges within specific age groups of adolescent rugby players. Only a small proportion of players (approximately 5%) shared the highest and lowest tertiles for speed, relative peak power and body mass. Physical size was not related to injury. The mean body mass of current community rugby union players was above the 75th percentile on normative growth-charts. The notion that bigger, faster, and more powerful characteristics occur simultaneously in adolescent rugby players was not supported in the present study. Current practices in body mass-based criteria for playing down an age group lack a sufficient evidence for decision-making. Dispensation solely based on body mass may not address mismatch in junior rugby union. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Space-time wind speed forecasting for improved power system dispatch

KAUST Repository

Zhu, Xinxin

2014-02-27

To support large-scale integration of wind power into electric energy systems, state-of-the-art wind speed forecasting methods should be able to provide accurate and adequate information to enable efficient, reliable, and cost-effective scheduling of wind power. Here, we incorporate space-time wind forecasts into electric power system scheduling. First, we propose a modified regime-switching, space-time wind speed forecasting model that allows the forecast regimes to vary with the dominant wind direction and with the seasons, hence avoiding a subjective choice of regimes. Then, results from the wind forecasts are incorporated into a power system economic dispatch model, the cost of which is used as a loss measure of the quality of the forecast models. This, in turn, leads to cost-effective scheduling of system-wide wind generation. Potential economic benefits arise from the system-wide generation of cost savings and from the ancillary service cost savings. We illustrate the economic benefits using a test system in the northwest region of the United States. Compared with persistence and autoregressive models, our model suggests that cost savings from integration of wind power could be on the scale of tens of millions of dollars annually in regions with high wind penetration, such as Texas and the Pacific northwest. © 2014 Sociedad de Estadística e Investigación Operativa.

An Adaptive Frequency Strategy for Variable Speed Wind Turbines: Application to High Wind Integration Into Power Systems

Directory of Open Access Journals (Sweden)

Ana Fernández-Guillamón

2018-06-01

Full Text Available This paper presents a new frequency controller for variable speed wind turbines connected to the grid under power imbalance conditions. It is based on the fast power reserve emulation technique, having two different operation modes: overproduction and recovery mode. In the first mode, the active power provided by wind turbines is set over the mechanical power, reducing their rotational speed. This overproduction power is estimated according to the frequency excursion. In the second mode, the active power is established under the mechanical power to recover the initial rotational speed through a smooth trajectory. The power system considered for simulation purposes includes thermal, hydro-power and wind-power plants. The controller proposed has been evaluated under different mix-generation scenarios implemented in Matlab/Simulink. Extensive results and comparison to previous proposals are also included in the paper.

Speed adaptation in a powered transtibial prosthesis controlled with a neuromuscular model.

Science.gov (United States)

Markowitz, Jared; Krishnaswamy, Pavitra; Eilenberg, Michael F; Endo, Ken; Barnhart, Chris; Herr, Hugh

2011-05-27

Control schemes for powered ankle-foot prostheses would benefit greatly from a means to make them inherently adaptive to different walking speeds. Towards this goal, one may attempt to emulate the intact human ankle, as it is capable of seamless adaptation. Human locomotion is governed by the interplay among legged dynamics, morphology and neural control including spinal reflexes. It has been suggested that reflexes contribute to the changes in ankle joint dynamics that correspond to walking at different speeds. Here, we use a data-driven muscle-tendon model that produces estimates of the activation, force, length and velocity of the major muscles spanning the ankle to derive local feedback loops that may be critical in the control of those muscles during walking. This purely reflexive approach ignores sources of non-reflexive neural drive and does not necessarily reflect the biological control scheme, yet can still closely reproduce the muscle dynamics estimated from biological data. The resulting neuromuscular model was applied to control a powered ankle-foot prosthesis and tested by an amputee walking at three speeds. The controller produced speed-adaptive behaviour; net ankle work increased with walking speed, highlighting the benefits of applying neuromuscular principles in the control of adaptive prosthetic limbs.

Resonant converter topologies for constant-current power supplies and their applications

International Nuclear Information System (INIS)

Borage, Mangesh

2013-01-01

Power electronics, in general, and power supplies, in particular, is an important field of accelerator technology due to its widespread use, for instance in dc, ramp or pulse magnet power supplies, high voltage power supplies for electrostatic accelerators and RF amplifies, power supplies for vacuum pumps, vacuum gauges, beam diagnostic devices etc. It has been possible to meet stringent performance requirements with the continuing advancement in the field of power electronics. Resonant converters have been an active area of research in power electronics field due to variety of topologies, diverse, peculiar and useful characteristics. While the majority of the previous work on resonant converters has been directed towards developing methods of analysis and control techniques for the mentioned applications, very little has been done to explore their suitability for application as a constant-current power supply, which is either inherently required or can be advantageously applied in power supplies for various accelerator subsystems and other industrial applications such as electric arc welding, laser diode drivers, magnet illumination systems, battery charging, electrochemical processes etc.

The Benefit of Variable-Speed Turbine Operation for Low Temperature Thermal Energy Power Recovery

OpenAIRE

Brasz, Joost J.

2014-01-01

This paper analyzes, given the large variation in turbine discharge pressure with changing ambient temperatures, whether variable-speed radial-inflow turbine operation has a similar benefit for Organic Rankine Cycle (ORC) power recovery systems as variable-speed centrifugal compression has for chiller applications. The benefit of variable-speed centrifugal compression over fixed-speed operation is a reduction in annual electricity consumption of almost 40 %. Air-conditioning systems are by ne...

Optimization of powered Stirling heat engine with finite speed thermodynamics

International Nuclear Information System (INIS)

Ahmadi, Mohammad H.; Ahmadi, Mohammad Ali; Pourfayaz, Fathollah; Bidi, Mokhtar; Hosseinzade, Hadi; Feidt, Michel

2016-01-01

Highlights: • Based on finite speed method and direct method, the optimal performance is investigated. • The effects of major parameters on the optimal performance are investigated. • The accuracy of the results was compared with previous works. - Abstract: Popular thermodynamic analyses including finite time thermodynamic analysis was lately developed based upon external irreversibilities while internal irreversibilities such as friction, pressure drop and entropy generation were not considered. The aforementioned disadvantage reduces the reliability of the finite time thermodynamic analysis in the design of an accurate Stirling engine model. Consequently, the finite time thermodynamic analysis could not sufficiently satisfy researchers for implementing in design and optimization issues. In this study, finite speed thermodynamic analysis was employed instead of finite time thermodynamic analysis for studying Stirling heat engine. The finite speed thermodynamic analysis approach is based on the first law of thermodynamics for a closed system with finite speed and the direct method. The effects of heat source temperature, regenerating effectiveness, volumetric ratio, piston stroke as well as rotational speed are included in the analysis. Moreover, maximum output power in optimal rotational speed was calculated while pressure losses in the Stirling engine were systematically considered. The result reveals the accuracy and the reliability of the finite speed thermodynamic method in thermodynamic analysis of Stirling heat engine. The outcomes can help researchers in the design of an appropriate and efficient Stirling engine.

Upper body strength and power are associated with shot speed in men's ice hockey

Directory of Open Access Journals (Sweden)

Juraj Bežák

2017-06-01

Full Text Available Background: Recent studies that addressed shot speed in ice hockey have focused on the relationship between shot speed and variables such as a player's skills or hockey stick construction and its properties. There has been a lack of evidence that considers the relationship between shot speed and player strength, particularly in players at the same skill level. Objective: The aim of this study was to identify the relationship between maximal puck velocity of two shot types (the wrist shot and the slap shot and players' upper body strength and power. Methods: Twenty male professional and semi-professional ice hockey players (mean age 23.3 ± 2.4 years participated in this study. The puck velocity was measured in five trials of the wrist shot and five trials of the slap shot performed by every subject. All of the shots were performed on ice in a stationary position 11.6 meters in front of an electronic device that measures the speed of the puck. The selected strength and power variables were: muscle power in concentric contraction in the countermovement bench press with 40 kg and 50 kg measured with the FiTRODyne Premium device; bench press one-repetition maximum; and grip strength measured by digital hand dynamometer. Results: The correlations between strength/power variables and the puck velocity in the wrist shot and the slap shot ranged between .29-.72 and .16-.62, respectively. Puck velocities produced by wrist shots showed significant correlations with bench press muscle power with 40 kg (p = .004 and 50 kg (p < .001; and one-repetition maximum in bench press (p = .004. The slap shot puck velocity was significantly associated with bench press muscle power with 40 kg (p = .014 and 50 kg (p = .004. Conclusions: This study provides evidence that there are significant associations between shot speed and upper body strength and power.

Special speed-power training as the basis of technical skillfulness improvement in sport aerobic

Directory of Open Access Journals (Sweden)

T.V. Moshenska

2015-12-01

Full Text Available Purpose: to theoretically work out and experimentally substantiate effectiveness of authors’ methodic of speed-power qualities’ training in sport aerobic. Material: 20 sportsmen participated in the research: boys and girls of 8-12 years’ age. Assessment of speed-power fitness was conducted by results of commonly accepted tests, applied in sport practice. Results: we have developed complexes of jump exercises, which envisage varying of conditions of exercises’ fulfillment at the account of pushing conditions (jumps in depth, jumps over obstacles and jumps on elevated platforms. When fulfilling jumps in motion the main was achievement of maximal height with fixing of jump’s form in flight. Conclusions: we offer six complexes of exercises for speed-power training in sport aerobic. These complexes are recommended to be fulfilled at the end of preparatory part of training session during 15-20 minutes.

Virtual Refrigerant Mass Flow and Power Sensors for Variable-Speed Compressors

OpenAIRE

Kim, Woohyun; Braun, James E.

2012-01-01

The use of variable-speed compressors in heat pumps and air conditioners has increased in recent years in order to improve comfort and energy efficiency. At the same time, there is a trend towards embedding more sensors in this type of equipment to facilitate real-time energy monitoring and diagnostics. Although compressor mass flow rate and power consumption are useful indices for performance monitoring and diagnostics, they are expensive to measure. The virtual variable-speed compressor sen...

A nonlinear dynamics approach for incorporating wind-speed patterns into wind-power project evaluation.

Science.gov (United States)

Huffaker, Ray; Bittelli, Marco

2015-01-01

Wind-energy production may be expanded beyond regions with high-average wind speeds (such as the Midwest U.S.A.) to sites with lower-average speeds (such as the Southeast U.S.A.) by locating favorable regional matches between natural wind-speed and energy-demand patterns. A critical component of wind-power evaluation is to incorporate wind-speed dynamics reflecting documented diurnal and seasonal behavioral patterns. Conventional probabilistic approaches remove patterns from wind-speed data. These patterns must be restored synthetically before they can be matched with energy-demand patterns. How to accurately restore wind-speed patterns is a vexing problem spurring an expanding line of papers. We propose a paradigm shift in wind power evaluation that employs signal-detection and nonlinear-dynamics techniques to empirically diagnose whether synthetic pattern restoration can be avoided altogether. If the complex behavior of observed wind-speed records is due to nonlinear, low-dimensional, and deterministic system dynamics, then nonlinear dynamics techniques can reconstruct wind-speed dynamics from observed wind-speed data without recourse to conventional probabilistic approaches. In the first study of its kind, we test a nonlinear dynamics approach in an application to Sugarland Wind-the first utility-scale wind project proposed in Florida, USA. We find empirical evidence of a low-dimensional and nonlinear wind-speed attractor characterized by strong temporal patterns that match up well with regular daily and seasonal electricity demand patterns.

High speed and high functional inverter power supplies for plasma generation and control, and their performance

International Nuclear Information System (INIS)

Uesugi, Yoshihiko; Razzak, Mohammad A.; Kondo, Kenji; Kikuchi, Yusuke; Takamura, Shuichi; Imai, Takahiro; Toyoda, Mitsuhiro

2003-01-01

The Rapid development of high power and high speed semiconductor switching devices has led to their various applications in related plasma fields. Especially, a high speed inverter power supply can be used as an RF power source instead of conventional linear amplifiers and a power supply to control the magnetic field in a fusion plasma device. In this paper, RF thermal plasma production and plasma heating experiments are described emphasis placed on using a static induction transistor inverter at a frequency range between 200 kHz and 2.5 MHz as an RF power supply. Efficient thermal plasma production is achieved experimentally by using a flexible and easily operated high power semiconductor inverter power supply. Insulated gate bipolar transistor (IGBT) inverter power supplies driven by a high speed digital signal processor are applied as tokamak joule coil and vertical coil power supplies to control plasma current waveform and plasma equilibrium. Output characteristics, such as the arbitrary bipolar waveform generation of a pulse width modulation (PWM) inverter using digital signal processor (DSP) can be successfully applied to tokamak power supplies for flexible plasma current operation and fast position control of a small tokamak. (author)

Low speed turbines for nuclear power plants

International Nuclear Information System (INIS)

Ugol'nikov, V.V.; Kosyak, Yu.F.; Virchenko, M.A.

1975-01-01

Work of the Kharkov turbine plant on planning and manufacture for nuclear power plants of low-speed (1500 rpm) turbines with a power of 500-1000 MW is described. The selection of a construction diagram for the turbine assembly, determined basically by the presence or absence of parts of average pressure, is considered. Special construction features of the condenser and turbine are described. Turbine K-500, with a rate of 1500 rpm, was calculated for operation in a two-loop nuclear power plant with saturated steam with intermediate separation and two-stage steam regeneration. On the base of this turbine, three models of 1000-MW turbines were developed. The first model has a cylinder of average pressure (TsSD) and a lateral condenser. The second has no TsSD but a low location of the condensers. The third has no TsSD and the condensers are located laterally. Calculations of the heat efficiency of the three types of turbines showed that several advantages are offered by the model with a TsSD. Better aerodynamic properties of the exhaust nozzles and condensers with lateral location allows decreasing the specific heat consumption to 0.5-1% or, at the same power, a 10-20% decrease in cooling water consumption

Ensemble Nonlinear Autoregressive Exogenous Artificial Neural Networks for Short-Term Wind Speed and Power Forecasting.

Science.gov (United States)

Men, Zhongxian; Yee, Eugene; Lien, Fue-Sang; Yang, Zhiling; Liu, Yongqian

2014-01-01

Short-term wind speed and wind power forecasts (for a 72 h period) are obtained using a nonlinear autoregressive exogenous artificial neural network (ANN) methodology which incorporates either numerical weather prediction or high-resolution computational fluid dynamics wind field information as an exogenous input. An ensemble approach is used to combine the predictions from many candidate ANNs in order to provide improved forecasts for wind speed and power, along with the associated uncertainties in these forecasts. More specifically, the ensemble ANN is used to quantify the uncertainties arising from the network weight initialization and from the unknown structure of the ANN. All members forming the ensemble of neural networks were trained using an efficient particle swarm optimization algorithm. The results of the proposed methodology are validated using wind speed and wind power data obtained from an operational wind farm located in Northern China. The assessment demonstrates that this methodology for wind speed and power forecasting generally provides an improvement in predictive skills when compared to the practice of using an "optimal" weight vector from a single ANN while providing additional information in the form of prediction uncertainty bounds.

Intelligent approach to maximum power point tracking control strategy for variable-speed wind turbine generation system

Energy Technology Data Exchange (ETDEWEB)

Lin, Whei-Min; Hong, Chih-Ming [Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung 80424 (China)

2010-06-15

To achieve maximum power point tracking (MPPT) for wind power generation systems, the rotational speed of wind turbines should be adjusted in real time according to wind speed. In this paper, a Wilcoxon radial basis function network (WRBFN) with hill-climb searching (HCS) MPPT strategy is proposed for a permanent magnet synchronous generator (PMSG) with a variable-speed wind turbine. A high-performance online training WRBFN using a back-propagation learning algorithm with modified particle swarm optimization (MPSO) regulating controller is designed for a PMSG. The MPSO is adopted in this study to adapt to the learning rates in the back-propagation process of the WRBFN to improve the learning capability. The MPPT strategy locates the system operation points along the maximum power curves based on the dc-link voltage of the inverter, thus avoiding the generator speed detection. (author)

Variable-speed wind power system with improved energy capture via multilevel conversion

Science.gov (United States)

Erickson, Robert W.; Al-Naseem, Osama A.; Fingersh, Lee Jay

2005-05-31

A system and method for efficiently capturing electrical energy from a variable-speed generator are disclosed. The system includes a matrix converter using full-bridge, multilevel switch cells, in which semiconductor devices are clamped to a known constant DC voltage of a capacitor. The multilevel matrix converter is capable of generating multilevel voltage wave waveform of arbitrary magnitude and frequencies. The matrix converter can be controlled by using space vector modulation.

A low power and low distortion rail-to-rail input/output amplifier using constant current technique

International Nuclear Information System (INIS)

Liu Yan; Zhao Yiqiang; Zhang Shilin; Zhao Hongliang

2011-01-01

A rail-to-rail amplifier with constant transconductance, intended for audio processing, is presented. The constant transconductance is obtained by a constant current technique based on the input differential pairs operating in the weak inversion region. MOSFETs working in the weak inversion region have the advantages of low power and low distortion. The proposed rail-to-rail amplifier, fabricated in a standard 0.35 μm CMOS process, occupies a core die area of 75 x 183 μm 2 . Measured results show that the maximum power consumption is 85.37 μW with a supply voltage of 3.3 V and the total harmonic distortion level is 1.2% at 2 kHz. (semiconductor integrated circuits)

Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

DEFF Research Database (Denmark)

Lee, Hyewon; Hwang, Min; Muljadi, Eduard

2017-01-01

In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG...... demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.......) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power...

A Simple and Effective Approach for the Prediction of Turbine Power Production From Wind Speed Forecast

Directory of Open Access Journals (Sweden)

Marino Marrocu

2017-11-01

Full Text Available An accurate forecast of the power generated by a wind turbine is of paramount importance for its optimal exploitation. Several forecasting methods have been proposed either based on a physical modeling or using a statistical approach. All of them rely on the availability of high quality measures of local wind speed, corresponding generated power and on numerical weather forecasts. In this paper, a simple and effective wind power forecast technique, based on the probability distribution mapping of wind speed forecast and observed power data, is presented and it is applied to two turbines located on the island of Borkum (Germany in the North Sea. The wind speed forecast of the ECMWF model at 100 m from the ground is used as the prognostic meteorological parameter. Training procedures are based entirely on relatively short time series of power measurements. Results show that our approach has skills that are similar or better than those obtained using more standard methods when measured with mean absolute error.

Power fluctuation and power loss of wind turbines due to wind shear and tower shadow

Institute of Scientific and Technical Information of China (English)

Binrong WEN; Sha WEI; Kexiang WEI; Wenxian YANG; Zhike PENG; Fulei CHU

2017-01-01

The magnitude and stability of power output are two key indices of wind turbines.This study investigates the effects of wind shear and tower shadow on power output in terms of power fluctuation and power loss to estimate the capacity and quality of the power generated by a wind turbine.First,wind speed models,particularly the wind shear model and the tower shadow model,are described in detail.The widely accepted tower shadow model is modified in view of the cone-shaped towers of modem large-scale wind turbines.Power fluctuation and power loss due to wind shear and tower shadow are analyzed by performing theoretical calculations and case analysis within the framework of a modified version of blade element momentum theory.Results indicate that power fluctuation is mainly caused by tower shadow,whereas power loss is primarily induced by wind shear.Under steady wind conditions,power loss can be divided into wind farm loss and rotor loss.Wind farm loss is constant at 3α(3α-1)R2/(8H2).By contrast,rotor loss is strongly influenced by the wind turbine control strategies and wind speed.That is,when the wind speed is measured in a region where a variable-speed controller works,the rotor loss stabilizes around zero,but when the wind speed is measured in a region where the blade pitch controller works,the rotor loss increases as the wind speed intensifies.The results of this study can serve as a reference for accurate power estimation and strategy development to mitigate the fluctuations in aerodynamic loads and power output due to wind shear and tower shadow.

Fuzzy logic speed control for the engine of an air-powered vehicle

Directory of Open Access Journals (Sweden)

Qihui Yu

2016-03-01

Full Text Available To improve the condition of air and eliminate exhaust gas pollution, this article proposes a compressed air power system. Instead of an internal combustion engine, the automobile is equipped with a compressed air engine, which transforms the energy of compressed air into mechanical motion energy. A prototype was built, and the compressed air engine was tested on an experimental platform. The output torque and energy efficiency were obtained from experimental results. When the supply pressure was set at 2 MPa and the speed was 420 r min−1, the output torque, the output power, and the energy efficiency were 56 N m, 1.93 kW, and 25%, respectively. To improve the efficiency of the system, a fuzzy logic speed control strategy is proposed and simulated. The experimental study verified that the theoretical evaluation of the system was reasonable, and this research can be referred to as the design and control of air-powered vehicles.

A novel technology for control of variable speed pumped storage power plant

Institute of Scientific and Technical Information of China (English)

Seyed Mohammad Hassan Hosseini; Mohammad Reza Semsar

2016-01-01

Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control (DTFC) of a variable speed pumped storage power plant (VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP’s control strategies is studied. At the first, a wind turbine with the capacity 2.2 kW and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts (including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter (2LVSC) and three-level voltage source converter (3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion (THD) and ripple of rotor torque and flux.

Nature of tracing dimension, imaginary order of freedom and our observed time passing at constant speed

International Nuclear Information System (INIS)

Nagao, S

2009-01-01

Nature of the time and requirements to work as a time dimension are investigated. A potential scenario of the development of the universe is conceptually investigated starting from energy as vibration in multiple dimensions. A model is proposed, in which the Big Bang is a phase transition of energy from vibration in 4-dimensional space to energy distribution in 3-D surface of a 4-D sphere. The Time which we observe passing at a constant speed is not such a reference frame which we unintentionally believe to be the time, but the radius dimension of the 4-D sphere. The feature of the Dark Matter and the mystery of the Dark Energy are naturally explained from the model.

Nature of tracing dimension, imaginary order of freedom and our observed time passing at constant speed

Energy Technology Data Exchange (ETDEWEB)

Nagao, S, E-mail: snagao@lilac.plala.or.j [Business Development and Licensing Department, Nippon Boehringer Ingelheim Co., Ltd., ThinkPark Tower, 2-1-1, Osaki, Shinagawa, Tokyo 141-6017 (Japan)

2009-06-01

Nature of the time and requirements to work as a time dimension are investigated. A potential scenario of the development of the universe is conceptually investigated starting from energy as vibration in multiple dimensions. A model is proposed, in which the Big Bang is a phase transition of energy from vibration in 4-dimensional space to energy distribution in 3-D surface of a 4-D sphere. The Time which we observe passing at a constant speed is not such a reference frame which we unintentionally believe to be the time, but the radius dimension of the 4-D sphere. The feature of the Dark Matter and the mystery of the Dark Energy are naturally explained from the model.

Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

DEFF Research Database (Denmark)

Pedersen, Mads M.; Larsen, Torben J.; Madsen, Helge Aa

2017-01-01

In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can...... be performed from a few hours or days of measurements. In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup...... anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation...

Efficiency improvement of variable speed electrical drives for HVAC applications

Energy Technology Data Exchange (ETDEWEB)

Abrahamsen, F.; Blaabjerg, F.; Pedersen, J.K. [Aalborg Univ., Inst. of Energy Technology, Aalborg East (Denmark)

2000-07-01

A large part of the produced electrical energy is consumed by ventilators, pumps and compressors, the so-called HVAC applications. A lot of this energy can be saved by speed control, but even with the large saving obtained alone by introduction of variable speed, it is still essential to optimise the control of the variable speed drive and to optimise the electrical machine with respect to efficiency. Experiments are made with energy optimal induction motor control on a 2.2 kW variable speed pump system. It is demonstrated that 10% of the consumed energy can typically be saved by energy optimal motor control compared with constant V/Hz control. In a comparison of induction motors and permanent magnet synchronous motors for a variable speed pump application it is shown that for 2.2 kW motors an investment in high-efficiency or PM motors are typically paid back within 2.5 years and 7 years respectively. For a 90 kW PM motor the pay-back time would be 24 years. It is today not profitable to use PM motors for variable speed HVAC applications above 2 kW rated motor power. A further study is required to determine this limit in power rating more precisely. (orig.)

Accurate calibration of steam turbine speed control system and its influence on primary regulation at electric grid

Energy Technology Data Exchange (ETDEWEB)

Irrazabal Bohorquez, Washington Orlando; Barbosa, Joao Roberto [Technological Institute of Aeronautics (ITA/CTA), Sao Jose dos Campos, SP (Brazil). Center for Reference on Gas Turbine and Energy], E-mail: barbosa@ita.br

2010-07-01

In an interconnected electric system there are two very important parameters: the field voltage and the frequency system. The frequency system is very important for the primary regulation of the electric grid. Each turbomachine actuating as generator interconnected to the grid has an automatic speed regulator to keep the rotational speed and mechanical power of the prime machine operating at the set conditions and stable frequency. The electric grid is a dynamical system and in every moment the power units are exposed to several types of disturbances, which cause unbalance of the mechanical power developed by prime machine and the consumed electric power at the grid. The steam turbine speed control system controls the turbine speed to support the electric grid primary frequency at the same time it controls the frequency of the prime machine. Using a mathematical model for the speed control system, the transfer functions were calculated, as well as the proportionality constants of each element of the steam turbine automatic speed regulator. Among other parameters, the droop characteristic of steam turbine and the dynamic characteristics of the automatic speed regulator elements were calculated. Another important result was the determination of the behavior of the speed control when disturbances occur with the improvement of the calibration precision of the control system. (author)

Coordinated frequency control from offshore wind power plants connected to multi terminal DC system considering wind speed variation

DEFF Research Database (Denmark)

Sakamuri, Jayachandra N.; Altin, Müfit; Hansen, Anca Daniela

2017-01-01

A coordinated fast primary frequency control scheme from offshore wind power plants (OWPPs) integrated to a three terminal high voltage DC (HVDC) system is proposed in this study. The impact of wind speed variation on the OWPP active power output and thus on the AC grid frequency and DC grid...... the active power support from OWPP with a ramp rate limiter and (iii) An alternative method for the wind turbine overloading considering rotor speed. The effectiveness of the proposed control scheme is demonstrated on a wind power plant integrated into a three terminal HVDC system developed in DIg......SILIENT PowerFactory. The results show that the proposed coordinated frequency control method performs effectively at different wind speeds and minimises the secondary effects on frequency and DC voltage....

Bifurcation Analysis of a DC-DC Bidirectional Power Converter Operating with Constant Power Loads

Science.gov (United States)

Cristiano, Rony; Pagano, Daniel J.; Benadero, Luis; Ponce, Enrique

Direct current (DC) microgrids (MGs) are an emergent option to satisfy new demands for power quality and integration of renewable resources in electrical distribution systems. This work addresses the large-signal stability analysis of a DC-DC bidirectional converter (DBC) connected to a storage device in an islanding MG. This converter is responsible for controlling the balance of power (load demand and generation) under constant power loads (CPLs). In order to control the DC bus voltage through a DBC, we propose a robust sliding mode control (SMC) based on a washout filter. Dynamical systems techniques are exploited to assess the quality of this switching control strategy. In this sense, a bifurcation analysis is performed to study the nonlinear stability of a reduced model of this system. The appearance of different bifurcations when load parameters and control gains are changed is studied in detail. In the specific case of Teixeira Singularity (TS) bifurcation, some experimental results are provided, confirming the mathematical predictions. Both a deeper insight in the dynamic behavior of the controlled system and valuable design criteria are obtained.

Mildly disabled persons with multiple sclerosis use similar net joint power strategies as healthy controls when walking speed increases

DEFF Research Database (Denmark)

Brincks, John; Sørensen, Henrik; Dalgas, Ulrik

2018-01-01

flexors in mildly disabled persons with MS and healthy controls at different walking speeds. METHODS:Thirteen persons with MS and thirteen healthy controls participated and peak net joint power was calculated using 3D motion analysis. RESULTS:In general, no differences were found between speed......-matched healthy controls and persons with MS, but the fastest walking speed was significantly higher in healthy controls (2.42 m/s vs. 1.70 m/s). The net joint power increased in hip flexors, hip extensors, hip abductors, knee extensors and plantar flexors in both groups, when walking speed increased. Significant...... correlations between changes in walking speed and changes in net joint power of plantar flexors, hip extensors and hip flexors existed in healthy controls and persons with MS, and in net knee extensor absorption power of persons with MS only. CONCLUSION:In contrast to previous studies, these findings suggest...

Relationship of the Functional Movement Screen In-Line Lunge to Power, Speed, and Balance Measures

OpenAIRE

Hartigan, Erin H.; Lawrence, Michael; Bisson, Brian M.; Torgerson, Erik; Knight, Ryan C.

2014-01-01

Background: The in-line lunge of the Functional Movement Screen (FMS) evaluates lateral stability, balance, and movement asymmetries. Athletes who score poorly on the in-line lunge should avoid activities requiring power or speed until scores are improved, yet relationships between the in-line lunge scores and other measures of balance, power, and speed are unknown. Hypothesis: (1) Lunge scores will correlate with center of pressure (COP), maximum jump height (MJH), and 36.6-meter sprint time...

Second-order Sliding Mode Control of DFIG Based Variable Speed Wind Turbine for Maximum Power Point Tracking

Institute of Scientific and Technical Information of China (English)

Xiangjie Liu; Chengcheng Wang; Yaozhen Han

2017-01-01

This paper proposes a super-twisting second order sliding mode control scheme to maximize the wind energy capture of a doubly fed induction generator based variable speed wind turbine (VSWT) system, and minimize the reactive power simultaneously. Two second order sliding mode controllers are designed to achieve the control objectives, reduce mechanical stress and improve control accuracy. By regulating the generator rotor voltage, one controller makes the wind turbine rotor speed track the optimal speed, which can maximize power generation. The other maintains the rotor current at rated value to minimize the reactive power. A quadratic form Lyapunov function is adopted to determine the range of controller parameters and guarantee the finite time stability. Simulation results on a 1.5 MW doubly fed induction generator (DFIG)-based variable speed wind turbine demonstrate the validity of the proposed control strategy.

Variability of the Wind Turbine Power Curve

Directory of Open Access Journals (Sweden)

Mahesh M. Bandi

2016-09-01

Full Text Available Wind turbine power curves are calibrated by turbine manufacturers under requirements stipulated by the International Electrotechnical Commission to provide a functional mapping between the mean wind speed v ¯ and the mean turbine power output P ¯ . Wind plant operators employ these power curves to estimate or forecast wind power generation under given wind conditions. However, it is general knowledge that wide variability exists in these mean calibration values. We first analyse how the standard deviation in wind speed σ v affects the mean P ¯ and the standard deviation σ P of wind power. We find that the magnitude of wind power fluctuations scales as the square of the mean wind speed. Using data from three planetary locations, we find that the wind speed standard deviation σ v systematically varies with mean wind speed v ¯ , and in some instances, follows a scaling of the form σ v = C × v ¯ α ; C being a constant and α a fractional power. We show that, when applicable, this scaling form provides a minimal parameter description of the power curve in terms of v ¯ alone. Wind data from different locations establishes that (in instances when this scaling exists the exponent α varies with location, owing to the influence of local environmental conditions on wind speed variability. Since manufacturer-calibrated power curves cannot account for variability influenced by local conditions, this variability translates to forecast uncertainty in power generation. We close with a proposal for operators to perform post-installation recalibration of their turbine power curves to account for the influence of local environmental factors on wind speed variability in order to reduce the uncertainty of wind power forecasts. Understanding the relationship between wind’s speed and its variability is likely to lead to lower costs for the integration of wind power into the electric grid.

Power consumption analysis of constant bit rate video transmission over 3G networks

DEFF Research Database (Denmark)

Ukhanova, Ann; Belyaev, Evgeny; Wang, Le

2012-01-01

This paper presents an analysis of the power consumption of video data transmission with constant bit rate over 3G mobile wireless networks. The work includes the description of the radio resource control transition state machine in 3G networks, followed by a detailed power consumption analysis...... and measurements of the radio link power consumption. Based on this description and analysis, we propose our power consumption model. The power model was evaluated on a smartphone Nokia N900, which follows 3GPP Release 5 and 6 supporting HSDPA/HSUPA data bearers. We also propose a method for parameter selection...... for the 3GPP transition state machine that allows to decrease power consumption on a mobile device taking signaling traffic, buffer size and latency restrictions into account. Furthermore, we discuss the gain in power consumption vs. PSNR for transmitted video and show the possibility of performing power...

On special relativity with cosmological constant

International Nuclear Information System (INIS)

Guo Hanying; Huang Chaoguang; Xu Zhan; Zhou Bin

2004-01-01

Based on the principle of relativity and the postulate of invariant speed and length, we propose the theory of special relativity with cosmological constant SRc,R, in which the cosmological constant is linked with the invariant length. Its relation with the doubly special relativity is briefly mentioned

Mildly disabled persons with multiple sclerosis use similar net joint power strategies as healthy controls when walking speed increases.

Science.gov (United States)

Brincks, John; Christensen, Lars Ejsing; Rehnquist, Mette Voigt; Petersen, Jesper; Sørensen, Henrik; Dalgas, Ulrik

2018-01-01

To improve walking in persons with multiple sclerosis (MS), it is essential to understand the underlying mechanisms of walking. This study examined strategies in net joint power generated or absorbed by hip flexors, hip extensors, hip abductors, knee extensors, and plantar flexors in mildly disabled persons with MS and healthy controls at different walking speeds. Thirteen persons with MS and thirteen healthy controls participated and peak net joint power was calculated using 3D motion analysis. In general, no differences were found between speed-matched healthy controls and persons with MS, but the fastest walking speed was significantly higher in healthy controls (2.42 m/s vs. 1.70 m/s). The net joint power increased in hip flexors, hip extensors, hip abductors, knee extensors and plantar flexors in both groups, when walking speed increased. Significant correlations between changes in walking speed and changes in net joint power of plantar flexors, hip extensors and hip flexors existed in healthy controls and persons with MS, and in net knee extensor absorption power of persons with MS only. In contrast to previous studies, these findings suggest that mildly disabled persons with MS used similar kinetic strategies as healthy controls to increase walking speed.

Correlation of Pc5 wave power inside and outside themagnetosphere during high speed streams

Directory of Open Access Journals (Sweden)

R. L. Kessel

2004-01-01

Full Text Available We show a clear correlation between the ULF wave power (Pc5 range inside and outside the Earth's magnetosphere during high speed streams in 1995. We trace fluctuations beginning 200R_E upstream using Wind data, to fluctuations just upstream from Earth's bow shock and in the magnetosheath using Geotail data and compare to pulsations on the ground at the Kilpisjarvi ground station. With our 5-month data set we draw the following conclusions. ULF fluctuations in the Pc5 range are found in high speed streams; they are non-Alfvénic at the leading edge and Alfvénic in the central region. Compressional and Alfvénic fluctuations are modulated at the bow shock, some features of the waveforms are preserved in the magnetosheath, but overall turbulence and wave power is enhanced by about a factor of 10. Parallel (compressional and perpendicular (transverse power are at comparable levels in the solar wind and magnetosheath, both in the compression region and in the central region of high speed streams. Both the total parallel and perpendicular Pc5 power in the solar wind (and to a lesser extent in the magnetosheath correlate well with the total Pc5 power of the ground-based H-component magnetic field. ULF fluctuations in the magnetosheath during high speed streams are common at frequencies from 1–4mHz and can coincide with the cavity eigenfrequencies of 1.3, 1.9, 2.6, and 3.4mHz, though other discrete frequencies are also often seen.

Key words. Interplanetary physics (MHD waves and turbulence – Magnetospheric physics (solar wind-magnetosphere interactions; MHD waves and instabilities

The Design of a High Speed Low Power Phase Locked Loop

CERN Document Server

Liu, Tiankuan; Hou, Suen; Liang, Zhihua; Liu, Chonghan; Su, Da-Shung; Teng, Ping-Kun; Xiang, Annie C; Ye, Jingbo

2009-01-01

The upgrade of the ATLAS Liquid Argon Calorimeter readout system calls for the development of radiation tolerant, high speed and low power serializer ASIC. We have designed a phase locked loop using a commercial 0.25-μm Silicon-on- Sapphire (SoS) CMOS technology. Post-layout simulation indicates that tuning range is 3.79 – 5.01 GHz and power consumption is 104 mW. The PLL has been submitted for fabrication. The design and simulation results are presented.

Dynamic influences of wind power on the power system

Energy Technology Data Exchange (ETDEWEB)

Rosas, Pedro

2003-03-01

The thesis first presents the basics influences of wind power on the power system stability and quality by pointing out the main power quality issues of wind power in a small-scale case and following, the expected large-scale problems are introduced. Secondly, a dynamic wind turbine model that supports power quality assessment of wind turbines is presented. Thirdly, an aggregate wind farm model that support power quality and stability analysis from large wind farms is presented. The aggregate wind farm model includes the smoothing of the relative power fluctuation from a wind farm compared to a single wind turbine. Finally, applications of the aggregate wind farm model to the power systems are presented. The power quality and stability characteristics influenced by large-scale wind power are illustrated with three cases. In this thesis, special emphasis has been given to appropriate models to represent the wind acting on wind farms. The wind speed model to a single wind turbine includes turbulence and tower shadow effects from the wind and the rotational sampling turbulence due to the rotation of the blades. In a park scale, the wind speed model to the wind farm includes the spatial coherence between different wind turbines. Here the wind speed model is applied to a constant rotational speed wind turbine/farm, but the model is suitable to variable speed wind turbine/farm as well. The cases presented here illustrate the influences of the wind power on the power system quality and stability. The flicker and frequency deviations are the main power quality parameters presented. The power system stability concentrates on the voltage stability and on the power system oscillations. From the cases studied, voltage and the frequency variations were smaller than expected from the large-scale wind power integration due to the low spatial correlation of the wind speed. The voltage quality analysed in a Brazilian power system and in the Nordel power system from connecting large

Variability of Wind Speeds and Power over Europe

Science.gov (United States)

Tambke, J.; von Bremen, L.; de Decker, J.; Schmidt, M.; Steinfeld, G.; Wolff, J.-O.

2010-09-01

This study comprises two parts: First, we describe the vertical wind speed and turbulence profiles that result from our improved PBL scheme and compare it to observations and 1-dimensional approaches (Monin-Obukhov etc.). Second, we analyse the spatio-temporal correlations in our meso-scale simulations for the years 2004 to 2007 over entire Europe, with special focus on the Irish, North and Baltic Sea. 1.) Vertical Wind Speed Profiles The vertical wind profile above the sea has to be modelled with high accuracy for tip heights up to 160m in order to achieve precise wind resource assessments, to calculate loads and wakes of wind turbines as well as for reliable short-term wind power forecasts. We present an assessment of different models for wind profiles in unstable, neutral and stable thermal stratification. The meso-scale models comprise MM5, WRF and COSMO-EU (LME). Both COSMO-EU from the German Weather Service DWD and WRF use a turbulence closure of 2.5th order - and lead to similar results. Especially the limiting effect of low boundary layer heights on the wind shear in very stable stratification is well captured. In our new WRF-formulation for the mixing length in the Mellor-Yamada-Janjic (MYJ) parameterisation of the Planetary Boundary Layer (PBL-scheme), the master length scale itself depends on the Monin-Obukhov-Length as a parameter for the heat flux effects on the turbulent mixing. This new PBL-scheme shows a better performance for all weather conditions than the original MYJ-scheme. Apart from the low-boundary-layer-effect in very stable situations (which are seldom), standard Monin-Obukhov formulations in combination with the Charnock relation for the sea surface roughness show good agreement with the FINO1-data (German Bight). Interesting results were achieved with two more detailed micro-scale approaches: - the parameterization proposed by Pena, Gryning and Hasager [BLM 2008] that depends on the boundary layer height - our ICWP-model, were the flux

Effects of High Intensity Interval Training on Increasing Explosive Power, Speed, and Agility

Science.gov (United States)

Fajrin, F.; Kusnanik, N. W.; Wijono

2018-01-01

High Intensity Interval Training (HIIT) is a type of exercise that combines high-intensity exercise and low intensity exercise in a certain time interval. This type of training is very effective and efficient to improve the physical components. The process of improving athletes achievement related to how the process of improving the physical components, so the selection of a good practice method will be very helpful. This study aims to analyze how is the effects of HIIT on increasing explosive power, speed, and agility. This type of research is quantitative with quasi-experimental methods. The design of this study used the Matching-Only Design, with data analysis using the t-test (paired sample t-test). After being given the treatment for six weeks, the results showed there are significant increasing in explosive power, speed, and agility. HIIT in this study used a form of exercise plyometric as high-intensity exercise and jogging as mild or moderate intensity exercise. Increase was due to the improvement of neuromuscular characteristics that affect the increase in muscle strength and performance. From the data analysis, researchers concluded that, Exercises of High Intensity Interval Training significantly effect on the increase in Power Limbs, speed, and agility.

Relationship of the functional movement screen in-line lunge to power, speed, and balance measures.

Science.gov (United States)

Hartigan, Erin H; Lawrence, Michael; Bisson, Brian M; Torgerson, Erik; Knight, Ryan C

2014-05-01

The in-line lunge of the Functional Movement Screen (FMS) evaluates lateral stability, balance, and movement asymmetries. Athletes who score poorly on the in-line lunge should avoid activities requiring power or speed until scores are improved, yet relationships between the in-line lunge scores and other measures of balance, power, and speed are unknown. (1) Lunge scores will correlate with center of pressure (COP), maximum jump height (MJH), and 36.6-meter sprint time and (2) there will be no differences between limbs on lunge scores, MJH, or COP. Descriptive laboratory study. Level 3. Thirty-seven healthy, active participants completed the first 3 tasks of the FMS (eg, deep squat, hurdle step, in-line lunge), unilateral drop jumps, and 36.6-meter sprints. A 3-dimensional motion analysis system captured MJH. Force platforms measured COP excursion. A laser timing system measured 36.6-m sprint time. Statistical analyses were used to determine whether a relationship existed between lunge scores and COP, MJH, and 36.6-m speed (Spearman rho tests) and whether differences existed between limbs in lunge scores (Wilcoxon signed-rank test), MJH, and COP (paired t tests). Lunge scores were not significantly correlated with COP, MJH, or 36.6-m sprint time. Lunge scores, COP excursion, and MJH were not statistically different between limbs. Performance on the FMS in-line lunge was not related to balance, power, or speed. Healthy participants were symmetrical in lunging measures and MJH. Scores on the FMS in-line lunge should not be attributed to power, speed, or balance performance without further examination. However, assessing limb symmetry appears to be clinically relevant.

The fundamental constants a mystery of physics

CERN Document Server

Fritzsch, Harald

2009-01-01

The speed of light, the fine structure constant, and Newton's constant of gravity — these are just three among the many physical constants that define our picture of the world. Where do they come from? Are they constant in time and across space? In this book, physicist and author Harald Fritzsch invites the reader to explore the mystery of the fundamental constants of physics in the company of Isaac Newton, Albert Einstein, and a modern-day physicist

Maximum generation power evaluation of variable frequency offshore wind farms when connected to a single power converter

Energy Technology Data Exchange (ETDEWEB)

Gomis-Bellmunt, Oriol; Sumper, Andreas [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Universitat Politecnica de Catalunya UPC, Av. Diagonal, 647, Pl. 2, 08028 Barcelona (Spain); IREC Catalonia Institute for Energy Research, Barcelona (Spain); Junyent-Ferre, Adria; Galceran-Arellano, Samuel [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Universitat Politecnica de Catalunya UPC, Av. Diagonal, 647, Pl. 2, 08028 Barcelona (Spain)

2010-10-15

The paper deals with the evaluation of power generated by variable and constant frequency offshore wind farms connected to a single large power converter. A methodology to analyze different wind speed scenarios and system electrical frequencies is presented and applied to a case study, where it is shown that the variable frequency wind farm concept (VF) with a single power converter obtains 92% of the total available power, obtained with individual power converters in each wind turbine (PC). The PC scheme needs multiple power converters implying drawbacks in terms of cost, maintenance and reliability. The VF scheme is also compared to a constant frequency scheme CF, and it is shown that a significant power increase of more than 20% can be obtained with VF. The case study considers a wind farm composed of four wind turbines based on synchronous generators. (author)

Effect of 8 days of a hypergravity condition on the sprinting speed and lower-body power of elite rugby players.

Science.gov (United States)

Barr, Matthew J; Gabbett, Tim J; Newton, Robert U; Sheppard, Jeremy M

2015-03-01

-Sprinting speed and lower-body power are considered to be key physical abilities for rugby players. A method of improving the lower-body power of athletes is simulated hypergravity. This method involves wearing a weighted vest at all times during the day for an extended period of time. There are no studies that have examined the effect of hypergravity on speed or the benefit for rugby players. An experimental group (n = 8) and a control group (n = 7) of national team rugby players took part in the study, which consisted of rugby, conditioning, speed, and strength sessions. The experimental group wore a weighted vest equating to 12% of their body mass for 8 days. All players were tested for speed and lower-body power before, 2 days after, and 9 days after the intervention. Speed testing involved the athletes completing 40-m sprints with timing lights and high-speed video cameras assessing acceleration and maximal velocity sprinting kinematics. Lower-body power was assessed using weighted countermovement jumps (CMJs). No group differences were found for sprinting speed at any point. The experimental group displayed a large decrease in acceleration ground contact time (-0.01 ± 0.005 s, d = 1.07) and a moderate increase in 15-kg CMJ velocity (0.07 ± 0.11 m·s, d = 0.71). Individual responses showed that players in the experimental group had both negative and positive speed and power responses to the training intervention. Simulated hypergravity for 8 days is likely ineffective at improving sprinting speed while undergoing standard rugby training.

Power Quality Control and Design of Power Converter for Variable-Speed Wind Energy Conversion System with Permanent-Magnet Synchronous Generator

Directory of Open Access Journals (Sweden)

Yüksel Oğuz

2013-01-01

Full Text Available The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

Power quality control and design of power converter for variable-speed wind energy conversion system with permanent-magnet synchronous generator.

Science.gov (United States)

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

POWER SPECTRAL DENSITY OF FLUCTUATIONS OF BULK AND THERMAL SPEEDS IN THE SOLAR WIND

International Nuclear Information System (INIS)

Šafránková, J.; Němeček, Z.; Němec, F.; Přech, L.; Chen, C. H. K.; Zastenker, G. N.

2016-01-01

This paper analyzes solar wind power spectra of bulk and thermal speed fluctuations that are computed with a time resolution of 32 ms in the frequency range of 0.001–2 Hz. The analysis uses measurements of the Bright Monitor of the Solar Wind on board the Spektr-R spacecraft that are limited to 570 km s 1 bulk speed. The statistics, based on more than 42,000 individual spectra, show that: (1) the spectra of bulk and thermal speeds can be fitted by two power-law segments; (2) despite their large variations, the parameters characterizing frequency spectrum fits computed on each particular time interval are very similar for both quantities; (3) the median slopes of the bulk and thermal speeds of the segment attributed to the MHD scale are 1.43 and 1.38, respectively, whereas they are 3.08 and 2.43 in the kinetic range; (4) the kinetic range slopes of bulk and thermal speed spectra become equal when either the ion density or magnetic field strength are high; (5) the break between MHD and kinetic scales seems to be controlled by the ion β parameter; (6) the best scaling parameter for bulk and thermal speed variations is a sum of the inertial length and proton thermal gyroradius; and (7) the above conclusions can be applied to the density variations if the background magnetic field is very low.

POWER SPECTRAL DENSITY OF FLUCTUATIONS OF BULK AND THERMAL SPEEDS IN THE SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

Šafránková, J.; Němeček, Z.; Němec, F.; Přech, L. [Charles University, Faculty of Mathematics and Physics, V Holešovičkách 2, 180 00 Prague 8 (Czech Republic); Chen, C. H. K. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Zastenker, G. N., E-mail: jana.safrankova@mff.cuni.cz [Space Research Institute of Russian Academy of Sciences, Moscow, Russia, Profsoyuznaya ul. 84/32, Moscow 117997 (Russian Federation)

2016-07-10

This paper analyzes solar wind power spectra of bulk and thermal speed fluctuations that are computed with a time resolution of 32 ms in the frequency range of 0.001–2 Hz. The analysis uses measurements of the Bright Monitor of the Solar Wind on board the Spektr-R spacecraft that are limited to 570 km s{sup 1} bulk speed. The statistics, based on more than 42,000 individual spectra, show that: (1) the spectra of bulk and thermal speeds can be fitted by two power-law segments; (2) despite their large variations, the parameters characterizing frequency spectrum fits computed on each particular time interval are very similar for both quantities; (3) the median slopes of the bulk and thermal speeds of the segment attributed to the MHD scale are 1.43 and 1.38, respectively, whereas they are 3.08 and 2.43 in the kinetic range; (4) the kinetic range slopes of bulk and thermal speed spectra become equal when either the ion density or magnetic field strength are high; (5) the break between MHD and kinetic scales seems to be controlled by the ion β parameter; (6) the best scaling parameter for bulk and thermal speed variations is a sum of the inertial length and proton thermal gyroradius; and (7) the above conclusions can be applied to the density variations if the background magnetic field is very low.

Preliminary tests of a high speed vertical axis windmill model

Energy Technology Data Exchange (ETDEWEB)

South, P; Rangi, R S

1971-01-01

This report discusses a fixed-pitch vertical axis windmill that combines the inherent simplicity of this type of machine with a high aerodynamic efficiency and a high relative velocity. A three-bladed rotor was selected as the basic design, having constant chord symmetric airfoil blades configured in a catenary curve such that the rotor diameter is equal to the rotor height. In wind tunnel tests using a 30 inch scale model, it was found that once this rotor was given a very low rotational speed, it picked up speed and ran at a rotor tip velocity/wind speed ratio greater than 1. The number of blades was varied in the testing. A maximum power coefficient of 0.67 was achieved at 17 ft/s wind speed at a tip speed/wind speed ratio of 7.25 for a 2-bladed rotor. Increasing the number of blades above 3 did not result in higher power. The rotor could operate in gusts which double the mean wind velocity. Examination of Reynolds number effects, and taking into account the scale of the model, it was concluded that a full-scale windmill could run at lower velocity ratios than those predicted by the model tests, and that it could self-start under no-load conditions if the cut-in rpm are at least half the rpm for maximum power at the prevailing wind speed. Preliminary estimates show that a 15 ft diameter windmill of this design, designed to operate with a safety factor of 2.5 up to a maximum wind speed of 60 ft/s, would weigh ca 150 lb and could be marketed for ca $60.00, excluding the driven unit, if sufficient quantities were produced to make tooling costs negligible. Similarly, a 30 ft windmill would weigh ca 1000 lb and cost ca $400.00. 2 refs., 6 figs.

Design of constant current charging power supply for J-TEXT ohmic field capacitor banks

International Nuclear Information System (INIS)

Lv Shudong; Zhang Ming; Rao Bo; Yu Kexun; Yang Cheng

2014-01-01

The charging characteristic of the capacitor charging power supply was analyzed with practical series resonant topology. The method that setting two current taps and regulating PWM switching frequency was putted forward with close loop controlling algorithm to charge the multi-group capacitor banks with constant current. A capacitor charging power supply with the max output current 6.5 A and the max output voltage 2000 V is designed. Experimental results show that, this power supply can charge the four capacitor banks to any four different voltages in 1 minute with charging accuracy less than 1%, and meet the requirements of J-TEXT ohmic field power system. (authors)

Relationship of the Functional Movement Screen In-Line Lunge to Power, Speed, and Balance Measures

Science.gov (United States)

Hartigan, Erin H.; Lawrence, Michael; Bisson, Brian M.; Torgerson, Erik; Knight, Ryan C.

2014-01-01

Background: The in-line lunge of the Functional Movement Screen (FMS) evaluates lateral stability, balance, and movement asymmetries. Athletes who score poorly on the in-line lunge should avoid activities requiring power or speed until scores are improved, yet relationships between the in-line lunge scores and other measures of balance, power, and speed are unknown. Hypothesis: (1) Lunge scores will correlate with center of pressure (COP), maximum jump height (MJH), and 36.6-meter sprint time and (2) there will be no differences between limbs on lunge scores, MJH, or COP. Study Design: Descriptive laboratory study. Level of Evidence: Level 3. Methods: Thirty-seven healthy, active participants completed the first 3 tasks of the FMS (eg, deep squat, hurdle step, in-line lunge), unilateral drop jumps, and 36.6-meter sprints. A 3-dimensional motion analysis system captured MJH. Force platforms measured COP excursion. A laser timing system measured 36.6-m sprint time. Statistical analyses were used to determine whether a relationship existed between lunge scores and COP, MJH, and 36.6-m speed (Spearman rho tests) and whether differences existed between limbs in lunge scores (Wilcoxon signed-rank test), MJH, and COP (paired t tests). Results: Lunge scores were not significantly correlated with COP, MJH, or 36.6-m sprint time. Lunge scores, COP excursion, and MJH were not statistically different between limbs. Conclusion: Performance on the FMS in-line lunge was not related to balance, power, or speed. Healthy participants were symmetrical in lunging measures and MJH. Clinical Relevance: Scores on the FMS in-line lunge should not be attributed to power, speed, or balance performance without further examination. However, assessing limb symmetry appears to be clinically relevant. PMID:24790688

Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

Directory of Open Access Journals (Sweden)

M. M. Pedersen

2017-11-01

Full Text Available In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can be performed from a few hours or days of measurements.In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting.Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production. This is the research question addressed in this paper.The method is first tested using aeroelastic simulations where the dependence of the radial position and effect of multiple blade-mounted flow sensors are also investigated. Next the method is evaluated on the basis of full-scale measurements on a pitch-regulated, variable-speed 3.6 MW wind turbine.It is concluded that the wind speed derived from the blade-mounted flow sensor is highly correlated with the

Radiographic constant exposure technique

DEFF Research Database (Denmark)

Domanus, Joseph Czeslaw

1985-01-01

The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...

High-Speed, Low-Power ADC for Digital Beam Forming (DBF) Systems, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Ridgetop Group will design a high-speed, low-power silicon germanium (SiGe)-based, analog-to-digital converter (ADC) to be a key element for digital beam forming...

High-Speed, Low-Power ADC for Digital Beam Forming (DBF) Systems, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — In Phase 1, Ridgetop Group designed a high-speed, yet low-power silicon germanium (SiGe)-based, analog-to-digital converter (ADC) to be a key element for digital...

Are the force characteristics of synchronous handcycling affected by speed and the method to impose power?

NARCIS (Netherlands)

Arnet, U.; van Drongelen, S.V.; van der Woude, L.H.V.; Veeger, H.E.J.

2012-01-01

Objective: To investigate the influence of exercise conditions (speed and method to impose power) on the applied force, force effectiveness and distribution of work during handcycling. Method: Ten able-bodied men performed handcycling on a treadmill. To test the effect of speed, subjects propelled

Are the force characteristics of synchronous handcycling affected by speed and the method to impose power?

NARCIS (Netherlands)

Arnet, Ursina; van Drongelen, Stefan; Veeger, DirkJan H. E. J.; van der Woude, Lucas H. V.

Objective: To investigate the influence of exercise conditions (speed and method to impose power) on the applied force, force effectiveness and distribution of work during handcycling. Method: Ten able-bodied men performed handcycling on a treadmill. To test the effect of speed, subjects propelled

Power consumption analysis of constant bit rate data transmission over 3G mobile wireless networks

DEFF Research Database (Denmark)

Wang, Le; Ukhanova, Ann; Belyaev, Evgeny

2011-01-01

This paper presents the analysis of the power consumption of data transmission with constant bit rate over 3G mobile wireless networks. Our work includes the description of the transition state machine in 3G networks, followed by the detailed energy consumption analysis and measurement results...... of the radio link power consumption. Based on these description and analysis, we propose power consumption model. The power model was evaluated on the smartphone Nokia N900, which follows a 3GPP Release 5 and 6 supporting HSDPA/HSPA data bearers. Further we propose method of parameters selection for 3GPP...... transition state machine that allows to decrease power consumption on the mobile device....

Non-minimally coupled varying constants quantum cosmologies

International Nuclear Information System (INIS)

Balcerzak, Adam

2015-01-01

We consider gravity theory with varying speed of light and varying gravitational constant. Both constants are represented by non-minimally coupled scalar fields. We examine the cosmological evolution in the near curvature singularity regime. We find that at the curvature singularity the speed of light goes to infinity while the gravitational constant vanishes. This corresponds to the Newton's Mechanics limit represented by one of the vertex of the Bronshtein-Zelmanov-Okun cube [1,2]. The cosmological evolution includes both the pre-big-bang and post-big-bang phases separated by the curvature singularity. We also investigate the quantum counterpart of the considered theory and find the probability of transition of the universe from the collapsing pre-big-bang phase to the expanding post-big-bang phase

Highly-stabilized power supply for synchrotron accelerators. High speed, low ripple power supply

Energy Technology Data Exchange (ETDEWEB)

Sato, Kenji [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Kumada, Masayuki; Fukami, Kenji; Koseki, Shoichiro; Kubo, Hiroshi; Kanazawa, Toru

1997-02-01

In synchrotron accelerators, in order to utilize high energy beam effectively, those are operated by repeating acceleration and taking-out at short period. In order to accelerate by maintaining beam track stable, the tracking performance with the error less than 10{sup -3} in the follow-up of current is required for the power supply. Further, in order to maintain the intensity and uniformity of beam when it is taken out, very low ripple is required for output current. The power supply having such characteristics has been developed, and applied to the HIMAC and the SPring-8. As the examples of the application of synchrotrons, the accelerators for medical treatment and the generation of synchrotron radiation are described. As to the power supply for the deflection magnets and quadrupole magnets of synchrotron accelerators, the specifications of the main power supply, the method of reducing ripple, the method of improving tracking, and active filter control are reported. As to the test results, the measurement of current ripple and tracking error is shown. The lowering of ripple was enabled by common mode filter and the symmetrical connection of electromagnets, and high speed response was realized by the compensation for delay with active filter. (K.I.)

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller.

Science.gov (United States)

Kleinheyer, Matthias; Timms, Daniel L; Tansley, Geoffrey D; Nestler, Frank; Greatrex, Nicholas A; Frazier, O Howard; Cohn, William E

2016-09-01

Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Robust control of speed and temperature in a power plant gas turbine.

Science.gov (United States)

Najimi, Ebrahim; Ramezani, Mohammad Hossein

2012-03-01

In this paper, an H(∞) robust controller has been designed for an identified model of MONTAZER GHAEM power plant gas turbine (GE9001E). In design phase, a linear model (ARX model) which is obtained using real data has been applied. Since the turbine has been used in a combined cycle power plant, its speed and also the exhaust gas temperature should be adjusted simultaneously by controlling fuel signals and compressor inlet guide vane (IGV) position. Considering the limitations on the system inputs, the aim of the control is to maintain the turbine speed and the exhaust gas temperature within desired interval under uncertainties and load demand disturbances. Simulation results of applying the proposed robust controller on the nonlinear model of the system (NARX model), fairly fulfilled the predefined aims. Simulations also show the improvement in the performance compared to MPC and PID controllers for the same conditions. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

DEVELOPMENT AND INFLUENCE OF SPEED POWER ON RESULTS PROGRESSION OF LOW VISION JAVELIN THROWERS

Directory of Open Access Journals (Sweden)

Milan Matić

2013-07-01

Full Text Available Power is a motor skill important for low vision javelin throwers. The motor skill development (power, speed, endurance etc. linked to the fact that javelin is the lightest throwing device, we come to conclusion that the result in this discipline depends much more on the speed and flexibility than on the power. Nevertheless, development of speed power significantly influences the acquiring of good results in above mentioned discipline. While working with low vision sportsmen the attention should be focused on possible limitations in training of power that could be determined by some kind of illness or injury primarly caused the low vision. Experimental method od survey based on one sample was applied (case study. Equipment used in the experiments were adjusted to the needs, age and level of condition of examinee- Grlica Miloš (current European Record Breaker, 3rd on the World’s Championship 2012 in New Zealand, discipline of javlin throwing, category F12. The survey consisted of two-months cycle in the period from 01/04/2012 until 01/06/2012 as a part of preparation for Paralympic Games in London 2012. Measured variables include: 5kg ball throwing in front and above, standing long jump, 4kg ball throwing exercise aut. Based on the applied tests a conclusion can be made that the impact of force on acquiring better results, in this discipline, is very strong. Regardless the acquired results, in our opinion too big and too fast improvement in this area of physical preparation can be contraproductive due to the occurence of inadequate movements in joints which are esential for the discipline. Power development is definitely crucial segment in modeling of training process for javelin throwers. There are many surveys and articles about this topic but very little focusing on disabled people. Future work should examine special characteristics and differences regarding this population.

Flicker Mitigation by Speed Control of Permanent Magnet Synchronous Generator Variable-Speed Wind Turbines

DEFF Research Database (Denmark)

Hu, Weihao; Zhang, Yunqian; Chen, Zhe

2013-01-01

operation. A new method of flicker mitigation by controlling the rotational speed is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the rotational speed of the PMSG. Simulation results show that damping the 3p active power...... oscillation by using the flicker mitigation speed controller is an effective means for flicker mitigation of variable speed wind turbines with full-scale back-to-back power converters and PMSG during continuous operation.......Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a full-scale back-to-back power converter and permanent magnet synchronous generator (PMSG...

Flicker Mitigation by Speed Control of Permanent Magnet Synchronous Generator Variable-Speed Wind Turbines

Directory of Open Access Journals (Sweden)

Yanting Hu

2013-07-01

Full Text Available Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a full-scale back-to-back power converter and permanent magnet synchronous generator (PMSG developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. The 3p (three times per revolution power oscillation due to wind shear and tower shadow effects is the significant part in the flicker emission of variable speed wind turbines with PMSG during continuous operation. A new method of flicker mitigation by controlling the rotational speed is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the rotational speed of the PMSG. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation speed controller is an effective means for flicker mitigation of variable speed wind turbines with full-scale back-to-back power converters and PMSG during continuous operation.

Influence of “J”-Curve Spring Stiffness on Running Speeds of Segmented Legs during High-Speed Locomotion

Directory of Open Access Journals (Sweden)

Runxiao Wang

2016-01-01

Full Text Available Both the linear leg spring model and the two-segment leg model with constant spring stiffness have been broadly used as template models to investigate bouncing gaits for legged robots with compliant legs. In addition to these two models, the other stiffness leg spring models developed using inspiration from biological characteristic have the potential to improve high-speed running capacity of spring-legged robots. In this paper, we investigate the effects of “J”-curve spring stiffness inspired by biological materials on running speeds of segmented legs during high-speed locomotion. Mathematical formulation of the relationship between the virtual leg force and the virtual leg compression is established. When the SLIP model and the two-segment leg model with constant spring stiffness and with “J”-curve spring stiffness have the same dimensionless reference stiffness, the two-segment leg model with “J”-curve spring stiffness reveals that (1 both the largest tolerated range of running speeds and the tolerated maximum running speed are found and (2 at fast running speed from 25 to 40/92 m s−1 both the tolerated range of landing angle and the stability region are the largest. It is suggested that the two-segment leg model with “J”-curve spring stiffness is more advantageous for high-speed running compared with the SLIP model and with constant spring stiffness.

IMPROVING MODEL OF CHANNEL AIRBORN ELECTRICAL POWER SYSTEM OF ALTERNATING CURRENT

Directory of Open Access Journals (Sweden)

Yu. P. Artemenko

2015-01-01

Full Text Available This article is devoted to math modeling of channel of alternating current airborne electrical power-supply system. Mathematical modeling of generator, voltage regulator, constant speed drive is considered.

Application of Boost Converter to Increase the Speed Range of Dual-stator Winding Induction Generator in Wind Power Systems

DEFF Research Database (Denmark)

Kavousi, Ayoub; Fathi, S. Hamid; Milimonfared, Jafar

2018-01-01

In this paper, a topology using a Dual-stator Winding Induction Generator (DWIG) and a boost converter is proposed for the variable speed wind power application. At low rotor speeds, the generator saturation limits the voltage of the DWIG. Using a boost converter, higher DC voltage can be produced...... while the DWIG operates at Maximum Power Point Tracking (MPPT) even at low speed and low voltage conditions. Semiconductor Excitation Controller (SEC) of the DWIG utilizes Control-Winding Voltage Oriented Control (CWVOC) method to adjust the voltage, considering V/f characteristics. For the proposed...... topology, the SEC capacity and the excitation capacitor is optimized by analyzing the SEC reactive current considering wind turbine power-speed curve, V/f strategy, and the generator parameters. The method shows that the per-unit capacity of the SEC can be limited to the inverse of DWIG magnetizing...

Nuclear and thermal power plant power ramping capability

International Nuclear Information System (INIS)

Golovach, E.A.

1983-01-01

The possibilities of step power increase by NPP and TPP units under emergency conditions of power grids operation are considered. The data analysis has shown that power units ramping capability with WWER-440, WWER-1000 and RBMK-1000 reactors is higher than that of 300 MW power units on fossil fuel, at the initial time interval (0-30 s). These NPP power units satisfy as to ramping capability the energy system requirements. Higher NPP power units ramping capability is explained by the fact that relative pressure before turbine valves is decreased less than in straight-through boilers while the steam volumes time constant of steam separator-superheaters is less than that of intermediate superheatings. Higher power unit ramping capability with WWER-440 and RBMK-1000 reactors as compared with the WWER-1000 reactor is pointed out as well as the increase of WWER-1000 power unit capability using high-speed turbines

A quadri-constant fraction discriminator

International Nuclear Information System (INIS)

Wang Wei; Gu Zhongdao

1992-01-01

A quad Constant Fraction (Amplitude and Rise Time Compensation) Discriminator Circuit is described, which is based on the ECL high-speed dual comparator AD 9687. The CFD (ARCD) is of the constant fraction timing type (the amplitude and rise time compensation timing type) employing a leading edge discriminator to eliminate error triggers caused by noises. A timing walk measurement indicates a timing walk of less than +- 150 ps from -50 mV to -5 V

Permanent-magnet motor with two-part rotor for wide speed range

International Nuclear Information System (INIS)

Baines, G.D.; Chalmers, B.J.; Akmese, R.

1998-01-01

The paper describes a synchronous motor with a two-part rotor comprising a surface-magnet part and a reluctance part mounted adjacent to each other on the same axis. Machine parameters and physical design details are selected in order to obtain constant-power characteristics over a 3:1 speed range by field-weakening. Test results demonstrate the achievement of the desired characteristics, in good agreement with computed predictions. (orig.)

Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

Science.gov (United States)

Peak, S. C.

1982-01-01

An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

Robust transient stabilisation problem for a synchronous generator in a power network

Science.gov (United States)

Verrelli, C. M.; Damm, G.

2010-04-01

The robust transient stabilisation problem (with stability proof€) of a synchronous generator in an uncertain power network with transfer conductances is rigorously formulated and solved. The generator angular speed and electrical power are required to be kept close, when mechanical and electrical perturbations occur, to the synchronous speed and mechanical input power, respectively, while the generator terminal voltage is to be regulated, when perturbations are removed, to its pre-fault reference constant value. A robust adaptive nonlinear feedback control algorithm is designed on the basis of a third-order model of the synchronous machine: only two system parameters (synchronous machine damping and inertia constants) along with upper and lower bounds on the remaining uncertain ones are supposed to be known. The conditions to be satisfied by the remote network dynamics for guaranteeing ℒ2 and ℒ∞ robustness and asymptotic relative speed and voltage regulation to zero are weaker than those required by the single machine-infinite bus approximation: dynamic interactions between the local deviations of the generator states from the corresponding equilibrium values and the remote generators states are allowed.

Circuit Regulates Speed Of dc Motor

Science.gov (United States)

Weaver, Charles; Padden, Robin; Brown, Floyd A., Jr.

1990-01-01

Driving circuit regulates speed of small dc permanent-magnet motor in tape recorder. Two nested feedback loops maintain speed within 1 percent of constant value. Inner loop provides coarse regulation, while outer loop removes most of variation in speed that remains in the presence of regulation by the inner loop. Compares speed of motor with commanded speed and adjusts current supplied to motor accordingly.

High speed micromachining with high power UV laser

Science.gov (United States)

Patel, Rajesh S.; Bovatsek, James M.

2013-03-01

Increasing demand for creating fine features with high accuracy in manufacturing of electronic mobile devices has fueled growth for lasers in manufacturing. High power, high repetition rate ultraviolet (UV) lasers provide an opportunity to implement a cost effective high quality, high throughput micromachining process in a 24/7 manufacturing environment. The energy available per pulse and the pulse repetition frequency (PRF) of diode pumped solid state (DPSS) nanosecond UV lasers have increased steadily over the years. Efficient use of the available energy from a laser is important to generate accurate fine features at a high speed with high quality. To achieve maximum material removal and minimal thermal damage for any laser micromachining application, use of the optimal process parameters including energy density or fluence (J/cm2), pulse width, and repetition rate is important. In this study we present a new high power, high PRF QuasarR 355-40 laser from Spectra-Physics with TimeShiftTM technology for unique software adjustable pulse width, pulse splitting, and pulse shaping capabilities. The benefits of these features for micromachining include improved throughput and quality. Specific example and results of silicon scribing are described to demonstrate the processing benefits of the Quasar's available power, PRF, and TimeShift technology.

Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines With Full-Scale Back-to-Back Power Converters

DEFF Research Database (Denmark)

Hu, Weihao; Chen, Zhe; Wang, Zhaoan

2009-01-01

/EMTDC. Flicker emission of this system is investigated. Reactive power compensation is mostly adopted for flicker mitigation. However, the flicker mitigation technique shows its limits, when the grid impedance angle is low in some distribution networks. A new method of flicker mitigation by controlling active...... power is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the dc-link voltage of the full-scale converter. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation controller...... is an effective means for flicker mitigation of variable-speed wind turbines with full-scale back-to-back power converters during continuous operation....

Changes in speed distribution: Applying aggregated safety effect models to individual vehicle speeds.

Science.gov (United States)

Vadeby, Anna; Forsman, Åsa

2017-06-01

This study investigated the effect of applying two aggregated models (the Power model and the Exponential model) to individual vehicle speeds instead of mean speeds. This is of particular interest when the measure introduced affects different parts of the speed distribution differently. The aim was to examine how the estimated overall risk was affected when assuming the models are valid on an individual vehicle level. Speed data from two applications of speed measurements were used in the study: an evaluation of movable speed cameras and a national evaluation of new speed limits in Sweden. The results showed that when applied on individual vehicle speed level compared with aggregated level, there was essentially no difference between these for the Power model in the case of injury accidents. However, for fatalities the difference was greater, especially for roads with new cameras where those driving fastest reduced their speed the most. For the case with new speed limits, the individual approach estimated a somewhat smaller effect, reflecting that changes in the 15th percentile (P15) were somewhat larger than changes in P85 in this case. For the Exponential model there was also a clear, although small, difference between applying the model to mean speed changes and individual vehicle speed changes when speed cameras were used. This applied both for injury accidents and fatalities. There were also larger effects for the Exponential model than for the Power model, especially for injury accidents. In conclusion, applying the Power or Exponential model to individual vehicle speeds is an alternative that provides reasonable results in relation to the original Power and Exponential models, but more research is needed to clarify the shape of the individual risk curve. It is not surprising that the impact on severe traffic crashes was larger in situations where those driving fastest reduced their speed the most. Further investigations on use of the Power and/or the

Dynamic Analysis of Fluid Power Drive-trains for Variable Speed Wind Turbines : A Parameter Study

NARCIS (Netherlands)

Jarquin Laguna, A.; Diepeveen, N.F.B.

2013-01-01

In the pursuit of making wind energy technology more economically attractive, the application of fluid power technology for the transmission of wind energy is being developed by several parties all over the world. This paper presents a dynamic model of a fluid power transmission for variable speed

Lifetime of titanium filament at constant current

International Nuclear Information System (INIS)

Chou, T.S.; Lanni, C.

1981-01-01

Titanium Sublimation Pump (TSP) represents the most efficient and the least expensive method to produce Ultra High Vacuum (UHV) in storage rings. In ISABELLE, a proton storage accelerator under construction at Brookhaven National Laboratory, for example, TSP provides a pumping speed for hydrogen of > 2 x 10 6 l/s. Due to the finite life of titanium filaments, new filaments have to be switched in before the end of filament burn out, to ensure smooth operation of the accelerator. Therefore, several operational modes that can be used to activate the TSP were studied. The constant current mode is a convenient way of maintaining constant evaporating rate by increasing the power input while the filament diameter decreases as titanium evaporates. The filaments used in this experiment were standard Varian 916-0024 filaments made of Ti 85%, Mo 15% alloy. During their lifetime at a constant current of 48 amperes, the evaporation rate rose to a maximum at about 10% of their life and then flattened out to a constant value, 0.25 g/hr. The maximum evaporation rate occurs coincidently with the recrystallization of 74% Ti 26% Mo 2 from microstructure crystalline at higher titanium concentration to macrostructure crystalline at lower titanium concentration. As the macrocrystal grows, the slip plane develops at the grain boundary resulting in high resistance at the slip plane which will eventually cause the filament burn out due to local heating

Flame Speed and Self-Similar Propagation of Expanding Turbulent Premixed Flames

Science.gov (United States)

Chaudhuri, Swetaprovo; Wu, Fujia; Zhu, Delin; Law, Chung K.

2012-01-01

In this Letter we present turbulent flame speeds and their scaling from experimental measurements on constant-pressure, unity Lewis number expanding turbulent flames, propagating in nearly homogeneous isotropic turbulence in a dual-chamber, fan-stirred vessel. It is found that the normalized turbulent flame speed as a function of the average radius scales as a turbulent Reynolds number to the one-half power, where the average radius is the length scale and the thermal diffusivity is the transport property, thus showing self-similar propagation. Utilizing this dependence it is found that the turbulent flame speeds from the present expanding flames and those from the Bunsen geometry in the literature can be unified by a turbulent Reynolds number based on flame length scales using recent theoretical results obtained by spectral closure of the transformed G equation.

Long Term Effects of Different Training Modalities on Power, Speed, Skill and Anaerobic Capacity in Young Male Basketball Players

Science.gov (United States)

Balčiūnas, Mindaugas; Stonkus, Stanislovas; Abrantes, Catarina; Sampaio, Jaime

2006-01-01

The purpose of this study was to identify the effect of 4 months of different training modalities on power, speed, skill and anaerobic capacity in 15-16 year old male basketball players. Thirty five Lithuanian basketball players were randomly assigned into three groups: power endurance group (intermittent exercise, PE, n = 12), general endurance group (continuous exercise, GE, n = 11) and control group (regular basketball training, CG, n = 12). The power endurance model was based in basketball game external structure whereas the general endurance model was based in continuous actions that frequently occur during the basketball game. The training models were used for 16 weeks in sessions conducted 3 times a week during 90 minutes each in the competition period. The following tests were performed: 20 m speed run, Squat jump, Countermovement jump, Running-based Anaerobic Sprint Test (RAST), 2 min. shooting test and the Shuttle ball-dribbling test. A 3×2 repeated measures ANOVA revealed no statistically significant differences in the 20 m speed run, Squat jump and Countermovement jump (p > 0.05). On the other hand, RAST showed significant increases in PE, with greater increases during the 5th and 6th runs. The PE training model also produced a significant improvement in the shuttle ball-dribbling test (48.7 ± 1.5 in the pretest, 45.5 ± 1.3 in the posttest, p training modalities were able to maintain initial values of speed and power, however, the anaerobic capacity and skill increased only in the players from the power endurance group. Therefore, the power endurance training (intermittent high intensity exercise) may be more beneficial to prepare junior players according to the game cardiovascular and metabolic specific determinants. Key Points Power endurance training produced significant increases in anaerobic capacity during the competition period. Power endurance training did not have a detrimental effect on power or speed performance during the competition

Long term effects of different training modalities on power, speed, skill and anaerobic capacity in young male basketball players.

Science.gov (United States)

Balčiūnas, Mindaugas; Stonkus, Stanislovas; Abrantes, Catarina; Sampaio, Jaime

2006-01-01

The purpose of this study was to identify the effect of 4 months of different training modalities on power, speed, skill and anaerobic capacity in 15-16 year old male basketball players. Thirty five Lithuanian basketball players were randomly assigned into three groups: power endurance group (intermittent exercise, PE, n = 12), general endurance group (continuous exercise, GE, n = 11) and control group (regular basketball training, CG, n = 12). The power endurance model was based in basketball game external structure whereas the general endurance model was based in continuous actions that frequently occur during the basketball game. The training models were used for 16 weeks in sessions conducted 3 times a week during 90 minutes each in the competition period. The following tests were performed: 20 m speed run, Squat jump, Countermovement jump, Running-based Anaerobic Sprint Test (RAST), 2 min. shooting test and the Shuttle ball-dribbling test. A 3×2 repeated measures ANOVA revealed no statistically significant differences in the 20 m speed run, Squat jump and Countermovement jump (p > 0.05). On the other hand, RAST showed significant increases in PE, with greater increases during the 5(th) and 6(th) runs. The PE training model also produced a significant improvement in the shuttle ball-dribbling test (48.7 ± 1.5 in the pretest, 45.5 ± 1.3 in the posttest, p training modalities were able to maintain initial values of speed and power, however, the anaerobic capacity and skill increased only in the players from the power endurance group. Therefore, the power endurance training (intermittent high intensity exercise) may be more beneficial to prepare junior players according to the game cardiovascular and metabolic specific determinants. Key PointsPower endurance training produced significant increases in anaerobic capacity during the competition period.Power endurance training did not have a detrimental effect on power or speed performance during the competition

Model and simulation of the hydraulic turbine speed regulator of the Atucha I nuclear power plant

International Nuclear Information System (INIS)

Copparoni, G.; Etchepareborda, A.; Urrutia, G.

1992-01-01

The hydraulics turbines of Atucha I Nuclear Power Plant takes advantage of condenser cooling water level difference between the plant and the river to recover about 2,5 MW e. It also supplies emergency power until diesel generators start up. Speed regulation is needed due to the transients that during this process occur. The purpose is to minimize the diesels start up time, and to avoid overshoots on the internal grid frequency. The hydraulic turbine, its speed regulator and the electric system associated with this transient have been modeled. The models and some simulation results are presented in this work. (author)

The concept of mass angular scattering power and its relation to the diffusion constant

Energy Technology Data Exchange (ETDEWEB)

Sandison, George A.; Papiez, Lech S. [School of Health Sciences, Purdue University, West Lafayette, IN (United States)

1998-09-01

An understanding of the scattering of high energy charged particle beams by tissue is required in radiotherapy since the particle trajectories determine the pattern of radiation dose deposition in patients. Numerical calculations of radiation dose often utilize energy dependent values of the angular scattering power. However, the physics literature is replete with confused interpretations of the concept of angular scattering power and its relation to the single scattering cross section for the medium or the diffusion constant in the diffusional limit. The purpose of this article is to clarify these notions.

Anisotropic constant-roll inflation

Energy Technology Data Exchange (ETDEWEB)

Ito, Asuka; Soda, Jiro [Kobe University, Department of Physics, Kobe (Japan)

2018-01-15

We study constant-roll inflation in the presence of a gauge field coupled to an inflaton. By imposing the constant anisotropy condition, we find new exact anisotropic constant-roll inflationary solutions which include anisotropic power-law inflation as a special case. We also numerically show that the new anisotropic solutions are attractors in the phase space. (orig.)

Simple Exact Algorithm for Transistor Sizing of Low-Power High-Speed Arithmetic Circuits

Directory of Open Access Journals (Sweden)

Tooraj Nikoubin

2010-01-01

Full Text Available A new transistor sizing algorithm, SEA (Simple Exact Algorithm, for optimizing low-power and high-speed arithmetic integrated circuits is proposed. In comparison with other transistor sizing algorithms, simplicity, accuracy, independency of order and initial sizing factors of transistors, and flexibility in choosing the optimization parameters such as power consumption, delay, Power-Delay Product (PDP, chip area or the combination of them are considered as the advantages of this new algorithm. More exhaustive rules of grouping transistors are the main trait of our algorithm. Hence, the SEA algorithm dominates some major transistor sizing metrics such as optimization rate, simulation speed, and reliability. According to approximate comparison of the SEA algorithm with MDE and ADC for a number of conventional full adder circuits, delay and PDP have been improved 55.01% and 57.92% on an average, respectively. By comparing the SEA and Chang's algorithm, 25.64% improvement in PDP and 33.16% improvement in delay have been achieved. All the simulations have been performed with 0.13 m technology based on the BSIM3v3 model using HSpice simulator software.

Brayton dynamic isotope power systems update

International Nuclear Information System (INIS)

Davis, K.A.; Pietsch, A.; Casagrande, R.D.

1986-01-01

Brayton dynamic power systems are uniquely suited for space applications. They are compact and highly efficient, offer inherent reliability due to only one moving part, and utilize a single phase and inert working fluid. Additional features include gas bearings, constant speed, and operation at essentially constant temperature. The design, utilizing an inert gas working fluid and gas bearing, is unaffected by zero gravity and can be easily started and restarted in space at low temperatures. This paper describes the salient features of the BIPS as a Dynamic Isotope Power System (DIPS), summarizes the development work to date, establishes the maturity of the design, provides an update on materials technology, and reviews systems integration considerations

Investigation on a Power Coupling Steering System for Dual-Motor Drive Tracked Vehicles Based on Speed Control

Directory of Open Access Journals (Sweden)

Li Zhai

2017-08-01

Full Text Available Double-motor drive tracked vehicles (2MDTV are widely used in the tracked vehicle industry due to the development of electric vehicle drive systems. The aim of this paper is to solve the problem of insufficient propulsion motor torque in low-speed, small-radius steering and insufficient power in high-speed large-radius steering. In order to do this a new type of steering system with a coupling device is designed and a closed-loop control strategy based on speed is adopted to improve the lateral stability of the vehicle. The work done entails modeling and simulating the 2MDTV and the proposed control strategy in RecurDyn and Matlab/Simulink. The simulation results show that the 2MDTV with the coupling device outputs more torque and power in both steering cases compared to the 2MDTV without the coupling device, and the steering stability of the vehicle is improved by using the strategy based on speed.

Investigation on the Development of a Sliding Mode Controller for Constant Power Loads in Microgrids

Directory of Open Access Journals (Sweden)

Eklas Hossain

2017-07-01

Full Text Available To implement renewable energy resources, microgrid systems have been adopted and developed into the technology of choice to assure mass electrification in the next decade. Microgrid systems have a number of advantages over conventional utility grid systems, however, they face severe instability issues due to the continually increasing constant power loads. To improve the stability of the entire system, the load side compensation technique is chosen because of its robustness and cost effectiveness. In this particular occasion, a sliding mode controller is developed for a microgrid system in the presence of constant power loads to assure a certain control objective of keeping the output voltage constant at 480 V. After that, a robustness analysis of the sliding mode controller against parametric uncertainties was performed and the sliding mode controller’s robustness against parametric uncertainties, frequency variations, and additive white Gaussian noise (AWGN are presented. Later, the performance of the proportional integral derivative (PID and sliding mode controller are compared in the case of nonlinearity, parameter uncertainties, and noise rejection to justify the selection of the sliding mode controller over the PID controller. All the necessary calculations are reckoned mathematically and results are verified in a virtual platform such as MATLAB/Simulink with a positive outcome.

A Review of Electronic Inductor Technique for Power Factor Correction in Three-Phase Adjustable Speed Drives

DEFF Research Database (Denmark)

Davari, Pooya; Yang, Yongheng; Zare, Firuz

2016-01-01

(SiC) power devices. Moreover, the influence of partial loading on component sizing in Adjustable Speed Drives (ASDs) is studied. Finally the analytical loss modelling of power switches is utilized for efficiency measurement. The theoretical analyses are verified by experimental benchmarking in an ASD...

Psychomotor and Motor Speed in Power Athletes Self-Administering Testosterone and Anabolic Steroids.

Science.gov (United States)

Era, Pertti; And Others

1988-01-01

Self-administered testosterone and anabolic steroids resulted in insignificant improvement in psychomotor and motor speed tests of power athletes. This study is part of a larger study on the effects of such drugs on endocrinology, metabolism and neuromuscular functions. Methodolgy and results are discussed. (Author/JL)

Modeling and numerical techniques for high-speed digital simulation of nuclear power plants

International Nuclear Information System (INIS)

Wulff, W.; Cheng, H.S.; Mallen, A.N.

1987-01-01

Conventional computing methods are contrasted with newly developed high-speed and low-cost computing techniques for simulating normal and accidental transients in nuclear power plants. Six principles are formulated for cost-effective high-fidelity simulation with emphasis on modeling of transient two-phase flow coolant dynamics in nuclear reactors. Available computing architectures are characterized. It is shown that the combination of the newly developed modeling and computing principles with the use of existing special-purpose peripheral processors is capable of achieving low-cost and high-speed simulation with high-fidelity and outstanding user convenience, suitable for detailed reactor plant response analyses

Utility-scale variable-speed wind turbines using a doubly-fed generator with a soft-switching power converter

Energy Technology Data Exchange (ETDEWEB)

Weigand, C.H.; Lauw, H.K.; Marckx, D.A. [Electronic Power Conditioning, Inc., Corvallis, OR (United States)

1996-12-31

Utility-scale wind turbines operating at variable RPM have been studied for a considerable period of time. Whereas the increase in energy output originally has been considered the principal benefit of variable-speed operation, the ability to tightly control the drive-train torque by electronic means is becoming another very important cost factor, especially for turbine ratings above 500 kilowatts. This cost benefit becomes even more significant as optimum turbine ratings today are approaching (and surpassing) 1 Megawatt. Having identified the benefits for the turbine, the designer is confronted with the task of finding the most cost-effective variable-speed generation system which allows him to make use of the benefits, yet does not introduce well-known electrical problems associated with state-of-the-art variable-speed generator controls, such as drastically reduced generator winding life, excessive harmonics on the utility, and poor utility power factor. This paper will indicate that for high-power (> 500 kW), utility-scale wind turbines a doubly-fed generator system in connection with a soft-switching resonant power converter is the least-cost variable-speed generation system offering all of the desired benefits, yet avoids the introduction of the potential electrical problems stated above. 3 refs., 3 figs., 1 tab.

On the constant-roll inflation

Science.gov (United States)

Yi, Zhu; Gong, Yungui

2018-03-01

The primordial power spectra of scalar and tensor perturbations during slow-roll inflation are usually calculated with the method of Bessel function approximation. For constant-roll or ultra slow-roll inflation, the method of Bessel function approximation may be invalid. We compare the numerical results with the analytical results derived from the Bessel function approximation, and we find that they differ significantly on super-horizon scales if the constant slow-roll parameter ηH is not small. More accurate method is needed for calculating the primordial power spectrum for constant-roll inflation.

Self-Powered Wind Sensor System for Detecting Wind Speed and Direction Based on a Triboelectric Nanogenerator.

Science.gov (United States)

Wang, Jiyu; Ding, Wenbo; Pan, Lun; Wu, Changsheng; Yu, Hua; Yang, Lijun; Liao, Ruijin; Wang, Zhong Lin

2018-04-24

The development of the Internet of Things has brought new challenges to the corresponding distributed sensor systems. Self-powered sensors that can perceive and respond to environmental stimuli without an external power supply are highly desirable. In this paper, a self-powered wind sensor system based on an anemometer triboelectric nanogenerator (a-TENG, free-standing mode) and a wind vane triboelectric nanogenerator (v-TENG, single-electrode mode) is proposed for simultaneously detecting wind speed and direction. A soft friction mode is adopted instead of a typical rigid friction for largely enhancing the output performance of the TENG. The design parameters including size, unit central angle, and applied materials are optimized to enhance sensitivity, resolution, and wide measurement scale. The optimized a-TENG could deliver an open-circuit voltage of 88 V and short-circuit current of 6.3 μA, corresponding to a maximum power output of 0.47 mW (wind speed of 6.0 m/s), which is capable of driving electronics for data transmission and storage. The current peak value of the a-TENG signal is used for analyzing wind speed for less energy consumption. Moreover, the output characteristics of a v-TENG are further explored, with six actual operation situations, and the v-TENG delivers fast response to the incoming wind and accurately outputs the wind direction data. As a wind sensor system, wind speed ranging from 2.7 to 8.0 m/s can be well detected (consistent with a commercial sensor) and eight regular directions can be monitored. Therefore, the fabricated wind sensor system has great potential in wireless environmental monitoring applications.

Study on application of a high-speed trigger-type SFCL (TSFCL) for interconnection of power systems with different reliabilities

International Nuclear Information System (INIS)

Kim, Hye Ji; Yoon, Yong Tae

2016-01-01

Highlights: • Application of TSFCL to interconnect systems with different reliabilities is proposed. • TSFCL protects a grid by preventing detrimental effects from being delivered through the interconnection line. • A high-speed TSFCL with high impedance for transmission systems is required to be developed. - Abstract: Interconnection of power systems is one effective way to improve power supply reliability. However, differences in the reliability of each power system create a greater obstacle for the stable interconnection of power systems, as after interconnection a high-reliability system is affected by frequent faults in low reliability side systems. Several power system interconnection methods, such as the back-to-back method and the installation of either transformers or series reactors, have been investigated to counteract the damage caused by faults in the other neighboring systems. However, these methods are uneconomical and require complex operational management plans. In this work, a high-speed trigger-type superconducting fault current limiter (TSFCL) with large-impedance is proposed as a solution to maintain reliability and power quality when a high reliability power system is interconnected with a low reliability power system. Through analysis of the reliability index for the numerical examples obtained from a PSCAD/EMTDC simulator, a high-speed TSFCL with a large-impedance is confirmed to be effective for the interconnection between power systems with different reliabilities.

The injection equipment of future high-speed DI diesel engines with respect to power and pollution requirements

Energy Technology Data Exchange (ETDEWEB)

Dolenc, A. (Monobloc Dieselmotoren GmbH, Vienna (AT))

1990-01-01

The development of high specific output DI diesel engines started at the low-speed end some 50 years ago primarily for marine and traction applications. Movement towards the high-speed end has been slow but steady with the majority of truck engines being very conservatively rated. There has been recent major effort on the automotive car and light commercial vehicle diesel application leading to lightweight DI diesel engines with an engine speed of 4000-5000 r/min and a rated power of 50 kW/litre displacement. These are expected to be on the market in a short period of time. The key point of this development has been the injection equipment including combustion control. In this area the use of modulated injection has the possibility of solving power and pollution requirements. (author).

High-speed AC motors

Energy Technology Data Exchange (ETDEWEB)

Jokinen, T.; Arkkio, A. [Helsinki University of Technology Laboratory of Electromechanics, Otaniemi (Finland)

1997-12-31

The paper deals with various types of highspeed electric motors, and their limiting powers. Standard machines with laminated rotors can be utilised if the speed is moderate. The solid rotor construction makes it possible to reach higher power and speed levels than those of laminated rotors. The development work on high-speed motors done at Helsinki University of Technology is presented, too. (orig.) 12 refs.

Compact, Low-Power, and High-Speed Graphene-Based Integrated Photonic Modulator Technology

Science.gov (United States)

2017-11-02

Compact, Low-Power, and High-Speed Graphene- Based Integrated Photonic Modulator Technology The views, opinions and/or findings contained in this...Graphene-Based Integrated Photonic Modulator Technology Report Term: 0-Other Email: sorger@gwu.edu Distribution Statement: 1-Approved for public release...which is an all-time record at Georgia Tech. Protocol Activity Status: Technology Transfer: Nothing to Report PARTICIPANTS: Person Months Worked

Optimal wind energy penetration in power systems: An approach based on spatial distribution of wind speed

International Nuclear Information System (INIS)

Zolfaghari, Saeed; Riahy, Gholam H.; Abedi, Mehrdad; Golshannavaz, Sajjad

2016-01-01

Highlights: • Chronological wind speeds at distinct locations of the wind farm are not the same. • Spatial distribution of wind speed affects wind farm’s output power expectation. • Neglecting wind speed’s spatial doubt leads to mistake in wind energy penetration. • Scenario-based method can be used for effective wind capacity penetration level. - Abstract: Contributing in power system expansions, the present study establishes an efficient scheme for optimal integration of wind energy resources. The proposed approach highly concerns the spatial distribution of wind speed at different points of a wind farm. In mathematical statements, a suitable probability distribution function (PDF) is well-designed for representing such uncertainties. In such conditions, it is likely to have dissimilar output powers for individual and identical wind turbines. Thus, the overall aggregated PDF of a wind farm remarkably influences the critical parameters including the expected power and energy, capacity factor, and the reliability metrics such as loss of load expectation (LOLE) and expected energy not supplied (EENS). Furthermore, the proposed approach is deployed for optimal allocation of wind energy in bulk power systems. Hence, two typical test systems are numerically analyzed to interrogate the performance of the proposed approach. The conducted survey discloses an over/underestimation of harvestable wind energy in the case of overlooking spatial distributions. Thus, inaccurate amounts of wind farm’s capacity factor, output power, energy and reliability indices might be estimated. Meanwhile, the number of wind turbines may be misjudged to be installed. However, the proposed approach yields in a fair judgment regarding the overall performance of the wind farm. Consequently, a reliable penetration level of wind energy to the power system is assured. Extra discussions are provided to deeply assess the promising merits of the founded approach.

Low-latency video transmission over high-speed WPANs based on low-power video compression

DEFF Research Database (Denmark)

Belyaev, Evgeny; Turlikov, Andrey; Ukhanova, Ann

2010-01-01

This paper presents latency-constrained video transmission over high-speed wireless personal area networks (WPANs). Low-power video compression is proposed as an alternative to uncompressed video transmission. A video source rate control based on MINMAX quality criteria is introduced. Practical...

System design of the traction power supply for the high-speed line Beijing - Tianjin

Energy Technology Data Exchange (ETDEWEB)

Altmann, Martin; Fischer, Andreas; Tornow, Torsten [Siemens AG, Erlangen (Germany)

2011-11-15

The high-speed line Beijing - Tianjin connecting the Capital Beijing with the harbour city Tianjin is the first high-speed line in China dedicated only to passenger traffic and is operated at 300 km/h. The commercial service started in due time for the Olympic games in 2008. For the system design and a reliable traction power supply the simulation software Sitras {sup registered} Sidytrac was used. The program incorporates all modules necessary for the overall system design and relating detailed investigations. Measurements during system integration test validated the simulation results. (orig.)

Effect of the Power Balance® hologram on balance, flexibility, strength and speed-coordination among university students

Directory of Open Access Journals (Sweden)

Rafael Merino Marban, Daniel Mayorga Vega, Emilio Fernández Rodríguez, Francisco José Santana Pérez, Oscar Romero Ramos

2011-01-01

Full Text Available Based on the body’s energy field, the inventors of Power Balance® have created a hologram that theoretically runs through frequencies that are in our natural environment. Its creators say that people may experience improve balance, strength, flexibility, endurance, concentration, coordination and recovery time, among others. The purpose of this research is to evaluate the effect of Power Balance® hologram on balance, flexibility, strength and speed-coordination in university students. A sample of 105 young volunteers’ physical education students (age 20.91 ± 3.36 years, mass 69.69 ± 11.35 kg, height 171.70 ± 8.07 cm was used. A between-group experimental design with double-blind control group was used to evaluate the possible effects of the Power Balance ® on the dynamic balance, flexibility, abdominal strength, endurance and speed-coordination measured with the Dynamic Balance Test, Sit and Reach, Sit-ups in 30 seconds and Race 10 x 5 m, respectively. A t of Student for independent and dependent samples was used to assess the potential effects between-group and intra-group, respectively. Power Balance®’s hologram produces no significant effects on the balance, flexibility, strength and speed-coordination among university students

Diagnosis of power generator sets by analyzing the crank shaft angular speed

International Nuclear Information System (INIS)

Desbazeille, M.

2010-07-01

This thesis deals with the diagnosis of a powerful 20-cylinder diesel engine which runs a generator set in a nuclear plant. The objective is to make a diagnosis by analyzing the crank shaft angular speed variations. Only combustion related faults are investigated. As the engine is very large, the first crank shaft natural modes are in the low frequencies. Torsional vibrations of the flexible crank shaft strongly complicate the analysis of the angular speed variations. Little attention has been paid to such large engines in the literature. First, a dynamical model with the assumption of a flexible crank shaft is established. The parameters of the model are optimized with the help of actual data. Then, an original automated diagnosis based on pattern recognition of the angular speed waveforms is proposed. Indeed, any faulty cylinder in combustion stroke will distort the angular speed waveform in a specific way which depends on its location with respect to nodes and anti-nodes of the modes. Reference patterns, representative of the engine conditions, are computed with the model constituting the main originality of this work. Promising results are obtained in operational phase. An experimental fuel leakage fault was correctly diagnosed, including detection and localization of the faulty cylinder and an indication of the severity of the fault. (author)

Higher-order superclustering in the Ostriker explosion scenario I. Three-point correlation functions of clusters in the constant and power-law models

International Nuclear Information System (INIS)

Jing Yipeng.

1989-08-01

We study the three-point correlation functions ρ(r, u, v) of clusters in the two types of explosion models by numerical simulations. The clusters are identified as the ''knots'' where three shells intersect. The shells are assumed to have the constant radii (the constant models) or have the power law radius distributions (the power law models). In both kinds of models, we find that ρ can be approximately expressed by the scaling form: ρ = Q(ξ 1 ξ 2 + ξ 2 ξ 3 + ξ 3 ξ 1 ), and Q is about 1, which are consistent with the observations. More detailed studies of r-, u- and v-dependences of Q show that Q remains constant in the constant models. In the power-law models, Q is independent of the shape parameters u and v, while it has some moderate r-dependences (variations with r about a factor of 1 or 2). (author). 27 refs, 9 figs

A novel 2 T P-channel nano-crystal memory for low power/high speed embedded NVM applications

International Nuclear Information System (INIS)

Zhang Junyu; Wang Yong; Liu Jing; Zhang Manhong; Xu Zhongguang; Huo Zongliang; Liu Ming

2012-01-01

We introduce a novel 2 T P-channel nano-crystal memory structure for low power and high speed embedded non-volatile memory (NVM) applications. By using the band-to-band tunneling-induced hot-electron (BTBTIHE) injection scheme, both high-speed and low power programming can be achieved at the same time. Due to the use of a select transistor, the 'erased states' can be set to below 0 V, so that the periphery HV circuit (high-voltage generating and management) and read-out circuit can be simplified. Good memory cell performance has also been achieved, including a fast program/erase (P/E) speed (a 1.15 V memory window under 10 μs program pulse), an excellent data retention (only 20% charge loss for 10 years). The data shows that the device has strong potential for future embedded NVM applications. (semiconductor devices)

Virtual Impedance Based Stability Improvement for DC Microgrids with Constant Power Loads

DEFF Research Database (Denmark)

Lu, Xiaonan; Sun, Kai; Huang, Lipei

2014-01-01

DC microgrid provides an efficient way to integrate different kinds of renewable energy sources with DC couplings. In this paper, in order to improve the stability of DC microgrids with constant power loads (CPLs), a virtual impedance based method is proposed. The CPLs have inherent instability....... To validate the stability with the above stabilizers in a DC microgrid with parallel interfacing converters and CPL, the impedance matching approach is employed. The output impedance of the source converter and input impedance of the load are calculated respectively, and the influence of droop control...

The Effects of Frontal- and Sagittal-Plane Plyometrics on Change-of-Direction Speed and Power in Adolescent Female Basketball Players.

Science.gov (United States)

McCormick, Brian T; Hannon, James C; Newton, Maria; Shultz, Barry; Detling, Nicole; Young, Warren B

2016-01-01

Plyometrics is a popular training modality for basketball players to improve power and change-of-direction speed. Most plyometric training has used sagittal-plane exercises, but improvements in change-of-direction speed have been greater in multi-direction programs. To determine the benefits of a 6-wk frontal-plane plyometric (FPP) training program compared with a 6-wk sagittal-plane plyometric (SPP) training program with regard to power and change-of-direction speed. Fourteen female varsity high school basketball players participated in the study. Multiple 2 × 2 repeated-measures ANOVAs were used to determine differences for the FPP and SPP groups from preintervention to postintervention on 4 tests of power and 2 tests of change-of-direction speed. There was a group main effect for time in all 6 tests. There was a significant group × time interaction effect in 3 of the 6 tests. The SPP improved performance of the countermovement vertical jump more than the FPP, whereas the FPP improved performance of the lateral hop (left) and lateral-shuffle test (left) more than the SPP. The standing long jump, lateral hop (right), and lateral-shuffle test (right) did not show a significant interaction effect. These results suggest that basketball players should incorporate plyometric training in all planes to improve power and change-of-direction speed.

Control of a Stand-Alone Variable Speed Wind Energy Supply System †

Directory of Open Access Journals (Sweden)

Mohamed M. Hamada

2013-04-01

Full Text Available This paper presents a simple control strategy for the operation of a variable speed stand-alone wind turbine with a permanent magnet synchronous generator (PMSG. The PMSG is connected to a three phase resistive load through a switch mode rectifier and a voltage source inverter. Control of the generator side converter is used to achieve maximum power extraction from the available wind power. Control of the DC-DC bidirectional buck-boost converter, which is connected between batteries bank and DC-link voltage, is used to maintain the DC-link voltage at a constant value. It is also used to make the batteries bank stores the surplus of wind energy and supplies this energy to the load during a wind power shortage. The load side voltage source inverter uses a relatively complex vector control scheme to control the output load voltage in terms of amplitude and frequency. The control strategy works under wind speed variation as well as with variable load. Extensive simulation results have been performed using MATLAB/SIMULINK.

Influence of local wind speed and direction on wind power dynamics – Application to offshore very short-term forecasting

DEFF Research Database (Denmark)

Gallego, Cristobal; Pinson, Pierre; Madsen, Henrik

2011-01-01

Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some of these e......Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some...... on one-step ahead forecasting and a time series resolution of 10 min. It has been found that the local wind direction contributes to model some features of the prevailing winds, such as the impact of the wind direction on the wind variability, whereas the non-linearities related to the power...... transformation process can be introduced by considering the local wind speed. In both cases, conditional parametric models showed a better performance than the one achieved by the regime-switching strategy. The results attained reinforce the idea that each explanatory variable allows the modelling of different...

High-speed Stochastic Fatigue Testing

DEFF Research Database (Denmark)

Brincker, Rune; Sørensen, John Dalsgaard

1990-01-01

Good stochastic fatigue tests are difficult to perform. One of the major reasons is that ordinary servohydraulic loading systems realize the prescribed load history accurately at very low testing speeds only. If the speeds used for constant amplitude testing are applied to stochastic fatigue...

High-speed BWR power plant simulations on the special-purpose peripheral processor AD10

International Nuclear Information System (INIS)

Wulff, W.; Cheng, H.S.; Lekach, S.V.; Mallen, A.N.

1985-01-01

A newly developed technique is described for fast, on-line simulations of normal and accidental transients in nuclear power plants. The technique is based on the utilization of the special-purpose peripheral processor AD10, which is specifically designed for high-speed systems simulations through integration of large systems of nonlinear ordinary differential equations. The Peach Bottom-II Boiling Water Reactor power plant has been simulated and results are presented. It is shown that the new technique not only advances safety analyses but also supports plant monitoring, failure diagnosis and accident mitigation, as well as the training of nuclear power plant operators. (author)

Instantaneous power control of a high speed permanent magnet synchronous generator based on a sliding mode observer and a phase locked loop

Science.gov (United States)

Duan, Jiandong; Fan, Shaogui; Wu, Fengjiang; Sun, Li; Wang, Guanglin

2018-06-01

This paper proposes an instantaneous power control method for high speed permanent magnet synchronous generators (PMSG), to realize the decoupled control of active power and reactive power, through vector control based on a sliding mode observer (SMO), and a phase locked loop (PLL). Consequently, the high speed PMSG has a high internal power factor, to ensure efficient operation. Vector control and accurate estimation of the instantaneous power require an accurate estimate of the rotor position. The SMO is able to estimate the back electromotive force (EMF). The rotor position and speed can be obtained using a combination of the PLL technique and the phase compensation method. This method has the advantages of robust operation, and being resistant to noise when estimating the position of the rotor. Using instantaneous power theory, the relationship between the output active power, reactive power, and stator current of the PMSG is deduced, and the power constraint condition is analysed for operation at the unit internal power factor. Finally, the accuracy of the rotor position detection, the instantaneous power detection, and the control methods are verified using simulations and experiments.

Role of various Dirac covariants in the BS wave functions in decay constant calculations of pseudoscalar mesons using a power counting scheme

International Nuclear Information System (INIS)

Bhatnagar, S.; Mahecha, J.

2008-09-01

We have employed the framework of Bethe-Salpeter equation under Covariant Instantaneous Ansatz to calculate the leptonic decay constants of unequal mass pseudoscalar mesons. In the Dirac structure of BS wave function, the covariants are incorporated from their complete set in accordance with a recently proposed power counting rule, order-by-order in powers of inverse of meson mass. The decay constants are calculated incorporating both Leading Order (LO) as well as Next-to-leading Order (NLO) Dirac covariants. The contribution of both LO as well as NLO covariants to decay constants are studied in detail in this paper. The results are found to improve dramatically, and hence validating the power counting rule which also provides a practical means of incorporating Dirac covariants in the BS wave function of a hadron. (author)

Design optimization under uncertainty and speed variability for a piezoelectric energy harvester powering a tire pressure monitoring sensor

Science.gov (United States)

Toghi Eshghi, Amin; Lee, Soobum; Kazem Sadoughi, Mohammad; Hu, Chao; Kim, Young-Cheol; Seo, Jong-Ho

2017-10-01

Energy harvesting (EH) technologies to power small sized electronic devices are attracting great attention. Wasted energy in a vehicle’s rotating tire has a great potential to enable self-powered tire pressure monitoring sensors (TPMS). Piezoelectric type energy harvesters can be used to collect vibrational energy and power such systems. Due to the presence of harsh acceleration in a rotating tire, a design tradeoff needs to be studied to prolong the harvester’s fatigue life as well as to ensure sufficient power generation. However, the design by traditional deterministic design optimization (DDO) does not show reliable performance due to the lack of consideration of various uncertainty factors (e.g., manufacturing tolerances, material properties, and loading conditions). In this study, we address a new EH design formulation that considers the uncertainty in car speed, dimensional tolerances and material properties, and solve this design problem using reliability-based design optimization (RBDO). The RBDO problem is formulated to maximize compactness and minimize weight of a TPMS harvester while satisfying power and durability requirements. A transient analysis has been done to measure the time varying response of EH such as power generation, dynamic strain, and stress. A conservative design formulation is proposed to consider the expected power from varied speed and stress at higher speed. When compared to the DDO, the RBDO results show that the reliability of EH is increased significantly by scarifying the objective function. Finally, experimental test has been conducted to demonstrate the merits of RBDO design over DDO.

Connecting Fundamental Constants

International Nuclear Information System (INIS)

Di Mario, D.

2008-01-01

A model for a black hole electron is built from three basic constants only: h, c and G. The result is a description of the electron with its mass and charge. The nature of this black hole seems to fit the properties of the Planck particle and new relationships among basic constants are possible. The time dilation factor in a black hole associated with a variable gravitational field would appear to us as a charge; on the other hand the Planck time is acting as a time gap drastically limiting what we are able to measure and its dimension will appear in some quantities. This is why the Planck time is numerically very close to the gravitational/electric force ratio in an electron: its difference, disregarding a π√(2) factor, is only 0.2%. This is not a coincidence, it is always the same particle and the small difference is between a rotating and a non-rotating particle. The determination of its rotational speed yields accurate numbers for many quantities, including the fine structure constant and the electron magnetic moment

Maximum Power Point Tracking in Variable Speed Wind Turbine Based on Permanent Magnet Synchronous Generator Using Maximum Torque Sliding Mode Control Strategy

Institute of Scientific and Technical Information of China (English)

Esmaeil Ghaderi; Hossein Tohidi; Behnam Khosrozadeh

2017-01-01

The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy.In this strategy,fhst,the rotor speed is set at an optimal point for different wind speeds.As a result of which,the tip speed ratio reaches an optimal point,mechanical power coefficient is maximized,and wind turbine produces its maximum power and mechanical torque.Then,the maximum mechanical torque is tracked using electromechanical torque.In this technique,tracking error integral of maximum mechanical torque,the error,and the derivative of error are used as state variables.During changes in wind speed,sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking (MPPT).In this method,the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal.The result of the second order integral in this model includes control signal integrity,full chattering attenuation,and prevention from large fluctuations in the power generator output.The simulation results,calculated by using MATLAB/m-file software,have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator (PMSG).

A new architecture for low-power high-speed pipelined ADCs using double-sampling and opamp-sharing techniques

NARCIS (Netherlands)

Abdinia, S.; Yavari, M.

2009-01-01

This paper presents a low-voltage low-power pipelined ADC with 1V supply voltage in a 90nm CMOS process. A new architecture is proposed to reduce the power consumption in high-speed pipelined analog-to-digital converters (ADCs). The presented architecture utilizes a combination of two current

Nonlinear control for core power of pressurized water nuclear reactors using constant axial offset strategy

Directory of Open Access Journals (Sweden)

Gholam Reza Ansarifar

2015-12-01

Full Text Available One of the most important operations in nuclear power plants is load following, in which an imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation is considered to be a constraint for the load following operation. In this paper, the design of a sliding mode control (SMC, which is a robust nonlinear controller, is presented. SMC is a means to control pressurized water nuclear reactor (PWR power for the load following operation problem in a way that ensures xenon oscillations are kept bounded within acceptable limits. The proposed controller uses constant axial offset (AO strategy to ensure xenon oscillations remain bounded. The constant AO is a robust state constraint for the load following problem. The reactor core is simulated based on the two-point nuclear reactor model with a three delayed neutron groups. The stability analysis is given by means of the Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the SMC exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability. Results show that the proposed controller for the load following operation is so effective that the xenon oscillations are kept bounded in the given region.

The effects of passive leg press training on jumping performance, speed, and muscle power.

Science.gov (United States)

Liu, Chiang; Chen, Chuan-Shou; Ho, Wei-Hua; Füle, Róbert János; Chung, Pao-Hung; Shiang, Tzyy-Yuang

2013-06-01

Passive leg press (PLP) training was developed based on the concepts of the stretch-shortening cycle (SSC) and the benefits of high muscle contraction velocity. Passive leg press training enables lower limb muscle groups to apply a maximum downward force against a platform moved up and down at high frequency by an electric motor. Thus, these muscle groups accomplished both concentric and eccentric isokinetic contractions in a passive, rapid, and repetitive manner. This study investigates the effects of 10 weeks of PLP training at high and low movement frequencies have on jumping performance, speed, and muscle power. The authors selected 30 college students who had not performed systematic resistance training in the previous 6 months, including traditional resistance training at a squat frequency of 0.5 Hz, PLP training at a low frequency of 0.5 Hz, and PLP training at a high frequency of 2.5 Hz, and randomly divided them into 3 groups (n = 10). The participants' vertical jump, drop jump, 30-m sprint performance, explosive force, and SSC efficiency were tested under the same experimental procedures at pre- and post-training. Results reveal that high-frequency PLP training significantly increased participants' vertical jump, drop jump, 30-m sprint performance, instantaneous force, peak power, and SSC efficiency (p training (p training significantly increased participants' vertical jump, 30-m sprint performance, instantaneous force, and peak power (p training only increased participants' 30-m sprint performance and peak power (p training at high movement frequency. A PLP training machine powered by an electrical motor enables muscles of the lower extremities to contract faster compared with voluntary contraction. Therefore, muscle training with high contraction velocity is one of the main methods of increasing muscle power. Passive leg press training is a unique method for enhancing jump performance, speed, and muscle power.

Energy and economic analysis of an ICE-based variable speed-operated micro-cogenerator

Energy Technology Data Exchange (ETDEWEB)

Caresana, Flavio; Bartolini, Carlo Maria [Universita Politecnica delle Marche, Dipartimento di Energetica, Via Brecce Bianche, Ancona (AN) 60100 (Italy); Brandoni, Caterina [Universita Telematica e-Campus, Ingegneria Energetica, Via Isimbardi 10, Novedrate (CO) 22060 (Italy); Feliciotti, Petro [Universita Politecnica delle Marche, Dipartimento di Ingegneria Informatica, Gestionale e dell' Automazione, Via Brecce Bianche, Ancona (AN) 60100 (Italy)

2011-03-15

Micro-combined heat and power (CHP) systems are a key resource to meet the EUCO{sub 2} reduction agreed in the Kyoto Protocol. In the near future they are likely to spread significantly through applications in the residential and service sectors, since they can provide considerably higher primary energy efficiencies than plants generating electricity and heat separately. A 28 kW{sub e} natural gas, automotive-derived internal combustion engine CHP system was modeled with a view to comparing constant and variable speed operation modes. Besides their energy performances, the paper addresses the major factors involved in their economic evaluation and describes a method to assess their economic feasibility. Typical residential and service sector applications were chosen as test cases and the results discussed in terms of energy performances and of profitability. They showed that interesting savings can be obtained with respect to separate generation, and that they are higher for the household application in variable speed operating conditions. In fact the plant's energy performance is greatly enhanced by the possibility, for any given power, to regulate the engine's rotational speed. From the economic viewpoint, despite the higher initial cost of the variable speed concept, the system involves a shorter pay-back period and ensures greater profit. (author)

Energy and economic analysis of an ICE-based variable speed-operated micro-cogenerator

International Nuclear Information System (INIS)

Caresana, Flavio; Brandoni, Caterina; Feliciotti, Petro; Bartolini, Carlo Maria

2011-01-01

Micro-combined heat and power (CHP) systems are a key resource to meet the EUCO 2 reduction agreed in the Kyoto Protocol. In the near future they are likely to spread significantly through applications in the residential and service sectors, since they can provide considerably higher primary energy efficiencies than plants generating electricity and heat separately. A 28 kW e natural gas, automotive-derived internal combustion engine CHP system was modeled with a view to comparing constant and variable speed operation modes. Besides their energy performances, the paper addresses the major factors involved in their economic evaluation and describes a method to assess their economic feasibility. Typical residential and service sector applications were chosen as test cases and the results discussed in terms of energy performances and of profitability. They showed that interesting savings can be obtained with respect to separate generation, and that they are higher for the household application in variable speed operating conditions. In fact the plant's energy performance is greatly enhanced by the possibility, for any given power, to regulate the engine's rotational speed. From the economic viewpoint, despite the higher initial cost of the variable speed concept, the system involves a shorter pay-back period and ensures greater profit.

Determination of the wind power systems load to achieve operation in the maximum energy area

Science.gov (United States)

Chioncel, C. P.; Tirian, G. O.; Spunei, E.; Gillich, N.

2018-01-01

This paper analyses the operation of the wind turbine, WT, in the maximum power point, MPP, by linking the load of the Permanent Magnet Synchronous Generator, PMSG, with the wind speed value. The load control methods at wind power systems aiming an optimum performance in terms of energy are based on the fact that the energy captured by the wind turbine significantly depends on the mechanical angular speed of the wind turbine. The presented control method consists in determining the optimal mechanical angular speed, ωOPTIM, using an auxiliary low power wind turbine, WTAUX, operating without load, at maximum angular velocity, ωMAX. The method relies on the fact that the ratio ωOPTIM/ωMAX has a constant value for a given wind turbine and does not depend on the time variation of the wind speed values.

Nominal power density analysis of thermoelectric pins with non-constant cross sections

International Nuclear Information System (INIS)

Shi, Yaoguang; Mei, Deqing; Yao, Zhehe; Wang, Yancheng; Liu, Haiyan; Chen, Zichen

2015-01-01

Highlights: • Nominal power density of TEGs with non-constant cross sections pins is analyzed. • An analytical model of nominal power density (NPD) is developed. • Influences of shape parameter on NPD for different geometric pins are investigated. • Effects of dimensionless efficiency and the temperature ratio on NPD are examined. - Abstract: The investigation of the geometric structure of TEG (thermoelectric generator) pins is essential, as their geometry determines the performance of devices. In this study, nominal power density (NPD) is used to find a better geometric structure of thermoelectric pins of TEGs, since a comparison of maximum dimensionless efficiencies for different geometric pins cannot be used to identify the optimum geometry. The influence of shape parameter on NPD for TEG pins in linear, quadratic and exponential cross-sectional functions is studied. The NPD decreases when the shape parameter increases for different geometric pins, while the maximum values of NPD are the same. Then, the effects of dimensionless efficiency and the temperature ratio on the NPD are analyzed. The NPD decreases with the increase in dimensionless efficiency and temperature ratio. Pins with linear variation in cross section have the highest NPD among the three geometries of pins evaluated

Assessment of wind speed and wind power through three stations in Egypt, including air density variation and analysis results with rough set theory

International Nuclear Information System (INIS)

Essa, K.S.M.; Embaby, M.; Marrouf, A.A.; Koza, A.M.; Abd El-Monsef, M.E.

2007-01-01

It is well known that the wind energy potential is proportional to both air density and the third power of the wind speed average over a suitable time period. The wind speed and air density have random variables depending on both time and location. The main objective of this work is to derive the most general wind energy potential of the wind formulation putting into consideration the time variable in both wind speed and air density. The correction factor is derived explicitly in terms of the cross-correlation and the coefficients of variation.The application is performed for environmental and wind speed measurements at the Cairo Airport, Kosseir and Hurguada, Egypt. Comparisons are made between Weibull, Rayleigh, and actual data distributions of wind speed and wind power of one year 2005. A Weibull distribution is the best match to the actual probability distribution of wind speed data for most stations. The maximum wind energy potential was 373 W/m 2 in June at Hurguada (Red Sea coast) where the annual mean value was 207 W/m 2 . By Using Rough Set Theory, We Find That the Wind Power Depends on the Wind Speed with greater than air density

Optimal number of circulating water pumps in a nuclear power plant

International Nuclear Information System (INIS)

Xia, Lin; Liu, Deyou; Zhou, Ling; Wang, Feng; Wang, Pei

2015-01-01

Highlights: • We present a novel method to optimize the number of variable speed pumps. • The economic effect of variable speed pumps number optimization is presented. • We present a novel method to optimize the number of constant speed pumps. • The proposed pumps number optimization method is more accurate than the widely used method. - Abstract: A circulating cooling system that uses variable speed pumps (VSPs) or constant-speed pumps (CSPs) as circulating water pumps (CWPs) is optimized to improve the cycle efficiency of nuclear power plants. This study focused on the optimal number of VSPs and CSPs. A novel method is proposed to optimize the number of VSPs with varying dry-bulb temperature and relative humidity, which could help decrease operation costs by $243,310 per year. This method is also used to optimize the number of CSPs and is compared with another widely used method that optimizes the number of CSPs according to the varying condenser inlet water temperature. A comparison shows that the proposed method is more accurate than the widely used method

Optimal number of circulating water pumps in a nuclear power plant

Energy Technology Data Exchange (ETDEWEB)

Xia, Lin [College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, Jiangsu (China); Liu, Deyou, E-mail: liudyhhuc@163.com [College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, Jiangsu (China); Zhou, Ling, E-mail: zlhhu@163.com [College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, Jiangsu (China); Wang, Feng [School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225009, Jiangsu (China); Wang, Pei [College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, Jiangsu (China)

2015-07-15

Highlights: • We present a novel method to optimize the number of variable speed pumps. • The economic effect of variable speed pumps number optimization is presented. • We present a novel method to optimize the number of constant speed pumps. • The proposed pumps number optimization method is more accurate than the widely used method. - Abstract: A circulating cooling system that uses variable speed pumps (VSPs) or constant-speed pumps (CSPs) as circulating water pumps (CWPs) is optimized to improve the cycle efficiency of nuclear power plants. This study focused on the optimal number of VSPs and CSPs. A novel method is proposed to optimize the number of VSPs with varying dry-bulb temperature and relative humidity, which could help decrease operation costs by $243,310 per year. This method is also used to optimize the number of CSPs and is compared with another widely used method that optimizes the number of CSPs according to the varying condenser inlet water temperature. A comparison shows that the proposed method is more accurate than the widely used method.

Influence of the level of fit of a density probability function to wind-speed data on the WECS mean power output estimation

International Nuclear Information System (INIS)

Carta, Jose A.; Ramirez, Penelope; Velazquez, Sergio

2008-01-01

Static methods which are based on statistical techniques to estimate the mean power output of a WECS (wind energy conversion system) have been widely employed in the scientific literature related to wind energy. In the static method which we use in this paper, for a given wind regime probability distribution function and a known WECS power curve, the mean power output of a WECS is obtained by resolving the integral, usually using numerical evaluation techniques, of the product of these two functions. In this paper an analysis is made of the influence of the level of fit between an empirical probability density function of a sample of wind speeds and the probability density function of the adjusted theoretical model on the relative error ε made in the estimation of the mean annual power output of a WECS. The mean power output calculated through the use of a quasi-dynamic or chronological method, that is to say using time-series of wind speed data and the power versus wind speed characteristic of the wind turbine, serves as the reference. The suitability of the distributions is judged from the adjusted R 2 statistic (R a 2 ). Hourly mean wind speeds recorded at 16 weather stations located in the Canarian Archipelago, an extensive catalogue of wind-speed probability models and two wind turbines of 330 and 800 kW rated power are used in this paper. Among the general conclusions obtained, the following can be pointed out: (a) that the R a 2 statistic might be useful as an initial gross indicator of the relative error made in the mean annual power output estimation of a WECS when a probabilistic method is employed; (b) the relative errors tend to decrease, in accordance with a trend line defined by a second-order polynomial, as R a 2 increases

PERFORMANCE OF DIFFERENT CMOS LOGIC STYLES FOR LOW POWER AND HIGH SPEED

OpenAIRE

Sreenivasa Rao.Ijjada; Ayyanna.G; G.Sekhar Reddy; Dr.V.Malleswara Rao

2011-01-01

Designing high-speed low-power circuits with CMOS technology has been a major research problem for many years. Several logic families have been proposed and used to improve circuit performance beyond that of conventional static CMOS family. Fast circuit families are becoming attractive in deep sub micron technologies since the performance benefits obtained from process scaling are decreasing as feature size decreases. This paper presents CMOS differential circuit families such as Dual rail do...

Bicycle Design : A different approach to improving on the world human powered speed records

NARCIS (Netherlands)

Epema, H.K.; Van den Brand, S.; Gregoor, W.; Kooijman, J.D.G.; Pereboom, H.P.; Wielemaker, D.C.; Van der Zweep, C.J.

2012-01-01

The current International Human Powered Vehicle Association world records for faired bicycles stand at 133.284km/h for the 200m flying start speed record and 91.562 km for the hour record. Traditionally the recumbent bicycles that have been developed for breaking one of either of these records have

LONG TERM EFFECTS OF DIFFERENT TRAINING MODALITIES ON POWER, SPEED, SKILL AND ANAEROBIC CAPACITY IN YOUNG MALE BASKETBALL PLAYERS

Directory of Open Access Journals (Sweden)

Mindaugas Balciunas

2006-03-01

Full Text Available The purpose of this study was to identify the effect of 4 months of different training modalities on power, speed, skill and anaerobic capacity in 15-16 year old male basketball players. Thirty five Lithuanian basketball players were randomly assigned into three groups: power endurance group (intermittent exercise, PE, n = 12, general endurance group (continuous exercise, GE, n = 11 and control group (regular basketball training, CG, n = 12. The power endurance model was based in basketball game external structure whereas the general endurance model was based in continuous actions that frequently occur during the basketball game. The training models were used for 16 weeks in sessions conducted 3 times a week during 90 minutes each in the competition period. The following tests were performed: 20 m speed run, Squat jump, Countermovement jump, Running-based Anaerobic Sprint Test (RAST, 2 min. shooting test and the Shuttle ball-dribbling test. A 3×2 repeated measures ANOVA revealed no statistically significant differences in the 20 m speed run, Squat jump and Countermovement jump (p > 0.05. On the other hand, RAST showed significant increases in PE, with greater increases during the 5th and 6th runs. The PE training model also produced a significant improvement in the shuttle ball-dribbling test (48.7 ± 1.5 in the pretest, 45.5 ± 1.3 in the posttest, p < 0.05. Globally, our results suggest that both training modalities were able to maintain initial values of speed and power, however, the anaerobic capacity and skill increased only in the players from the power endurance group. Therefore, the power endurance training (intermittent high intensity exercise may be more beneficial to prepare junior players according to the game cardiovascular and metabolic specific determinants

Power-Quality-Oriented Optimization in Multiple Three-Phase Adjustable Speed Drives

DEFF Research Database (Denmark)

Yang, Yongheng; Davari, Pooya; Blaabjerg, Frede

2016-01-01

As an almost standardized configuration, Diode Rectifiers (DRs) and Silicon-Controlled Rectifiers (SCRs) are commonly employed as the front-end topology in three-phase Adjustable Speed Drive (ASD) systems. Features of this ASD configuration include: structural and control simplicity, small volume......, low cost, and high reliability during operation. Yet, DRs and SCRs bring harmonic distortions in the mains and thus lowering the overall efficiency. Power quality standards/rules are thus released. For multiple ASD systems, certain harmonics of the total grid current can be mitigated by phase......-shifting the currents drawn by SCR-fed drives, and thus it is much flexible to reduce the Total Harmonic Distortion (THD) level in such applications. However, the effectiveness of this harmonic mitigation scheme for multiple ASD systems depends on: a) the number of parallel drives, b) the power levels, and c...

A short-term ensemble wind speed forecasting system for wind power applications

Science.gov (United States)

Baidya Roy, S.; Traiteur, J. J.; Callicutt, D.; Smith, M.

2011-12-01

This study develops an adaptive, blended forecasting system to provide accurate wind speed forecasts 1 hour ahead of time for wind power applications. The system consists of an ensemble of 21 forecasts with different configurations of the Weather Research and Forecasting Single Column Model (WRFSCM) and a persistence model. The ensemble is calibrated against observations for a 2 month period (June-July, 2008) at a potential wind farm site in Illinois using the Bayesian Model Averaging (BMA) technique. The forecasting system is evaluated against observations for August 2008 at the same site. The calibrated ensemble forecasts significantly outperform the forecasts from the uncalibrated ensemble while significantly reducing forecast uncertainty under all environmental stability conditions. The system also generates significantly better forecasts than persistence, autoregressive (AR) and autoregressive moving average (ARMA) models during the morning transition and the diurnal convective regimes. This forecasting system is computationally more efficient than traditional numerical weather prediction models and can generate a calibrated forecast, including model runs and calibration, in approximately 1 minute. Currently, hour-ahead wind speed forecasts are almost exclusively produced using statistical models. However, numerical models have several distinct advantages over statistical models including the potential to provide turbulence forecasts. Hence, there is an urgent need to explore the role of numerical models in short-term wind speed forecasting. This work is a step in that direction and is likely to trigger a debate within the wind speed forecasting community.

Event-driven control of a speed varying digital displacement machine

DEFF Research Database (Denmark)

Pedersen, Niels Henrik; Johansen, Per; Andersen, Torben O.

2017-01-01

. The controller synthesis is carried out as a discrete optimal deterministic problem with full state feedback. Based on a linear analysis of the feedback control system, stability is proven in a pre-specified operation region. Simulation of a non-linear evaluation model with the controller implemented shows great...... be treated as a Discrete Linear Time Invariant control problem with synchronous sampling rate. To make synchronous linear control theory applicable for a variable speed digital displacement machine, a method based on event-driven control is presented. Using this method, the time domain differential equations...... are converted into the spatial (position) domain to obtain a constant sampling rate and thus allowing for use of classical control theory. The method is applied to a down scaled digital fluid power motor, where the motor speed is controlled at varying references under varying pressure and load torque conditions...

An innovative high-power constant-current pulsed-arc power-supply for a high-density pulsed-arc-plasma ion-source using a LaB6-filament.

Science.gov (United States)

Ueno, A; Oguri, H; Ikegami, K; Namekawa, Y; Ohkoshi, K; Tokuchi, A

2010-02-01

An innovative high-power constant-current (CC) pulsed-arc (PA) power-supply (PS) indispensable for a high-density PA plasma ion-source using a lanthanum hexaboride (LaB(6)) filament was devised by combining a constant-voltage (CV) PA-PS, which is composed of an insulated gate bipolar transistor (IGBT) switch, a CV direct-current (dc) PS and a 270 mF capacitor with a CC-PA-PS, which is composed of an IGBT-switch, a CC-dc-PS and a 400 microH inductor, through the inductor. The hybrid-CC-PA-PS succeeded in producing a flat arc-pulse with a peak power of 56 kW (400 A x 140 V) and a duty factor of more than 1.5% (600 micros x 25 Hz) for Japan Proton Accelerator Research Complex (J-PARC) H(-) ion-source stably. It also succeeded in shortening the 99% rising-time of the arc-pulse-current to about 20 micros and tilting up or down the arc-pulse-current arbitrarily and almost linearly by changing the setting voltage of its CV-dc-PS.

An innovative high-power constant-current pulsed-arc power-supply for a high-density pulsed-arc-plasma ion-source using a LaB6-filament

International Nuclear Information System (INIS)

Ueno, A.; Oguri, H.; Ikegami, K.; Namekawa, Y.; Ohkoshi, K.; Tokuchi, A.

2010-01-01

An innovative high-power constant-current (CC) pulsed-arc (PA) power-supply (PS) indispensable for a high-density PA plasma ion-source using a lanthanum hexaboride (LaB 6 ) filament was devised by combining a constant-voltage (CV) PA-PS, which is composed of an insulated gate bipolar transistor (IGBT) switch, a CV direct-current (dc) PS and a 270 mF capacitor with a CC-PA-PS, which is composed of an IGBT-switch, a CC-dc-PS and a 400 μH inductor, through the inductor. The hybrid-CC-PA-PS succeeded in producing a flat arc-pulse with a peak power of 56 kW (400 Ax140 V) and a duty factor of more than 1.5%(600 μsx25 Hz) for Japan Proton Accelerator Research Complex (J-PARC) H - ion-source stably. It also succeeded in shortening the 99% rising-time of the arc-pulse-current to about 20 μs and tilting up or down the arc-pulse-current arbitrarily and almost linearly by changing the setting voltage of its CV-dc-PS.

Reactive power generation in high speed induction machines by continuously occurring space-transients

Science.gov (United States)

Laithwaite, E. R.; Kuznetsov, S. B.

1980-09-01

A new technique of continuously generating reactive power from the stator of a brushless induction machine is conceived and tested on a 10-kw linear machine and on 35 and 150 rotary cage motors. An auxiliary magnetic wave traveling at rotor speed is artificially created by the space-transient attributable to the asymmetrical stator winding. At least two distinct windings of different pole-pitch must be incorporated. This rotor wave drifts in and out of phase repeatedly with the stator MMF wave proper and the resulting modulation of the airgap flux is used to generate reactive VA apart from that required for magnetization or leakage flux. The VAR generation effect increases with machine size, and leading power factor operation of the entire machine is viable for large industrial motors and power system induction generators.

Design of a Solid-State Fast Voltage Compensator for klystron modulators requiring constant AC power consumption

CERN Document Server

Aguglia, Davide; Viarouge, Philippe; Cros, Jerome

2014-01-01

This paper proposes a novel topological solution for klystron modulators integrating a Fast Voltage Compensator which allows an operation at constant power consumption from the utility grid. This kind of solution is mandatory for the CLIC project under study, which requires several hundreds of synchronously operated klystron modulators for a total pulsed power of 39 GW. The topology is optimized for the challenging CLIC specifications, which require a very precise output voltage flat-top as well as fast rise and fall times (3µs). The Fast Voltage Compensator is integrated in the modulator such that it only has to manage the capacitor charger current and a fraction of the charging voltage. Consequently, its dimensioning power and cost is minimized.

Partial analysis of wind power limit for large disturbance using fixed speed wind turbine

International Nuclear Information System (INIS)

Santos Fuentefria, Ariel; Cairo Rodriguez, Daniel; Boza Valerino, Juan Gualberto

2014-01-01

The amount of wind power that allow an electric network without losing his stability as known as wind power limit. The wind power limit fundamentally depends on the wind turbine technology and the weakness level of the system. To know the system behaviors in dynamic performance having into account the worst disturbance is a very important matter, a short circuit in one of the most power transference line or the loss of a large generation unit was a large disturbance that can affect system stability. The wind power limit may change with the nature of the disturbance. To know the wind power limit considering this conditions allow use the wind at maximum level. In the present paper the behavior of fixed speed wind turbine for different fault types is analyzed, at those conditions, the wind power is increasing until the system become voltage unstable. For the analysis the IEEE 14 Bus Test Case is used. The Power System Analysis Toolbox (PSAT) package is used for the simulation. (author)

Improvement of maximum power point tracking perturb and observe algorithm for a standalone solar photovoltaic system

International Nuclear Information System (INIS)

Awan, M.M.A.; Awan, F.G.

2017-01-01

Extraction of maximum power from PV (Photovoltaic) cell is necessary to make the PV system efficient. Maximum power can be achieved by operating the system at MPP (Maximum Power Point) (taking the operating point of PV panel to MPP) and for this purpose MPPT (Maximum Power Point Trackers) are used. There are many tracking algorithms/methods used by these trackers which includes incremental conductance, constant voltage method, constant current method, short circuit current method, PAO (Perturb and Observe) method, and open circuit voltage method but PAO is the mostly used algorithm because it is simple and easy to implement. PAO algorithm has some drawbacks, one is low tracking speed under rapid changing weather conditions and second is oscillations of PV systems operating point around MPP. Little improvement is achieved in past papers regarding these issues. In this paper, a new method named 'Decrease and Fix' method is successfully introduced as improvement in PAO algorithm to overcome these issues of tracking speed and oscillations. Decrease and fix method is the first successful attempt with PAO algorithm for stability achievement and speeding up of tracking process in photovoltaic system. Complete standalone photovoltaic system's model with improved perturb and observe algorithm is simulated in MATLAB Simulink. (author)

Design, manufacture and evaluation of a new flexible constant velocity mechanism for transmission of power between parallel shafts

Energy Technology Data Exchange (ETDEWEB)

Yaghoubi, Majid [University of Tehran, Tehran (Iran, Islamic Republic of); Sanaeifar, Alireza [Shiraz University, Shiraz (Iran, Islamic Republic of)

2015-08-15

This paper presents a new mechanism (coupling) for power transmission between parallel shafts in more ranges. The mechanism consists of one drive shaft and one driven shaft, 3 S-shape transmitter links and 8 connecting links. The advantage of this mechanism is that the velocity ratio between input and output shafts remains constant at all movements, and its capacity to offset misalignments is greater than that of other couplings. This research also includes a kinematic analysis and simulations using Visual NASTRAN, Autodesk inventor dynamic and COSMOS motion to prove that the mechanism exhibits a constant velocity. Finally, the mechanism was fabricated and evaluated; results showed that the mechanism can practically transmit a constant velocity ratio.

Design, manufacture and evaluation of a new flexible constant velocity mechanism for transmission of power between parallel shafts

International Nuclear Information System (INIS)

Yaghoubi, Majid; Sanaeifar, Alireza

2015-01-01

This paper presents a new mechanism (coupling) for power transmission between parallel shafts in more ranges. The mechanism consists of one drive shaft and one driven shaft, 3 S-shape transmitter links and 8 connecting links. The advantage of this mechanism is that the velocity ratio between input and output shafts remains constant at all movements, and its capacity to offset misalignments is greater than that of other couplings. This research also includes a kinematic analysis and simulations using Visual NASTRAN, Autodesk inventor dynamic and COSMOS motion to prove that the mechanism exhibits a constant velocity. Finally, the mechanism was fabricated and evaluated; results showed that the mechanism can practically transmit a constant velocity ratio.

Transient analysis of variable-speed wind turbines at wind speed disturbances and a pitch control malfunction

International Nuclear Information System (INIS)

Melicio, R.; Mendes, V.M.F.; Catalao, J.P.S.

2011-01-01

As wind power generation undergoes rapid growth, new technical challenges emerge: dynamic stability and power quality. The influence of wind speed disturbances and a pitch control malfunction on the quality of the energy injected into the electric grid is studied for variable-speed wind turbines with different power-electronic converter topologies. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with permanent magnet synchronous generators. The performance of disturbance attenuation and system robustness is ascertained. Simulation results are presented and conclusions are duly drawn.

Transient analysis of variable-speed wind turbines at wind speed disturbances and a pitch control malfunction

Energy Technology Data Exchange (ETDEWEB)

Melicio, R. [Department of Electromechanical Engineering, University of Beira Interior, R. Fonte do Lameiro, 6201-001 Covilha (Portugal); Mendes, V.M.F. [Department of Electrical Engineering and Automation, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emidio Navarro, 1950-062 Lisbon (Portugal); Catalao, J.P.S. [Department of Electromechanical Engineering, University of Beira Interior, R. Fonte do Lameiro, 6201-001 Covilha (Portugal); Center for Innovation in Electrical and Energy Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)

2011-04-15

As wind power generation undergoes rapid growth, new technical challenges emerge: dynamic stability and power quality. The influence of wind speed disturbances and a pitch control malfunction on the quality of the energy injected into the electric grid is studied for variable-speed wind turbines with different power-electronic converter topologies. Additionally, a new control strategy is proposed for the variable-speed operation of wind turbines with permanent magnet synchronous generators. The performance of disturbance attenuation and system robustness is ascertained. Simulation results are presented and conclusions are duly drawn. (author)

Inflation with a smooth constant-roll to constant-roll era transition

Science.gov (United States)

Odintsov, S. D.; Oikonomou, V. K.

2017-07-01

In this paper, we study canonical scalar field models, with a varying second slow-roll parameter, that allow transitions between constant-roll eras. In the models with two constant-roll eras, it is possible to avoid fine-tunings in the initial conditions of the scalar field. We mainly focus on the stability of the resulting solutions, and we also investigate if these solutions are attractors of the cosmological system. We shall calculate the resulting scalar potential and, by using a numerical approach, we examine the stability and attractor properties of the solutions. As we show, the first constant-roll era is dynamically unstable towards linear perturbations, and the cosmological system is driven by the attractor solution to the final constant-roll era. As we demonstrate, it is possible to have a nearly scale-invariant power spectrum of primordial curvature perturbations in some cases; however, this is strongly model dependent and depends on the rate of the final constant-roll era. Finally, we present, in brief, the essential features of a model that allows oscillations between constant-roll eras.

An adaptive nonlinear internal-model control for the speed control of homopolar salient-pole BLDC motor

Science.gov (United States)

CheshmehBeigi, Hassan Moradi

2018-05-01

In this paper, a novel speed control method for Homopolar Brushless DC (HBLDC) motor based on the adaptive nonlinear internal-model control (ANIMC) is presented. Rotor position information is obtained online by the Hall-Effect sensors placed on the motor's shaft, and is used to calculate the accurate model and accurate inverse model of the HBLDC motor. The online inverse model of the motor is used in the controller structure. To suppress the reference ? error, the negative feedback of difference between the motor speed and its model output ? is applied in the proposed controller. An appropriate signal is the output of the controller, which drives the power switches to converge the motor speed to the constant desired speed. Simulations and experiments are carried out on a ? three-phase HBLDC motor. The proposed drive system operates well in the speed response and has good robustness with respect to the disturbances. To validate the theoretical analysis, several experimental results are discussed in this paper.

Brane world cosmologies with varying speed of light

International Nuclear Information System (INIS)

Youm, Donam

2001-02-01

We study cosmologies in the Randall-Sundrum models, incorporating the possibility of time-varying speed of light and Newton's constant. The cosmologies with varying speed of light (VSL) were proposed by Moffat and by Albrecht and Magueijo as an alternative to inflation for solving the cosmological problems. We consider the case in which the speed of light varies with time after the radion or the scale of the extra dimension has been stabilized. We elaborate on the conditions under which the flatness problem and the cosmological constant problem can be resolved. Particularly, the VSL cosmologies may provide a possible mechanism for bringing the quantum corrections to the fine-tuned brane tensions after the SUSY breaking under control. (author)

A high speed, low power consumption LVDS interface for CMOS pixel sensors

Energy Technology Data Exchange (ETDEWEB)

Shi, Zhan, E-mail: sz1134@163.com [Dalian University of Technology, No. 2 Linggong Road, 116024 Dalian (China); Tang, Zhenan, E-mail: tangza@dlut.edu.cn [Dalian University of Technology, No. 2 Linggong Road, 116024 Dalian (China); Tian, Yong [Dalian University of Technology, No. 2 Linggong Road, 116024 Dalian (China); Pham, Hung; Valin, Isabelle; Jaaskelainen, Kimmo [IPHC, 23 rue du Loess 67037 Strasbourg (France); CNRS, UMR7178, 67037 Strasbourg (France)

2015-01-01

The use of CMOS Pixel Sensors (CPSs) offers a promising approach to the design of vertex detectors in High Energy Physics (HEP) experiments. As the CPS equipping the upgraded Solenoidal Tracker at RHIC (STAR) pixel detector, ULTIMATE perfectly illustrates the potential of CPSs for HEP applications. However, further development of CPSs with respect to readout speed is required to fulfill the readout time requirement of the next generation HEP detectors, such as the upgrade of A Large Ion Collider Experiment (ALICE) Inner Tracking System (ITS), the International Linear Collider (ILC), and the Compressed Baryonic Matter (CBM) vertex detectors. One actual limitation of CPSs is related to the speed of the Low-Voltage Differential Signaling (LVDS) circuitry implementing the interface between the sensor and the Data Acquisition (DAQ) system. To improve the transmission rate while keeping the power consumption at a low level, a source termination technique and a special current comparator were adopted for the LVDS driver and receiver, respectively. Moreover, hardening techniques are used. The circuitry was designed and submitted for fabrication in a 0.18-µm CMOS Image Sensor (CIS) process at the end of 2011. The test results indicated that the LVDS driver and receiver can operate properly at the data rate of 1.2 Gb/s with power consumption of 19.6 mW.

Relationship between strength, power, speed, and change of direction performance of female softball players.

Science.gov (United States)

Nimphius, Sophia; McGuigan, Michael R; Newton, Robert U

2010-04-01

The purpose of this study was to investigate (a) the cross-sectional relationship of strength, power, and performance variables in trained female athletes and (b) determine if the relationship between these variables changes over the course of a season. Ten female softball players (age = 18.1 +/- 1.6 years, height = 166.5 +/- 8.9 cm, and weight = 72.4 +/- 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (one repetition maximum [1RM]), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, unloaded countermovement vertical jump height (VJH) 1 base and 2 base sprint performance and change of direction performance on dominant and nondominant sides. The testing sessions occurred pre, mid, and post a 20-week training period. Relationship between body weight (BW), relative strength (1RM/BW), VJH, relative PP, relative PF, PV, speed, and change of direction variables were assessed by Pearson product-moment correlation coefficient at each testing session. Significant relationships were found across all time points with BW, speed, and change of direction measures (r = 0.70-0.93) and relative strength and measures of speed and change of direction ability (r = -0.73-0.85). There were no significant relationships between VJH and any measure of performance at any time point. In conclusion, BW and relative strength have strong to very strong correlations with speed and change of direction ability, and these correlations remain consistent over the course of the season. However, it seems as if many relationships vary with time, and their relationships should therefore be investigated longitudinally to better determine if these cross-sectional relationships truly reflect a deterministic relationship.

High-throughput machining using a high-average power ultrashort pulse laser and high-speed polygon scanner

Science.gov (United States)

Schille, Joerg; Schneider, Lutz; Streek, André; Kloetzer, Sascha; Loeschner, Udo

2016-09-01

High-throughput ultrashort pulse laser machining is investigated on various industrial grade metals (aluminum, copper, and stainless steel) and Al2O3 ceramic at unprecedented processing speeds. This is achieved by using a high-average power picosecond laser in conjunction with a unique, in-house developed polygon mirror-based biaxial scanning system. Therefore, different concepts of polygon scanners are engineered and tested to find the best architecture for high-speed and precision laser beam scanning. In order to identify the optimum conditions for efficient processing when using high-average laser powers, the depths of cavities made in the samples by varying the processing parameter settings are analyzed and, from the results obtained, the characteristic removal values are specified. For overlapping pulses of optimum fluence, the removal rate is as high as 27.8 mm3/min for aluminum, 21.4 mm3/min for copper, 15.3 mm3/min for stainless steel, and 129.1 mm3/min for Al2O3, when a laser beam of 187 W average laser powers irradiates. On stainless steel, it is demonstrated that the removal rate increases to 23.3 mm3/min when the laser beam is very fast moving. This is thanks to the low pulse overlap as achieved with 800 m/s beam deflection speed; thus, laser beam shielding can be avoided even when irradiating high-repetitive 20-MHz pulses.

Capacitated Vehicle Routing with Non-Uniform Speeds

DEFF Research Database (Denmark)

Gørtz, Inge Li; Molinaro, Marco; Nagarajan, Viswanath

2011-01-01

-uniform speeds (that we call Heterogenous CVRP), and present a constant-factor approximation algorithm. The technical heart of our result lies in achieving a constant approximation to the following TSP variant (called Heterogenous TSP). Given a metric denoting distances between vertices, a depot r containing k...

Influence of the level of fit of a density probability function to wind-speed data on the WECS mean power output estimation

Energy Technology Data Exchange (ETDEWEB)

Carta, Jose A. [Department of Mechanical Engineering, University of Las Palmas de Gran Canaria, Campus de Tafira s/n, 35017 Las Palmas de Gran Canaria, Canary Islands (Spain); Ramirez, Penelope; Velazquez, Sergio [Department of Renewable Energies, Technological Institute of the Canary Islands, Pozo Izquierdo Beach s/n, 35119 Santa Lucia, Gran Canaria, Canary Islands (Spain)

2008-10-15

Static methods which are based on statistical techniques to estimate the mean power output of a WECS (wind energy conversion system) have been widely employed in the scientific literature related to wind energy. In the static method which we use in this paper, for a given wind regime probability distribution function and a known WECS power curve, the mean power output of a WECS is obtained by resolving the integral, usually using numerical evaluation techniques, of the product of these two functions. In this paper an analysis is made of the influence of the level of fit between an empirical probability density function of a sample of wind speeds and the probability density function of the adjusted theoretical model on the relative error {epsilon} made in the estimation of the mean annual power output of a WECS. The mean power output calculated through the use of a quasi-dynamic or chronological method, that is to say using time-series of wind speed data and the power versus wind speed characteristic of the wind turbine, serves as the reference. The suitability of the distributions is judged from the adjusted R{sup 2} statistic (R{sub a}{sup 2}). Hourly mean wind speeds recorded at 16 weather stations located in the Canarian Archipelago, an extensive catalogue of wind-speed probability models and two wind turbines of 330 and 800 kW rated power are used in this paper. Among the general conclusions obtained, the following can be pointed out: (a) that the R{sub a}{sup 2} statistic might be useful as an initial gross indicator of the relative error made in the mean annual power output estimation of a WECS when a probabilistic method is employed; (b) the relative errors tend to decrease, in accordance with a trend line defined by a second-order polynomial, as R{sub a}{sup 2} increases. (author)

Improvement of low speed induction generator performances and reducing the power of excitation and voltage control system

Energy Technology Data Exchange (ETDEWEB)

Budisan, N. [Politechnica Univ. of Timisoara (Romania); Hentea, T.; Mahil, S. [Purdue Univ. Calumet, Hammond, IN (United States); Madescu, G. [Romanian Academy, Timisoara (Romania)

1996-12-31

In this paper we present the results of our investigations concerning the utilization of induction generators at very low speed. It is shown that, by proper design, it is possible to obtain high efficiency and high power factor values. The optimized induction generators require lower reactive power resulting in lower size and price of the excitation control system. 4 refs., 2 figs.

A low power 20 GHz comparator in 90 nm COMS technology

Science.gov (United States)

Kai, Tang; Qiao, Meng; Zhigong, Wang; Ting, Guo

2014-05-01

A low power 20 GHz CMOS dynamic latched regeneration comparator for ultra-high-speed, low-power analog-to-digital converters (ADCs) is proposed. The time constant in both the tracking and regeneration phases of the latch are analyzed based on the small signal model. A dynamic source-common logic (SCL) topology is adopted in the master-slave latch to increase the tracking and regeneration speeds. Implemented in 90 nm CMOS technology, this comparator only occupies a die area of 65 × 150 μm2 with a power dissipation of 14 mW from a 1.2 V power supply. The measurement results show that the comparator can work up to 20 GHz. Operating with an input frequency of 1 GHz, the circuit can oversample up to 20 Giga-sampling-per-second (GSps) with 5 bits resolution; while operating at Nyquist, the comparator can sample up to 20 GSps with 4 bits resolution. The comparator has been successfully used in a 20 GSps flash ADC and the circuit can be also used in other high speed applications.

Speed regulating Effects of Incentive-based Intelligent Speed Adaptation in the short and medium term

DEFF Research Database (Denmark)

Agerholm, Niels

Speed regulating Effects of Incentive-based Intelligent Speed Adaptation in the short and medium term Despite massive improvements in vehicles’ safety equipment, more information and safer road network, inappropriate road safety is still causing that more than 250 people are killed and several...... thousands injured each year in Denmark. Until a few years ago the number of fatalities in most countries had decreased while the amount of traffic increased. However, this trend has been replaced by a more uncertain development towards a constant or even somewhat increasing risk. Inappropriate speeding...... is a central cause for the high number of fatalities on the roads. Despite speed limits, speed limit violating driving behaviour is still widespread in Denmark. Traditional solutions to prevent speed violation have been enforcement, information, and enhanced road design. It seems, however, hard to achieve...

Production in constant evolution

International Nuclear Information System (INIS)

Lozano, T.

2009-01-01

The Cofrentes Nuclear Power Plant now has 25 years of operation behind it: a quarter century adding value and demonstrating the reasons why it is one of the most important energy producing facilities in the Spanish power market. Particularly noteworthy is the enterprising spirit of the plant, which has strived to continuously improve with the large number of modernization projects that it has undertaken over the past 25 years. The plant has constantly evolved thanks to the amount of investments made to improve safety and reliability and the perseverance to stay technologically up to date. Efficiency, training and teamwork have been key to the success of the plant over these 25 years of constant change and progress. (Author)

Power conditioning accessories. Construction of a delayed drop-out relay and test of constant voltage transformers

International Nuclear Information System (INIS)

Keroe, E.; Kaufmann, H.; Koeck, J.; Scarpatetti, R.; Vuister, P.

1983-10-01

A delayed drop-out relay aimed to protect electronic measuring equipment during voltage fluctuations and power failures and transients is described. The results of a test on the performance of three resonant voltage transformers (GOULD GT 3000, CVT Isoreg 15-025 and Philips 1412/00) coupled with this relay, are presented. It is found that with this set-up, instrument malfunction and breakdown can be effectively prevented under the normal power conditions met in European countries or the USA. Under more severe conditions, usually met in the developing countries, a more careful selection has to be made; the test recommends the Philips transformer. It is also recommended that for best results the constant voltage transformers should be used at 75-80% of their rated power

Energy saving opportunity with variable speed drive in primary air-handling unit

International Nuclear Information System (INIS)

Li, J.S.M.

2007-01-01

Air conditioners used in the court buildings in Kowloon City, Hong Kong were retrofitted with variable speed drives in the primary air handling unit (PAU) in an effort to reduce energy consumption. The initial effect of this retrofit was investigated along with the feasibility of using a carbon dioxide (CO 2 ) based demand control ventilation to reduce energy consumption while optimizing indoor air quality. The air flow in most air conditioning fans is either constant or controlled by motorized inlet guide vanes. Although this controls the flow and may reduce the load on the fan, this constriction adds an energy loss, resulting in inefficient operation. Variable speed drives should be used on the PAU in order to maintain system efficiency. As the speed of the fans are reduced, the flow will decrease proportionally, while the power required by the fan will reduce the cube of the speed. Therefore, if the fresh air supply can be controlled by reducing the speed of the fan motor, then flow control would be more efficient. The energy saving associated with variable fresh air supply flow rate was evaluated along with the cost to building owners. This paper presented the results of the potential energy and cost savings associated with this retrofit, and included implementation cost and pay back period. It was estimated that about 20 per cent of power consumption and electricity costs can be saved per year, with a simple payback period of 2 years. 7 refs., 3 tabs., 3 figs

Standards for measurements and testing of wind turbine power quality

Energy Technology Data Exchange (ETDEWEB)

Soerensen, P [Risoe National Lab., Roskilde (Denmark); Gerdes, G; Klosse, R; Santjer, F [DEWI, Wilhelmshaven (Germany); Robertson, N; Davy, W [NEL, Glasgow (United Kingdom); Koulouvari, M; Morfiadakis, E [CRES, Pikermi (Greece); Larsson, Aa [Chalmers Univ. of Technology, Goeteborg (Sweden)

1999-03-01

The present paper describes the work done in power quality sub-task of the project `European Wind Turbine Testing Procedure Developments` funded by the EU SMT program. The objective of the power quality sub-task has been to make analyses and new recommendation(s) for the standardisation of measurement and verification of wind turbine power quality. The work has been organised in three major activities. The first activity has been to propose measurement procedures and to verify existing and new measurement procedures. This activity has also involved a comparison of the measurements and data processing of the participating partners. The second activity has been to investigate the influence of terrain, grid properties and wind farm summation on the power quality of wind turbines with constant rotor speed. The third activity has been to investigate the influence of terrain, grid properties and wind farm summation on the power quality of wind turbines with variable rotor speed. (au)

Temperature prediction in high speed bone grinding using motor PWM signal.

Science.gov (United States)

Tai, Bruce L; Zhang, Lihui; Wang, Anthony C; Sullivan, Stephen; Wang, Guangjun; Shih, Albert J

2013-10-01

This research explores the feasibility of using motor electrical feedback to estimate temperature rise during a surgical bone grinding procedure. High-speed bone grinding is often used during skull base neurosurgery to remove cranial bone and approach skull base tumors through the nasal corridor. Grinding-induced heat could propagate and potentially injure surrounding nerves and arteries, and therefore, predicting the temperature in the grinding region would benefit neurosurgeons during the operation. High-speed electric motors are controlled by pulse-width-modulation (PWM) to alter the current input and thus maintain the rotational speed. Assuming full mechanical to thermal power conversion in the grinding process, PWM can be used as feedback for heat generation and temperature prediction. In this study, the conversion model was established from experiments under a variety of grinding conditions and an inverse heat transfer method to determine heat flux. Given a constant rotational speed, the heat conversion was represented by a linear function, and could predict temperature from the experimental data with less than 20% errors. Such results support the advance of this technology for practical application. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Kummer strikes back : new DH speed records

NARCIS (Netherlands)

Bernstein, D.J.; Chuengsatiansup, C.; Lange, T.; Schwabe, P.; Sarkar, P.; Iwata, T.

2014-01-01

This paper sets new speed records for high-security constant-time variable-base-point Diffie-Hellman software: 305395 Cortex-A8-slow cycles; 273349 Cortex-A8-fast cycles; 88916 Sandy Bridge cycles; 88448 Ivy Bridge cycles; 54389 Haswell cycles. There are no higher speeds in the literature for any of

L1 Adaptive Speed Control of a Small Wind Energy Conversion System for Maximum Power Point Tracking

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Rasmussen, Claus Nygaard

2014-01-01

This paper presents the design of an L1 adaptive controller for maximum power point tracking (MPPT) of a small variable speed Wind Energy Conversion System (WECS). The proposed controller generates the optimal torque command for the vector controlled generator side converter (GSC) based on the wi......) is used to carry out case studies using Matlab/Simulink. The case study results show that the designed L1 adaptive controller has good tracking performance even with unmodeled dynamics and in the presence of parameter uncertainties and unknown disturbances.......This paper presents the design of an L1 adaptive controller for maximum power point tracking (MPPT) of a small variable speed Wind Energy Conversion System (WECS). The proposed controller generates the optimal torque command for the vector controlled generator side converter (GSC) based on the wind...

Voluntary muscle activation improves with power training and is associated with changes in gait speed in mobility-limited older adults

DEFF Research Database (Denmark)

Hvid, Lars G; Strotmeyer, Elsa S; Skjødt, Mathias

2016-01-01

Incomplete voluntary muscle activation may contribute to impaired muscle mechanical function and physical function in older adults. Exercise interventions have been shown to increase voluntary muscle activation, although the evidence is sparse for mobility-limited older adults, particularly...... in association with physical function. This study examined the effects of 12weeks of power training on outcomes of voluntary muscle activation and gait speed in mobility-limited older adults from the Healthy Ageing Network of Competence (HANC) study. We included 37 older men and women with a usual gait speed...... in TG (r=0.67, pactivation is improved in mobility-limited older adults following 12-weeks of progressive power training, and is associated with improved maximal gait speed. Incomplete voluntary muscle activation should be considered one of the key mechanisms...

Wind, Wave, and Tidal Energy Without Power Conditioning

Science.gov (United States)

Jones, Jack A.

2013-01-01

Most present wind, wave, and tidal energy systems require expensive power conditioning systems that reduce overall efficiency. This new design eliminates power conditioning all, or nearly all, of the time. Wind, wave, and tidal energy systems can transmit their energy to pumps that send high-pressure fluid to a central power production area. The central power production area can consist of a series of hydraulic generators. The hydraulic generators can be variable displacement generators such that the RPM, and thus the voltage, remains constant, eliminating the need for further power conditioning. A series of wind blades is attached to a series of radial piston pumps, which pump fluid to a series of axial piston motors attached to generators. As the wind is reduced, the amount of energy is reduced, and the number of active hydraulic generators can be reduced to maintain a nearly constant RPM. If the axial piston motors have variable displacement, an exact RPM can be maintained for all, or nearly all, wind speeds. Analyses have been performed that show over 20% performance improvements with this technique over conventional wind turbines

Constant Jacobian Matrix-Based Stochastic Galerkin Method for Probabilistic Load Flow

Directory of Open Access Journals (Sweden)

Yingyun Sun

2016-03-01

Full Text Available An intrusive spectral method of probabilistic load flow (PLF is proposed in the paper, which can handle the uncertainties arising from renewable energy integration. Generalized polynomial chaos (gPC expansions of dependent random variables are utilized to build a spectral stochastic representation of PLF model. Instead of solving the coupled PLF model with a traditional, cumbersome method, a modified stochastic Galerkin (SG method is proposed based on the P-Q decoupling properties of load flow in power system. By introducing two pre-calculated constant sparse Jacobian matrices, the computational burden of the SG method is significantly reduced. Two cases, IEEE 14-bus and IEEE 118-bus systems, are used to verify the computation speed and efficiency of the proposed method.

风力发电系统中的风速测量技术%Wind Speed Measurement Technology in Wind Power Generation System

Institute of Scientific and Technical Information of China (English)

雷鹏; 刘文红; 张帅; 邱天爽

2015-01-01

风速测量在风力发电系统中影响着风力机组的转速和功率的控制,风速值的准确性将影响整个风机的效率.首先介绍了几种在风力发电系统中常用的风速测量仪,简述了其原理、结构特点,然后分析了各种风速测量方法的优缺点及适用范围,最后展望了软测量技术在风力发电系统风速测量中的应用前景.%The wind speed measurement in wind power system, the influence of the wind turbine speed and power control, the accuracy of the wind speed value will affect the efficiency of the whole wind turbine. In this paper, the wind speed measuring instrument for wind power generation system is introduced, and its principle and structure characteristics are described. Then the advantages and disadvantages of various wind speed measurement methods are analyzed.

A novel vibration-based fault diagnostic algorithm for gearboxes under speed fluctuations without rotational speed measurement

Science.gov (United States)

Hong, Liu; Qu, Yongzhi; Dhupia, Jaspreet Singh; Sheng, Shuangwen; Tan, Yuegang; Zhou, Zude

2017-09-01

The localized failures of gears introduce cyclic-transient impulses in the measured gearbox vibration signals. These impulses are usually identified from the sidebands around gear-mesh harmonics through the spectral analysis of cyclo-stationary signals. However, in practice, several high-powered applications of gearboxes like wind turbines are intrinsically characterized by nonstationary processes that blur the measured vibration spectra of a gearbox and deteriorate the efficacy of spectral diagnostic methods. Although order-tracking techniques have been proposed to improve the performance of spectral diagnosis for nonstationary signals measured in such applications, the required hardware for the measurement of rotational speed of these machines is often unavailable in industrial settings. Moreover, existing tacho-less order-tracking approaches are usually limited by the high time-frequency resolution requirement, which is a prerequisite for the precise estimation of the instantaneous frequency. To address such issues, a novel fault-signature enhancement algorithm is proposed that can alleviate the spectral smearing without the need of rotational speed measurement. This proposed tacho-less diagnostic technique resamples the measured acceleration signal of the gearbox based on the optimal warping path evaluated from the fast dynamic time-warping algorithm, which aligns a filtered shaft rotational harmonic signal with respect to a reference signal assuming a constant shaft rotational speed estimated from the approximation of operational speed. The effectiveness of this method is validated using both simulated signals from a fixed-axis gear pair under nonstationary conditions and experimental measurements from a 750-kW planetary wind turbine gearbox on a dynamometer test rig. The results demonstrate that the proposed algorithm can identify fault information from typical gearbox vibration measurements carried out in a resource-constrained industrial environment.

Power Loss Analysis for Wind Power Grid Integration Based on Weibull Distribution

Directory of Open Access Journals (Sweden)

Ahmed Al Ameri

2017-04-01

Full Text Available The growth of electrical demand increases the need of renewable energy sources, such as wind energy, to meet that need. Electrical power losses are an important factor when wind farm location and size are selected. The capitalized cost of constant power losses during the life of a wind farm will continue to high levels. During the operation period, a method to determine if the losses meet the requirements of the design is significantly needed. This article presents a Simulink simulation of wind farm integration into the grid; the aim is to achieve a better understanding of wind variation impact on grid losses. The real power losses are set as a function of the annual variation, considering a Weibull distribution. An analytical method has been used to select the size and placement of a wind farm, taking into account active power loss reduction. It proposes a fast linear model estimation to find the optimal capacity of a wind farm based on DC power flow and graph theory. The results show that the analytical approach is capable of predicting the optimal size and location of wind turbines. Furthermore, it revealed that the annual variation of wind speed could have a strong effect on real power loss calculations. In addition to helping to improve utility efficiency, the proposed method can develop specific designs to speeding up integration of wind farms into grids.

High-speed elevators controlled by inverters

Energy Technology Data Exchange (ETDEWEB)

Sakai, Yoshio; Takahashi, Hideaki; Nakamura, Kiyoshi; Kinoshita, Hiroshi

1988-10-25

The super-high-speed elevator with superiority to 300m/min of speed, requires both the large capacity power and wide range speed controls. Therefore, in order to materialize the smooth and quiet operation characteristics, by applying the inverter control, the low torque ripple control in the low frequency range and high frequency large capacity inverting for lowering the motor in noise are necessary with their being assured of reliability. To satisfy the above necessary items, together with the development of a sine wave pulse width and frequency modulation (PWM/PFM) control system, to more precisely enable the sine wave electric current control, and 3kHz switching power converter, using a 800A power transistor module, a supervoltage control circuit under the extraordinary condition was designed. As a result of commercializing a 360m/min super-high speed inverter elevator, the power source unit, due to the effect of high power factor, could be reduced by 30% in capacity and also the higher harmonic wave including ratio could be considerably lowered to the inferiority to 5%. 2 references, 7 figures, 1 table.

Role of parasitic capacitances in power MOSFET turn-on switching speed limits

DEFF Research Database (Denmark)

Cittanti, Davide; Iannuzzo, Francesco; Hoene, Eckart

2017-01-01

This paper describes the effect of MOSFET internal capacitances on the channel current during the turn-on switching transition: an intrinsic theoretical switching speed limit is found and detailed mathematically. The set of analytical equations is solved and the effect of the displacement currents...... is highlighted with ideal simulated waveforms. A laboratory experiment is thus performed, in order to prove the theoretical predictions: a 25 mΩ SiC CREE power MOSFET is turned on in a no-load condition (zero drain current), starting from different drain-source voltage values. Finally, a LTSpice equivalent...

Performance analysis of wind turbines at low tip-speed ratio using the Betz-Goldstein model

International Nuclear Information System (INIS)

Vaz, Jerson R.P.; Wood, David H.

2016-01-01

Highlights: • General formulations for power and thrust at any tip-speed ratio are developed. • The Joukowsky model for the blades is modified with specific vortex distributions. • Betz-Goldstein model is shown to be the most consistent at low tip-speed ratio. • The effects of finite blade number are assessed using tip loss factors. • Tip loss for finite blade number may complicate the vortex breakdown. - Abstract: Analyzing wind turbine performance at low tip-speed ratio is challenging due to the relatively high level of swirl in the wake. This work presents a new approach to wind turbine analysis including swirl for any tip-speed ratio. The methodology uses the induced velocity field from vortex theory in the general momentum theory, in the form of the turbine thrust and torque equations. Using the constant bound circulation model of Joukowsky, the swirl velocity becomes infinite on the wake centreline even at high tip-speed ratio. Rankine, Vatistas and Delery vortices were used to regularize the Joukowsky model near the centreline. The new formulation prevents the power coefficient from exceeding the Betz-Joukowsky limit. An alternative calculation, based on the varying circulation for Betz-Goldstein optimized rotors is shown to have the best general behavior. Prandtl’s approximation for the tip loss and a recent alternative were employed to account for the effects of a finite number of blades. The Betz-Goldstein model appears to be the only one resistant to vortex breakdown immediately behind the rotor for an infinite number of blades. Furthermore, the dependence of the induced velocity on radius in the Betz-Goldstein model allows the power coefficient to remain below Betz-Joukowsky limit which does not occur for the Joukowsky model at low tip-speed ratio.

Performance Analysis of Modified Drain Gating Techniques for Low Power and High Speed Arithmetic Circuits

Directory of Open Access Journals (Sweden)

Shikha Panwar

2014-01-01

Full Text Available This paper presents several high performance and low power techniques for CMOS circuits. In these design methodologies, drain gating technique and its variations are modified by adding an additional NMOS sleep transistor at the output node which helps in faster discharge and thereby providing higher speed. In order to achieve high performance, the proposed design techniques trade power for performance in the delay critical sections of the circuit. Intensive simulations are performed using Cadence Virtuoso in a 45 nm standard CMOS technology at room temperature with supply voltage of 1.2 V. Comparative analysis of the present circuits with standard CMOS circuits shows smaller propagation delay and lesser power consumption.

Speed scaling for weighted flow time

NARCIS (Netherlands)

Bansal, N.; Pruhs, K.R.; Stein, C.

2007-01-01

In addition to the traditional goal of efficiently managing time and space, many computers now need to efficiently manage power usage. For example, Intel's SpeedStep and AMD's PowerNOW technologies allow the Windows XP operating system to dynamically change the speed of the processor to prolong

Low-power grating detection system chip for high-speed low-cost length and angle precision measurement

Science.gov (United States)

Hou, Ligang; Luo, Rengui; Wu, Wuchen

2006-11-01

This paper forwards a low power grating detection chip (EYAS) on length and angle precision measurement. Traditional grating detection method, such as resister chain divide or phase locked divide circuit are difficult to design and tune. The need of an additional CPU for control and display makes these methods' implementation more complex and costly. Traditional methods also suffer low sampling speed for the complex divide circuit scheme and CPU software compensation. EYAS is an application specific integrated circuit (ASIC). It integrates micro controller unit (MCU), power management unit (PMU), LCD controller, Keyboard interface, grating detection unit and other peripherals. Working at 10MHz, EYAS can afford 5MHz internal sampling rate and can handle 1.25MHz orthogonal signal from grating sensor. With a simple control interface by keyboard, sensor parameter, data processing and system working mode can be configured. Two LCD controllers can adapt to dot array LCD or segment bit LCD, which comprised output interface. PMU alters system between working and standby mode by clock gating technique to save power. EYAS in test mode (system action are more frequently than real world use) consumes 0.9mw, while 0.2mw in real world use. EYAS achieved the whole grating detection system function, high-speed orthogonal signal handling in a single chip with very low power consumption.

An integrated control method for a wind farm to reduce frequency deviations in a small power system

International Nuclear Information System (INIS)

Kaneko, Toshiaki; Uehara, Akie; Senjyu, Tomonobu; Yona, Atsushi; Urasaki, Naomitsu

2011-01-01

Output power of wind turbine generator (WTG) is not constant and fluctuates due to wind speed changes. To reduce the adverse effects of the power system introducing WTGs, there are several published reports on output power control of WTGs detailing various researches based on pitch angle control, variable speed wind turbines, energy storage systems, and so on. In this context, this paper presents an integrated control method for a WF to reduce frequency deviations in a small power system. In this study, the WF achieves the frequency control with two control schemes: load estimation and short-term ahead wind speed prediction. For load estimation in the small power system, a minimal-order observer is used as disturbance observer. The estimated load is utilized to determine the output power command of the WF. To regulate the output power command of the WF according to wind speed changing, short-term ahead wind speed is predicted by using least-squares method. The predicted wind speed adjusts the output power command of the WF as a multiplying factor with fuzzy reasoning. By means of the proposed method, the WF can operate according to the wind and load conditions. In the WF system, each output power of the WTGs is controlled by regulating each pitch angle. For increasing acquisition power of the WF, a dispatch control method also is proposed. In the pitch angle control system of each WTG, generalized predictive control (GPC) is applied to enhance the control performance. Effectiveness of the proposed method is verified by the numerical simulations.

Maximum Range of a Projectile Thrown from Constant-Speed Circular Motion

Science.gov (United States)

Poljak, Nikola

2016-01-01

The problem of determining the angle ? at which a point mass launched from ground level with a given speed v[subscript 0] will reach a maximum distance is a standard exercise in mechanics. There are many possible ways of solving this problem, leading to the well-known answer of ? = p/4, producing a maximum range of D[subscript max] = v[superscript…

Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low wind power potentials

Science.gov (United States)

Miller, Lee; Kleidon, Axel

2017-04-01

Wind turbines generate electricity by removing kinetic energy from the atmosphere. Large numbers of wind turbines are likely to reduce wind speeds, which lowers estimates of electricity generation from what would be presumed from unaffected conditions. Here, we test how well wind power potentials that account for this effect can be estimated without explicitly simulating atmospheric dynamics. We first use simulations with an atmospheric general circulation model (GCM) that explicitly simulates the effects of wind turbines to derive wind power limits (GCM estimate), and compare them to a simple approach derived from the climatological conditions without turbines [vertical kinetic energy (VKE) estimate]. On land, we find strong agreement between the VKE and GCM estimates with respect to electricity generation rates (0.32 and 0.37 We m-2) and wind speed reductions by 42 and 44%. Over ocean, the GCM estimate is about twice the VKE estimate (0.59 and 0.29 We m-2) and yet with comparable wind speed reductions (50 and 42%). We then show that this bias can be corrected by modifying the downward momentum flux to the surface. Thus, large-scale limits to wind power can be derived from climatological conditions without explicitly simulating atmospheric dynamics. Consistent with the GCM simulations, the approach estimates that only comparatively few land areas are suitable to generate more than 1 We m-2 of electricity and that larger deployment scales are likely to reduce the expected electricity generation rate of each turbine. We conclude that these atmospheric effects are relevant for planning the future expansion of wind power.

Strength, power, speed, and agility of women basketball players according to playing position.

Science.gov (United States)

Delextrat, Anne; Cohen, Daniel

2009-10-01

The aim of the present study was to investigate the effect of playing position on strength, power, speed, and agility performances of women basketball players. Thirty subjects playing at national level participated in this study. They were divided into 3 groups according to playing position: guards (positions 1 and 2), forwards (positions 3 and 4), and centers (position 5). Each subject performed 8 tests presented in a random order: The 30-second Wingate Anaerobic test (WAnT), isokinetic testing of the knee extensors, 2 types of jump tests, a 20-m sprint, the agility T-test, a suicide run, and a basketball chest pass. Statistical differences between playing positions were assessed using a 1-way analysis of variance (ANOVA) and Scheffe post hoc analyses. Results showed that guards performed significantly better than centers for the relative peak and mean power achieved during the WAnT (+13% and +16.9%, respectively), relative peak torque of knee extensors (+19.5%), single-leg jump (+21.8), suicide run (+7.5%), and agility T-test (+6.4%, p training must be undertaken according to playing position. The ability to perform the suicide run, the single-leg jump, and the different movements involved in the agility T-test must be developed in guards. In contrast, speed over short distances and strength development of lower body and upper body should be performed by all playing positions.

A fast-start pacing strategy speeds pulmonary oxygen uptake kinetics and improves supramaximal running performance.

Directory of Open Access Journals (Sweden)

Tiago Turnes

Full Text Available The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake (VO2 kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min visited the laboratory for a series of tests that were performed until exhaustion: 1 an incremental test; 2 three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3 two to four constant speed tests for the determination of the highest constant speed (HS that still allowed achieving maximal oxygen uptake; and 4 an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; P = 0.029; subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; P = 0.037. Moreover, the mean VO2 response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; P = 0.025. In conclusion, middle-distance running performances with a duration of 2-3 min are improved and VO2 response time is faster when a fast-start is adopted.

Comparison of the effectiveness of analytical wake models for wind farm with constant and variable hub heights

International Nuclear Information System (INIS)

Wang, Longyan; Tan, Andy C.C.; Cholette, Michael; Gu, Yuantong

2016-01-01

Highlights: • The effectiveness of three analytical wake models is studied. • The results of the analytical wake models are compared with the CFD simulations. • The results of CFD simulation are verified by comparison to the offshore wind farm observation data. • The onshore wind farm with both constant and different hub height turbines are analyzed. • PARK model is able to predict the total wind farm power production well with tuned surface roughness value. - Abstract: Extensive power losses of wind farm have been witnessed due to the wake interactions between wind turbines. By applying analytical wake models which describe the wind speed deficits in the wake quantitatively, the power losses can be regained to a large extent through wind farm layout optimization, and this has been extensively reported in literature. Nevertheless, the effectiveness of the analytical wake models in predicting the wind farm power production have rarely been studied and compared for wind farm with both constant and variable wind turbine hub heights. In this study, the effectiveness of three different analytical wake models (PARK model, Larsen model and B-P model) is thoroughly compared over a wide range of wake properties. After the validation with the observation data from offshore wind farm, CFD simulations are used to verify the effectiveness of the analytical wake models for an onshore wind farm. The results show that when using the PARK model the surface roughness value (z 0 ) must be carefully tuned to achieve good performance in predicting the wind farm power production. For the other two analytical wake models, their effectiveness varies depending on the situation of wind farm (offshore or onshore) and the wind turbine hub heights (constant or variable). It was found that the results of B-P model agree well with the CFD simulations for offshore wind farm, but not for the onshore wind farm. The Larsen model is more accurate for the wind farm with variable wind turbine

Maximizing Energy Capture of Fixed-Pitch Variable-Speed Wind Turbines

Energy Technology Data Exchange (ETDEWEB)

Pierce, K.; Migliore, P.

2000-08-01

Field tests of a variable-speed, stall-regulated wind turbine were conducted at a US Department of Energy Laboratory. A variable-speed generating system, comprising a doubly-fed generator and series-resonant power converter, was installed on a 275-kW, downwind, two-blade wind turbine. Gearbox, generator, and converter efficiency were measured in the laboratory so that rotor aerodynamic efficiency could be determined from field measurement of generator power. The turbine was operated at several discrete rotational speeds to develop power curves for use in formulating variable-speed control strategies. Test results for fixed-speed and variable-speed operation are presented along with discussion and comparison of the variable-speed control methodologies. Where possible, comparisons between fixed-speed and variable-speed operation are shown.

Critical wind speed at which trees break

Science.gov (United States)

Virot, E.; Ponomarenko, A.; Dehandschoewercker, É.; Quéré, D.; Clanet, C.

2016-02-01

Data from storms suggest that the critical wind speed at which trees break is constant (≃42 m /s ), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.

Critical wind speed at which trees break.

Science.gov (United States)

Virot, E; Ponomarenko, A; Dehandschoewercker, É; Quéré, D; Clanet, C

2016-02-01

Data from storms suggest that the critical wind speed at which trees break is constant (≃42m/s), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.

Assessment of Power Potential of Tidal Currents and Impacts of Power Extraction on Flow Speeds in Indonesia

Science.gov (United States)

Orhan, K.; Mayerle, R.

2016-12-01

A methodology comprising of the estimates of power yield, evaluation of the effects of power extraction on flow conditions, and near-field investigations to deliver wake characteritics, recovery and interactions is described and applied to several straits in Indonesia. Site selection is done with high-resolution, three-dimensional flow models providing sufficient spatiotemporal coverage. Much attention has been given to the meteorological forcing, and conditions at the open sea boundaries to adequately capture the density gradients and flow fields. Model verification using tidal records shows excellent agreement. Sites with adequate depth for the energy conversion using horizontal axis tidal turbines, average kinetic power density greater than 0.5 kW/m2, and surface area larger than 0.5km2 are defined as energy hotspots. Spatial variation of the average extractable electric power is determined, and annual tidal energy resource is estimated for the straits in question. The results showed that the potential for tidal power generation in Indonesia is likely to exceed previous predictions reaching around 4,800MW. To assess the impact of the devices, flexible mesh models with higher resolutions have been developed. Effects on flow conditions, and near-field turbine wakes are resolved in greater detail with triangular horizontal grids. The energy is assumed to be removed uniformly by sub-grid scale arrays of turbines, and calculations are made based on velocities at the hub heights of the devices. An additional drag force resulting in dissipation of the pre-existing kinetic power from %10 to %60 within a flow cross-section is introduced to capture the impacts. It was found that the effect of power extraction on water levels and flow speeds in adjacent areas is not significant. Results show the effectivess of the method to capture wake characteritics and recovery reasonably well with low computational cost.

Variable speed DFIG wind energy system for power generation and harmonic current mitigation

Energy Technology Data Exchange (ETDEWEB)

Gaillard, A.; Saadate, S. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, Nancy Universite - Universite Henri Poincare Nancy 1, BP239, 54506 Vandoeuvre les Nancy Cedex (France); Poure, P. [Laboratoire d' Instrumentation Electronique de Nancy, Nancy Universite - Universite Henri Poincare Nancy 1, BP239, 54506 Vandoeuvre les Nancy Cedex (France); Machmoum, M. [IREENA, 37 Boulevard de l' Universite, BP 406, 44602 Saint-Nazaire Cedex (France)

2009-06-15

This paper presents a novel approach for simultaneous power generation and harmonic current mitigation using variable speed WECS with DFIG. A new control strategy is proposed to upgrade the DFIG control to achieve simultaneously a green active and reactive power source with active filtering capability. To ensure high filtering performance, we studied an improved harmonic isolator in the time-domain, based on a new high selectivity filter developed in our laboratory. We examined two solutions for harmonic current mitigation: first, by compensating the whole harmonic component of the grid currents or second, by selective isolation of the predominant harmonic currents to ensure active filtering of the 5th and 7th harmonics. Simulation results for a 3 MW WECS with DFIG confirm the effectiveness and the performance of the two proposed approaches. (author)

Design criteria and candidate electrical power systems for a reusable Space Shuttle booster.

Science.gov (United States)

Merrifield, D. V.

1972-01-01

This paper presents the results of a preliminary study to establish electrical power requirements, investigate candidate power sources, and select a representative power generation concept for the NASA Space Shuttle booster stage. Design guidelines and system performance requirements are established. Candidate power sources and combinations thereof are defined and weight estimates made. The selected power source concept utilizes secondary silver-zinc batteries, engine-driven alternators with constant speed drive, and an airbreathing gas turbine. The need for cost optimization, within safety, reliability, and performance constraints, is emphasized as being the most important criteria in design of the final system.

Design of practical sliding-mode controllers with constant switching frequency for power converters

Energy Technology Data Exchange (ETDEWEB)

Navarro-Lopez, Eva M. [School of Computer Science, Centre for Interdisciplinary Computational and Dynamical Analysis, The University of Manchester, Oxford Road, Kilburn Building, Manchester M13 9PL (United Kingdom); Cortes, Domingo [Seccion de Mecatronica, Departamento de Ingenieria Electrica, CINVESTAV-IPN, Av. IPN 2508, Col. San Pedro Zacatenco, 07360 Mexico City (Mexico); Castro, Christian [Centro de Investigacion en Computacion del IPN, Av. Jose Othon de Mendizabal s/n, Col. Nueva Industrial Vallejo, 07738 Mexico City (Mexico)

2009-05-15

A novel experimentally motivated method in order to design a family of easy-to-implement sliding-mode controllers for power converters is proposed. Two main results are presented. First, the relation between sliding-mode control and average control is reinterpreted so that the limitation of the switching frequency for the closed-loop system is achieved in a more direct way than other methods so far reported in the literature. For this purpose, a class of sliding surfaces which makes the associated equivalent control be the system average control is proposed. Second, the achievement of a constant switching frequency in the controlled system is assured without requiring the sliding-mode-based controller to be modified, unlike most previous works. As a result, the proposed sliding surfaces-type can be directly implemented via a pulse-width modulator. The control methodology is implemented for the voltage control in a boost converter prototype in which the load is considered unknown. Experimental results confirm high performance and robustness under parameters variation. Furthermore, the solution proposed is easy to implement and well-suited for other power converters. (author)

A Systematic Review of the Association Between Physical Fitness and Musculoskeletal Injury Risk: Part 3 - Flexibility, Power, Speed, Balance, and Agility.

Science.gov (United States)

de la Motte, Sarah J; Lisman, Peter; Gribbin, Timothy C; Murphy, Kaitlin; Deuster, Patricia A

2017-12-11

We performed a systematic review and evaluation of the existing scientific literature on the association between flexibility, power, speed, balance, and agility, and musculoskeletal injury (MSK-I) risk in military and civilian populations. MEDLINE, EBSCO, EMBASE, and the Defense Technical Information Center were searched for original studies published from 1970 through 2015 that examined associations between these physical fitness measures (flexibility, power, speed, balance, and agility) and MSK-I. Methodological quality and strength of the evidence were determined following criteria adapted from previously published systematic reviews. Twenty-seven of 4,229 citations met our inclusion criteria. Primary findings indicate there is (a) moderate evidence that hamstring flexibility, as measured by performance on a sit-and-reach test or active straight-leg raise test assessed with goniometry, and ankle flexibility, assessed with goniometry, are associated with MSK-I risk; (b) moderate evidence that lower body power, as measured by performance on a standing broad jump or vertical jump with no countermovement, is associated with MSK-I risk; (c) moderate evidence that slow sprint speed is associated with MSK-I risk; (d) moderate evidence that poor performance on a single-leg balance test is associated with increased risk for ankle sprain; and (e) insufficient evidence that agility is associated with MSK-I risk. Several measures of flexibility, power, speed, and balance are risk factors for training-related MSK-I in military and civilian athletic populations. Importantly, these findings can be useful for military, first responder, and athletic communities who are seeking evidence-based metrics for assessing or stratifying populations for risk of MSK-I.

Survey of variable speed operation of wind turbines

Energy Technology Data Exchange (ETDEWEB)

Carlson, Ola; Hylander, J.; Thorborg, K. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Electric Power Engineering

1996-12-01

During the last five years the production and operation of variable-speed wind turbines have advanced from a few experimental machines to a serial production of at least 10 MW of installed capacity of variable speed machines per week. The rated power of serial wind turbines is today around 600 kW and for the prototypes up to 3000 kW. Variable speed operation of wind turbines can be obtained with several different types of electrical generating systems, such as synchronous generators with diode rectifiers and thyristor inverters or induction generators with IGBT-converters, for the wide speed range. For the narrow speed range the wound motor induction generator with a rotor cascade or a controlled rotor resistance is preferable. The development of permanent magnetic material and the reduction of costs of the power electronic components have opened a possibility of designing cost-effective wind turbines with a directly driven generator. Pitch control together with variable speed will make it possible to limit the power variation within a few percent, 2 to 5 %, of the rated power. 7 refs, 4 figs, 2 tabs

Modeling and Control of a DC-grid Hybrid Power System with Battery and Variable Speed Diesel Generators

OpenAIRE

Syverud, Tron Hansen

2016-01-01

Hybrid electric power systems (HPS) have successfully been integrated in the road-traffic industry due to enhanced efficiency and environmental benefits. Recently this concept has been implemented in the marine sector. In this master thesis, the construction of a DC hybrid power system for a marine vessel is outlined in detail. The HPS is developed in Matlbat/Simulink and comprises two set of diesel generators with variable speed, six-pulse diode bridges, a battery bank, bidire...

Critical Speed Control for a Fixed Blade Variable Speed Wind Turbine

Directory of Open Access Journals (Sweden)

Morgan Rossander

2017-10-01

Full Text Available A critical speed controller for avoiding a certain rotational speed is presented. The controller is useful for variable speed wind turbines with a natural frequency in the operating range. The controller has been simulated, implemented and tested on an open site 12 kW vertical axis wind turbine prototype. The controller is based on an adaptation of the optimum torque control. Two lookup tables and a simple state machine provide the control logic of the controller. The controller requires low computational resources, and no wind speed measurement is needed. The results suggest that the controller is a feasible method for critical speed control. The skipping behavior can be adjusted using only two parameters. While tested on a vertical axis wind turbine, it may be used on any variable speed turbine with the control of generator power.

Four-level time decomposition quasi-static power flow and successive disturbances analysis. [Power system disturbances

Energy Technology Data Exchange (ETDEWEB)

Jovanovic, S M [Nikola Tesla Inst., Belgrade (YU)

1990-01-01

This paper presents a model and an appropriate numerical procedure for a four-level time decomposition quasi-static power flow and successive disturbances analysis of power systems. The analysis consists of the sequential computation of the zero, primary, secondary and tertiary quasi-static states and of the estimation of successive structural disturbances during the 1200 s dynamics after a structural disturbance. The model is developed by detailed inspection of the time decomposition characteristics of automatic protection and control devices. Adequate speed of the numerical procedure is attained by a specific application of the inversion matrix lemma and the decoupled model constant coefficient matrices. The four-level time decomposition quasi-static method is intended for security and emergency analysis. (author).

Variable speed control in wells turbine-based oscillating water column devices: optimum rotational speed

Science.gov (United States)

Lekube, J.; Garrido, A. J.; Garrido, I.

2018-03-01

The effects of climate change and global warming reveal the need to find alternative sources of clean energy. In this sense, wave energy power plants, and in particular Oscillating Water Column (OWC) devices, offer a huge potential of energy harnessing. Nevertheless, the conversion systems have not reached a commercially mature stage yet so as to compete with conventional power plants. At this point, the use of new control methods over the existing technology arises as a doable way to improve the efficiency of the system. Due to the non-uniform response that the turbine shows to the rotational speed variation, the speed control of the turbo-generator may offer a feasible solution for efficiency improvement during the energy conversion. In this context, a novel speed control approach for OWC systems is presented in this paper, demonstrating its goodness and affording promising results when particularized to the Mutriku’s wave power plant.

Battery Recharging Issue for a Two-Power-Level Flywheel System

Directory of Open Access Journals (Sweden)

Janaína Gonçalves de Oliveira

2010-01-01

Full Text Available A novel battery recharging system for an all-electric driveline comprising a flywheel with a permanent magnet double wound synchronous machine (motor/generator is presented. The double winding enables two voltage levels and two different power levels. This topology supersedes other all-electric drivelines. The battery operates in a low-power regime supplying the average power whereas the flywheel delivers and absorbs power peaks, which are up to a higher order of magnitude. The topology presents new challenges for the power conversion system, which is the focus of this investigation. The main challenge is the control of the power flow to the battery when the vehicle is parked despite the decay of the flywheel machine voltage; which is dependent on its charge state, that is, rotational speed. The design and simulation of an unidirectional DC/DC buck/boost converter for a variable rotational speed flywheel is presented. Conventional power electronic converters are used in a new application, which can maintain a constant current or voltage on the battery side. Successful PI current control has been implemented and simulated, together with the complete closed loop system.

Impact of Shaft Stiffness on Inertial Response of Fixed Speed Wind Turbines

Institute of Scientific and Technical Information of China (English)

2012-01-01

Future power＇ system faces several challenges, one of them is the high penetration level of intermittent wind power generation, providing small or even no inertial response and being not contributing to the frequency stability. The effect of shaft stiffness on inertial response of fixed speed wind turbines is presented. Four different drive-train models based on the multi-body system are developed. The small-signal analysis demonstrates no significant differences between models in terms of electro-mechanical eigen-values for increasing shaft stiffness. The natural resonance frequency of drive-train torsion modes shows slightly different values between damped and undamped models, but no significant differences are found in the number-mass models. Time-domain simulations show the changes in the active power contribution of a wind farm based on a fixed speed wind turbine during the system frequency disturbance. The changes in the kinetic energy during the dynamic process are calculated and their contribution to the inertia constant is small and effective. The largest contribution of the kinetic energy is provided at the beginning of the system frequency disturbance to reduce the rate of the frequency change, it is positive for the frequency stability.

Continuous-waveform constant-current isolated physiological stimulator

Science.gov (United States)

Holcomb, Mark R.; Devine, Jack M.; Harder, Rene; Sidorov, Veniamin Y.

2012-04-01

We have developed an isolated continuous-waveform constant-current physiological stimulator that is powered and controlled by universal serial bus (USB) interface. The stimulator is composed of a custom printed circuit board (PCB), 16-MHz MSP430F2618 microcontroller with two integrated 12-bit digital to analog converters (DAC0, DAC1), high-speed H-Bridge, voltage-controlled current source (VCCS), isolated USB communication and power circuitry, two isolated transistor-transistor logic (TTL) inputs, and a serial 16 × 2 character liquid crystal display. The stimulators are designed to produce current stimuli in the range of ±15 mA indefinitely using a 20V source and to be used in ex vivo cardiac experiments, but they are suitable for use in a wide variety of research or student experiments that require precision control of continuous waveforms or synchronization with external events. The device was designed with customization in mind and has features that allow it to be integrated into current and future experimental setups. Dual TTL inputs allow replacement by two or more traditional stimulators in common experimental configurations. The MSP430 software is written in C++ and compiled with IAR Embedded Workbench 5.20.2. A control program written in C++ runs on a Windows personal computer and has a graphical user interface that allows the user to control all aspects of the device.

Comparison between OpenFOAM CFD & BEM theory for variable speed – variable pitch HAWT

Directory of Open Access Journals (Sweden)

ElQatary Islam

2014-01-01

Full Text Available OpenFoam is used to compare computational fluid dynamics (CFD with blade element momentum theory (BEM for a variable speed - variable pitch HAWT (Horizontal Axis Wind Turbine. The wind turbine is first designed using the BEM to determine the blade chord, twist and operating conditions. The wind turbine blade has an outer diameter of 14 m, uses a NACA 63–415 profile for the entire blade and root to tip twist distribution of 15deg (Figure 3. The RPM varies from 20–75 for freestream velocities varying between 3–10.5 m/s (variable speed and a constant RPM of 78.78 for velocities ranging between 11–25 m/s (variable pitch. OpenFOAM is used to investigate the wind turbine performance at several operating points including cut-in wind speed (3 m/s, rated wind speed (10.5 m/s and in the variable pitch zone. Simulation results show that in the variable-speed operating range, both CFD and BEM compare reasonably well. This agreement can be attributed to the fact that the complex three-dimensional flow around the turbine blades can be split into two radial segments. For radii less than the mid-span, the flow is three-dimensional, whereas for radii greater than the mid-span, the flow is approximately two-dimensional. Since the majority of the power is produced from sections beyond the mid-span, the agreement between CFD and BEM is reasonable. For the variable-pitch operating range the CFD results and BEM deviate considerably. In this case the majority of the power is produced from the inner sections in which the flow is three-dimensional and can no longer be predicted by the BEM. The results show that differences in pitch angles up to 10deg can result to regulate the power for high wind speeds in the variable-pitch operation zone.

Constant strength fuel-fuel cell

International Nuclear Information System (INIS)

Vaseen, V.A.

1980-01-01

A fuel cell is an electrochemical apparatus composed of both a nonconsumable anode and cathode; and electrolyte, fuel oxidant and controls. This invention guarantees the constant transfer of hydrogen atoms and their respective electrons, thus a constant flow of power by submergence of the negative electrode in a constant strength hydrogen furnishing fuel; when said fuel is an aqueous absorbed hydrocarbon, such as and similar to ethanol or methnol. The objective is accomplished by recirculation of the liquid fuel, as depleted in the cell through specific type membranes which pass water molecules and reject the fuel molecules; thus concentrating them for recycle use

Smoothing Control of Wind Farm Output by Using Kinetic Energy of Variable Speed Wind Power Generators

Science.gov (United States)

Sato, Daiki; Saitoh, Hiroumi

This paper proposes a new control method for reducing fluctuation of power system frequency through smoothing active power output of wind farm. The proposal is based on the modulation of rotaional kinetic energy of variable speed wind power generators through power converters between permanent magnet synchronous generators (PMSG) and transmission lines. In this paper, the proposed control is called Fluctuation Absorption by Flywheel Characteristics control (FAFC). The FAFC can be easily implemented by adding wind farm output signal to Maximum Power Point Tracking control signal through a feedback control loop. In order to verify the effectiveness of the FAFC control, a simulation study was carried out. In the study, it was assumed that the wind farm consisting of PMSG type wind power generator and induction machine type wind power generaotors is connected with a power sysem. The results of the study show that the FAFC control is a useful method for reducing the impacts of wind farm output fluctuation on system frequency without additional devices such as secondary battery.

Long Term Effects of Different Training Modalities on Power, Speed, Skill and Anaerobic Capacity in Young Male Basketball Players

OpenAIRE

Balčiūnas, Mindaugas; Stonkus, Stanislovas; Abrantes, Catarina; Sampaio, Jaime

2006-01-01

The purpose of this study was to identify the effect of 4 months of different training modalities on power, speed, skill and anaerobic capacity in 15-16 year old male basketball players. Thirty five Lithuanian basketball players were randomly assigned into three groups: power endurance group (intermittent exercise, PE, n = 12), general endurance group (continuous exercise, GE, n = 11) and control group (regular basketball training, CG, n = 12). The power endurance model was based in basketbal...

Power maximization of variable-speed variable-pitch wind turbines using passive adaptive neural fault tolerant control

Science.gov (United States)

Habibi, Hamed; Rahimi Nohooji, Hamed; Howard, Ian

2017-09-01

Power maximization has always been a practical consideration in wind turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-speed variable-pitch wind turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the wind turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the wind turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including wind speed and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method.

Variable Speed Rotor System, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Variable speed rotors will give helicopters several advantages: higher top speed, greater fuel efficiency, momentary emergency over-power, resonance detuning...

Analysis of Disturbance Source Inducing by The Variable Speed Wind Turbine System Forced Power Oscillations

DEFF Research Database (Denmark)

Tan, Jin; Hu, Weihao; Wang, Xiaoru

2015-01-01

The main focus of forced low frequency oscillations is to analyze the disturbance source and the origin of forced oscillations. In this paper, the origin of low-frequency periodical oscillations induced by wind turbines’ mechanical power is investigated and the mechanism is studied of fluctuating...... power transfer through permanent magnet generator wind turbine system. Considering the tower shadow and the wind shear effect, the mechanical and generator coupling model is developed by PSCAD. Simulation is done to analyze the impacts on output power of operation points and mechanical fluctuation...... components. It is shown that when the oscillation frequency of tower shadow coincides with the system natural frequency, it may cause forced oscillations, whereas, the wind shear and natural wind speed fluctuation are not likely to induce forced oscillations....

Day-ahead wind speed forecasting using f-ARIMA models

International Nuclear Information System (INIS)

Kavasseri, Rajesh G.; Seetharaman, Krithika

2009-01-01

With the integration of wind energy into electricity grids, it is becoming increasingly important to obtain accurate wind speed/power forecasts. Accurate wind speed forecasts are necessary to schedule dispatchable generation and tariffs in the day-ahead electricity market. This paper examines the use of fractional-ARIMA or f-ARIMA models to model, and forecast wind speeds on the day-ahead (24 h) and two-day-ahead (48 h) horizons. The models are applied to wind speed records obtained from four potential wind generation sites in North Dakota. The forecasted wind speeds are used in conjunction with the power curve of an operational (NEG MICON, 750 kW) turbine to obtain corresponding forecasts of wind power production. The forecast errors in wind speed/power are analyzed and compared with the persistence model. Results indicate that significant improvements in forecasting accuracy are obtained with the proposed models compared to the persistence method. (author)

Improved Wind Speed Prediction Using Empirical Mode Decomposition

Directory of Open Access Journals (Sweden)

ZHANG, Y.

2018-05-01

Full Text Available Wind power industry plays an important role in promoting the development of low-carbon economic and energy transformation in the world. However, the randomness and volatility of wind speed series restrict the healthy development of the wind power industry. Accurate wind speed prediction is the key to realize the stability of wind power integration and to guarantee the safe operation of the power system. In this paper, combined with the Empirical Mode Decomposition (EMD, the Radial Basis Function Neural Network (RBF and the Least Square Support Vector Machine (SVM, an improved wind speed prediction model based on Empirical Mode Decomposition (EMD-RBF-LS-SVM is proposed. The prediction result indicates that compared with the traditional prediction model (RBF, LS-SVM, the EMD-RBF-LS-SVM model can weaken the random fluctuation to a certain extent and improve the short-term accuracy of wind speed prediction significantly. In a word, this research will significantly reduce the impact of wind power instability on the power grid, ensure the power grid supply and demand balance, reduce the operating costs in the grid-connected systems, and enhance the market competitiveness of the wind power.

Time optimal paths for high speed maneuvering

Energy Technology Data Exchange (ETDEWEB)

Reister, D.B.; Lenhart, S.M.

1993-01-01

Recent theoretical results have completely solved the problem of determining the minimum length path for a vehicle with a minimum turning radius moving from an initial configuration to a final configuration. Time optimal paths for a constant speed vehicle are a subset of the minimum length paths. This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed vehicle. The time optimal paths consist of sequences of axes of circles and straight lines. The maximum principle introduces concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. We explore the properties of the optimal paths and present some experimental results for a mobile robot following an optimal path.

Constant-roll tachyon inflation and observational constraints

Science.gov (United States)

Gao, Qing; Gong, Yungui; Fei, Qin

2018-05-01

For the constant-roll tachyon inflation, we derive the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts and the tensor to scalar ratio to the first order of epsilon1 by using the method of Bessel function approximation. The derived ns-r results are compared with the observations, we find that only the constant-roll inflation with ηH being a constant is consistent with the observations and observations constrain the constant-roll inflation to be slow-roll inflation. The tachyon potential is also reconstructed for the constant-roll inflation which is consistent with the observations.

An Integrated Power-Efficient Active Rectifier With Offset-Controlled High Speed Comparators for Inductively Powered Applications

Science.gov (United States)

Lee, Hyung-Min; Ghovanloo, Maysam

2011-01-01

We present an active full-wave rectifier with offset-controlled high speed comparators in standard CMOS that provides high power conversion efficiency (PCE) in high frequency (HF) range for inductively powered devices. This rectifier provides much lower dropout voltage and far better PCE compared to the passive on-chip or off-chip rectifiers. The built-in offset-control functions in the comparators compensate for both turn-on and turn-off delays in the main rectifying switches, thus maximizing the forward current delivered to the load and minimizing the back current to improve the PCE. We have fabricated this active rectifier in a 0.5-μm 3M2P standard CMOS process, occupying 0.18 mm2 of chip area. With 3.8 V peak ac input at 13.56 MHz, the rectifier provides 3.12 V dc output to a 500 Ω load, resulting in the PCE of 80.2%, which is the highest measured at this frequency. In addition, overvoltage protection (OVP) as safety measure and built-in back telemetry capabilities have been incorporated in our design using detuning and load shift keying (LSK) techniques, respectively, and tested. PMID:22174666

A high speed low power low offset dynamic comparator used in SHA-less pipelined ADC

Science.gov (United States)

Shubin, Liu; Zhangming, Zhu; Yintang, Yang; Lianxi, Liu

2014-05-01

A novel fully differential high speed high resolution low offset CMOS dynamic comparator has been implemented in the SMIC 0.18 μm process used for a sample-and-hold amplifier (SHA)-less pipelined analog-to-digital converters (ADC). Based on the analysis and optimization between delay time and offset, an enhanced reset architecture with transmission gate was introduced to speed up the comparison and reset procedure. Four inputs with two cross coupled differential pairs, reconstituted bias circuit for tail current transistor and common centroid layouts make the comparator more robust against mismatch and process variations. The simulation results demonstrate that the proposed design achieves 1 mV sensitivity at 2.2 GHz sampling rate with a power consumption of 510 μW, while the mean offset voltage is equal to 10.244 mV.

Torque- and Speed Control of a Pitch Regulated Wind Turbine

Energy Technology Data Exchange (ETDEWEB)

Rasila, Mika

2003-07-01

Variable speed operated wind turbines has the potential to reduce fatigue loads, compared to fixed speed wind turbines. With pitch controllable rotor blades limitation of the power at high wind speeds is obtained. The thesis describes different controlling aspects concerning wind turbines and how these together can be used to optimize the system's performance. Torque control is used in order to achieve reduction on the mechanical loads on the drive-train for low wind speeds and limitation of power output for high wind speeds. In the high wind speed interval torque control is effective in order to limit the output power if a sufficiently fast pitch actuator is used. In the middle wind speed interval filter utilization can be used to give a reference signal to the controller in order to reduce speed and torque variations.

Shadows over the speed of light

Czech Academy of Sciences Publication Activity Database

Mareš, Jiří J.; Hubík, Pavel; Špička, Václav; Stávek, J.; Šesták, Jaroslav; Krištofik, Jozef

T151, č. 1 (2012), s. 1-7 ISSN 0031-8949 Institutional research plan: CEZ:AV0Z10100521 Keywords : speed of light * special relativity * Maxwell’s constant Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.032, year: 2012

Winding Design for Minimum Power Loss and Low-Cost Manufacture in Application to Fixed-Speed PM Generator

OpenAIRE

Wrobel, Rafal; Staton, David; Lock, Richard J; Booker, Julian D; Drury, David

2015-01-01

This paper presents the results from a coupled thermal and power loss analysis of an open-slot permanent-magnet (PM) generator. The research focus has been placed on the winding design providing minimum power loss at an ac operation, together with low-cost manufacture. The analyzed PM generator is intended to operate at a fixed speed, allowing for the winding design to be finely tuned for a single operating point. Such a design approach has not been widely reported in literature, and the exis...

Stability Enhancement Based on Virtual Impedance for DC Microgrids with Constant Power Loads

DEFF Research Database (Denmark)

Lu, Xiaonan; Sun, Kai; Guerrero, Josep M.

2015-01-01

In this paper, a converter-based DC microgrid is studied. By considering the impact of each component in DC microgrids on system stability, a multi-stage configuration is employed, which includes the source stage, interface converter stage between buses and common load stage. In order to study th....... It can be seen that by using the proposed stabilizers, the unstable poles induced by the CPLs are forced to move into the stable region. The proposed method is verified by the MATLAB/Simulink model of multi-stage DC microgrids with three distributed power generation units.......In this paper, a converter-based DC microgrid is studied. By considering the impact of each component in DC microgrids on system stability, a multi-stage configuration is employed, which includes the source stage, interface converter stage between buses and common load stage. In order to study...... the overall stability of the above DC microgrid with constant power loads (CPLs), a comprehensive small-signal model is derived by analyzing the interface converters in each stage. The instability issue induced by the CPLs is revealed by using the criteria of impedance matching. Meanwhile, virtual...

The speed-curvature power law in Drosophila larval locomotion.

Science.gov (United States)

Zago, Myrka; Lacquaniti, Francesco; Gomez-Marin, Alex

2016-10-01

We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to three-quarters rather than to the usual two-thirds found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species. © 2016 The Authors.

Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory

DEFF Research Database (Denmark)

Álvarez-Asencio, R.; Thormann, Esben; Rutland, M.W.

2013-01-01

A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power s...... spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever. © 2013 AIP Publishing LLC....

The design and realization of general high-speed RAIN100B DAQ module based on powerPC MPC5200B processor

International Nuclear Information System (INIS)

Xue Tao; Gong Guanghua; Shao Beibei

2010-01-01

In order to deal with the DAQ function of nuclear electronics, department of engineering physics of Tsinghua University design and realize a general, high-speed RAIN100B DAQ module based on Freescale's PowerPC MPC5200B processor.And the RAIN100B was used on GEM detector DAQ, it can reach up to 90Mbps data speed. The result is also presented and discussed. (authors)

Parallel computational in nuclear group constant calculation

International Nuclear Information System (INIS)

Su'ud, Zaki; Rustandi, Yaddi K.; Kurniadi, Rizal

2002-01-01

In this paper parallel computational method in nuclear group constant calculation using collision probability method will be discuss. The main focus is on the calculation of collision matrix which need large amount of computational time. The geometry treated here is concentric cylinder. The calculation of collision probability matrix is carried out using semi analytic method using Beckley Naylor Function. To accelerate computation speed some computer parallel used to solve the problem. We used LINUX based parallelization using PVM software with C or fortran language. While in windows based we used socket programming using DELPHI or C builder. The calculation results shows the important of optimal weight for each processor in case there area many type of processor speed

An Adaptive, Multi-Rate Linear Quadratic Regulator for a Shipboard MVDC Distribution System with Constant Power Loads

Science.gov (United States)

2017-09-01

investigation into the factors which most strongly influence ROA size would be instructive. The genetic algorithm could be modified to assess ROA size and an...DISTRIBUTION SYSTEM WITH CONSTANT POWER LOADS 5. FUNDING NUMBERS REL95 REK4K 6. AUTHOR(S) Adam J. Mills 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS...ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING /MONITORING AGENCY NAME(S) AND

Nonlinear Robust Control for Low Voltage Direct-Current Residential Microgrids with Constant Power Loads

Directory of Open Access Journals (Sweden)

Martín-Antonio Rodríguez-Licea

2018-05-01

Full Text Available A Direct Current (DC microgrid is a concept derived from a smart grid integrating DC renewable sources. The DC microgrids have three particularities: (1 integration of different power sources and local loads through a DC link; (2 on-site power source generation; and (3 alternating loads (on-off state. This kind of arrangement achieves high efficiency, reliability and versatility characteristics. The key device in the development of the DC microgrid is the power electronic converter (PEC, since it allows an efficient energy conversion between power sources and loads. However, alternating loads with strictly-controlled PECs can provide negative impedance behavior to the microgrid, acting as constant power loads (CPLs, such that the overall closed-loop system becomes unstable. Traditional CPL compensation techniques rely on a damping increment by the adaptation of the source or load voltage level, adding external circuitry or by using some advanced control technique. However, none of them provide a simple and general solution for the CPL problem when abrupt changes in parameters and/or in alternating loads/sources occur. This paper proposes a mathematical modeling and a robust control for the basic PECs dealing with CPLs in continuous conduction mode. In particular, the case of the low voltage residential DC microgrid with CPLs is taken as a benchmark. The proposed controller can be easily tuned for the desired response even by the non-expert. Basic converters with voltage mode control are taken as a basis to show the feasibility of this analysis, and experimental tests on a 100-W testbed include abrupt parameter changes such as input voltage.

Utilization technique on variable speed device

International Nuclear Information System (INIS)

1989-12-01

This reports of workshop on power technology describes using technique on variable speed device, which deals with alternating current situation and prospect of current variable speed device, technical trend and prospect of electronics, reduce expenses by variable speed device, control technique, measurement technology, high voltage variable speed device, recent trend of inverter technology, low voltage and high voltage variable speed device control device, operating variable speed device in cooling fan, FDF application and defect case of variable speed device, cooling pump application of water variable transformer, inverter application and energy effect of ventilation equipment, application of variable speed device and analysis of the result of operation and study for application of variable speed technology.

Simulation and study of power quality issues in a fixed speed wind farm substation.

Science.gov (United States)

Magesh, T; Chellamuthu, C

2015-01-01

Power quality issues associated with the fixed speed wind farm substation located at Coimbatore district are investigated as the wind generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for wind, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled wind turbine. Various scenarios and their effects on the performance of the wind farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the wind farm before implementation.

Design and Pitch Angle Optimisation of Horizontal Axis Hydrokinetic Turbine with Constant Tip Speed Ratio

Directory of Open Access Journals (Sweden)

Nigam Suyash

2017-01-01

Full Text Available Booming population and associated energy demands, looming threat of exhaustion of conventional sources of energy and the severe environmental repercussions of the same call for alternate sources of clean energy. Hydrokinetic turbine is one such developing technology which harnesses zero-head free flow of water and affects hydrological ecology minimally. This paper discusses the optimisation of Horizontal Axis Hydrokinetic Turbine (HAHkT blade chord length and twist angle using blade element momentum (BEM theory to achieve a constant optimal angle of attack (AoA, thus maximising the power output. To achieve this while maintaining robustness at the hub end and eliminate cavitation, two different hydrofoils (S832 and E817 are selected. S832 is simulated using ANSYS 14.0 at low (00 and high (150 angles of attack and compared against more widely used NACA 4412 to study flow separation characteristics. This is followed by calculating angles of relative flow, ratios of chord length and subsequently twist angles for each blade element using MATLAB simulations. A blade model is thus developed for visualisation using computer aided designing after obtaining optimal chord lengths and pitch angles.

THE EFFECTS OF SINGLE LEG HOP PROGRESSION AND DOUBLE LEGS HOP PROGRESSION EXERCISE TO INCREASE SPEED AND EXPLOSIVE POWER OF LEG MUSCLE

Directory of Open Access Journals (Sweden)

Nining W. Kusnanik

2015-05-01

Full Text Available The main purpose of this study was to determine the effect of single leg hop progression and double legs hop progression exercise to increase speed and explosive power of leg muscles. Plyometric is one of the training methods that can increase explosive power. There are many models of plyometric training including single leg hop progression and double leg hop progression. This research was experimental using match subject design techniques. The subjects of this study were 39 students who joined basketball school club. There were 3 groups in this study: Group 1 were 13 students who given sin¬gle leg hop progression exercise, Group 2 were 13 students who given double legs hop progression exercise, Group 3 were 13 students who given conventional exercise. The data was collected during pre test and post test by testing 30m speed running and vertical jump. The data was analyzed using Analysis of Varians (Anova. It was found that there were significantly increased on speed and explosive power of leg muscles of Group 1 and Group 2. It can be stated that single leg hop progression exercise was more effective than double leg hop progression exercise. The recent findings supported the hypothesis that single leg hop progression and double legs hop progression exercise can increase speed and explosive power of leg muscles. These finding were supported by some previous studies (Singh, et al, 2011; Shallaby, H.K., 2010. The single leg hop progression is more effective than double legs hop progression. This finding was consistent with some previous evidences (McCurdy, et al, 2005; Makaruk et al, 2011.

Energy Implications of Retrofitting Retail Sector Rooftop Units with Stepped-Speed and Variable-Speed Functionality

Energy Technology Data Exchange (ETDEWEB)

Studer, D.; Romero, R.; Herrmann, L.; Benne, K.

2012-04-01

Commercial retailers understand that retrofitting constant-speed RTU fan motors with stepped- or variable-speed alternatives could save significant energy in most U.S. climate zones. However, they lack supporting data, both real-world and simulation based, on the cost effectiveness and climate zone-specific energy savings associated with this measure. Thus, building managers and engineers have been unable to present a compelling business case for fan motor upgrades to upper management. This study uses whole-building energy simulation to estimate the energy impact of this type of measure so retailers can determine its economic feasibility.

CHANGE ON SPEED AIR CHARACTERISTICS THE POWER INDICATOR INDEXES OF PNEUMATIC ENGINE WITHOUT HEATING THE CHARGE DURING THE ADMITTANCE

Directory of Open Access Journals (Sweden)

A. Voronkov

2014-10-01

Full Text Available The experimental data on change according to speed characteristics of power indicator indexes of the four cylinder pneumatic engine D/S = 76/66 with a slide-valve air distributor at unchangeable temperature of compressed input air is considered.

Modeling wind speed and wind power distributions in Rwanda

Energy Technology Data Exchange (ETDEWEB)

Safari, Bonfils [Department of Physics, National University of Rwanda, P.O. Box 117, Huye District, South Province (Rwanda)

2011-02-15

Utilization of wind energy as an alternative energy source may offer many environmental and economical advantages compared to fossil fuels based energy sources polluting the lower layer atmosphere. Wind energy as other forms of alternative energy may offer the promise of meeting energy demand in the direct, grid connected modes as well as stand alone and remote applications. Wind speed is the most significant parameter of the wind energy. Hence, an accurate determination of probability distribution of wind speed values is very important in estimating wind speed energy potential over a region. In the present study, parameters of five probability density distribution functions such as Weibull, Rayleigh, lognormal, normal and gamma were calculated in the light of long term hourly observed data at four meteorological stations in Rwanda for the period of the year with fairly useful wind energy potential (monthly hourly mean wind speed anti v{>=}2 m s{sup -1}). In order to select good fitting probability density distribution functions, graphical comparisons to the empirical distributions were made. In addition, RMSE and MBE have been computed for each distribution and magnitudes of errors were compared. Residuals of theoretical distributions were visually analyzed graphically. Finally, a selection of three good fitting distributions to the empirical distribution of wind speed measured data was performed with the aid of a {chi}{sup 2} goodness-of-fit test for each station. (author)

Multifunctional TENG for Blue Energy Scavenging and Self-Powered Wind-Speed Sensor

KAUST Repository

Xi, Yi

2017-02-17

Triboelectric nanogenerator (TENG) has been considered to be a more effective technology to harvest various types of mechanic vibration energies such as wind energy, water energy in the blue energy, and so on. Considering the vast energy from the blue oceans, harvesting of the water energy has attracted huge attention. There are two major types of “mechanical” water energy, water wave energy in random direction and water flow kinetic energy. However, although the most reported TENG can be used to efficiently harvest one type of water energy, to simultaneously collect two or more types of such energy still remains challenging. In this work, two different freestanding, multifunctional TENGs are successfully developed that can be used to harvest three types of energies including water waves, air flowing, and water flowing. These two new TENGs designed in accordance with the same freestanding model yield the output voltages of 490 and ≈100 V with short circuit currents of 24 and 2.7 µA, respectively, when operated at a rotation frequency of 200 rpm and the movement frequency of 3 Hz. Moreover, the developed multifunctional TENG can also be explored as a self-powered speed sensor of wind by correlating the short-circuit current with the wind speed.

Sliding mode direct power control of RSC for DFIGs driven by variable speed wind turbines

Directory of Open Access Journals (Sweden)

E.G. Shehata

2015-12-01

Full Text Available In spite of its several advantages, a classic direct power control (DPC of doubly fed induction generators (DFIGs driven by variable speed wind turbines has some drawbacks. In this paper, a simple and robust total sliding mode controller (TSMC is designed to improve the classical DPC performance without complicating the overall scheme. The TSMC is designed to regulate the DFIG stator active and reactive powers. Two integral switching functions are selected for describing the switching surfaces of the active and reactive powers. Reaching phase stability problem of the classical sliding mode controller is avoided in the proposed TSMC. Neither current control loops nor accurate values of machine parameters are required in the proposed scheme. In addition, axes transformation of the stator voltage and current are eliminated. The grid side converter is controlled based on DPC principle to regulate both DC-link voltage and total reactive power. The feasibility of the proposed DPC scheme is validated through simulation studies on a 1.5 MW wind power generation system. The performance of the proposed and conventional DPC schemes is compared under different operating conditions.

A New Control Method to Mitigate Power Fluctuations for Grid Integrated PV/Wind Hybrid Power System Using Ultracapacitors

Science.gov (United States)

Jayalakshmi, N. S.; Gaonkar, D. N.

2016-08-01

The output power obtained from solar-wind hybrid system fluctuates with changes in weather conditions. These power fluctuations cause adverse effects on the voltage, frequency and transient stability of the utility grid. In this paper, a control method is presented for power smoothing of grid integrated PV/wind hybrid system using ultracapacitors in a DC coupled structure. The power fluctuations of hybrid system are mitigated and smoothed power is supplied to the utility grid. In this work both photovoltaic (PV) panels and the wind generator are controlled to operate at their maximum power point. The grid side inverter control strategy presented in this paper maintains DC link voltage constant while injecting power to the grid at unity power factor considering different operating conditions. Actual solar irradiation and wind speed data are used in this study to evaluate the performance of the developed system using MATLAB/Simulink software. The simulation results show that output power fluctuations of solar-wind hybrid system can be significantly mitigated using the ultracapacitor based storage system.

Modeling pedestrian crossing speed profiles considering speed change behavior for the safety assessment of signalized intersections.

Science.gov (United States)

Iryo-Asano, Miho; Alhajyaseen, Wael K M

2017-11-01

Pedestrian safety is one of the most challenging issues in road networks. Understanding how pedestrians maneuver across an intersection is the key to applying countermeasures against traffic crashes. It is known that the behaviors of pedestrians at signalized crosswalks are significantly different from those in ordinary walking spaces, and they are highly influenced by signal indication, potential conflicts with vehicles, and intersection geometries. One of the most important characteristics of pedestrian behavior at crosswalks is the possible sudden speed change while crossing. Such sudden behavioral change may not be expected by conflicting vehicles, which may lead to hazardous situations. This study aims to quantitatively model the sudden speed changes of pedestrians as they cross signalized crosswalks under uncongested conditions. Pedestrian speed profiles are collected from empirical data and speed change events are extracted assuming that the speed profiles are stepwise functions. The occurrence of speed change events is described by a discrete choice model as a function of the necessary walking speed to complete crossing before the red interval ends, current speed, and the presence of turning vehicles in the conflict area. The amount of speed change before and after the event is modeled using regression analysis. A Monte Carlo simulation is applied for the entire speed profile of the pedestrians. The results show that the model can represent the pedestrian travel time distribution more accurately than the constant speed model. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of In-Flight Processing of Alumina Powder Using a DC-RF Hybrid Plasma Flow System at Constant Low Operating Power

Science.gov (United States)

Nishiyama, H.; Onodera, M.; Igawa, J.; Nakajima, T.

2009-12-01

The aim of this study is to provide the optimum operating conditions for enhancing in-flight alumina particle heating as much as possible for particle spheroidization and aggregation of melted particles using a DC-RF hybrid plasma flow system even at constant low operating power based on the thermofluid considerations. It is clarified that the swirl flow and higher operating pressure enhance the particle melting and aggregation of melted particles coupled with increasing gas temperature downstream of a plasma uniformly in the radial direction at constant electrical discharge conditions.

Development of sensor-less control strategies for grid connected PMSG based variable speed wind energy conversion system with improved power quality features

Energy Technology Data Exchange (ETDEWEB)

Chandra, A. [Quebec Univ., Montreal, PQ (Canada). Dept. of Electrical Engineering

2010-07-01

Interest in renewable energy sources has grown in recent years in response to concerns of increasing pollution levels and depleting fossil fuels. Among renewable energy sources, wind energy generation is the fastest growing technology and one of the most cost-effective and environmental friendly means to generate electricity from renewable sources. Modern wind turbines are ready to be deployed in large scale as a result of recent developments in wind power technology. Variable speed permanent magnet synchronous generators (PMSG) based wind energy conversion systems (WECS) are becoming more popular. The use of a permanent magnet reduces size, cost and weight of overall WECS. In addition, the absence of field winding and its excitation system avoids heat dissipation in the rotor winding, thereby improving overall efficiency of the WECS. This type of configuration is more appropriate for remote locations, particularly for off-shore wind application, where the geared doubly fed induction generator usually requires regular maintenance due to tearing-wearing in brushes, windings and gear box. This presentation discussed the development of sensor-less control strategies for grid connected PMSG based variable speed wind energy conversion system with improved power quality features. A novel adaptive network-based fuzzy inference system was used to estimate the speed and position of variable speed PMSG under fluctuating wind conditions. A novel control strategy was developed for the grid interfacing inverter incorporating power quality improvement features at point of common coupling.

High-speed LWR transients simulation for optimizing emergency response

International Nuclear Information System (INIS)

Wulff, W.; Cheng, H.S.; Lekach, S.V.; Mallen, A.N.; Stritar, A.

1984-01-01

The purpose of computer-assisted emergency response in nuclear power plants, and the requirements for achieving such a response, are presented. An important requirement is the attainment of realistic high-speed plant simulations at the reactor site. Currently pursued development programs for plant simulations are reviewed. Five modeling principles are established and a criterion is presented for selecting numerical procedures and efficient computer hardware to achieve high-speed simulations. A newly developed technology for high-speed power plant simulation is described and results are presented. It is shown that simulation speeds ten times greater than real-time process-speeds are possible, and that plant instrumentation can be made part of the computational loop in a small, on-site minicomputer. Additional technical issues are presented which must still be resolved before the newly developed technology can be implemented in a nuclear power plant

New perspectives on constant-roll inflation

Science.gov (United States)

Cicciarella, Francesco; Mabillard, Joel; Pieroni, Mauro

2018-01-01

We study constant-roll inflation using the β-function formalism. We show that the constant rate of the inflaton roll is translated into a first order differential equation for the β-function which can be solved easily. The solutions to this equation correspond to the usual constant-roll models. We then construct, by perturbing these exact solutions, more general classes of models that satisfy the constant-roll equation asymptotically. In the case of an asymptotic power law solution, these corrections naturally provide an end to the inflationary phase. Interestingly, while from a theoretical point of view (in particular in terms of the holographic interpretation) these models are intrinsically different from standard slow-roll inflation, they may have phenomenological predictions in good agreement with present cosmological data.

Maximum wind energy extraction strategies using power electronic converters

Science.gov (United States)

Wang, Quincy Qing

2003-10-01

This thesis focuses on maximum wind energy extraction strategies for achieving the highest energy output of variable speed wind turbine power generation systems. Power electronic converters and controls provide the basic platform to accomplish the research of this thesis in both hardware and software aspects. In order to send wind energy to a utility grid, a variable speed wind turbine requires a power electronic converter to convert a variable voltage variable frequency source into a fixed voltage fixed frequency supply. Generic single-phase and three-phase converter topologies, converter control methods for wind power generation, as well as the developed direct drive generator, are introduced in the thesis for establishing variable-speed wind energy conversion systems. Variable speed wind power generation system modeling and simulation are essential methods both for understanding the system behavior and for developing advanced system control strategies. Wind generation system components, including wind turbine, 1-phase IGBT inverter, 3-phase IGBT inverter, synchronous generator, and rectifier, are modeled in this thesis using MATLAB/SIMULINK. The simulation results have been verified by a commercial simulation software package, PSIM, and confirmed by field test results. Since the dynamic time constants for these individual models are much different, a creative approach has also been developed in this thesis to combine these models for entire wind power generation system simulation. An advanced maximum wind energy extraction strategy relies not only on proper system hardware design, but also on sophisticated software control algorithms. Based on literature review and computer simulation on wind turbine control algorithms, an intelligent maximum wind energy extraction control algorithm is proposed in this thesis. This algorithm has a unique on-line adaptation and optimization capability, which is able to achieve maximum wind energy conversion efficiency through

Light speed and the expansion of the universe

Energy Technology Data Exchange (ETDEWEB)

Nagao, Shigeto, E-mail: snagao@lilac.plala.or.jp [Business Development and Licensing, Nippon Boehringer Ingelheim Co., Ltd (Japan)

2011-07-08

Based on the formerly proposed model of the time and universe, a time-course of the light speed along with the expansion of the universe is discussed. Formulas of light propagated distance of a supernova are derived, whose graphs showed an excellent consistency to the observed supernovae data. This outcome verifies that the universe has been expanding at a constant speed by our observed time as the model predicts.

A systematic method for correlating measurements of channel powers with the lattice constants in the neutron diffusion equations

International Nuclear Information System (INIS)

Buckler, A.N.

1978-10-01

The report describes the theoretical basis of the methods that have been developed for correlating measurements of spatially distributed quantities taken on the reactor with the lattice constants in the diffusion equations. The method can be used with any thermal reactor system of current interest, but the first application is to provide a replacement for the SAMSON code for Winfrith SGHW studies, where the measurements of interest are channel powers. (author)

Control design for a pitch-regulated, variable speed wind turbine

DEFF Research Database (Denmark)

Hansen, M.H.; Hansen, Anca Daniela; Larsen, Torben J.

2005-01-01

The three different controller designs presented herein are similar and all based on PI-regulation of rotor speed and power through the collective blade pitch angle and generator moment. The aeroelastic and electrical modelling used for the time-domainanalysis of these controllers are however...... different, which makes a directly quantitative comparison difficult. But there are some observations of similar behaviours should be mentioned: • Very similar step responses in rotor speed, pitch angle, and powerare seen for simulations with steps in wind speed. • All controllers show a peak in power...... for wind speed step-up over rated wind speed, which can be almost removed by changing the parameters of the frequency converter. • Responses of rotor speed, pitchangle, and power for different simulations with turbulent inflow are similar for all three controllers. Again, there seems to be an advantage...

Light speed variation from gamma ray burst GRB 160509A

Directory of Open Access Journals (Sweden)

Haowei Xu

2016-09-01

Full Text Available It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed. Even a tiny speed variation, when amplified by the cosmological distance, may be revealed by the observed time lags between photons with different energies from astrophysical sources. From the newly detected long gamma ray burst GRB 160509A, we find evidence to support the prediction for a linear form modification of light speed in cosmological space.

Light speed variation from gamma ray burst GRB 160509A

Energy Technology Data Exchange (ETDEWEB)

Xu, Haowei [School of Physics, State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Ma, Bo-Qiang, E-mail: mabq@pku.edu.cn [School of Physics, State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Center for High Energy Physics, Peking University, Beijing 100871 (China); Center for History and Philosophy of Science, Peking University, Beijing 100871 (China)

2016-09-10

It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed. Even a tiny speed variation, when amplified by the cosmological distance, may be revealed by the observed time lags between photons with different energies from astrophysical sources. From the newly detected long gamma ray burst GRB 160509A, we find evidence to support the prediction for a linear form modification of light speed in cosmological space.

Biomechanical parameters in lower limbs during natural walking and Nordic walking at different speeds.

Science.gov (United States)

Dziuba, Alicja K; Żurek, Grzegorz; Garrard, Ian; Wierzbicka-Damska, Iwona

2015-01-01

Nordic Walking (NW) is a sport that has a number of benefits as a rehabilitation method. It is performed with specially designed poles and has been often recommended as a physical activity that helps reduce the load to limbs. However, some studies have suggested that these findings might be erroneous. The aim of this paper was to compare the kinematic, kinetic and dynamic parameters of lower limbs between Natural Walking (W) and Nordic Walking (NW) at both low and high walking speeds. The study used a registration system, BTS Smart software and Kistler platform. Eleven subjects walked along a 15-metre path at low (below 2 m⋅s-1) and high (over 2 m⋅s-1) walking speeds. The Davis model was employed for calculations of kinematic, kinetic and dynamic parameters of lower limbs. With constant speed, the support given by Nordic Walking poles does not make the stroke longer and there is no change in pelvic rotation either. The only change observed was much bigger pelvic anteversion in the sagittal plane during fast NW. There were no changes in forces, power and muscle torques in lower limbs. The study found no differences in kinematic, kinetic and dynamic parameters between Natural Walking (W) and Nordic Walking (NW). Higher speeds generate greater ground reaction forces and muscle torques in lower limbs. Gait parameters depend on walking speed rather than on walking style.

On wind speed pattern and energy potential in Nigeria

International Nuclear Information System (INIS)

Adaramola, M.S.; Oyewola, O.M.

2011-01-01

The aim of this paper is to review wind speed distribution and wind energy availability in Nigeria and discuss the potential of using this resource for generation of wind power in the country. The power output from a wind turbine is strongly dependent on the wind speed and accurate information about the wind data in a targeted location is essential. The annual mean wind speeds in Nigeria range from about 2 to 9.5 m/s and the annual power density range between 3.40 and 520 kW/m 2 based on recent reported data. The trend shows that wind speeds are low in the south and gradually increases to relatively high speeds in the north. The areas that are suitable for exploitation of wind energy for electricity generation as well as for water pumping were identified. Also some of the challenges facing the development of wind energy and suggested solutions were presented. - Research Highlights: → Review of wind speed distribution and wind energy availability in Nigeria in presented. → The annual mean wind speeds in Nigeria range from about 2 to 9.5 m/s and the annual power density range between 3.40 and 520 kW/m 2 based on recent reported data. → The areas that are suitable for exploitation of wind energy for electricity generation as well as for water pumping were identified.

Game method application efficiency for speed and power capability development of trampoline athletes at the initial training stage

Directory of Open Access Journals (Sweden)

Alfia Deineko

2017-06-01

Full Text Available Purpose: to prove the effectiveness of using the game method for speed and power capability development of trampoline athletes at the initial training stage. Material & Methods: in the article the materials of the research that was carried out with the help of pedagogical testing of trampoliners of 7–8 years on the basis of the Children and Youth Sports School No. 7, Trampoline Department of Kharkov. Results: conducted pedagogical experiment showed the effectiveness of the developed methodology for the development of speed-strength abilities of trampoline athletes at the initial training stage using the game method. Conclusion: results of the experiment confirm the importance of the use of the game method for the development of speed-strength abilities in the initial training of young trampolines, which further affects the level of their technical preparedness and the effectiveness of competition activities.

Varying constants, black holes, and quantum gravity

International Nuclear Information System (INIS)

Carlip, S.

2003-01-01

Tentative observations and theoretical considerations have recently led to renewed interest in models of fundamental physics in which certain 'constants' vary in time. Assuming fixed black hole mass and the standard form of the Bekenstein-Hawking entropy, Davies, Davis and Lineweaver have argued that the laws of black hole thermodynamics disfavor models in which the fundamental electric charge e changes. I show that with these assumptions, similar considerations severely constrain 'varying speed of light' models, unless we are prepared to abandon cherished assumptions about quantum gravity. Relaxation of these assumptions permits sensible theories of quantum gravity with ''varying constants,'' but also eliminates the thermodynamic constraints, though the black hole mass spectrum may still provide some restrictions on the range of allowable models

Effects of Unloaded vs. Loaded Plyometrics on Speed and Power Performance of Elite Young Soccer Players

Directory of Open Access Journals (Sweden)

Ronaldo Kobal

2017-09-01

Full Text Available The purpose of this study was to investigate the effects of loaded and unloaded plyometric training strategies on speed and power performance of elite young soccer players. Twenty-three under-17 male soccer players (age: 15.9 ± 1.2 years, height: 178.3 ± 8.1 cm, body-mass (BM: 68.1 ± 9.3 kg from the same club took part in this study. The athletes were pair-matched in two training groups: loaded vertical and horizontal jumps using an haltere type handheld with a load of 8% of the athletes' body mass (LJ; n = 12 and unloaded vertical and horizontal plyometrics (UJ; n = 11. Sprinting speeds at 5-, 10-, and 20-m, mean propulsive power (MPP relative to the players' BM in the jump squat exercise, and performance in the squat jump (SJ and countermovement jump (CMJ were assessed pre- and post-training period. During the experimental period, soccer players performed 12 plyometric training sessions across a 6-week preseason period. Magnitude based inferences and standardized differences were used for statistical analysis. A very likely increase in the vertical jumps was observed for the LJ group (99/01/00 and 98/02/00 for SJ and CMJ, respectively. In the UJ group a likely increase was observed for both vertical jumps (83/16/01 and 90/10/00, for SJ and CMJ, respectively. An almost certainly decrease in the sprinting velocities along the 20-m course were found in the LJ group (00/00/100 for all split distances tested. Meanwhile, in the UJ likely to very likely decreases were observed for all sprinting velocities tested (03/18/79, 01/13/86, and 00/04/96, for velocities in 5-, 10-, and 20-m, respectively. No meaningful differences were observed for the MPP in either training group (11/85/04 and 37/55/08 for LJ and UJ, respectively. In summary, under-17 professional soccer players increased jumping ability after a 6-week preseason training program, using loaded or unloaded jumps. Despite these positive adaptations, both plyometric strategies failed to

Simulation and Study of Power Quality Issues in a Fixed Speed Wind Farm Substation

Directory of Open Access Journals (Sweden)

T. Magesh

2015-01-01

Full Text Available Power quality issues associated with the fixed speed wind farm substation located at Coimbatore district are investigated as the wind generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for wind, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled wind turbine. Various scenarios and their effects on the performance of the wind farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the wind farm before implementation.

Proposal for Ultrasonic Technique for evaluation elastic constants in UO2 pellets

International Nuclear Information System (INIS)

Lopes, Alessandra Susanne Viana Ragone; Baroni, Douglas Brandao; Bittencourt, Marcelo de Siqueira Queiroz; Souza, Mauro Carlos Lopes

2015-01-01

Pellets of uranium dioxide are used as fuel in nuclear power reactors, in which are exposed to high thermal gradients. This high energy will initiate fusion in the central part of the pellet. The expansion of the uranium dioxide pellets, resulting from fission products, can cause fissures or cracks, therefore, the study of their behavior is important. This work aims to develop and propose an ultrasonic technique to evaluate the elastic constants of UO 2 pellets. However, because of the difficulties in handling nuclear material, we proposed an initial study of alumina specimens. Alumina pellets are also ceramic material and their porosity and dimensions are in the similar range of dioxide uranium pellets. They also are used as thermal insulation in the fuel rods, operating under the same conditions. They were fabricated and used in two different sets of 10 alumina pellets with densities of 92% and 96%. The developed ultrasonic technique evaluates the traveling time of ultrasonic waves, longitudinal and transverse, and correlates the observed time and the elastic constants of the materials. Equations relating the speed of the ultrasonic wave to the elastic modulus, shear modulus and Poisson's ratio have led to these elastic constants, with graphics of correlation that showed excellent agreement with the literature available for Alumina. In view of the results and the ease of implementation of this technique, we believe that it may easily be used for dioxide uranium pellets, justifying further studies for that application. (author)

Variable speed control for Vertical Axis Wind Turbine

DEFF Research Database (Denmark)

Galinos, Christos; Larsen, Torben J.

A robust variable speed control for vertical axis wind turbine applications is implemented. It is a PI rotor speed controller based on an induction generator model operated at variable frequency. The generator dynamics are approximated by a first order differential equation with a prescribed slip....... In order to allow variability in the rotor speed an inverter is assumed which changes the nominal generator speed. Below rated power the optimum tip speed ratio is tracked, while above the power is constrained to rated. The wind speed which is needed in the control it is considered as a known signal...... the Inflow project. The investigation of the VAWT performance under different control parameters such as the PI gains has been performed by Christos Galinos. Deterministic and turbulent wind speed steps of 2 m/s from 6 m/s to 24 m/s and back to 12 m/s are applied. The controller gives smooth transient...

High-speed extended-term time-domain simulation for online cascading analysis of power system

Science.gov (United States)

Fu, Chuan

A high-speed extended-term (HSET) time domain simulator (TDS), intended to become a part of an energy management system (EMS), has been newly developed for use in online extended-term dynamic cascading analysis of power systems. HSET-TDS includes the following attributes for providing situational awareness of high-consequence events: (i) online analysis, including n-1 and n-k events, (ii) ability to simulate both fast and slow dynamics for 1-3 hours in advance, (iii) inclusion of rigorous protection-system modeling, (iv) intelligence for corrective action ID, storage, and fast retrieval, and (v) high-speed execution. Very fast on-line computational capability is the most desired attribute of this simulator. Based on the process of solving algebraic differential equations describing the dynamics of power system, HSET-TDS seeks to develop computational efficiency at each of the following hierarchical levels, (i) hardware, (ii) strategies, (iii) integration methods, (iv) nonlinear solvers, and (v) linear solver libraries. This thesis first describes the Hammer-Hollingsworth 4 (HH4) implicit integration method. Like the trapezoidal rule, HH4 is symmetrically A-Stable but it possesses greater high-order precision (h4 ) than the trapezoidal rule. Such precision enables larger integration steps and therefore improves simulation efficiency for variable step size implementations. This thesis provides the underlying theory on which we advocate use of HH4 over other numerical integration methods for power system time-domain simulation. Second, motivated by the need to perform high speed extended-term time domain simulation (HSET-TDS) for on-line purposes, this thesis presents principles for designing numerical solvers of differential algebraic systems associated with power system time-domain simulation, including DAE construction strategies (Direct Solution Method), integration methods(HH4), nonlinear solvers(Very Dishonest Newton), and linear solvers(SuperLU). We have

NTF – wind speed comparison

DEFF Research Database (Denmark)

Vesth, Allan; Gómez Arranz, Paula

The report describes measurements carried out on a given turbine. A comparison between wind speed on the met mast and Nacelle Wind speed are made and the results are presented on graphs and in a table. The data used for the comparison are the data that are same as used for the power curve report...

Simulating European wind power generation applying statistical downscaling to reanalysis data

International Nuclear Information System (INIS)

González-Aparicio, I.; Monforti, F.; Volker, P.; Zucker, A.; Careri, F.; Huld, T.; Badger, J.

2017-01-01

Highlights: •Wind speed spatial resolution highly influences calculated wind power peaks and ramps. •Reduction of wind power generation uncertainties using statistical downscaling. •Publicly available dataset of wind power generation hourly time series at NUTS2. -- Abstract: The growing share of electricity production from solar and mainly wind resources constantly increases the stochastic nature of the power system. Modelling the high share of renewable energy sources – and in particular wind power – crucially depends on the adequate representation of the intermittency and characteristics of the wind resource which is related to the accuracy of the approach in converting wind speed data into power values. One of the main factors contributing to the uncertainty in these conversion methods is the selection of the spatial resolution. Although numerical weather prediction models can simulate wind speeds at higher spatial resolution (up to 1 × 1 km) than a reanalysis (generally, ranging from about 25 km to 70 km), they require high computational resources and massive storage systems: therefore, the most common alternative is to use the reanalysis data. However, local wind features could not be captured by the use of a reanalysis technique and could be translated into misinterpretations of the wind power peaks, ramping capacities, the behaviour of power prices, as well as bidding strategies for the electricity market. This study contributes to the understanding what is captured by different wind speeds spatial resolution datasets, the importance of using high resolution data for the conversion into power and the implications in power system analyses. It is proposed a methodology to increase the spatial resolution from a reanalysis. This study presents an open access renewable generation time series dataset for the EU-28 and neighbouring countries at hourly intervals and at different geographical aggregation levels (country, bidding zone and administrative

Comprehensive Modeling and Analysis of Rotorcraft Variable Speed Propulsion System With Coupled Engine/Transmission/Rotor Dynamics

Science.gov (United States)

DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well

2013-01-01

This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean

Simplified equations for the rotational speed response to inflow velocity variation in fixed-pitch small wind turbines

Energy Technology Data Exchange (ETDEWEB)

Suzuki, H; Hasegawa, Y, E-mail: hsuzuki@nitech.ac.jp [Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2015-02-01

We propose simplified equations for the rotational speed response to inflow velocity variation in fixed-pitch small wind turbines. The present formulation is derived by introducing a series expansion for the torque coefficient at the constant tip-speed ratio. By focusing on the first- and second-order differential coefficients of the torque coefficient, we simplify the original differential equation. The governing equation based only on the first-order differential coefficient is found to be linear, whereas the second-order differential coefficient introduces nonlinearity. We compare the numerical solutions of the three governing equations for rotational speed in response to sinusoidal and normal-random variations of inflow velocity. The linear equation gives accurate solutions of amplitude and phase lag. Nonlinearity occurs in the mean value of rotational speed variation. We also simulate the rotational speed in response to a step input of inflow velocity using the conditions of two previous studies, and note that the form of this rotational speed response is a system of first-order time lag. We formulate the gain and time constant for this rotational speed response. The magnitude of the gain is approximately three when the wind turbine is operated at optimal tip-speed ratio. We discuss the physical meaning of the derived time constant. (paper)

Exhaust emissions of volatile organic compounds of powered two-wheelers: effect of cold start and vehicle speed. Contribution to greenhouse effect and tropospheric ozone formation.

Science.gov (United States)

Costagliola, M Antonietta; Murena, Fabio; Prati, M Vittoria

2014-01-15

Powered two-wheeler (PTW) vehicles complying with recent European type approval standards (stages Euro 2 and Euro 3) were tested on chassis dynamometer in order to measure exhaust emissions of about 25 volatile organic compounds (VOCs) in the range C1-C7, including carcinogenic compounds as benzene and 1,3-butadiene. The fleet consists of a moped (engine capacity ≤ 50 cm(3)) and three fuel injection motorcycles of different engine capacities (150, 300 and 400 cm(3)). Different driving conditions were tested (US FPT cycle, constant speed). Due to the poor control of the combustion and catalyst efficiency, moped is the highest pollutant emitter. In fact, fuel injection strategy and three way catalyst with lambda sensor are able to reduce VOC motorcycles' emission of about one order of magnitude with respect to moped. Cold start effect, that is crucial for the assessment of actual emission of PTWs in urban areas, was significant: 30-51% of extra emission for methane. In the investigated speed range, moped showed a significant maximum of VOC emission factor at minimum speed (10 km/h) and a slightly decreasing trend from 20 to 60 km/h; motorcycles showed on the average a less significant peak at 10 km/h, a minimum at 30-40 km/h and then an increasing trend with a maximum emission factor at 90 km/h. Carcinogenic VOCs show the same pattern of total VOCs. Ozone Formation Potential (OFP) was estimated by using Maximum Incremental Reactivity scale. The greatest contribution to tropospheric ozone formation comes from alkenes group which account for 50-80% to the total OFP. VOC contribution effect on greenhouse effect is negligible with respect to CO2 emitted. © 2013.

14 CFR 27.87 - Height-speed envelope.

Science.gov (United States)

2010-01-01

... applicable power failure condition in paragraph (b) of this section, a limiting height-speed envelope must be... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Height-speed envelope. 27.87 Section 27.87... STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight Performance § 27.87 Height-speed envelope. (a) If there is any...

Systematics of constant roll inflation

Science.gov (United States)

Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.

2018-02-01

We study constant roll inflation systematically. This is a regime, in which the slow roll approximation can be violated. It has long been thought that this approximation is necessary for agreement with observations. However, recently it was understood that there can be inflationary models with a constant, and not necessarily small, rate of roll that are both stable and compatible with the observational constraint ns ≈ 1. We investigate systematically the condition for such a constant-roll regime. In the process, we find a whole new class of inflationary models, in addition to the known solutions. We show that the new models are stable under scalar perturbations. Finally, we find a part of their parameter space, in which they produce a nearly scale-invariant scalar power spectrum, as needed for observational viability.

Low speed phaselock speed control system. [for brushless dc motor

Science.gov (United States)

Fulcher, R. W.; Sudey, J. (Inventor)

1975-01-01

A motor speed control system for an electronically commutated brushless dc motor is provided which includes a phaselock loop with bidirectional torque control for locking the frequency output of a high density encoder, responsive to actual speed conditions, to a reference frequency signal, corresponding to the desired speed. The system includes a phase comparator, which produces an output in accordance with the difference in phase between the reference and encoder frequency signals, and an integrator-digital-to-analog converter unit, which converts the comparator output into an analog error signal voltage. Compensation circuitry, including a biasing means, is provided to convert the analog error signal voltage to a bidirectional error signal voltage which is utilized by an absolute value amplifier, rotational decoder, power amplifier-commutators, and an arrangement of commutation circuitry.

Exploiting maximum energy from variable speed wind power generation systems by using an adaptive Takagi-Sugeno-Kang fuzzy model

International Nuclear Information System (INIS)

Galdi, V.; Piccolo, A.; Siano, P.

2009-01-01

Nowadays, incentives and financing options for developing renewable energy facilities and the new development in variable speed wind technology make wind energy a competitive source if compared with conventional generation ones. In order to improve the effectiveness of variable speed wind systems, adaptive control systems able to cope with time variances of the system under control are necessary. On these basis, a data driven designing methodology for TSK fuzzy models design is presented in this paper. The methodology, on the basis of given input-output numerical data, generates the 'best' TSK fuzzy model able to estimate with high accuracy the maximum extractable power from a variable speed wind turbine. The design methodology is based on fuzzy clustering methods for partitioning the input-output space combined with genetic algorithms (GA), and recursive least-squares (LS) optimization methods for model parameter adaptation

Research of digital constant fraction discriminator in PET system

International Nuclear Information System (INIS)

Du Yaoyao; Hu Xuanhou; Wu Jianping; Wang Peilin; Li Xiaohui; Li Daowu; Li Ke; Wei Long

2012-01-01

The research on digital constant fraction discriminator of spike pulse signal in PET detector is introduced. Based on FPGA technique, rapid signal's time information is extracted via DCFD algorithm after a high-speed ADC digitization. Experiment results show that time resolution of DCFD is 772 ps, which meets the requirement of time measurement in PET system well. (authors)

A methodology to generate statistically dependent wind speed scenarios

Energy Technology Data Exchange (ETDEWEB)

Morales, J.M.; Conejo, A.J. [Department of Electrical Engineering, Univ. Castilla - La Mancha, Campus Universitario s/n, 13071 Ciudad Real (Spain); Minguez, R. [Environmental Hydraulics Institute ' ' IH Cantabria' ' , Univ. Cantabria, Avenida de los Castros s/n, 39005 Santander (Spain)

2010-03-15

Wind power - a renewable energy source increasingly attractive from an economic viewpoint - constitutes an electricity production alternative of growing relevance in current electric energy systems. However, wind power is an intermittent source that cannot be dispatched at the will of the producer. Modeling wind power production requires characterizing wind speed at the sites where the wind farms are located. The wind speed at a particular location can be described through a stochastic process that is spatially correlated with the stochastic processes describing wind speeds at other locations. This paper provides a methodology to characterize the stochastic processes pertaining to wind speed at different geographical locations via scenarios. Each one of these scenarios embodies time dependencies and is spatially dependent of the scenarios describing other wind stochastic processes. The scenarios generated by the proposed methodology are intended to be used within stochastic programming decision models to make informed decisions pertaining to wind power production. The methodology proposed is accurate in reproducing wind speed historical series as well as computationally efficient. A comprehensive case study is used to illustrate the capabilities of the proposed methodology. Appropriate conclusions are finally drawn. (author)

A methodology to generate statistically dependent wind speed scenarios

International Nuclear Information System (INIS)

Morales, J.M.; Minguez, R.; Conejo, A.J.

2010-01-01

Wind power - a renewable energy source increasingly attractive from an economic viewpoint - constitutes an electricity production alternative of growing relevance in current electric energy systems. However, wind power is an intermittent source that cannot be dispatched at the will of the producer. Modeling wind power production requires characterizing wind speed at the sites where the wind farms are located. The wind speed at a particular location can be described through a stochastic process that is spatially correlated with the stochastic processes describing wind speeds at other locations. This paper provides a methodology to characterize the stochastic processes pertaining to wind speed at different geographical locations via scenarios. Each one of these scenarios embodies time dependencies and is spatially dependent of the scenarios describing other wind stochastic processes. The scenarios generated by the proposed methodology are intended to be used within stochastic programming decision models to make informed decisions pertaining to wind power production. The methodology proposed is accurate in reproducing wind speed historical series as well as computationally efficient. A comprehensive case study is used to illustrate the capabilities of the proposed methodology. Appropriate conclusions are finally drawn.

Relationship Between Change of Direction, Speed and Power in Male and Female National Olympic Team Handball Athletes.

Science.gov (United States)

Pereira, Lucas A; Nimphius, Sophia; Kobal, Ronaldo; Kitamura, Katia; Turisco, Luiz A L; Orsi, Rita C; Cal Abad, César Cs; Loturco, Irineu

2018-02-22

The aims of this study were to (1) assess the relationship between selected speed-power related abilities (determined by 20-m sprint, unloaded countermovement and squat jumps [CMJ and SJ] and loaded jump squat [JS]) and performance in two distinct change of direction (COD) protocols (Zigzag and T-Test), and (2) determine the magnitude of difference between female and male Brazilian National Olympic Team handball athletes. Fifteen male and twenty-three female elite handball athletes volunteered to perform the following assessments: SJ and CMJ; Zigzag and T-Test; 20-m sprint with 5-, 10-, and 20-m splits, and mean propulsive power (MPP) in JS. Pearson product moment correlation (Phandball athletes.

Reducing Heating In High-Speed Cinematography

Science.gov (United States)

Slater, Howard A.

1989-01-01

Infrared-absorbing and infrared-reflecting glass filters simple and effective means for reducing rise in temperature during high-speed motion-picture photography. "Hot-mirror" and "cold-mirror" configurations, employed in projection of images, helps prevent excessive heating of scenes by powerful lamps used in high-speed photography.

Relationships between field-based measures of strength and power and golf club head speed.

Science.gov (United States)

Read, Paul J; Lloyd, Rhodri S; De Ste Croix, Mark; Oliver, Jon L

2013-10-01

Increased golf club head speed (CHS) has been shown to result in greater driving distances and is also correlated with golf handicap. The purpose of this study was to investigate the relationships between field-based measures of strength and power and golf CHS with a secondary aim to determine the reliability of the selected tests. A correlation design was used to assess the following variables: anthropometrics, squat jump (SJ) height and squat jump peak power (SJPP), unilateral countermovement jump (CMJ) heights (right leg countermovement jump and left leg countermovement jump [LLCMJ]), bilateral CMJ heights, countermovement jump peak power (CMJPP), and medicine ball seated throw (MBST) and medicine ball rotational throw (MBRT). Fouty-eight male subjects participated in the study (age: 20.1 ± 3.2 years, height: 1.76 ± 0.07 m, mass: 72.8 ± 7.8 kg, handicap: 5.8 ± 2.2). Moderate significant correlations were reported between CHS and MBRT (r = 0.67; p golf athletes using the proposed battery of field tests. Additionally, movements that are more concentrically dominant in nature may display stronger relationships with CHS due to MBST and SJ displaying the highest explained variance after a stepwise linear regression.

Influence of the braking power control of the traction asynchronous machine in the voltage vector control system under DC

Directory of Open Access Journals (Sweden)

Юлія Олександрівна Слободенюк

2016-11-01

Full Text Available At braking the traction motors are transferred to generator mode and produce electrical energy which passes to the contact mains or storage device in the DC mains for further use. Such braking is called regenerative. The resulting electrical energy can be spent by trains in traction mode. Regenerative braking reduces the consumption of electric power for traction. In electric railways of our country more than 3% of the consumed electrical energy is given back to contact mains annually. As this takes place there arises the task to control the braking of the traction motors with minimal impact on electric power quality and maintaining proper braking performance. Based on the analysis of the characteristics of the brake traction of an electric locomotive with asynchronous electric machines the main braking modes have been chosen: at a constant sliding speed and the stator constant voltage; at constant braking power and the stator constant voltage; at a power value more than the nominal braking power; at a constant load torque; at a constant frequency of the stator. The vector control system with the formation of the reactive component of the stator current and the EMF regulator was chosen, basing on the working conditions characteristics in the electric braking mode (recuperation; namely, that the characteristics are defined by the laws regulating the frequency and voltage across the stator windings. This control system can fully reproduce any predetermined trajectory of traction and braking performance and adjust braking power. The offered system with recuperation can be used as a means of compensation in emergency situations with a power failure

Small Horizontal Axis Wind Turbine under High Speed Operation: Study of Power Evaluation

Science.gov (United States)

Moh. M. Saad, Magedi; Mohd, Sofian Bin; Zulkafli, Mohd Fadhli Bin; Abdullah, Aslam Bin; Rahim, Mohammad Zulafif Bin; Subari, Zulkhairi Bin; Rosly, Nurhayati Binti

2017-10-01

Mechanical energy is produced through the rotation of wind turbine blades by air that convert the mechanical energy into electrical energy. Wind turbines are usually designed to be use for particular applications and design characteristics may vary depending on the area of use. The variety of applications is reflected on the size of turbines and their infrastructures, however, performance enhancement of wind turbine may start by analyzing the small horizontal axis wind turbine (SHAWT) under high wind speed operation. This paper analyzes the implementations of SHAWT turbines and investigates their performance in both simulation and real life. Depending on the real structure of the rotor geometry and aerodynamic test, the power performance of the SHAWT was simulated using ANSYS-FLUENT software at different wind speed up to 33.33 m/s (120km/h) in order to numerically investigate the actual turbine operation. Dynamic mesh and user define function (UDF) was used for revolving the rotor turbine via wind. Simulation results were further validated by experimental data and hence good matching was yielded. And for reducing the energy producing cost, car alternator was formed to be used as a small horizontal wind turbine. As a result, alternator-based turbine system was found to be a low-cost solution for exploitation of wind energy.

A Simple Sensorless Scheme for Induction Motor Drives Fed by a Matrix Converter Using Constant Air-Gap Flux and PQR Transformation

DEFF Research Database (Denmark)

Blaabjerg, Frede; Lee, Kyo Beum

2007-01-01

This paper presents a new and simple method for sensorless operation of matrix converter drives using a constant air-gap flux and the imaginary power flowing to the motor. To improve low-speed sensorless performance, the non-linearities of a matrix converter drive such as commutation delays, turn......-on and turn-off times of switching devices, and on-state switching device voltage drop are modeled using PQR transformation and compensated using a reference current control scheme. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system...

Planck intermediate results. XXIV. Constraints on variation of fundamental constants

CERN Document Server

Ade, P A R; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Battaner, E.; Benabed, K.; Benoit-Levy, A.; Bernard, J.P.; Bersanelli, M.; Bielewicz, P.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Burigana, C.; Butler, R.C.; Calabrese, E.; Chamballu, A.; Chiang, H.C.; Christensen, P.R.; Clements, D.L.; Colombo, L.P.L.; Couchot, F.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Diego, J.M.; Dole, H.; Dore, O.; Dupac, X.; Ensslin, T.A.; Eriksen, H.K.; Fabre, O.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Gonzalez-Nuevo, J.; Gorski, K.M.; Gregorio, A.; Gruppuso, A.; Hansen, F.K.; Hanson, D.; Harrison, D.L.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hovest, W.; Huffenberger, K.M.; Jaffe, A.H.; Jones, W.C.; Keihanen, E.; Keskitalo, R.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lamarre, J.M.; Lasenby, A.; Lawrence, C.R.; Leonardi, R.; Lesgourgues, J.; Liguori, M.; Lilje, P.B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P.M.; Macias-Perez, J.F.; Mandolesi, N.; Maris, M.; Martin, P.G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Meinhold, P.R.; Melchiorri, A.; Mendes, L.; Menegoni, E.; Mennella, A.; Migliaccio, M.; Miville-Deschenes, M.A.; Moneti, A.; Montier, L.; Morgante, G.; Moss, A.; Munshi, D.; Murphy, J.A.; Naselsky, P.; Nati, F.; Natoli, P.; Norgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C.A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G.W.; Prunet, S.; Rachen, J.P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L.D.; Stolyarov, V.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.S.; Sygnet, J.F.; Tauber, J.A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Uzan, J.P.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L.A.; Yvon, D.; Zacchei, A.; Zonca, A.

2015-01-01

Any variation of the fundamental physical constants, and more particularly of the fine structure constant, $\\alpha$, or of the mass of the electron, $m_e$, would affect the recombination history of the Universe and cause an imprint on the cosmic microwave background angular power spectra. We show that the Planck data allow one to improve the constraint on the time variation of the fine structure constant at redshift $z\\sim 10^3$ by about a factor of 5 compared to WMAP data, as well as to break the degeneracy with the Hubble constant, $H_0$. In addition to $\\alpha$, we can set a constraint on the variation of the mass of the electron, $m_{\\rm e}$, and on the simultaneous variation of the two constants. We examine in detail the degeneracies between fundamental constants and the cosmological parameters, in order to compare the limits obtained from Planck and WMAP and to determine the constraining power gained by including other cosmological probes. We conclude that independent time variations of the fine structu...

Efficient high speed communications over electrical powerlines for a large number of users

Energy Technology Data Exchange (ETDEWEB)

Lee, J.; Tripathi, K.; Latchman, H.A. [Florida Univ., Gainesville, FL (United States). Dept. of Electrical and Computer Engineering

2007-07-01

Affordable broadband Internet communication is currently available for residential use via cable modem and other forms of digital subscriber lines (DSL). Powerline communication (PLC) systems were never considered seriously for communications due to their low speed and high development cost. However, due to technological advances PLCs are now spreading to local area networks and broadband over power line systems. This paper presented a newly proposed modification to the standard HomePlug 1.0 MAC protocol to make it a constant contention window-based scheme. The HomePlug 1.0 was developed based on orthogonal frequency division multiplexing (OFDM) and carrier sense multiple access with collision avoidance (CSMA/CA). It is currently the most commonly used technology of power line communications, supporting a transmission rate of up to 14 Mbps on the power line. However, the throughput performance of this original scheme becomes critical when the number of users increases. For that reason, a constant contention window based medium access control protocol algorithm of HomePlug 1.0 was proposed under the assumption that the number of active stations is known. An analytical framework based on Markov Chains was developed in order to model this modified protocol under saturation conditions. Modeling results accurately matched the actual performance of the system. This paper revealed that the performance can be improved significantly if the variables were parameterized in terms of the number of active stations. 15 refs., 1 tab., 6 figs.

Wheel speed management control system for spacecraft

Science.gov (United States)

Goodzeit, Neil E. (Inventor); Linder, David M. (Inventor)

1991-01-01

A spacecraft attitude control system uses at least four reaction wheels. In order to minimize reaction wheel speed and therefore power, a wheel speed management system is provided. The management system monitors the wheel speeds and generates a wheel speed error vector. The error vector is integrated, and the error vector and its integral are combined to form a correction vector. The correction vector is summed with the attitude control torque command signals for driving the reaction wheels.

Adjustable speed drive study, part 1

Science.gov (United States)

Wallace, A.

1989-08-01

Advances in speed control for motors in recent years, notably those in power electronics, have widened the range of application for several adjustable speed drive (ASD) types to include the smaller horsepower sizes. The dc motor drive, formerly in almost universal use for speed control, is being challenged by the high efficiency induction motor/pulse width modulation (PWM) drive; and for special small horsepower size applications, by the permanent magnet motor/PWM inverter drive or by the switched reluctance motor drive. The main characteristics of the several ASD types suitable for small horsepower size applications are discussed, as well as their unwanted side effects: poor power factor, harmonic distortion of the supply, acoustic noise, and electromagnetic interference. A procedure is recommended for determining which, if any, ASD to use.

Area, speed and power measurements of FPGA-based complex orthogonal space-time block code channel encoders

Science.gov (United States)

Passas, Georgios; Freear, Steven; Fawcett, Darren

2010-01-01

Space-time coding (STC) is an important milestone in modern wireless communications. In this technique, more copies of the same signal are transmitted through different antennas (space) and different symbol periods (time), to improve the robustness of a wireless system by increasing its diversity gain. STCs are channel coding algorithms that can be readily implemented on a field programmable gate array (FPGA) device. This work provides some figures for the amount of required FPGA hardware resources, the speed that the algorithms can operate and the power consumption requirements of a space-time block code (STBC) encoder. Seven encoder very high-speed integrated circuit hardware description language (VHDL) designs have been coded, synthesised and tested. Each design realises a complex orthogonal space-time block code with a different transmission matrix. All VHDL designs are parameterisable in terms of sample precision. Precisions ranging from 4 bits to 32 bits have been synthesised. Alamouti's STBC encoder design [Alamouti, S.M. (1998), 'A Simple Transmit Diversity Technique for Wireless Communications', IEEE Journal on Selected Areas in Communications, 16:55-108.] proved to be the best trade-off, since it is on average 3.2 times smaller, 1.5 times faster and requires slightly less power than the next best trade-off in the comparison, which is a 3/4-rate full-diversity 3Tx-antenna STBC.

Alterations in speed of squat movement and the use of accommodated resistance among college athletes training for power.

Science.gov (United States)

Rhea, Matthew R; Kenn, Joseph G; Dermody, Bryan M

2009-12-01

The purpose of this study was to assess the effect of heavy/slow movements and variable resistance training on peak power and strength development. Forty-eight National Collegiate Athletic Association (NCAA) Division I athletes (age: 21.4 +/- 2.1 years, all men) were recruited for this 12-week training intervention study. Maximum strength and jumping power were assessed before and after the training program. Athletes were randomly assigned to 1 of 3 training groups: heavy resistance/slow movement (Slow), lighter resistance and fast movement (Fast), or fast movements with accommodated resistance (FACC). All training groups performed similar training programs comprising free weight resistance training with lower-body compound exercises. The only difference among the training interventions was the speed at which subjects performed the squat exercise and the use of bands (Slow group: 0.2-0.4 meters/second; Fast group: 0.6-0.8 meters/second; FACC group trained 0.6-0.8 meters/second with the addition of accommodated resistance in the form of large elastic bands). Post-test data revealed a significant difference between power improvements between the Slow and FACC groups (p = 0.02). Percent increases and effect sizes (ES) demonstrated a much greater treatment effect in the FACC group (17.8%, ES = 1.06) with the Fast group (11.0%, ES = 0.80) adapting more than the Slow group (4.8%, ES = 0.28). The FACC and Slow groups improved strength comparatively (FACC: 9.44%, ES = 1.10; Slow: 9.59%, ES = 1.08). The Fast group improved strength considerably less, 3.20% with an effect size of only 0.38. Variable resistance training with elastic bands appears to provide greater performance benefits with regard to peak force and peak power than heavy, slow resistance exercise. Sports conditioning professionals can utilize bands, and high-speed contractions, to increase power development.

Complementary Aerodynamic Performance Datasets for Variable Speed Power Turbine Blade Section from Two Independent Transonic Turbine Cascades

Science.gov (United States)

Flegel, Ashlie B.; Welch, Gerard E.; Giel, Paul W.; Ames, Forrest E.; Long, Jonathon A.

2015-01-01

Two independent experimental studies were conducted in linear cascades on a scaled, two-dimensional mid-span section of a representative Variable Speed Power Turbine (VSPT) blade. The purpose of these studies was to assess the aerodynamic performance of the VSPT blade over large Reynolds number and incidence angle ranges. The influence of inlet turbulence intensity was also investigated. The tests were carried out in the NASA Glenn Research Center Transonic Turbine Blade Cascade Facility and at the University of North Dakota (UND) High Speed Compressible Flow Wind Tunnel Facility. A large database was developed by acquiring total pressure and exit angle surveys and blade loading data for ten incidence angles ranging from +15.8deg to -51.0deg. Data were acquired over six flow conditions with exit isentropic Reynolds number ranging from 0.05×106 to 2.12×106 and at exit Mach numbers of 0.72 (design) and 0.35. Flow conditions were examined within the respective facility constraints. The survey data were integrated to determine average exit total-pressure and flow angle. UND also acquired blade surface heat transfer data at two flow conditions across the entire incidence angle range aimed at quantifying transitional flow behavior on the blade. Comparisons of the aerodynamic datasets were made for three "match point" conditions. The blade loading data at the match point conditions show good agreement between the facilities. This report shows comparisons of other data and highlights the unique contributions of the two facilities. The datasets are being used to advance understanding of the aerodynamic challenges associated with maintaining efficient power turbine operation over a wide shaft-speed range.

High speed heterostructure devices

CERN Document Server

Beer, Albert C; Willardson, R K; Kiehl, Richard A; Sollner, T C L Gerhard

1994-01-01

Volume 41 includes an in-depth review of the most important, high-speed switches made with heterojunction technology. This volume is aimed at the graduate student or working researcher who needs a broad overview andan introduction to current literature. Key Features * The first complete review of InP-based HFETs and complementary HFETs, which promise very low power and high speed * Offers a complete, three-chapter review of resonant tunneling * Provides an emphasis on circuits as well as devices.

Introducing a system of wind speed distributions for modeling properties of wind speed regimes around the world

International Nuclear Information System (INIS)

Jung, Christopher; Schindler, Dirk; Laible, Jessica; Buchholz, Alexander

2017-01-01

Highlights: • Evaluation of statistical properties of 10,016 empirical wind speed distributions. • Analysis of the shape of empirical wind speed distributions by L-moment ratios. • Introduction of a new system of wind speed distributions (Swd). • Random forests classification of the most appropriate distribution. • Comprehensive goodness of Swd fit evaluation on a global scale. - Abstract: Accurate modeling of empirical wind speed distributions is a crucial step in the estimation of average wind turbine power output. For this purpose, the Weibull distribution has often been fitted to empirical wind speed distributions. However, the Weibull distribution has been found to be insufficient to reproduce many wind speed regimes existing around the world. Results from previous studies demonstrate that numerous one-component distributions as well as mixture distributions provide a better goodness-of-fit to empirical wind speed distributions than the Weibull distribution. Moreover, there is considerable interest to apply a single system of distributions that can be utilized to reproduce the large majority of near-surface wind speed regimes existing around the world. Therefore, a system of wind speed distributions was developed that is capable of reproducing the main characteristics of existing wind speed regimes. The proposed system consists of two one-component distributions (Kappa and Wakeby) and one mixture distribution (Burr-Generalized Extreme Value). A random forests classifier was trained in order to select the most appropriate of these three distributions for each of 10,016 globally distributed empirical wind speed distributions. The shape of the empirical wind speed distributions was described by L-moment ratios. The L-moment ratios were used as predictor variables for the random forests classifier. The goodness-of-fit of the system of wind speed distributions was evaluated according to eleven goodness-of-fit metrics, which were merged into one

14 CFR 29.1517 - Limiting height-speed envelope.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limiting height-speed envelope. 29.1517... Operating Limitations § 29.1517 Limiting height-speed envelope. For Category A rotorcraft, if a range of... following power failure, the range of heights and its variation with forward speed must be established...

Regenerative Braking Compensatory Control Strategy Considering CVT Power Loss for Hybrid Electric Vehicles

Directory of Open Access Journals (Sweden)

Yang Yang

2018-02-01

Full Text Available Hybrid electric vehicles (HEV equipped with continuously variable transmission (CVT adjust the motor operating point continuously to achieve the optimal motor operating efficiency during regenerative braking. Traditional control strategies consider the CVT efficiency as constant, while the CVT efficiency varies in different operating conditions. In order to reflect the transmission efficiency more accurately during regenerative braking, the CVT theoretical torque loss model is firstly established which then leads to the battery–front motor–CVT joint operating efficiency model. The joint operating efficiency model indicates that the system efficiency is influenced by input speed, input torque, CVT speed ratio, and battery SOC (state of charge. The compensatory strategy for the front motor barking force is proposed to make full use of its braking power and the CVT speed ratio control strategy is modified to maintain the optimal operating efficiency of the system. The simulations are performed under three typical braking conditions and UDDS, NYCC, US06 respectively, the results show that the modified control strategy increases the front motor braking power and improves the system operating efficiency.

Kummer strikes back : new DH speed records

NARCIS (Netherlands)

Bernstein, D.J.; Chuengsatiansup, C.; Lange, T.; Schwabe, P.

2014-01-01

This paper introduces high-security constant-time variable-base-point Diffie--Hellman software using just 274593 Cortex-A8 cycles, 91460 Sandy Bridge cycles, 90896 Ivy Bridge cycles, or 72220 Haswell cycles. The only higher speed appearing in the literature for any of these platforms is a claim of

Regulation strategies for wind power fluctuations depending on demand in Spain

Energy Technology Data Exchange (ETDEWEB)

Martin-Martinez, Sergio; Vigueras-Rodriguez, Antonio; Gomez-Lazaro, Emilio [Universidad de Castilla-La Mancha, Albacete (Spain). Energy Research Inst.; Fuentes, Juan Alvaro; Molina-Garcia, Angel [Cartagena Univ. (Spain). Dept. of Electrical Engineering

2010-07-01

Power systems need more flexibility as far as significant amounts of load are being covered by wind power. The variations of large wind power production impose some adverse effects on the power system. Some of these effects are the cycling losses on centralized units, discarded wind energy and increase of reserve requirements. Cycling losses derived from a non-optimal operation on great thermal and hydro power plants is an important issue produced by the stochastic wind power nature. Discarded wind energy is produced when the system can not assimilate all the wind power production. Reserve requirements are increased to keep the system balance with the secondary control. Different control functions have been developed for active power production. Some of them are balance control, delta control and power gradient limitation. Balance control consists in adjusting the production in steps to a set point constant production. The delta production constraint consists on limiting the current production to a fix delta power value below the possible production. This constraint is usually used for increasing the regulation capabilities in the wind farm. The Delta constraint can also be used jointly with the negative ramp limiting strategy, allowing then also to fix a maximum negative gradient for the cases in which the wind speed is decreasing and it is possible to limit that descend by reducing the delta value. The power gradient limiting strategy consists in a limitation of the maximum increasing gradient of the current production, i.e. it prevents the farm production from increasing too fast when the wind speed is rising or when the farm is to be started in high wind. It the wind speed is decreasing, then the constraint does not have any function. On the other hand, the negative ramp limiting strategy consists in a limitation of the maximum decreasing gradient of the current production. If the wind speed is increasing, then the constraint does not have any function. This

A Comparison Study between Two MPPT Control Methods for a Large Variable-Speed Wind Turbine under Different Wind Speed Characteristics

Directory of Open Access Journals (Sweden)

Dongran Song

2017-05-01

Full Text Available Variable speed wind turbines (VSWTs usually adopt a maximum power point tracking (MPPT method to optimize energy capture performance. Nevertheless, obtained performance offered by different MPPT methods may be affected by the impact of wind turbine (WT’s inertia and wind speed characteristics and it needs to be clarified. In this paper, the tip speed ratio (TSR and optimal torque (OT methods are investigated in terms of their performance under different wind speed characteristics on a 1.5 MW wind turbine model. To this end, the TSR control method based on an effective wind speed estimator and the OT control method are firstly presented. Then, their performance is investigated and compared through simulation test results under different wind speeds using Bladed software. Comparison results show that the TSR control method can capture slightly more wind energy at the cost of high component loads than the other one under all wind conditions. Furthermore, it is found that both control methods present similar trends of power reduction that is relevant to mean wind speed and turbulence intensity. From the obtained results, we demonstrate that, to further improve MPPT capability of large VSWTs, other advanced control methods using wind speed prediction information need to be addressed.

Novel high efficient speed sensorless controller for maximum power extraction from wind energy conversion systems

International Nuclear Information System (INIS)

Fathabadi, Hassan

2016-01-01

Highlights: • Novel sensorless MPPT technique without drawbacks of other sensor/sensorless methods. • Tracking the actual MPP of WECSs, no tracking the MPP of their wind turbines. • Actually extracting the highest output power from WECSs. • Novel MPPT technique having the MPPT efficiency more than 98.5% for WECSs. • Novel MPPT technique having short convergence time for WECSs. - Abstract: In this study, a novel high accurate sensorless maximum power point tracking (MPPT) method is proposed. The technique tracks the actual maximum power point of a wind energy conversion system (WECS) at which maximum output power is extracted from the system, not the maximum power point of its wind turbine at which maximum mechanical power is obtained from the turbine, so it actually extracts the highest output power from the system. The technique only uses input voltage and current of the converter used in the system, and neither needs any speed sensors (anemometer and tachometer) nor has the drawbacks of other sensor/sensorless based MPPT methods. The technique has been implemented as a MPPT controller by constructing a WECS. Theoretical results, the technique performance, and its advantages are validated by presenting real experimental results. The real static-dynamic response of the MPPT controller is experimentally obtained that verifies the proposed MPPT technique high accurately extracts the highest instant power from wind energy conversion systems with the MPPT efficiency of more than 98.5% and a short convergence time that is only 25 s for the constructed system having a total inertia and friction coefficient of 3.93 kg m 2 and 0.014 N m s, respectively.

Constant force linear permanent magnet actuators

NARCIS (Netherlands)

Paulides, J.J.H.; Encica, L.; Meessen, K.J.; Lomonova, E.A.

2009-01-01

In applications, such as vibration isolation, gravity compensation, pick-and-place machines, etc., there is a need for (long-stroke) passive constant force actuators combined with tubular permanent magnet actuators to minimize the power consumption, hence, passively counteract the gravitational

Constant-Temperature Calorimetry for In-Core Power Measurement

International Nuclear Information System (INIS)

Radcliff, Thomas D.; Miller, Don W.; Kauffman, Andrew C.

2000-01-01

Reactor thermal limits are based on fuel energy deposition and cladding temperature. This paper presents a two-wire in-core instrument that directly measures fuel energy deposition. The instrument is based on the addition of heat through resistive dissipation of input electrical energy to a small mass of reactor fuel or fuel analogue. A feedback loop controls the input electrical energy needed to maintain the fuel mass at a nearly constant temperature regardless of the nuclear energy deposited in the mass. Energy addition to the fuel and fuel temperature feedback to the controller are provided by a resistive heating element embedded in the fuel mass. As long as the external heat transfer environment remains constant, the input electrical energy is inversely related to the actual nuclear energy deposition. To demonstrate this instrument, we first scaled the sensor and controller parameters and then used the results to guide fabrication of prototype instruments. In-reactor testing was performed to measure the instrument sensitivity, linearity, bandwidth, and long-term drift characteristics of the prototypes. The instrument is shown to be capable of high-sensitivity, linear measurement of fuel energy deposition with sufficient bandwidth for safety-related measurements. It is also clear that a means to compensate the sensor for changes in the external heat transfer environment is required. Means of actively measuring heat losses and performing this compensation are discussed