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Performance Analysis of Three Phase PWM Voltage Source Inverter Fed Three Phase Induction Motor Drive  

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Full Text Available This paper deals with the performance analysis of three phase induction motor drive fed by a PWM voltage source inverter. The PWM method, which involves the modulation of conventional sinusoidal reference signal and a triangular carrier is used here to produce pulse width modulated output only for under modulation index. This paper work deals mainly with the performance analysis of three phase induction motor fed by PWM voltage source inverter in terms of phase current of inverter, rotor and stator current , speed ,electromagnetic torque developed and total harmonic distortion in line and phase voltage of inverter for under modulation range i.e. ma<1. For the implementation of the proposed drive the MATLAB/SIMLINK environment has been used. Two types of the switching techniques are available for the production of the balanced three phase output voltage i.e. either unipolar scheme or bipolar scheme but only unipolar scheme has been used as it offers several advantages. The performance of the inverter has been carried out by using the parameter total harmonic distortion. The impact of the modulation index on the performance of the inverter has been done in terms of the waveforms for inverter phase voltage, line voltage, line current, stator current, rotor current, rotor speed and electromagnetic torque developed by the motor

Amit Kumar Sharma; Tushar Deep Saxena; Shirazul Islam; Arun kumar Yadav

2013-01-01

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A single leg switched PWM method for three-phase H-Bridge Voltage Source Converters  

DEFF Research Database (Denmark)

This paper proposes a single leg switched or a hybrid PWM (HPWM) method for three-phase three-level H-Bridge Voltage Source Converters (3L-HB-VSCs). By means of the proposed modulation, a 3L-HB-VSC can generate the same output as a three-level neutral point clamped (3L-NPC) VSC with phase disposition (PD) PWM provided that the outputs of 3L-HBVSC are isolated by transformers or connected to open winding machines. Thus, the proposed method is called PD-HPWM. Moreover, it is emphasized that 3L-HB-VSC with HPWM utilizes its switches similar to 3L-NPC-VSC. Compared to 3L-NPC-VSCs, 3L-HB-VSCs (without neutral point clamping diodes) have simpler, more modular, and more reliable 2L circuit structure. Therefore, this method encourages the use of 3L-HB-VSCs in the applications utilizing transformers such as grid-side converters of multi-MW wind turbines. The proposed PWM method's performance is demonstrated by the simulations of a 6MW wind turbine's grid connection and experimentally verified via a smallscale prototype.

Senturk, Osman Selcuk; Helle, Lars

2009-01-01

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High Performance FPGA Based Digital Space Vector PWM Three Phase Voltage Source Inverter  

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Full Text Available This paper focuses on the design of a low power and high performance FPGA based Digital Space Vector Pulse Width Modulation (DSVPWM) controller for three phase voltage source inverter. A new method is proposed to realize easy, accurate and high performance DSVPWM technique based on FPGA with low resource consumption and reduced execution time than conventional methods. Equations of SVPWM are relatively complicated and need a considerable time to execute on a typical microcontroller, therefore a simple method is presented to minimize run time of instructions, e.g. the multiplication operation used in these equations is replaced by a proposed signed and unsigned shifter using 2 to 1 multiplexer unit. Total power consumption of controller is reduced to 37 mW at 100MHz clock frequency. The proposed DSVPWM technique algorithm was synthesized and implemented using Quartus II 9.1V and Cyclone II FPGA, to target device EP2C20F484C6. Also power is analyzed using XPower analyzer. Experimentation and results demonstrate that proposed method have high performance than other works.

Bahram Rashidi; Mehran Sabahi

2013-01-01

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An Active-Passive Capacitor-Commutated Converter for HVDC Systems with a Three-Phase Voltage-Source PWM Converter  

Science.gov (United States)

This paper introduces a new approach to the capacitor-commutated converters (CCCs) for HVDC systems. A small-rated three-phase voltage-source PWM converter is connected between a series commutation capacitor and thyristor converter through matching transformers. The PWM converter acts as auxiliary commutation-capacitor for the thyristor converter while the series passive capacitor acts as the main commutation capacitor. The capacitance, which is the sum of the small-rated active and series passive capacitors, is variable, so that stable commutation is obtained. In CCCs commutation failure occurs when the ac bus voltage is recovered whereas the proposed combined commutation-capacitor can achieve successful commutation for both rapidly decreasing and increasing ac bus voltages. The basic principle of the proposed active-passive capacitor commutated converter is discussed in detail. Then, constant margin-angle control with a constant firing angle of the thyristor converter is proposed using a function generator block. Digital simulation demonstrates the novelty and effectiveness of the proposed active-passive capacitor commutated converter.

Tanaka, Toshihiko; Funabiki, Shigeyuki; Nakazato, Masafumi

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Effective Improvement of DC Busline Voltage Utilization Factor in Two Switch-Auxiliary Quasi-Resonant DC Link Snubber Assisted Three Phase Voltage Source Type Soft-Switching PWM Inverter  

Science.gov (United States)

In recent years, a resonant snubber to minimize switching power losses and EMI noises have attracted special interest for the voltage-fed soft switching sinewave PWM inverters and active rectifiers. The authors have discussed the performance evaluations on lower noise and high efficiency for two switch auxiliary resonant DC link snubber assisted three-phase voltage-fed soft switching PWM inverter. It was proved that cost effective three phase soft switching inverter treated here is able to improve both efficiency and EMI noise. However, some practical problems to be improved have recognized for the soft-switching three phase PWM inverter treated here from a practical point of view. This three phase soft-switching inverter with two switch type auxiliary resonant DC link snubber has significant disadvantages of DC busline link voltage reduction for the existence of the zero voltage mode transition period as well as the larger size and physical volume of electrolytic capacitor incorporated into the resonant DC link snubber. The additional technology to minimize the busline DC link zero voltage period in order to overcome the practical problems mentioned above is newly proposed in this paper. From experimental and simulation viewpoints, the modified version of this soft-switching inverter is discussed and evaluated for the DC busline voltage utilization factor as compared with the previously developed one.

Nagai, Shinichiro; Sato, Shinji; Yamamoto, Masayoshi; Hiraki, Eiji; Nakaoka, Mutsuo

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Reduced Snubber Circuit Elements For Pwm Voltage Source Inverter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents the description and simulation of a new proposed arrangement of RLD/RCD snubber circuit used with pulse width modulated voltage source inverter. The new arrangement allows minimizing the number of active elements of RCD with 50%. This will help the designer to reduce the size of ...

Saied, Basil M.

7

Control and Modeling of Shaft Generator with PWM Voltage Source Inverter for ship  

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Full Text Available This papers deals with well – based mathematicalmodeling of variable speed alternator (Shaft Generator) withPWM voltage source inverter used in ship. Detailed knowledge ofelectromagnetic characteristics of shaft generator is necessary fordesign complex ship's power system. Such knowledge isobtainable only by numerical simulations. The dynamic behaviorof shaft generators, SPWM voltage source inverter and theircontrollers during load variations are also discussed with the helpof MATLAB/SIMULINK. Elimination of harmonic contentsusing sinusoidal pulse width modulation also discussed here.

Sathish Kumar T; Gowrishankar J

2012-01-01

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Modulation Index Effect on the 5-Level SHE-PWM Voltage Source Inverter  

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Full Text Available Harmonic content of the voltage source inverters is important and must be in the allowed ranges. Different method are proposed to decrease the Total Harmonic Distortion (THD) and caused to be sinusoidal the output voltage of inverters. One of these methods is using multilevel structure. In this structure many important parameters which are effective on voltage source inverter operation that among them we can mention to modulation index (MI). Variation of modulation index can change the THD. One of the harmonic reduction methods is using multilevel structure. In this paper, a sample 5-level SHE-PWM voltage source inverter is presented and all equation and choosing switching angles for elimination desired harmonics from different order. To investigate the effective parameters on the inverter operation, a typical 5-level inverter is simulated in PSPICE software. The simulation has been done for different values of modulation and its effect on the inverter operation is evaluated.

Hassan Feshki Farahani

2011-01-01

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for High-Power Three-Phase PWM Inverters  

UK PubMed Central (United Kingdom)

This dissertation is devoted to a unified and comprehensive study of zero-current-transition(ZCT) soft-switching techniques for high-power three-phase PWM inverter applications. Majorefforts in this study are as follows: 1) Conception of one new ZCT scheme and one new ZCTtopology; 2) Systematic comparison of a family of ZCT inverters; 3) Design, implementation andexperimental evaluation of two 55-kW prototype inverters for electric vehicle (EV) motor drivesthat are developed based on the proposed ZCT concepts; and 4) Investigation of the ZCTconcepts in megawatts high-frequency power conversions. The proposed ZCT techniques arealso applicable to three-phase power-factor-correction (PFC) rectifier applications.

Yong Li; Dan Chen; Guo-quan Lu

10

A new PWM algorithm for battery-source three-phase inverters  

Energy Technology Data Exchange (ETDEWEB)

A new PWM algorithm for battery-source three-phase inverters is described in this paper. The concept of the algorithm is to determine the pulsewidths by equating the areas of the segments of the sinusodial reference with the related output pulse areas. The algorithm is particularly suitable to handle a non-constant voltage source with good harmonic suppression. Since the pulsewidths are computable in real time with minimal storage requirement as well as compact hardware and software, it is especially suitable for single-chip microcomputer implementation. Experimental results show that the single-chip microcomputer Intel 8095-based battery-source inverter can control a 3 kW synchronous motor drive satisfactorily over a frequency range of 2 to 100Hz.

Chan, C.C. (Dept. of Electrical and Electronic Engineering, Univ. of Hong Kong, Pokfulam Road (HK)); Chau, K.T. (Dept. of Electrical Engineering, Hong Kong Polytechnic, Hung Hom (HK))

1991-01-01

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Analysis of Discontinuous Space Vector PWM Techniques for a Seven-Phase Voltage Source Inverter  

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Full Text Available This paper presents discontinuous space vector PWM (DPWM) techniques for a seven-phase voltage source inverter (VSI). Space vector model of a seven-phase VSI shows that there exist 128 space vectors with different lengths and maps into fourteen sided polygons. A number of possibilities could arise to implement modulation of inverter legs due to large number of available space voltage vectors. Two strategies are adopted here; one utilising large and two middle sets of space vectors to implement discontinuous space vector PWM. Clamping of legs of inverter to either positive or negative dc bus leads to discontinuity in the switching and consequently offers reduced switching loss modulation strategy. A significant reduction in switching losses can be achieved while employing DPWM in a seven-phase VSI. A generalised method is also proposed to realize the DPWM in a seven-phase VSI. Comparison of continuous and discontinuous PWM is presented in terms of switching current ripple. The experimental set-up is illustrated and the experimental results are presented.

Mohd. Arif Khan; Atif iqbal; Sk Moin Ahmad; zakir husain

2012-01-01

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Simulation Study of the Carrier-Based PWM Method in Three- Phase Flying Capacitor Inverters  

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Full Text Available This paper is a simulation study ofmodulation strategies in three-phase flying capacitorinverters. Under investigation are those strategies thatsolve the capacitor voltage balancing problem: phaseshiftPWM method, the saw-tooth rotation PWM methodand carrier redistribution PWM method. The results areshown through simulation.

Adrian ?chiop

2008-01-01

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On the Loading of Power Modules in a Three Phase Voltage Source Converter  

UK PubMed Central (United Kingdom)

The loading of free wheel diodes (FWD) andIGBTs in the power modules of a Voltage Source Converter(VSC) are investigated. In converter duty, the FWD isutilized more then the IGBT. Presently, most FWD's inpower modules are optimized for inverter duty. Thispractice tends to undersize the FWD from a converterviewpoint. This design philosophy is examined in the paper.For this purpose, the original dynamic thermal model ofIGBT and FWD were developed. Model parameters wereidentified from the manufacturers catalogue data. Amathematical model of the entire VSC was developed tocompute current, voltage, power and thermal conditions forthe power module and other components in converteroperation.I. INTRODUCTIONThe power module of Voltage Source Inverter (VSI) in anelectric drive consists an IGBT with an anti-parallel freewheel diode (FWD). The module is highly optimized forinverter duty applications with an assumption that driveoperates from moderately low to ...

Vladimir Blasko; Richard Lukaszewski

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An improved design of virtual output impedance loop for droop-controlled parallel three-phase Voltage Source Inverters  

DEFF Research Database (Denmark)

The virtual output impedance loop is known as an effective way to enhance the load sharing stability and quality of droop-controlled parallel inverters. This paper proposes an improved design of virtual output impedance loop for parallel three-phase voltage source inverters. In the approach, a virtual output impedance loop based on the decomposition of inverter output current is developed, where the positive- and negative-sequence virtual impedances are synthesized separately. Thus, the negative-sequence circulating current among the parallel inverters can be minimized by using a large negative-sequence virtual resistance even in the case of feeding a balanced three-phase load. Furthermore, to adapt to the variety of unbalanced loads, a dynamically-tuned negative-sequence resistance loop is designed, such that a good compromise between the quality of inverter output voltage and the performance of load sharing can be obtained. Finally, laboratory test results of two parallel three-phase voltage source inverters are shown to confirm the validity of the proposed method.

Wang, Xiongfei; Blaabjerg, Frede

2012-01-01

15

Analysis of Peak-to-Peak Current Ripple Amplitude in Seven-Phase PWM Voltage Source Inverters  

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Full Text Available Multiphase systems are nowadays considered for various industrial applications. Numerous pulse width modulation (PWM) schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported. Determination of current ripple in multiphase PWM voltage source inverters is important for both design and control purposes. This paper gives the complete analysis of the peak-to-peak current ripple distribution over a fundamental period for multiphase inverters, with particular reference to seven-phase VSIs. In particular, peak-to-peak current ripple amplitude is analytically determined as a function of the modulation index, and a simplified expression to get its maximum value is carried out. Although reference is made to the centered symmetrical PWM, being the most simple and effective solution to maximize the DC bus utilization, leading to a nearly-optimal modulation to minimize the RMS of the current ripple, the analysis can be readily extended to either discontinuous or asymmetrical modulations, both carrier-based and space vector PWM. A similar approach can be usefully applied to any phase number. The analytical developments for all different sub-cases are verified by numerical simulations.

Gabriele Grandi; Jelena Loncarski

2013-01-01

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3-Level Three Phase Soft-Switching PWM Rectifier with Single Auxiliary Resonant Commutated Snubber Circuit  

Science.gov (United States)

This paper presents a novel type of 3-level 3-phase 3-switch type voltage-fed soft-switching PWM AC/DC Converter with new Active Auxiliary Resonant Commutated Snubber topology which can operate under a condition of Zero Voltage Switching. The operating performances of the proposed three phase soft-switching PWM rectifier which is more suitable for power systems applications is evaluated on the basis of Simulation results.

Yamamoto, Msayoshi; Sato, Shinji; Nakaoka, Mutsuo

17

Control Schemes for Auxiliary Switches of Three-Phase PWM Resonant Snubber Inverters  

Science.gov (United States)

Control schemes for auxiliary switches of PWM controlled three-phase resonant snubber inverters (RSIs) are proposed. The control schemes proposed in this paper are based on a conventional PWM technique. To avoid zero voltage switching lost conditions, the conventional PWM technique is modified in the proposed schemes. The proposed control schemes are so simple that they are suitable for digital control. In this paper, a CPLD (Complex Programmable Logic Device)-based control IC, which realizes the proposed control schemes, for three-phase auxiliary RSIs is also proposed and implemented. The IC generates gate-signals for main- and auxiliary-devices of the three-phase RSI based on the proposed control schemes. The effectiveness of the proposed control schemes were verified through the experiments. As the results, ZVS (Zero Voltage Switching) turn-on at the main devices was achieved and a smooth sinusoidal output current was obtained by use of the control IC.

Hoshi, Nobukazu; Oguchi, Kuniomi

18

Intelligent Optimize Design of LCL Filter for Three-Phase Voltage-Source PWM Rectifier  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Compared to traditional L filter, a LCL filter is more effective on reducing harmonic distortion at switch frequency. So it is important to choose the LCL filter parameters to achieve good filtering effect. This paper introduces some traditional design methods. Design of a LCL filter by genetic algo...

Sun, Wei; Chen, Zhe; Wu, Xiaojie

19

Intelligent Optimize Design of LCL Filter for Three-Phase Voltage-Source PWM Rectifier  

DEFF Research Database (Denmark)

Compared to traditional L filter, a LCL filter is more effective on reducing harmonic distortion at switch frequency. So it is important to choose the LCL filter parameters to achieve good filtering effect. This paper introduces some traditional design methods. Design of a LCL filter by genetic algorithm (GA) and particle swam optimization (PSO) are presented in this paper and comparison of the two intelligent optimization. Simulation result and calculate data are provided to prove that intelligent optimization are more effective and simple than traditional methods.

Sun, Wei; Chen, Zhe

2009-01-01

20

Modeling, analysis, and design of stationary reference frame droop controlled parallel three-phase voltage source inverters  

DEFF Research Database (Denmark)

Power electronics based microgrids consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of three-phase VSIs are derived. The proposed voltage and current inner control loops and the mathematical models of the VSIs were based on the stationary reference frame. A hierarchical control for the paralleled VSI system was developed based on three levels. The primary control includes the droop method and the virtual impedance loops, in order to share active and reactive power. The secondary control restores the frequency and amplitude deviations produced by the primary control. And the tertiary control regulates the power flow between the grid and the microgrid. Also, a synchronization algorithm is presented in order to connect the microgrid to the grid. The evaluation of the hierarchical control is presented and discussed. Experimental results are provided to validate the performance and robustness of the VSIs functionality during Islanded and grid-connected operations, allowing a seamless transition between these modes through control hierarchies by regulating frequency and voltage, main-grid interactivity, and to manage power flows between the main grid and the VSIs.

Vasquez, Juan Carlos; Guerrero, Josep M.

2011-01-01

 
 
 
 
21

Converter-flux-based current control of voltage source PWM rectifiers - analysis and implementation  

Energy Technology Data Exchange (ETDEWEB)

Pulsewidth-modulated (PWM) rectifier technology is increasingly used in industrial applications like variable-speed motor drives, since it offers several desired features such as sinusoidal input currents, controllable power factor, bidirectional power flow and high quality DC output voltage. To achieve these features, however, an effective control system with fast and accurate current and DC voltage responses is required. From various control strategies proposed to meet these control objectives, in most cases the commonly known principle of the synchronous-frame current vector control along with some space-vector PWM scheme have been applied. Recently, however, new control approaches analogous to the well-established direct torque control (DTC) method for electrical machines have also emerged to implement a high-performance PWM rectifier. In this thesis the concepts of classical synchronous-frame current control and DTC-based PWM rectifier control are combined and a new converter-flux-based current control (CFCC) scheme is introduced. To achieve sufficient dynamic performance and to ensure a stable operation, the proposed control system is thoroughly analysed and simple rules for the controller design are suggested. Special attention is paid to the estimation of the converter flux, which is the key element of converter-flux-based control. Discrete-time implementation is also discussed. Line-voltage-sensorless reactive reactive power control methods for the L- and LCL-type line filters are presented. For the L-filter an open-loop control law for the d-axis current reference is proposed. In the case of the LCL-filter the combined open-loop control and feedback control is proposed. The influence of the erroneous filter parameter estimates on the accuracy of the developed control schemes is also discussed. A new zero vector selection rule for suppressing the zero-sequence current in parallel-connected PWM rectifiers is proposed. With this method a truly standalone and independent control of the converter units is allowed and traditional transformer isolation and synchronised-control-based solutions are avoided. The implementation requires only one additional current sensor. The proposed schemes are evaluated by the simulations and laboratory experiments. A satisfactory performance and good agreement between the theory and practice are demonstrated. (orig.)

Poellaenen, R.

2003-07-01

22

Space Vector PWM Signal Generation for a Three Phase Inverter and Hardware Implementation Using µ- Controller  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the space vector definitions for the flux, current and the voltage in a three phase system. In this paper, a Space Vector PWM signal generation for a conventional 3-phase inverter by comparing the reference phase voltages with the reference voltage vector is presented. The sector in which the tip of the reference vector lies is found out and the proposed Space Vector-PWM (SVPWM) method generates the inverter leg switching times, from the sampled reference phase voltage amplitudes in a sampling interval. Here Vdc is the conventional three phase inverter DC link voltage. To generate gating signals PIC ?- controller is used in addition to the interface circuit. The present work explains the gating signal generation and implementation by SVPWM using ?- controller.

B. Muralidhara,; A. Ramachandran; A. Srinivasan,; M. Channa Reddy

2010-01-01

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Research on Three-phase Voltage Type PWM Rectifier System Based on SVPWM Control  

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Full Text Available The fundamental principle of SVPWM is introduced in this study. The design on the structure of three-phase voltage type PWM rectifier system based on SVPWM control was also discussed. Then we calculate the DC capacitor and AC side inductance. The computer simulation tool MATLAB/Simulink is taken and the result is shown in the end. The result indicates that the design of such platform is feasible.

Haoran Shi; Wei Xu; Chenghua Fu; Yao Yang

2013-01-01

24

Three phase thyristor PWM converter with simultaneous commutation circuit; Ikkatsu renryu hoshiki sanso denryugata PWM thyristor converter  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we propose a novel three phase thyristor PWM converter using a GTO for the commutation of the three phase thyristor converter. The main thyristor can be commutated simultaneously by taming off the GTO of the commutation circuit without consuming the energy in the snubber circuit. The proposed commutation circuit is very simple. It can be constructed by using a GTO and axial circuit components (two diodes, a reactor and a capacitor). When the GTO turns off, the capacitor operates as the snubber circuit for the GTO device so that soft-switching action can be obtained. The commutation energy can be transferred through the capacitor to the do load without consuming the energy in the snubber circuit. Moreover, the additional voltage drop in the series diodes can be removed. So, the efficiency will be improved. 13 refs., 13 figs.

Minamoto, Y. [Niihama National College of Technology, Ehime (Japan); Onishi, T. [The University of Tokushima, Tokushima (Japan)

1995-12-20

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Comparative Study of two PWM techniques for Three Phase Shunt Hybrid Active Power Filter to Suppress Line Current Harmonics  

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Full Text Available This paper investigates the performanceand comparison of two pulse-width-modulation (PWM)techniques by employing direct current control strategyapplied to three phase shunt hybrid active power filter(SHAPF). The objective of SHAPF is to eliminate linecurrent harmonics and to incur reactive powercompensation. The direct current control strategy isimplemented using Standard PWM (S-PWM) and aModified PWM (M-WM), in order to compensatecurrent harmonic and reactive power generated bydifferent loads. The M-PWM control is based oncomparison of a triangular high frequency carriersignal with a low modulating signal and it’s negative.This low modulating signal namely +? and its negative–? are used at same instant in the comparison processto generate signal to semiconductor device. Theperformance of S-PWM and M-PWM technique andits capability to compensate for harmonic and reactivepower under different load conditions are examined.The Simulation work is carried out withMATLAB/SIMULINK.

SELVAMUTHUKUMARAN Rajasekar; NATARAJAN Muraly; PERIANAYAGAM Ajay-D-VimalRaj; MAHALINGAM Sudhakaran

2010-01-01

26

DC-bus voltage controllers for a three-phase voltage-source inverter for distributed generation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An important function of the bus voltage controller of voltage-source inverters (VSI) for distributed generation (DG) applications is to control the balance between ac and dc power. Nevertheless is the bus voltage controller not the critical part of the control of the VSI. Therefore it is justified ...

Meersman, Bart; Renders, Bert; Degroote, Lieven; Vandoorn, Tine; Vandevelde, Lieven

27

Microcontroller based PWM Inverter for Speed Control of a Three Phase Induction Motor  

Directory of Open Access Journals (Sweden)

Full Text Available Three phase induction motor has proven to be an extremely reliable electromechanical energy conversion device for over 100 years. The speed control of induction motor is a crying need for the real world industrial applications. However, there are so many options available for the precise speed control of induction motor except by changingthe frequency. Therefore to achieve the goal of speed control of induction motor, there is no alternative of inverters. With the availability of high speed power semiconductor devices, the three phase inverters play the key role for variable speed ac motor drives. In addition to the speed control, the inverter can also provide some unique features, like voltage control, torque control, power factor correction, auto breaking, built in protection system and so forth.In this paper, a three phases PWM inverter using MC3PHAC microcontroller with computer interface is proposed to run a squirrel case induction motor. Some results of the proposed inverter are presented.

M. A. Latif; M. J. Alam; M. A. Rashid; A. Karim; N. H. Ramly; I. Daut

2013-01-01

28

Microcontroller based PWM controlled four switch three phase inverter fed induction motor drive  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents PIC microcontroller based PWM inverter controlled four switch three phase inverter (FSTPI) fed Induction Motor drive. The advantage of this inverter that uses of 4 switches instead of conventional 6 switches is lesser switching losses, lower electromagnetic interference (EMI), less complexity of control algorithms and reduced interface circuits. Simulation and experimental work are carried out and results presented to demonstrate the feasibility of the proposed approach. Simulation is carried out using MATLAB SIMULINK and in the experimental work a prototype model is built to verify the simulation results. PIC microcontroller (PIC 16F877A) is used to generate the PWM pulses for FSTPI to drive the 0.5 hp 3-phase Induction Motor.

Mohanty Kant Nalin; Muthu Ranganath

2010-01-01

29

PWM Strategy and Its Output Control Range of Single-Phase to Three-Phase Matrix Converters  

Science.gov (United States)

This paper presents a novel PWM strategy for single-phase to three-phase matrix converters with a small capacitor that compensates for single-phase instanteneous electric power fluctuation. Output voltage and input current references are derived for obtaining a unity input power factor. In the proposed PWM strategy, the number of commutations in all the three phases during a control period is reduced to four. A design method for the small capacitor is developed on the basis of the control ranges of the output voltage and current. The effectiveness of the proposed PWM strategy is verified by experiments.

Yamashita, Tomomi; Takeshita, Takaharu

30

Three Phase Six-Switch PWM Buck Rectifier with Power Factor Improvement  

DEFF Research Database (Denmark)

Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, Three Phase Six-Switch PWM Buck Rectifier[1] is presented which operates at nearly unity power factor and provides variable output voltage. Small size energy storing components are required depending upon switching frequency. MATLAB simulation is performed and modified Sinusoidal Pulse Width Modulation(SPWM) switching technique is used in 3kW prototype converter to demonstrate low input current THD, nearly unity displacement factor, well regulated output voltage and reduced switching losses compared to conventional SPWM.

Zafar Ullah Khan, M; Mohsin Naveed, M.

2013-01-01

31

Three phase six-switch PWM buck rectifier with power factor improvement  

Science.gov (United States)

Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, three phase six-switch PWM buck rectifier is presented which operates at nearly unity power factor and provides variable output voltage. Small size energy storing components are required depending upon switching frequency. MATLAB simulation is performed and modified Sinusoidal Pulse Width Modulation (SPWM) switching technique is used in 3kW prototype converter to demonstrate low input current THD, nearly unity displacement factor, well regulated output voltage and reduced switching losses compared to conventional SPWM.

Zafarullah Khan, M.; Mohsin Naveed, M.; Akbar Hussain, D. M.

2013-06-01

32

One-Stage High-Frequency-Isolated Three-Phase PWM Rectifier  

Science.gov (United States)

The AC-DC converter, which has three-phase AC power as input and isolated DC power as output is used for the regulated DC power supply of the telecommunication power processing system for several kilowatt class applications. The conventional DC power supply for the telecommunication power system comprises a PWM rectifier with sinewave shaping input current unity power factor and a DC/DC converter connected to the PWM converter, which obtains DC48 V. Since power passes through these two power stage converters, the conversion power loss is difficult to provide high efficiency. In addition, the power components of the power converter make the compact design of the power supply difficult. To resolve these problems, this paper presents a new PWM rectifier as a one-stage power conversion scheme. It experiment, it is proved from a practical point of view that 92.1% of conversion efficiency and input current which can meet harmonics regulation of the Class A in IEC61000-3-2 are achieved.

Sato, Shinji

33

Performance Evaluations of A Single Inductor Type Resonant AC Link Snubber-Assisted Three-Phase Voltage Source Soft-Switching Inverter  

Science.gov (United States)

This paper presents a novel three-phase voltage source type soft-switching inverter using the main and auxiliary IGBT power module packages in order to reduce their switching power losses as well as its electromagnetic noises. A single inductor-assisted resonant AC link snubber circuit as one of some resonant snubbers to achieve the zero voltage soft-switching for the three-phase voltage source inverter (VSI) with instantaneous space voltage vector sinewave modulation strategy is originally demonstrated as compared with the other resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper for resistive and inductive loads. Furthermore, the practical basic operating performances of the new instananeous space vector modulated soft-switching VSI using IGBT power modules are evaluated and discussed on the basis of power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, as compared with those of hard-switching VSI.

Yoshida, Masanobu; Hiraki, Eiji; Nakaoka, Mutsuo

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A Three Phase PWM Rectifier: A Novel Optimization Technique to Find Scale Factor of PI Controller Parameters of AC/DC PWM Converter Using Genetic Algorithms  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this paper is to present a novel control scheme and designing of reactance parameter of PWM convereterand,  find the optimized value of parameters for voltage PI controller for three phase ac/dc PWM converter. Using new trends Genetic algorithms- are discussed, as well.Paper describes the application of Genetic Algorithms for optimization of controller parameters of PWM converter. The behavior of the stability region is plotted with different sampling periods.Genetic Algorithms used for off-line searching Using the MATLAB, the simulation model of the dc- link PWM ac/dc converter is built up. According to the simulation results, it is known that, the presented control strategy is feasible and valid, and the converter can work well under dc motor load condition, and thus the total harmonics distortion (THD) can be reduced quickly and effectively. The PWM rectifier operates as a rectifier to supply dc power to its load a dc motor and at the same time, to improve the power factor and to compensate harmonics drawn from non-linear loads connected on the ac line.

VISHNU MOHAN MISHRA; AMAR NATH TIWARI; NIKHLESH KUMAR SHARMA

2012-01-01

35

Digital state feedback control of a three phase sinusoidal PWM inverter  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a method of three phase voltage control sinusoidal PWM (Pulse Width Modulation) inverter. The state equation of the inverter main circuit has been derived and transformed to the d-q frame. Afterwards, an algorithm of dead-beat control has been developed by considering only the load current as disturbing variable. The advantage of dead-beat control is that it can control very fast within short time (sampling period) comparing to other methods. The main objective of the controller design is to get the sinusoidal voltage at inverter`s output with low harmonic distortions. To compensate the calculation delay and to realize physically, a 3d order prediction method has been adopted. A new switching technique has been developed. This switching technique can reduce unnecessary switching so that switching loss can be minimized. Finally, simulations has been done under a typical load condition (rectifier with capacitor load) and harmonic analysis has also been done. Throughout all simulations, very good results have been found where total harmonic distortions (THD) is less than 5%.

Matin, Md.A. [West Coast Univ., Los Angeles, CA (United States); Divsalar, D. [Jet Propulsion Lab., Pasadena, CA (United States)

1994-12-31

36

A Fuzzy-Logic-Based Controller for Three-Phase PWM Rectifier With Unity Power Factor Operation  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, direct power control (DPC) of three-phase PWM rectifiers based on fuzzy logic controller is presented, without line voltage sensors. The control technique is built upon the ideas of the well known direct torque control (DTC) for induction motors. The instantaneous active and reactive powers, directly controlled by selecting the optimum state of the converter, are used as the PWM control variables instead of the phase line currents being used. The proposed fuzzy logic controller presents the advantage to be based on linguistic description and does not require a mathematical model of the system. The controller ensures a good regulation of the output voltage, and guarantees the power factor close to one. The simulation results show that the designed fuzzy controller has a good dynamic behavior, a good rejection of impact load disturbance, and is very robust.

A. Bouafia; F. Krim

2008-01-01

37

Analysis and minimization of harmonics on the AC and DC sides of three-phase current-type PWM converters  

Energy Technology Data Exchange (ETDEWEB)

A new approach to analysis and minimization of harmonics on the ac and dc sides of three-phase current-type ac/dc Pm converters. Analysis results show that analysis and control methods that have been developed for voltage-type PWM converters can also be applied to the current-type ones. By using the proposed approach, the harmonics on the ac and dc sides of current-type PWM converters can be calculated easily without using conventional Fourier series approach which is time-consuming and complex. The analysis results are useful in designing the ac and dc sides filters. Experimental results are included in the report to show the validity of the proposed method. (author)

Dahomo, P.A.

1998-12-16

38

Newly-Proposed Hybrid Resonant Commutaion Bridge Leg Link Snubber-Assisted Three-Phase ZVZCS-PWM Soft-Switching Inverter.  

Science.gov (United States)

This paper presents the newly-proposed hybrid resonant commutation bridge leg link (HRCB) snubber circuit which can achieve zero voltage and zero current soft-switching commutation for single-phase and three-phase voltage source-type inverter, along with its unique features and operation principle. The circuit parameter design approach for the HRCB snubber circuit and the determination estimating scheme of the gate pulse timing processing which is more suitable and acceptable for single-phase and space voltage vector modulated three-phase voltage source inverter using the HRCB snubber circuit are described in this paper. In particular the three-phase voltage source soft-switching inverter associated with the proposed HRCB circuits are evaluated and discussed from simulation and experimental viewpoint. The practical effectiveness of the HRCB snubber-assisted three-phase voltage source soft-switching inverter using IGBT power modules which is based on the instantaneous space voltage vector modulation is clarified on the output voltage waveform, actual efficiency and electromagnetic noises in comparison with three-phase voltage source-type conventional hard-switching inverter.

Hiraki, Eiji; Yoshida, Masanobu; Hirota, Yoshihiko; Nakaoka, Mutsuo

39

Control strategy for three-phase four-wire PWM converter of integrated voltage compensation type active SFCL  

International Nuclear Information System (INIS)

The integrated voltage compensation type active superconducting fault current limiter (SFCL) is composed of three air-core superconducting transformers and a three-phase four-wire PWM converter. In order to realize the current-limiting characteristics of the integrated active SFCL, it is needed to control the three-phase four-wire PWM converter flexibly and reasonably. Thereby, the control strategy for the converter is analyzed in this paper. In dq0 reference frame, the mathematical model of the converter is founded. The double-loop control strategy, consisting of voltage outer loop and current inner loop, is presented. Moreover, the voltage balance control for the split DC link capacitors is also considered. Using MATLAB, the simulation model of the integrated active SFCL is built. According to the simulation results, it is known that, the presented control strategy is feasible and valid, and the converter can work well under unsymmetrical and symmetrical fault conditions, and then the fault current can be limited quickly and effectively.

2010-02-01

40

Comparative analysis of SPWM and SVPWM control for three phase inverter  

Directory of Open Access Journals (Sweden)

Full Text Available A voltage source inverter is commonly used to supply a three-phase induction motor with variable frequency and variable voltage for variable speed applications. A suitable pulse width modulation (PWM) technique is employed to obtain the required output voltage in the line side of the inverter. The different methods for PWM generation can be broadly classified into triangle comparison based PWM (TCPWM) and Space Vector based PWM (SVPWM). In TCPWM methods such as sine-triangle PWM, three phase reference modulating signals are compared against a common triangular carrier to generate the PWM signals for the three phases. In SVPWM methods, a revolving reference voltage vector is provided as voltage reference instead of three phase modulating waves. The magnitude and frequency of the fundamental component in the line side are controlled by the magnitude and frequency, respectively, of the reference vector. The highest possible peak phase fundamental is very less in sine triangle PWM when compared with space vector PWM. Space Vector Modulation (SVM) technique has become the important PWM technique for three phase voltage source inverters for the control of AC Induction, Brushless DC, Switched Reluctance and Permanent Magnet Synchronous Motors. The study of space vector modulation technique reveals that space vector modulation technique utilizes DC bus voltage more efficiently and generates less harmonic distortion when compared with Sinusoidal PWM (SPWM) technique. In this paper first a model for Space vector PWM is made and simulated using MATLAB/SIMULINK software and its performance is compared with Sinusoidal PWM. The simulation study reveals that Space vector PWM utilizes DC bus voltage more effectively and generates less THD when compared with sine PWM.

K. Vinoth Kumar; Prawin Angel Michael; Joseph P. John; S. Suresh Kumar

2010-01-01

 
 
 
 
41

Characterization of single-stage three-phase power-factor-correction circuit using modular single-phase PWM dc-to-dc converters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The complete dc characteristics of the three-phase modular power-factor-correction (PFC) converters using single-phase pulsewidth modulation (PWM) dc-to-dc converter modules for high-power application are studied. Using circuit averaging, the converter input and output quantities are determined nume...

Ho, YKE; Hui, SYR; Lee, YS

42

High-performance control of a three-phase voltage-source converter including feedforward compensation of the estimated load current  

International Nuclear Information System (INIS)

[en] In this paper a new control strategy for voltage-source converters (VSC) is introduced. The proposed strategy consists of a nonlinear feedback controller based on feedback linearization plus a feedforward compensation of the estimated load current. In our proposal an energy function and the direct-axis current are considered as outputs, in order to avoid the internal dynamics. In this way, a full linearization is obtained via nonlinear transformation and feedback. An estimate of the load current is feedforwarded to improve the performance of the whole system and to diminish the capacitor size. This estimation allows to obtain a more rugged and cheaper implementation. The estimate is calculated by using a nonlinear reduced-order observer. The proposal is validated through different tests. These tests include performance in presence of switching frequency, measurement filters delays, parameters uncertainties and disturbances in the input voltage.

2009-01-01

43

Scheme of power source voltage sensorless three-phase PWM AC/DC converter; Dengen den`atsu sensorless sanso PWM converter no ichihoshiki  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a control system that can control the power factor of a three-phase PWM converter (abbreviated to CV) to unity without using a power source voltage sensor. The control system consists of a current controlling section and a power source voltage estimating section. The current controlling section so determines an input voltage to the CV that a command current agrees with the actual current. The power source estimating section has a CV model corresponding to the CV, and estimates the phase angle between a power source voltage and an active value so that the error between the actual CV current and a model current in the CV model becomes zero. The paper details the configuration of an algorithm to execute this estimation. An experiment using a prototype of this system verified that a control system adopting this algorithm shows stable convergence characteristics as designed against disturbance to the active voltage values and the phase angles. The paper also describes that the estimation characteristics of the system are not affected even if a parameter error of 50% exists in the said model. 9 refs., 13 figs., 1 tab.

Takeshita, T.; Kobayashi, T.; Matsui, N. [Nagoya Institute of Technology, Nagoya (Japan)

1994-11-20

44

Control of Three-Phase PWM Rectifiers Using a Single DC Current Sensor  

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Full Text Available This paper presents a new current control method forthree-phase pulse width modulation rectifiers with active powerfactor correction. Conventional three-phase PFC controlrequires sensing of at least two input phase currents. Since theinput line should be isolated from the control circuitry, currenttransformer or Hall effects current sensors can be used forsensing the phase currents, these are bulkier and more expensivethan resistive current sensors. That type of electromagneticcurrent sensors are also difficult to integrate with the rest of thecontrol circuitry, it is a major barrier for low-cost integratedPFC control development. The new current control methodsolves these problems by using only the dc-rail current as thefeedback signal .The dc-rail current can be easily sensed by ashunt resistor, and the output signal can be directly used by thecontrol circuitry without isolation .The control method isdeveloped based on a nonlinear average current controlprinciple and avoids the steady-state phase error of conventionallinear PI control.

M.Prakash,; M.S.Jayakumar

2012-01-01

45

Um controlador de corrente de carga para o conversor em matriz trifásico para trifásico e para o inversor de frequência sem capacitor do elo de corrente contínua A controller for the three-phase to three-phase matrix converter and for the voltage source three-phase inverter without DC-link capacitor  

Directory of Open Access Journals (Sweden)

Full Text Available Com o avanço da tecnologia dos dispositivos semicondutores de potência os inversores de frequência atuam de forma importante em toda indústria. O inversor de frequência convencional contém elementos armazenadores de energia no seu elo de corrente contínua. Estes elementos armazenadores de energia são capacitores eletrolíticos e possibilitam manter a tensão do elo de corrente contínua constante. Entretanto, quanto maior sua capacitância maior é a distorção da corrente de entrada. Com a substituição do banco de capacitores eletrolíticos por um capacitor de filme, diminui-se a distorção nas correntes de entrada, porém distorções indesejadas aparecem na tensão do elo de corrente contínua e também nas correntes de saída. Estas distorções são compostas por componentes harmônicas de baixas frequências. O conversor em matriz trifásico-trifásico por sua vez, possibilita a transferência direta de energia da entrada (rede) diretamente para a saída (carga) sem a necessidade de elementos armazenadores de energia como acontece no inversor de frequência. Entretando o desbalanceamento das tensões da entrada afetam diretamente a forma de onda das tensões da saída. Dessa maneira, este trabalho propõe um método de controle de corrente do conversor em matriz e do inversor de frequência sem banco de capacitores do elo de corrente contínua com objetivo de compensar o desbalanceamento das tensões de saída do conversor em matriz e compensar também as componentes harmônicas de baixa frequência que aparecem nas correntes de saída do inversor de frequência. O método proposto utiliza um controlador do tipo PI e modulação por vetores espaciais para que a frequência de acionamento das chaves dos conversores seja constante.Voltage source three-phase inverter plays an important role in modern industry. The conventional voltage source inverter has a large electrolytic capacitor as energy store element in order to keep the DC-link voltage constant. However, a large electrolytic capacitor increases the input current distortion. Replacing the large electrolytic capacitor by a small film capacitor, the input current quality is improved but the DC-link voltage and the output currents are distorted by low order harmonic components. The three phase to three phase matrix converter performs electric energy direct transfer from the input to the output with sinusoidal input current although the distortion and the unbalance of the input voltages affects directly the output of the matrix converter. This paper proposes a load current control method to the matrix converter and also to the voltage source inverter in absence of the dc-link capacitor in order to compensate the distortion caused by low order harmonics components in the output currents. The proposed load current control scheme employs just one PI controller and since that the space vector modulation is used in this control, the switching frequency of the converter is kept constant. Theorical foundation, simulations results and experimental results are presented.

M. E. Oliveira Filho; A. J. Sguarezi Filho; J. R. Gazoli; E. Ruppert Filho

2010-01-01

46

Um controlador de corrente de carga para o conversor em matriz trifásico para trifásico e para o inversor de frequência sem capacitor do elo de corrente contínua/ A controller for the three-phase to three-phase matrix converter and for the voltage source three-phase inverter without DC-link capacitor  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Com o avanço da tecnologia dos dispositivos semicondutores de potência os inversores de frequência atuam de forma importante em toda indústria. O inversor de frequência convencional contém elementos armazenadores de energia no seu elo de corrente contínua. Estes elementos armazenadores de energia são capacitores eletrolíticos e possibilitam manter a tensão do elo de corrente contínua constante. Entretanto, quanto maior sua capacitância maior é a distorção d (more) a corrente de entrada. Com a substituição do banco de capacitores eletrolíticos por um capacitor de filme, diminui-se a distorção nas correntes de entrada, porém distorções indesejadas aparecem na tensão do elo de corrente contínua e também nas correntes de saída. Estas distorções são compostas por componentes harmônicas de baixas frequências. O conversor em matriz trifásico-trifásico por sua vez, possibilita a transferência direta de energia da entrada (rede) diretamente para a saída (carga) sem a necessidade de elementos armazenadores de energia como acontece no inversor de frequência. Entretando o desbalanceamento das tensões da entrada afetam diretamente a forma de onda das tensões da saída. Dessa maneira, este trabalho propõe um método de controle de corrente do conversor em matriz e do inversor de frequência sem banco de capacitores do elo de corrente contínua com objetivo de compensar o desbalanceamento das tensões de saída do conversor em matriz e compensar também as componentes harmônicas de baixa frequência que aparecem nas correntes de saída do inversor de frequência. O método proposto utiliza um controlador do tipo PI e modulação por vetores espaciais para que a frequência de acionamento das chaves dos conversores seja constante. Abstract in english Voltage source three-phase inverter plays an important role in modern industry. The conventional voltage source inverter has a large electrolytic capacitor as energy store element in order to keep the DC-link voltage constant. However, a large electrolytic capacitor increases the input current distortion. Replacing the large electrolytic capacitor by a small film capacitor, the input current quality is improved but the DC-link voltage and the output currents are distorted (more) by low order harmonic components. The three phase to three phase matrix converter performs electric energy direct transfer from the input to the output with sinusoidal input current although the distortion and the unbalance of the input voltages affects directly the output of the matrix converter. This paper proposes a load current control method to the matrix converter and also to the voltage source inverter in absence of the dc-link capacitor in order to compensate the distortion caused by low order harmonics components in the output currents. The proposed load current control scheme employs just one PI controller and since that the space vector modulation is used in this control, the switching frequency of the converter is kept constant. Theorical foundation, simulations results and experimental results are presented.

Oliveira Filho, M. E.; Sguarezi Filho, A. J.; Gazoli, J. R.; Ruppert Filho, E.

2010-10-01

47

High Efficient Low Noise Three Phase Voltage-Fed Soft-Switching Double PWM Converter System with A Single Resonant DC Link Snubber  

Science.gov (United States)

This paper presents a novel system prototype of auxiliary resonant DC link (ARDCL) assisted three phase double converter using IGBT power modules. In the ARDCL-based double converter, large current flows through the ARDCL circuit when the ARDCL circuit operates under heavier load current ranges. In addition to this, the gate pulse control timing sequences for switching power semiconductor devices used in the ARDCL circuit become more complicate actually. The active auxiliary resonant DC link snubber circuit has advantage point of small load currents which flow through the ARDCL circuit and does not actually require the complicated timing pulse control implementation for switching power semiconductor devices. In this paper, the system configuration double converter circuit and its operation principle are described for three phase voltage source type double soft-switching converter with a single ARDCL snubber. For a 10kVA prototype double converter system, conversion efficiency can be improved in addition to noise terminal voltage is reduced up to 20dBuV in maximum in the switching frequency range of 500kHz or more in comparison with the conventional three phase hard switching double converter system.

Sato, Shinji; Nagai, Shin-Ichiro; Yamamoto, Masayoshi; Rukonuzaaman, Md.; Nakaoka, Mutsuo

48

Advanced High Power DC-DC Converter using A Novel Type Voltage Source Full-Bridge Soft-Switching PWM Inverter with High Frequency Transformer Link for Arc Welding Applications  

Science.gov (United States)

This paper presents a new circuit topology of full-bridge soft-switching PWM inverter linked DC-DC power converter composed of conventional full-bridge high frequency PWM inverter with high frequency transformer and an active quasi-resonant snubber consisting of an additional power switching device in series with DC busline and a lossless capacitor in parallel with DC busline. Under this proposed high frequency soft-switching PWM inverter linked DC-DC converter, four power switches in the full-bridge arms and DC busline series switch can achieve ZVS at turn-off commutation. By developing the advanced soft-switching PWM high frequency inverter type DC-DC converter, although the conduction power loss of DC busline series power switch increases a little, the total turn-off switching loss of full-bridge high frequency inverter power modules can be sufficiently lowered more and more in the higher frequency range of 60kHz. As a result, when the switching frequency of high frequency inverter power stage using IGBT power modules is designed so as to be more than about 10kHz, the more the switching frequency of inverter increases, the more this high frequency soft-switching DC-DC converter has remarkable advantage as for the power conversion efficiency as compared with the conventional hard-switching PWM inverter DC-DC converter. Its practical effectiveness of high power density and high performance is actually proved for TIG arc welding equipment in industry.

Morimoto, Keiki; Doi, Toshimitsu; Manabe, Haruhiko; Ahmed, Tarek; Hiraki, Eiji; Lee, Hyun-Woo; Nakaoka, Mutsuo

49

A novel dynamic voltage restorer and its unbalanced control strategy based on space vector PWM  

Energy Technology Data Exchange (ETDEWEB)

A novel dynamic voltage restorer which is composed of a conventional three-phase voltage source inverter and an emitter follower is presented in this paper to reduce the adverse effects on sensitive loads caused by three-phase supply voltage unbalance in distribution systems. The adverse effect caused by the negative sequence component of the supply voltage can be eliminated and the load voltage magnitude can be restored to specified value by using the three-phase voltage-source inverter. The emitter follower is capable of eliminating the adverse effect caused by the zero sequence component of the supply voltage. An unbalanced control strategy based on space vector PWM is presented to realize the fast dynamic response of the dynamic voltage restorer. Feasibility of this method is verified by digital simulation. (Author)

Hongfa Ding; Shu Shuangyan; Duan Xianzhong; Gao Jun [Huazhong Univ. of Science and Technology, Dept. of Electrical Power Engineering, Wuhan (China)

2002-11-01

50

THREE-PHASE ACTIVE POWER FILTER CONTROLLER FOR BALANCED AND UNBALANCED NON-LINEAR LOAD  

Directory of Open Access Journals (Sweden)

Full Text Available The active power filter produces equal but opposite harmonic currents to the point of connection with the nonlinear load. This results in a reduction of the original distortion and correction of the power factor. A threephase insulated gate bipolar transistor based current controlled voltage source inverter with a dc bus capacitor is used as an active filter. The firing pulses to the shunt active filter will be generated by using sine PWM method. The models for three-phase active power filter controller for balanced and unbalanced non-linear load is made and is simulated using Matlab/simulink software.

G.NAGESWARA RAO; Dr.K. CHANDRA SEKHAR,; Dr.P. SANGAMESWARA RAJU

2010-01-01

51

Optimal operation of single-stage three-phase power factor correction circuit using modular PWM DC-to-DC converters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A critical conduction parameter A 3? is derived for the three-phase modular system. This parameter optimises the output filter to achieve the highest power factor of the system. The voltage conversion ratio required to achieve a high power factor to fulfil the harmonic requirements is also derived. ...

Ho, YKE; Hui, SYR; Lee, YS

52

Small-Signal Analysis of Single-Phase and Three-phase DC/AC and AC/DC PWM Converters with the Frequency-Shift Technique  

DEFF Research Database (Denmark)

A systematic approach to study dc/ac and ac/dc converters without the use of synchronous transformation is proposed. The use of a frequency-shift technique allows a straightforward analysis of single-phase and three-phase systems. The study of dc/ac and of ac/dc converters is reported to the study of dc/dc converters via a 50 Hz frequency-shift. The input admittance is calculated and measured for two study examples (a three-phase active rectifier and a single-phase photovoltaic inverter). These examples show that the purpose of a well designed controller for grid-connected converters is to minimize the input admittance in order to make the grid converter more robust to grid disturbance.

Blaabjerg, Frede; Aquila, A. Dell?

2004-01-01

53

Método experimental para determinação das capacitancias parasitas do motor de indução trifásico acionado por inversor MLP Experimental method for determining the parasitic capacitances of three-phase induction motor driven by PWM inverter  

Directory of Open Access Journals (Sweden)

Full Text Available A proposta deste trabalho é apresentar uma nova metodologia para determinação experimental das capacitancias parasitas do motor de indução trifásico de rotor em gaiola. As capacitancias parasitas fazem parte do circuito equivalente do motor para estudos de interferência eletromagnética causada no motor de indução em modo comum quando ele for acionado por inversor controlado por modulação por largura de pulsos (MLP). Os procedimentos propostos para o desenvolvimento deste novo método consistem em: a) determinação dos parâmetros do circuito equivalente do motor de indução trifásico, em regime permanente, através de ensaio em laboratório; b) estabelecer configurações de ligações entre o inversor MLP e o motor para medições das grandezas de interesse que são as seguintes: tensões de modo comum e de eixo, correntes de fuga e de eixo, através de circuito de medição desenvolvido para este fim; c) calcular os valores das capacitancias parasitas entre estator e carcaça do motor; estator e rotor; rotor e carcaça e de rolamento utilizando a expressão matemática da definição de capacitancia; d) utilizar o software Pspice para simular o sistema motor de indução trifásico, alimentado por inversor MLP, com os circuitos equivalentes em baixas e altas frequências; e) obter as formas de onda características do fenômeno de modo comum.Three-phase induction motors present stray capacitances. The aim of this paper is to present a new methodology to experimentally determine these capacitances and also evaluates the effects of electromagnetic interference on the motors in common mode. The proposed procedures to the development of this new methodology consists in: a) identification of the motor equivalent electrical circuit parameters through characteristic tests performed in the laboratory; b) to set up configurations between PWM inverter and the motor for voltage and current measurements: common mode and shaft voltages, leakage and shaft (bearing) currents by using a dedicated measuring circuit; c) to calculate the parasitic capacitance values between stator and frame, stator and rotor, rotor and frame and bearings of the motor using the capacitance characteristic equation; d) use the dedicated software Pspice to simulate the system composed by the three-phase induction motor fed by PWM inverter with the equivalent electrical circuit parameters; e) to determine the characteristic waveforms involved in the common mode phenomenon.

Rudolf Ribeiro Riehl; Ernesto Ruppert

2012-01-01

54

Método experimental para determinação das capacitancias parasitas do motor de indução trifásico acionado por inversor MLP/ Experimental method for determining the parasitic capacitances of three-phase induction motor driven by PWM inverter  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A proposta deste trabalho é apresentar uma nova metodologia para determinação experimental das capacitancias parasitas do motor de indução trifásico de rotor em gaiola. As capacitancias parasitas fazem parte do circuito equivalente do motor para estudos de interferência eletromagnética causada no motor de indução em modo comum quando ele for acionado por inversor controlado por modulação por largura de pulsos (MLP). Os procedimentos propostos para o desenvolvi (more) mento deste novo método consistem em: a) determinação dos parâmetros do circuito equivalente do motor de indução trifásico, em regime permanente, através de ensaio em laboratório; b) estabelecer configurações de ligações entre o inversor MLP e o motor para medições das grandezas de interesse que são as seguintes: tensões de modo comum e de eixo, correntes de fuga e de eixo, através de circuito de medição desenvolvido para este fim; c) calcular os valores das capacitancias parasitas entre estator e carcaça do motor; estator e rotor; rotor e carcaça e de rolamento utilizando a expressão matemática da definição de capacitancia; d) utilizar o software Pspice para simular o sistema motor de indução trifásico, alimentado por inversor MLP, com os circuitos equivalentes em baixas e altas frequências; e) obter as formas de onda características do fenômeno de modo comum. Abstract in english Three-phase induction motors present stray capacitances. The aim of this paper is to present a new methodology to experimentally determine these capacitances and also evaluates the effects of electromagnetic interference on the motors in common mode. The proposed procedures to the development of this new methodology consists in: a) identification of the motor equivalent electrical circuit parameters through characteristic tests performed in the laboratory; b) to set up co (more) nfigurations between PWM inverter and the motor for voltage and current measurements: common mode and shaft voltages, leakage and shaft (bearing) currents by using a dedicated measuring circuit; c) to calculate the parasitic capacitance values between stator and frame, stator and rotor, rotor and frame and bearings of the motor using the capacitance characteristic equation; d) use the dedicated software Pspice to simulate the system composed by the three-phase induction motor fed by PWM inverter with the equivalent electrical circuit parameters; e) to determine the characteristic waveforms involved in the common mode phenomenon.

Riehl, Rudolf Ribeiro; Ruppert, Ernesto

2012-04-01

55

Space Vector Pulse Width Modulation Scheme for a Seven-Phase Voltage Source Inverter  

Directory of Open Access Journals (Sweden)

Full Text Available This paper analyses a simple space vector PWM (SVPWM) scheme for a seven-phase voltage source inverter. At first the conventional method of producing sinusoidal output voltage  by utilizing six active and a zero space vectors are used to synthesis the input reference and then new PWM scheme called time equivalent space vector PWM is presented.  A comparison of the proposed scheme with the conventional scheme is presented based on various performance indices. Extensive Simulation results are provided to validate the findings

Mohd. Arif Khan; Atif Iqbal; Sk Moin Ahmad

2011-01-01

56

PIS Compensator Based Current Control for Three-Phase Utility Interface Converters  

Science.gov (United States)

Three phase voltage-source PWM converters are used as a utility interface. In such a case, the converter line currents are required to track sinusoidal references synchronized with the utility grid without a steady-state error. In this paper a current control method based on a sinusoidal internal model is employed. The method uses a sine transfer function with a specified resonant frequency, which is called an S-compensator. The combination of a PI compensator and an S-compensator is called a PIS compensator. The PIS compensator ensures that the steady-state error in response to any step changes in a reference signal at the resonant frequency and zero hertz reduces to zero. Experiment was carried out using a 1kVA prototype to verify the usefulness of the PIS compensator. Three utility-interface-converters, a voltage source PWM rectifier, an active filter, and STATCOM, were examined. Almost perfect current tracking performance without a steady-state error was observed.

Fukuda, Shoji; Imamura, Ryota

57

Starting Phenomena and Temperature-rise under vvvf Supply of Three-Phase Squirrel-Cage ac Traction Motor of Electric Locomotive  

Science.gov (United States)

In three-phase squirrel-cage ac traction motor, temperature-rise calculation during variable-voltage and variable-frequency starting is of vital importance and has to be predicted and critically examined. Under voltage source inverter supply with PWM, the generation of harmonics by inverter supply reduces the output during starting due to higher harmonic losses, thereby reducing the starting tractive effort in kN on locomotive wheel. Stator and rotor temperature-rises during starting have been determined for average acceleration torque in segmental zone (calculated from variable acceleration) which have been presented in the paper with both copper and aluminium alloy rotor bars.

Paul, R. N.; Arya, L. D.; Verma, H. K.

2012-09-01

58

Three-phase Resonant DC-link Converter  

DEFF Research Database (Denmark)

The purpose of the project is to develop a three-phase resonant converter suitable for standard speed drives. The motivation for working with resonant converters is found in the problem of the standard converter type used today. In standard converter type Pulse Width Modulated-Voltage Source Inverter, PWM-VSI, the switches are subject to high current and voltage stress during switching, which causes losses. The fast switching of modern switches reduces switching losses. Unfortunately this procedure increased dv/dt and the size of the input/output filters of the PWM-SVI must be increased. The high speed of the switches cannot be fully utilizied. By using a parallel resonant converter the switching happens at low or zero voltage which reduses switch losses. The dv/dt is controlled by the resonant circuit, and it is therefore reduced significantly. The perspective using a resonant converter is high switching frequency combined with a high converter efficiency and low dv/dt. In the first report several resonant converters are investigated to find a resonant converter that can complete with the standard PWM-VSI converter. Four converters were selected for the theoretical analysis, and the converters are simulated. An evaluation of the resonant converters is made, and one converter is selected for the realization. In the second report the realization of the selected resonant converter is described. This includes analysis, design and test of the converter. A new control principle, using no additional power electric components is eliminating the high voltage peaks associated with the resonant circuit. The resonant link voltage peaks are limited below 2.1 times the DC link voltages. A new principle eliminating former resonant converter stability problems are proposed, implemented and tested. A resonant converter efficiency of 97 [%] was measured. The low dv/dt of the converter makes it possible to drive long cables without filtering. A successful test with a 300 [m] long cable and an induction machine load wascarried out. It is concluded that a stable, high efficiency and high switching frequency three phase parallel resonant converter is realized.

Munk-Nielsen, Stig

1997-01-01

59

Multi-level voltage reinjection - a new concept in high voltage source conversion  

Energy Technology Data Exchange (ETDEWEB)

A voltage source converter is proposed, in which the multi-step output voltage waveform is achieved by the reinjection of different DC voltage levels via the common neutral point of the converter bridges. The number of clamping switches are substantially reduced, permitting the use of higher level numbers to achieve very low distortion without the assistance of PWM. The reinjection concept causes the voltage across the main bridges to vary in step waveforms and the commutations in the main valves to occur at zero voltage, with considerably reduced dynamic voltage stress and switching losses. (Author)

Liu, Y.H.; Arrillaga, J.; Watson, N.R. [Canterbury Univ., Dept. of Electrical and Computer Engineering, Canterbury (New Zealand)

2004-05-01

60

PWM Algorithms for Multilevel Inverter Supplied Multiphase Variable-Speed Drives  

Directory of Open Access Journals (Sweden)

Full Text Available Multiphase variable speed drives are nowadays regarded as serious contenders for various applications, due to the certain advantages that they possess when compared to threephase drives. On the other hand, the multilevel (predominantly three-level) voltage source inverter (VSI) has become an industrially accepted technology for medium-voltage three-phase drives. The logical next step is to integrate multilevel VSI and multiphase drive technologies, since benefits of each can then be combined. This paper will review recent advances in this area. Two different topologies of the multiphase supply will be considered and the emphasis will be placed on appropriate pulse width modulation (PWM) techniques that can be used in conjunction with the supply structure. The first topology utilises multilevel (three-level) VSI and the machine’s stator multiphase winding is star-connected with an isolated neutral point. In the second topology the winding is left open-ended and each side of the winding is connected to an isolated two-level VSI. This topology can also achieve three-level operation. Carrier-based and space vector based PWM strategies are considered and the obtainable performance is illustrated using experimental results.

Martin Jones; Obrad Dordevic; Nandor Bodo; Emil Levi

2012-01-01

 
 
 
 
61

Relationships between Harmonic Characteristics and Different Types of Voltage Source  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper discusses about harmonic characteristics due to different types of voltage sources. Usually, the voltage source is sinusoidal. But in actual condition the load that receive voltage sources through the elements where the output voltage of element as input to the load is not pure s...

Risnidar Chan; I. Daut; Syafruddin H; Yusniati Yusniati

62

A Novel Prototype of Auxiliary Edge Resonant Bridge Leg-Link Snubber-Assisted Soft-Switching Sinewave PWM Inverter  

Science.gov (United States)

This paper proposes a new circuit topology of the three-phase soft switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg-commutation-link soft-switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three-phase soft switching PWM double converter is more suitable and acceptable for a large capacity uninterruptible power supply, PFC converter, utility-interactive bi-directional converter and so forth. In this paper, the soft switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three-phase inverter switching. This three-phase soft switching commutation scheme can effectively minimize the switching surge related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three-phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have the relation of the trade-off in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three-phase soft-switching PWM double converter can perform to improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor devices which is much more improved to the low saturation voltage. The effectiveness of this is verified from a practical point of view.

Nakamura, Mantaro; Yamazaki, Takayuki; Fujii, Yuma; Ahmed, Tarek; Nakaoka, Mutsuo

63

Power conserving CMOS reference voltage source  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a power-conserving CMOS reference voltage generation circuit comprising first (101) and second (101') parallel reference voltage sources, coupled to a common ENABLE input, and having a common reference voltage output node (101''), each source including a first, p-channel (102,102') and a second, n-channel (103,103') CMOS transistor series-connected between Vcc and ground. The first and second transistors have respective gates connected at a common gate node (G, G') and respective drains connected to a common drain node (D, D'), characterized in that: the second reference voltage source (101') is of relatively large capacity compared to the first source (101), means (173,107'), responsive to a rising signal edge at the ENABLE input, are provided for temporarily enabling the second source (101'). This shortens the time required to drive the reference voltage at the output node (101'') to a desired level, i.e. enhancing the slew rate of the node, and means (190-194) are provided for interconnecting the common gate nodes (G,G') the common drain nodes (D,D'), and the common output reference voltage output node (101'') in response to a high signal on the ENABLE input and for isolating the nodes from one another in response to a low signal on the ENABLE input, thereby conserving power.

Lee, R.D.

1986-12-09

64

Three-phase transformers  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses problems involving open circuit and short-circuit tests on three phase transformers. A worked example is provided - taken from an examination paper of the Association of Mining, Electrical and Mechanical Engineers.

Davison, G.W.

1982-12-01

65

Development of high-voltage PWM power supply for electron beam bombarding furnace  

International Nuclear Information System (INIS)

The working principle and operation characteristics of a high-voltage PWM-BUCK DC/DC converter are discussed in this paper, and a practical engineering technical route is proposed to apply the converter to high power accelerating voltage source of electron beam bombarding furnace. Compared with the traditional thyristor phase-shifted high voltage source, the application results show that the suggested power supply has the advantages of lower current harmonic, higher power factor and higher operation efficiency. (authors)

2008-01-01

66

Performance analysis of samarium cobalt P.M. synchronous motor fed from PWM inverters  

International Nuclear Information System (INIS)

[en] This paper presents an analysis and performance of samarium cobalt permanent magnet (P.M.) synchronous motors fed from two types of voltage source pulse width modulated (PWM) inverters. The analysis and test results on the steady state performance of a P.M. motor fed from PWM inverters are presented. PWM inverters are used in variable voltage variable frequency applications to avoid a double conversion process of ordinary inverters. In drives, they are used for voltage and speed regulation of motors. Use of modulation technique in inverters also allow to eliminate or minimize selected harmonics from the inverter output voltage

1985-01-01

67

Development of Digital Hysteresis Current Control with PLL Loop Gain Compensation Strategy for PWM Inverters with Constant Switching Frequency  

Directory of Open Access Journals (Sweden)

Full Text Available Hysteresis current control is one of the simplest techniques used to control the magnitude and phase angle of motor current for motor drives systems. However, this technique presents several disadvantages such as operation at variable switching frequency which can reveal problems of filtering, interference between the phases in the case of the three-phase systems with insulated neutral connection or delta connection, and irregularity of the modulation pulses which especially causes an acoustic noise on the level of the machine for the high power drive. In this paper, a new technique is proposed for a variable-hysteresis-band controller based on dead beat control applied to three phase voltage source PWM inverters feeding AC motors. Its main aim is firstly ensure a constant switching frequency and secondly the synchronization of modulation pulses using the phase-locked-loop with loop gain compensation in order to ensure a better stability. The behavior of the proposed technique is verified by simulation.

N. Belhaouchet; L. Rahmani; S. Begag; H. Hamla

2008-01-01

68

Standalone self-excited induction generator with a three-phase four-wire active filter and energy storage system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a system, based on a selfexcited induction generator with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire voltage source inverter (VSI) and, connected to its dc ...

Barrado Rodrigo, José Antonio; Griñó Cubero, Robert; Valderrama Blavi, Hugo

69

Full-bridge type electric converter study using the ZVS-PWM-GEPAE commutation auxiliary cell; Estudo do conversor DC/DC do tipo full-bridge empregando a celula auxiliar de comutacao ZVS-PWM-GEPAE  

Energy Technology Data Exchange (ETDEWEB)

This work presents the analysis and design procedures of a new D C-D C Full Bridge PWM converter, using the ZVS-PWM-GEPAE commutation cell to achieve soft switching. Experimental results obtained from a laboratory prototype rated 1500 W area also presented. It is demonstrated that the inclusion of the auxiliary switches do not modify the PWM switching pattern. Bench tests on the prototype confirm that the proposed circuit exhibits high efficiency and behaves as a constant voltage source over an extended power output range. (author)

Castaldo, Fernando Cardoso

1994-07-01

70

A high-precision voltage source for EIT  

Science.gov (United States)

Electrical impedance tomography (EIT) utilizes electrodes placed on the surface of a body to determine the complex conductivity distribution within the body. EIT can be performed by applying currents through the electrodes and measuring the electrode voltages or by applying electrode voltages and measuring the currents. Techniques have also been developed for applying the desired currents using voltage sources. This paper describes a voltage source for use in applied-voltage EIT that includes the capability of measuring both the applied voltage and applied current. A calibration circuit and calibration algorithm are described which enables all voltage sources in an EIT system to be calibrated to a common standard. The calibration minimizes the impact of stray shunt impedance, passive component variability and active component non-ideality. Simulation data obtained using PSpice are used to demonstrate the effectiveness of the circuits and calibration algorithm.

Saulnier, Gary J; Liu, Ning; Ross, Alexander S

2006-01-01

71

Autonomous Three-Phase Induction Generator Supplying Unbalanced Loads  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a control method for a stand-alone micro hydro with induction generator (IG) supplying unbalanced three-phase loads. Besides voltage and frequency regulation, the phase balancing is ensured for this particular operating regime. The proposed control topology relies on a combination between a voltage source inverter (VSI) and a dump load (DL). The VSI imposes the system frequency and performs the unbalances compensation, while the DL deals with the voltage regulation. Experiments have yielded the reliability of this configuration during generator loading and unbalanced loads supply.

ION, C. P.; MARINESCU, C.

2013-01-01

72

A line-interactive UPS system implementation with series-parallel active power-line conditioning for three-phase, four-wire systems  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with active series-parallel power-line conditioning capabilities. Synchronous reference frame (SRF)-based controller is used for harmonic and reactive power compensation generated from any configuration of non-linear loads. Under normal line conditions the UPS system works with universal filtering capabilities, such as compensating the input currents and output voltages. Two three-phase pulsewidth modulation (PWM) converters, called series and parallel active filters, are used to perform the series and parallel active power-line compensation. The series active filter works as sinusoidal current source in phase with the input voltage, drawing from utility sinusoidal and balanced input currents with low total harmonic distortion (THD). The parallel active filter works as sinusoidal voltage source in phase with the input voltage, providing regulated and sinusoidal output voltages with low THD. The performance of the UPS system is evaluated in three-phase, four-wire systems. Experimental results are presented to confirm the theoretical studies.Este artigo apresenta um sistema de energia ininterrupta (SEI) line-interactive trifásico com capacidade de condicionamento ativo de potência série e paralelo. Um controlador baseado no sistema de eixo de referência síncrona (SRF) é usado na compensação de potência reativa e harmônica geradas por quaisquer configurações de cargas não lineares. Sob condições normais da rede elétrica o SEI trabalha na compensação das correntes de entrada e das tensões de saída. Dois conversores controlados em tensão e modulados por largura de pulso (PWM), chamados de filtros ativos série e paralelo, são usados para realizar o condicionamento ativo de potência série e paralelo. O filtro ativo série trabalha como uma fonte de corrente senoidal em fase com a tensão de entrada, drenando da rede correntes senoidais, balanceadas com baixas taxas de distorção harmônica (TDH). O filtro ativo paralelo trabalha como uma fonte de tensão senoidal em fase com a tensão de entrada, fornecendo para a carga tensões reguladas, senoidais e com baixas taxas de distorção harmônica. O desempenho do SEI é avaliado para sistemas trifásicos com quatro fios. Resultados experimentais são apresentados para confirmar os estudos teóricos.

Sérgio Augusto Oliveira da Silva; Pedro F. Donoso-Garcia; Porfírio C. Cortizo; Paulo F. Seixas

2005-01-01

73

Note: Galvanic isolated voltage source using a single photodiode.  

UK PubMed Central (United Kingdom)

A galvanic isolated voltage source able to provide several volts by using a single photodiode is described. A pulse-modulated laser beam is sent to a photodiode. By using a step-up transformer the amplitude of the variable voltage generated by the photodiode is increased. Adding a rectifier cell the variable voltage is converted back into a dc voltage.

Stoican OS

2010-04-01

74

Implementation of a Hybrid High Power Factor Three-Phase Unidirectional Rectifier  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new hybrid three phase rectifier composed by the parallel association of a single switch three phase boost rectifier with a pwm three phase unidirectional rectifier. According to this proposal each rectifier processes about half of the output rated power. The diode rectifier operates at a low frequency and has a higher output power rating Therefore ,the pwm unidirectional rectifier is designed to operate with a small power rating and a high switching frequency. In the proposed scheme, dsPIC30F2010 controller is used to produce signals. A resistive load(Two incandescent lamps with different watts) are used as load for testing the developed hardware. Textronics TDS2024B storage oscilloscope is used to store the gate pulses and waveforms. The perfectly sinusoidal input currents with improved power factor can be obtained by this hybrid rectifier.

Ankusha Biradar,; Prof.Nagabhushan.Patil

2013-01-01

75

Power Loss Calculation and Thermal Modelling for a Three Phase Inverter Drive System  

Directory of Open Access Journals (Sweden)

Full Text Available Power losses calculation and thermal modelling for a three-phase inverter power system is presented in this paper. Aiming a long real time thermal simulation, an accurate average power losses calculation based on PWM reconstruction technique is proposed. For carrying out the thermal simulation, a compact thermal model for a three-phase inverter power module is built. The thermal interference of adjacent heat sources is analysed using 3D thermal simulation. The proposed model can provide accurate power losses with a large simulation time-step and suitable for a long real time thermal simulation for a three phase inverter drive system for hybrid vehicle applications.

Z. Zhou; M. S. Khanniche; P. Igic; S. M. Towers; P. A. Mawby

2005-01-01

76

A battery-based, low-noise voltage source.  

UK PubMed Central (United Kingdom)

A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of +/-15 and +/-5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7 x 10(-7) over 6.5 h and a noise level equal or smaller than 30 nV/square root(Hz) is achieved.

Wagner A; Sturm S; Schabinger B; Blaum K; Quint W

2010-06-01

77

A battery-based, low-noise voltage source  

Science.gov (United States)

A highly stable, low-noise voltage source was designed to improve the stability of the electrode bias voltages of a Penning trap. To avoid excess noise and ground loops, the voltage source is completely independent of the public electric network and uses a 12 V car battery to generate output voltages of +/-15 and +/-5 V. First, the dc supply voltage is converted into ac-voltage and gets amplified. Afterwards, the signal is rectified, filtered, and regulated to the desired output value. Each channel can deliver up to 1.5 A. The current as well as the battery voltage and the output voltages can be read out via a universal serial bus (USB) connection for monitoring purposes. With the presented design, a relative voltage stability of 7×10-7 over 6.5 h and a noise level equal or smaller than 30 nV/Hz is achieved.

Wagner, Anke; Sturm, Sven; Schabinger, Birgit; Blaum, Klaus; Quint, Wolfgang

2010-06-01

78

[Voltage sources in mesial temporal area induced by etomidate].  

UK PubMed Central (United Kingdom)

INTRODUCTION: It has been recently shown that activation of the EEG by etomidate is a specific and safe technique during the evaluation of patients for epilepsy surgery. AIM: To analyze the pathophysiological properties of interictal activity induced by etomidate and compare with the interictal spontaneous activity. PATIENTS AND METHODS: We studied 13 patients by video-EEG with foramen ovale electrodes. Etomidate (0.1 mg/kg) was injected to activate the epileptogenic region. The activity of foramen ovale electrodes was adjusted to a monopolar voltage source. RESULTS: Interictal activity mediated by etomidate fits well to a monopolar model, in the same way that the basal interictal activity. The voltage sources distribution recorded during the interictal activity and distribution of voltage sources recorded in presence of etomidate have similar topographical properties. The equivalent charge induced by etomidate was higher than the basal one. CONCLUSIONS: The basal and etomidate induced activity have similar electrophysiological properties, suggesting that the same or similar structures are responsible of both. So, etomidate can be used as an specific inductor of EEG activity during presurgical evaluation.

Herrera-Peco I; Ortega GJ; Hernando-Requejo V; Sola RG; Pastor J

2010-09-01

79

Sliding mode Control using 3D-SVM for Three-phase Four-Leg Shunt Active Filter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a sliding mode control strategy for a three-phase shunt active power filter. The SAPF consists of four-leg voltage source inverter bridge. The SAPF ensures full compensation for harmonic phase currents, harmonic neutral current, reactive power compensation and unbalanced nonlinea...

Bouzidi Mansour; Benaissa Abdelkader; Barkat Said

80

Stable d-c high-voltage source  

International Nuclear Information System (INIS)

The electric circuit is proposed and described of a stable high-voltage d-c source for supplying radiation detectors. The output of a stable a-c low-voltage source is connected to the input of an amplifier whose output is connected by capacitance of a capacitor to the transformer primary. A rectifier or a voltage multiplier with filter is connected to the transformer secondary, with a feedback inserted between the transformer secondary and the amplifier input circuit. (J.K.).

1975-01-01

 
 
 
 
81

Parallel operation of voltage-source converters: issues and applications  

Energy Technology Data Exchange (ETDEWEB)

Technological advancements in power electronics have prompted the development of advanced AC/DC conversion systems with high efficiency and flexible performance. Among these devices, the Voltage-Source Converter (VSC) has become an essential building block. This paper considers the parallel operation of VSCs under different system conditions and how they can assist the operation of highly complex power networks. A multi-terminal VSC-based High Voltage Direct Current (M-VSC-HVDC) system is chosen to be modeled, simulated and then analyzed as an example of VSCs operating in parallel. (author)

Almeida, F.C.B.; Silva, D.S. [Federal University of Juiz de Fora (UFJF), MG (Brazil)], Emails: felipe.brum@engenharia.ufjf.br, salomaoime@yahoo.com.br; Ribeiro, P.F. [Calvin College, Grand Rapids, MI (United States); Federal University of Juiz de Fora (UFJF), MG (Brazil)], E-mail: pfribeiro@ieee.org

2009-07-01

82

PWM Converter Topologies.  

Science.gov (United States)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is d...

E. R. W. Meerman H. J. N. Spruyt

1989-01-01

83

PWM Converter Power Density Barriers  

Science.gov (United States)

Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm3 at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm3 at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm3 at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm3 results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

Kolar, Johann W.; Drofenik, Uwe; Biela, Juergen; Heldwein, Marcelo; Ertl, Hans; Friedli, Thomas; Round, Simon

84

Three Phase Two Leg Neutral Point Clamped Converter with output DC Voltage Regulation and Input Power Factor Correction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, a three-phase two leg neutral point clamped (NPC) converter is presented for power factor correction and dc-link voltage regulation. The adopted converter has simpler circuit configuration and less number of power switches compared to three-level PWM converter. In this circui...

Bogimi Sirisha; P. Satish Kumar; N. Susheela

85

New Space Vector Selection Scheme for VSI Supplied Dual Three-Phase Induction Machine  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a novel space vector selection scheme applicable for the control of dual three-phase induction motor drives supplied from a six-phase voltage source inverter (VSI). The vector selection method is based on the vector space decomposition technique (VSD). Unique vector selection pattern simplifies problems related to complicated implementation of standard VSD in commercially available digital signals processors (DSP). The proposed vector selection scheme is verified through a theoretical analysis, computer simulations and practical experimental results conducted on a dual three-phase test rig prototype with control algorithm implemented in Texas Instrument?s TMS320F2808 DSP.

MILICEVIC, D.; KATIC, V.; CORBA, Z.; GRECONICI, M.

2013-01-01

86

A Comparative Study of Sinusoidal PWM and Space Vector PWM of a Vector Controlled BLDC Motor  

Directory of Open Access Journals (Sweden)

Full Text Available This paper focuses on the vector control of a BLDC motor with two different concepts of Pulse Width Modulation- the Sinusoidal PWM and the Space Vector Modulation strategy. The paper deals with the basics of a BLDC motor, its dynamic modeling and its speed control using two different strategies of Pulse Width Modulation. The vector control is one of the methods used in variable frequency drives or variable speed drives to control the torque (and thus the speed) of three-phase AC electric motors by controlling the current. The results prove that the Space Vector Modulation technique helps to improve the performance and thus the efficiency of the system.

LYDIA ANU JOSE, K.B.KARTHIKEYAN

2013-01-01

87

Three-phase electric drive with modified electronic smoothing inductor  

DEFF Research Database (Denmark)

This paper presents a three-phase electric drive with a modified electronic smoothing inductor (MESI) having reduced size of passive components. The classical electronic smoothing inductor (ESI) is able to control a diode bridge output current and also reduce not only mains current harmonics but also output voltage ripple. ESI performs the function of an inductor that has controlled variable impedance. MESI requires active switches with lower ratings than ESI and has the same performance. In MESI, an active voltage source realized by a low-voltage switch-mode converter stage is inserted in series with DC-link capacitor. This increases power factor (PF) and reduces the total harmonic distortions (THDs) in current at mains. Input currents of the diode bridge which usually show high peak amplitudes are converted into a 120° rectangular shape which ideally results in a total PF of 0.955 and THDs of 31%, by electronic smoothing techniques.

Singh, Yash Veer; Rasmussen, Peter Omand

2010-01-01

88

Investigation of FPGA Based PWM Control Technique for AC Motors  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a Random Frequency PWM synchronized for a three phase inverter implemented with use of FPGA and applied to a 1-hp induction motor drive system for the reduction of harmonics and improvement of fundamental peak voltage. For providing alternating output voltage with a specific magnitude and frequency to industrial applications, three-phase inverter is preferred.  The gating signals to the inverter are produced by means of Random Frequency PWM to significantly reduce harmonics in comparison to currently used PWMs.  FPGA is used to produce gating signals to the switches in a three-phase bridge inverter since a faster speed of operation is needed. The simulation is carried on VHSIC Hardware Description Language (VHDL) using ModelSim. Then, this VHDL model is imported into Matlab environment and co-simulated using HDL Cosimulation toolbox. The simulation and experimental results are presented with a view to determine whether Random Frequency PWM performs better in terms of fundamental voltage and Total Harmonic Distortion.

Valantina Stephen; Padma Suresh

2013-01-01

89

A PWM strategy for acoustic noise reduction for grid-connected single-phase inverters  

Energy Technology Data Exchange (ETDEWEB)

This paper presented a newly proposed and improved pulse width modulation (PWM) strategy for grid-connected single-phase inverters. Small distributed generators using energy from renewable resources such as PV and wind systems typically use grid-connected single-phase inverters as voltage source inverters for good acoustic performance. PWM is generally applied in these inverters in order to achieve good waveforms of output current as required by interconnection standards. In routine simultaneous switching PWM methods, the current ripples through the inverter output filter inductor are at the carrier switching frequency, which is one of the major causes for inverter acoustic noise. The new PWM strategy effectively alleviates acoustic noise and improves output power quality. It is based on the principle of evenly splitting the switching of Insulated Gate Bipolar Transistors (IGBT) in each switching cycle among all IGBTs of the full bridge, thereby using a non-simultaneous mode of PWM which doubles the output current ripple frequency. This increases the inductor current ripple frequency to twice the carrier frequency. It is therefore possible to increase the current ripple frequency, or noise frequency into the range of ultrasonic which is inaudible to the human ear, without increasing the inverter's switching frequency to which the inverter's switching loss is proportional. In addition, this new PWM scheme can reduce the output current harmonics distortion and dc link current ripples. As such, lower capacitance in dc link capacitors and lower inductance of output inductor are needed. The improved PWM scheme was verified in a 3 kW grid-connected single-phase inverter. It was shown that the PWM strategy can be readily implemented with a digital signal processing microcontroller. 8 refs., 11 figs.

Shao, R.; Guo, Z.; Chang, L. [New Brunswick Univ., Fredericton, NB (Canada). Dept. of Electrical and Computer Engineering

2006-07-01

90

Nuevo algoritmo PWM híbrido de desempeño armónico superior/ A novel hybrid PWM algorithm having superior harmonic performance  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Este artículo presenta el diseño y validación de un nuevo algoritmo de modulación por ancho de pulso (PWM) híbrido que supera el desempeño armónico de varios algoritmos de modulación empleados en procesos de conversión de potencia en accionamientos eléctricos AC. A partir del análisis armónico de los algoritmos PWM más comunes en la literatura, se establece una metodología para diseñar un esquema de modulación híbrido que ofrece un desempeño armónico su (more) perior; este desempeño es verificado teórica y experimentalmente utilizando el factor de distorsión armónica total F DIST y el índice de distorsión armónica de corriente V WTHD. Abstract in english This paper presents a novel hybrid modulation algorithm which improves the harmonic performance of eight of the most common pulse width modulation (PWM) algorithms for voltage source inverters (VSI) in the electric drive field. From harmonic analysis of these eight algorithms, a methodology was established for designing a hybrid modulation scheme offering superior harmonic performance. The algorithm so designed was validated theoretically by calculating the total harmonic (more) distortion factor F DIST and experimentally by measuring the weighted total harmonic distortion factor V WTHD.

López Mesa, Diana Jimena; Camacho Muñoz, Guillermo Alberto; Díaz Chávez, Jaime Oscar; Gaviria López, Carlos Alberto; Bolaños Pantoja, Gilberto

2009-04-01

91

Multilevel cascade voltage source inverter with seperate DC sources  

Energy Technology Data Exchange (ETDEWEB)

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Peng, Fang Zheng (Oak Ridge, TN); Lai, Jih-Sheng (Knoxville, TN)

1997-01-01

92

Multilevel cascade voltage source inverter with seperate DC sources  

Energy Technology Data Exchange (ETDEWEB)

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Peng, Fang Zheng (Knoxville, TN); Lai, Jih-Sheng (Blacksburg, VA)

2002-01-01

93

High-Speed Fuses in IGBT based Voltage Source Converters  

DEFF Research Database (Denmark)

The demand for protection of power electronic applications has during the last couple of years increased regarding the high-power IGBT modules. Even with an active protection, a high power IGBT still has a risk of exhibiting a violent rupture in the case of a fault if IGBT fuses do not protect it. By introducing fuses into voltage source converters a better protection of IGBTs can be achieved. This paper is a complete overview of a research project carried out in cooperation by Aalborg University, Denmark and Cooper Bussmann International. This paper discusses three main issues regarding the IGBT fuse protection. First, the problem of adding inductance in the DC-link circuit is treated, second a short discussion of the protection of the IGBT module is done, and finally, the impact of the high frequency loading on the current carrying capability of the fuses is presented.

Iov, Florin; Blaabjerg, Frede

2005-01-01

94

Design of a Three-Phase Statcom-Based Inductive Static VAR Compensator Using DC Capacitor Voltage Control Scheme  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, a three-phase continuously controlled harmonic-free inductive static VAR compensator is presented. The compensator is built of a three-phase voltage source inverter based statcom. The phase currents of this compensator are linearly and continuously controlled by the statcom DC capacitor voltage. The control strategy is outlined by a process of forcing the capacitor voltage to follow a certain reference voltage which can be varied linearly from its maximum to its minimum values to produce balanced three-phase inductive currents varying in the range of zero to maximum value (I MAX) The proposed compensator was verified on the computer program PSpice.

Abdulkareem Mokif Obais; Jagadeesh Pasupuleti

2013-01-01

95

FIELD PROGRAMMABLE GATE ARRAY BASED RF-THI PULSE WIDTH MODULATION CONTROL FOR THREE PHASE NVERTER USING MATLAB MODELSIM COSIMULATION  

Directory of Open Access Journals (Sweden)

Full Text Available This study proposes different configurations of PWM techniques for harmonic reduction and improvement of fundamental peak voltage. For providing adjustable frequency power to industrial applications, three-phase inverter is preferred. The general aim of this study is to reduce the third order harmonics and improve the Harmonic Spread Factor by different PWM techniques using matlab modelsim cosimulation. The gating signals to the inverter are produced by means of SPWM, RFPWM, Third Harmonic Injection (THI) and Hybrid Random Frequency THIPWM. FPGA because of its suitability in time critical systems it is used to produce gating signals to the switches in a three-phase bridge inverter. This study will provide the insight of trends and technologies of Third Order Harmonic Elimination and improvement of HSF using different PWM techniques. In addition, a performance comparison of proposed methods with modified PWM methods is also provided. The result of the proposed work shows that there is improvement in fundamental voltage, THD, HSF when a combination of RF-THI PWM techniques is used.

Valantina Stephen; L. Padma Suresh; P. Muthukumar

2012-01-01

96

Voltage space vector's computation for current control in three phase converters/ Cómputo del vector espacial de voltaje para control de corriente en convertidores trifásicos  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Este trabajo presenta dos técnicas de control de corriente para convertidores trifásicos de voltaje trabajando como rectificadores controlados, operando con factor de potencia unitario. El primer algoritmo está basado en la escogencia del mejor vector natural, entre los 7 vectores espaciales naturales del convertidor de dos niveles de voltaje trifásico, mediante una función de costo. El segundo está basado en el cómputo y síntesis del vector espacial óptimo de co (more) nvertidores trifásicos tal que se obtiene el vector que proporciona un mínimo absoluto de la función de costo. El primer algoritmo es un método sencillo que controla muy bien el factor de potencia y presenta una considerable compensación del contenido armónico. El segundo algoritmo provee una nueva fórmula cerrada para calcular el vector de voltaje óptimo aplicado al convertidor. Para este segundo método se necesita generar la señal de control con un modulador de ancho de pulso para así controlar directamente la corriente de línea permitiendo seguir la referencia de corriente. Las simulaciones y resultados experimentales muestran las ventajas del algoritmo propuesto. Abstract in english This work presents two current loop techniques, for three phase voltage source converters (VSC) used as controlled rectifiers (CR) operating at unity power factor. The first one is based on choosing the best natural vector, among the natural space vectors produced by two level voltage source inverters, with the use of a cost function. The second one is based on computing and synthesizing a space vector such that an absolute minimum in the cost function is obtained. The fi (more) rst algorithm is a simple method that presents power factor correction and good total harmonic distortion compensation. The second algorithm provides a novel and closed form formula to calculate the optimum voltage vector applied by the converter. In this method, pulse width modulation (PWM) is required to modulate the voltage vector that controls directly the line current, to follow the current reference. The simulations and experimental results show the advantages of the proposed control algorithm.

Berzov, Alberto; Viola, Julio; Restrepo, José

2012-09-01

97

Semiconductor Light-Controlled Instrument Transducer with Direct PWM Output for Automatic Control Systems  

Directory of Open Access Journals (Sweden)

Full Text Available This work shows that the direct PWM output electric signal, with a duty cycle controlled by light intensity, can beobtained using a circuit containing a saw-tooth voltage generator connected in series with a dc voltage source and ametal (semitransparent gate) oxide semiconductor capacitor (MOS-C).The internal PWM signal conversion occurs by the use of non-equilibrium physical processes in the semiconductorsubstrate of the MOS-C. The 10-20 V amplitude limited square PWM output signal is obtained by the amplification ofthe sensor signal with a standard 60 dB transimpedance amplifier. The amplified output signal presents positive andnegative PWM waveforms that can be easily separated using diodes. The duty of the positive part is proportional tothe light intensity, whereas the negative part is inversely proportional to the intensity. The frequency operating rangeof this proposed instrument varies from 1 Hz to a few kilohertz. The duty cycle of the PWM output signal varies from2% to 98% when the incident light intensity varies in the microwatts range. These new transducers or sensors couldbe useful for automatic control, robotic applications, dimmer systems, feedback electronic systems, and non-contactoptical position sensing for nulling and centering measurements.

O. Malik; F. J. De la Hidalga-W

2013-01-01

98

Hardware-Resource Saving for Realization of Space Vector PWM Based on FPGA Using Bus-Clamping Technique  

Directory of Open Access Journals (Sweden)

Full Text Available The space vector pulse width modulation (SV-PWM) is more suitable and can increase the obtainable DC voltage utilization ratio very much compared to others PWM. Moreover, the modulation can obtain a better voltage total harmonic distortion (THD) factor. But until now, no studies that concern at hardware resources saving to realize SV-PWM based on FPGA. This paper proposes a new technique to realize SV-PWM based on FPGA. In order to get hardware resource saving, a simple technique to judge sectors, to calculate the firing pulses and to generate SV-PWM waveform without calculation of trigonometric function using bus-clamping technique is proposed. The technique has been implemented successfully based on APEX20KE FPGA to drive three phase induction machine 1.5 kW with low ripples in current and voltage, and has been shown that the proposed SVM method required the most minimum hardware resources compared to others research.

Tole Sutikno

2009-01-01

99

Performance of voltage source multilevel inverter - fed induction motor drive using Simulink  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with performance of voltage source multilevel inverter-fed induction motor drive. A Voltage source inverter (VSI) is compared with multilevel inverter. A conventional Voltage Source Inverter-fed induction motor drive is modeled and simulated using Matlab/ Simulink and the results are presented. Multilevel inverter employing Selective Harmonic Elimination (SHE) method is also simulated and the corresponding results are presented. The FFT spectrum for the outputs is analyzed to study the reduction in harmonics.

Neelashetty Kashappa; Ramesh Reddy K.

2011-01-01

100

An imroved design for ZVT DC-DC PWM converters with snubber assisted auxiliary switch  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este artigo propõe uma metodologia de projeto aprimorada para determinação dos componentes auxiliares para o conversor ZVT CC-CC PWM snubber assisted auxiliary switch. O procedimento de projeto proposto é baseado na redução das perdas de condução no circuito auxiliar. Isto é somente possível devido à localização do capacitor snubber de bloqueio, o qual é compartilhado por ambas as chaves ativas. Através do procedimento de projeto proposto o rendimento do co (more) nversor pode ser aumentado. Uma análise comparativa do rendimento é apresentada e os resultados experimentais, obtidos de protótipos de laboratório de 1 kW, 100 kHz, mostram uma melhoria relevante em relação ao rendimento apresentado pelo projeto original. Além disso, os resultados experimentais também confirmam que o projeto proposto para o conversor ZVT snubber assisted auxiliary switch torna-o competitivo em relação ao conversor ZVT PWM com fonte auxiliar de tensão constante (true PWM ZVS pole). Abstract in english This paper proposes an improved design to calculate the snubber auxiliary elements of ZVT DC-DC PWM converters with snubber assisted auxiliary switch. The proposed improved design guidelines are based on the reduction of the conduction losses through the auxiliary circuit. It is accomplished by the unique location of the turn-off snubber capacitor, which is shared by both active switches. By means of this improved design guidelines the converter efficiency can be increase (more) d. An efficiency comparative analysis is carried out and the experimental results, obtained from 1 kW, 100 kHz laboratory prototypes, show a relevant improvement in converter efficiency compared to the original converter design. In addition, experimental results also confirm that with the improved design the ZVT PWM converters with snubber assisted auxiliary switch can be competitive with ZVT PWM converters with constant auxiliary voltage source (True PWM ZVS pole).

Russi, J.; Martins, M. L.; Gründling, H. A.; Pinheiro, H.; Pinheiro, J. R.; Hey, H. L.

2005-03-01

 
 
 
 
101

An imroved design for ZVT DC-DC PWM converters with snubber assisted auxiliary switch  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes an improved design to calculate the snubber auxiliary elements of ZVT DC-DC PWM converters with snubber assisted auxiliary switch. The proposed improved design guidelines are based on the reduction of the conduction losses through the auxiliary circuit. It is accomplished by the unique location of the turn-off snubber capacitor, which is shared by both active switches. By means of this improved design guidelines the converter efficiency can be increased. An efficiency comparative analysis is carried out and the experimental results, obtained from 1 kW, 100 kHz laboratory prototypes, show a relevant improvement in converter efficiency compared to the original converter design. In addition, experimental results also confirm that with the improved design the ZVT PWM converters with snubber assisted auxiliary switch can be competitive with ZVT PWM converters with constant auxiliary voltage source (True PWM ZVS pole).Este artigo propõe uma metodologia de projeto aprimorada para determinação dos componentes auxiliares para o conversor ZVT CC-CC PWM snubber assisted auxiliary switch. O procedimento de projeto proposto é baseado na redução das perdas de condução no circuito auxiliar. Isto é somente possível devido à localização do capacitor snubber de bloqueio, o qual é compartilhado por ambas as chaves ativas. Através do procedimento de projeto proposto o rendimento do conversor pode ser aumentado. Uma análise comparativa do rendimento é apresentada e os resultados experimentais, obtidos de protótipos de laboratório de 1 kW, 100 kHz, mostram uma melhoria relevante em relação ao rendimento apresentado pelo projeto original. Além disso, os resultados experimentais também confirmam que o projeto proposto para o conversor ZVT snubber assisted auxiliary switch torna-o competitivo em relação ao conversor ZVT PWM com fonte auxiliar de tensão constante (true PWM ZVS pole).

J. Russi; M. L. Martins; H. A. Gründling; H. Pinheiro; J. R. Pinheiro; H. L. Hey

2005-01-01

102

Diode-assisted buck-boost voltage source inverters  

DEFF Research Database (Denmark)

This paper proposes buck-boost voltage source inverters with a unique X-shape diode-capacitor network inserted between inverter circuitry and dc source for producing a large voltage boost gain. Comparing with other voltage buck-boost techniques, the presented topologies with only a little more passive components can significantly enhance voltage boost capability for dc-ac inversion. With different front-end circuitries, the diode-assisted buck-boost inverters can show different operational principle and voltage boost ratio. Carefully analyzing the operational principle for the inherent energy charging and discharging processes of passive components reveals that the dc-link voltage can alternate between two levels, which therefore demonstrate the phenomena that the specified modulation schemes should note. A modulation scheme that can achieve optimized harmonic switching is first designed with symmetrical state placement in each switching sequence to avoid unnecessary voltage stress across both passive and active components. To reduce the total commutation count, the designed modulation scheme is then modified without increasing voltage stress. All theoretical findings were verified experimentally using a number of scale-down laboratory prototypes.

Gao, F.; Loh, P.C.

2007-01-01

103

[Voltage sources analysis in studies with foramen ovale electrodes  

UK PubMed Central (United Kingdom)

INTRODUCTION: Paroxysmal activity in medial temporal lobe epilepsy is originated in either hippocampal or parahippocampal regions. This activity can be directly recorded by foramen ovale electrodes. That paroxysmal activity will start from irritative or ictal areas. However, anatomo-functional relations between both regions are still debated. OBJECTIVE: We describe a new physical very simple model which allows to directly analysis the anatomo-physiological relations between sources for interictal and ictal areas. RESULTS: 1) The mathematical model allows to fit with minimum error and great precision the voltage sources originated from monopoles. 2) We can obtain this degree of precision with a matrix using an internodal distance of 0.1 mm (300x200 nodes) 3) Triplets of potentials with double sources with equal or specially with inverse charges have bigger error than monopolar charges. 4) Fitting real data obtained from a patient shows an error of 0.29 +/- 0.17% for interictal and 0.54 +/- 1.22% and 2.84 +/- 3.00% for two seizures (mean +/- SD). CONCLUSIONS: This model allows directly to know the relative anatomo-physiological relations between interictal and ictal sources in MTLE, which have a very important implications so for patho-physiological as therapeutics and outcome implications.

Pastor J; Rojo P; Sola RG

2004-02-01

104

IGBT Fuses for Protection Against Explosion in Voltage Source Converters  

DEFF Research Database (Denmark)

The consequences of electrical faults can be severe; not only to the equipment, but also in the worse case, to people if safety principles are not observed. Every year new applications based on DC-link Voltage Source Converters are added and the demand for protection of power electronics increases regarding the high-power IGBT modules. Due to the fact that the power level increases more energy is stored in the DC-link and even with an active protection, a high-power IGBT still has a risk of case rupture (explode) when a circuit failure condition occurs. A possible solution is a protection of the converter with standard High Speed Fuses or High Speed IGBT fuses. It is discussed that protection can be achieved by introduction of IGBT fuse located in the DC-link. Experiments show that explosion can be avoided by use of High Speed Fuse protection and the added inductance of standard High Speed- and IGBT Fuses in the DC-link is investigated. The current distribution in fuses is discussed when high frequency components are present in the load current. Further it is discussed how the extra cost for IGBT fuses may be balanced by ease of maintenance and less downtime of manufacturing equipment.

Blaabjerg, Frede; Iov, Florin

2004-01-01

105

Asymmetric Carrier Random PWM  

DEFF Research Database (Denmark)

This paper presents a new fixed carrier frequency random PWM method, where a new type of carrier wave is proposed for modulation. Based on the measurements, it is shown that the spread effect of the discrete components from the motor current spectra is very effective independent of the modulation index. The flat motor current spectrum generates an acoustical noise close to the white noise, which may improve the acoustical performance of the drive. The new carrier wave is easy to implement digitally, without employing any external circuits. The modulation method can be used in open, as well as in closed loop motor control applications.

Mathe, Laszlo; Lungeanu, Florin

2010-01-01

106

PWM conductance control  

Science.gov (United States)

Conductance (or current) control of switching regulators generally uses peak or hysteresis (e.g., LC3) controllers, the advantages and problems of which have been widely reported. The behavior of a simpler conventional pulsewidth-modulated (PWM) conductance control principle that has been used on space programs is described and analyzed. The chief advantage of the approach is that conventional integrated circuits and design techniques can be used, simplifying the designer's task. The design equations have been verified by both SPICE simulation and test results.

O'Sullivan, D.; Spruyt, H.; Crausaz, A.

107

PWM converter topologies  

Science.gov (United States)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is defined followed by two universal rules allowing for derivation of a wide variety of different topologies. A summary of different topology types is provided with steady state and small signal relations given for each. The survey shows 46 converter topologies of which 18 are known and 28 are new (under, patent application). The number of topologies could be increased to 68 if negative input voltages are considered.

Meerman, E. R. W.; Spruyt, H. J. N.

1989-08-01

108

Passive Lossless Snubbers For High Frequency PWM Converters  

UK PubMed Central (United Kingdom)

Introduction1. Seminar objectives2. Hard versus soft switching3. Diode reverse recovery4. IGBT behavior under hard switching5. Why soft switching?6. Soft switching terminology7. Soft switching by passive lossless snubbers8. Simulation toolsChapter 2. Passive lossless snubbers perspective1. Passive lossless snubber approaches2. Snubbers evolution3. The switched inductor (SIM) model4, Basic switching cell of common PWM converters5. Fundamental principles6. Practical aspectsChapter 3. Basics of resonant networks1. Reset of resonant elements2. Resonant networks - the vehicle of snubbing and energycirculation3. Basic resonant network parameters4. Ideal LC-network with ideal diode fed by a voltage source Vs5. Some trivial cases and practical aspects6. Resonant inductor designChapter 4. Switch turn-off lossless snubbers1. The 'one way' capacitor. Versions I and 2 (SNB 1 & SNB2)2. Switch turn-off lossless snubber (SNB3)3. Applying snubber SNB3

Sam Ben-yaakov; Gregory Ivensky

109

PWM pulse pattern optimization method using carrier frequency modulation. Carrier shuhasu hencho ni yoru PWM pulse pattern saitekikaho  

Energy Technology Data Exchange (ETDEWEB)

Sinusoidal inverters are getting more widely used keeping pace with the development of semiconductor switching elements. This paper discusses optimizing a PWM pulse pattern at an inverter output to drive an induction motor, proposes methods for improving distortion and torque ripples using a carrier frequency modulation (CFM), and describes a method for realizing the improvement through use of a single-chip microcomputer. The method defines evaluation parameters corresponding to the distortion and torque ripples, and optimizes the CFM depth to the parameters. The PWM pulse pattern has its voltage vector and time width so selected that the time integrated space vector of a three-phase voltage approaches a circular locus. Furthermore, the carrier frequency, that is the sampling frequency of the inverter, is also adjusted so that the above evaluation parameters are minimized. The addition of a new variable called the frequency modulation provides freedom in selecting an output characteristic as called for by the purpose. 12 refs., 18 figs.

Iwaji, Y.; Fukuda, S. (Hokkaido University, Sapporo (Japan))

1991-07-15

110

A classification methodology for zero-voltage transition PWM converters  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a classification methodology of the ZVT soft-transition technique, which is based on different ways of implementation of the auxiliary circuit voltage source. The merits and limitations of each class are presented and their key features and characteristics are discussed and experimentally analyzed on the 1kW/100kHz laboratory prototypes. By means of the proposed classification criteria, any ZVT topology can be classified, even the unpublished ones. Additionally, an overview of the main ZVT PWM converters proposed in the last decades is also presented.Este artigo propõe uma metodologia de classificação para a técnica de comutação suave conhecida como ZVT. Esta classificação é baseada nos diferentes modos de implementação da fonte auxiliar de tensão. Os méritos e limitações de cada classe são apresentados. As particularidades e características de cada classe são discutidas e analisadas experimental-mente em protótipos de laboratório de 1kW/100kHz. Por meio do critério de classificação proposto, qualquer topologia ZVT pode ser classificada, mesmo aquelas inéditas na literatura. Além disso, é apresentada uma visão geral dos principais con-versores ZVT PWM propostos nas últimas décadas.

M. L. Martins; J. L. Russi; H. L. Hey

2005-01-01

111

A Novel and Simple Current Controller for Three-Phase IGBT PWM Power Inverters  

UK PubMed Central (United Kingdom)

A new feedback current controller for three-phasepulse with modulated power inverters is presented. It is based ona current loop with two non linear three-level hysteresiscontrollers. The voltage vectors applied to the load areaccurately selected in order to minimise the output currenterror. Controller structure based on simple analog-digitalhardware implementation is shown and experimental results arepresented.I. INTRODUCTIONPower inverters play a key role in high-performanceac-motors variable speed drives (Fig. 1), where advancedcontrol techniques, based on the field orientation principle [1]or input-output linearization [2], could require fast andaccurate control of the motor current. The overallperformance of the drive is greatly influenced by the powerinverter control strategy. Usually they need a precise controlof the drive input current.Current controllers for power inverters can be classifiedaccording to their controller configuration [3]. On-off currentcon...

J. F. Martins; J. F. Silva; A. J. Pires

112

Asymmetrical three-phase induction motor performance through the use of dynamic capacitance witching  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a performance analysis for the asymmetrical three-phase induction motor fed by a single phase voltage source. High load diversity can be a constant through the working period of an induction motor. So the switching of capacitance along with load variation is a good strategy to keep the motor asymmetry balanced with the load instantaneous condition. Theoretical results of such switching are presented for a 2 HP asymmetrical induction motor. This analysis allowed us to get satisfactory conclusions on the performance of the asymmetrical motor when applied a dynamic capacitance switching system. (orig.)

Neto, L.M.; Teixcira, H.B.; Camacho, J.R. [Universidade Federal de Uberlandia, School of Electrical Engineering, Uberlandia (Brazil); Mendonca, R.G. de [CEFET-GO - Jatai Decentralized Unity, Electrotechnical Coordination, Jatai (Brazil)

2000-08-01

113

Unified analytical equation for theoretical determination of the harmonic components of modern PWM strategies  

DEFF Research Database (Denmark)

Pulse width modulation (PWM) is a key element of a voltage source inverter, inverter which is widely used for electric motor control and electric energy conversion. Several PWM methods have been proposed in the literature, focusing on performance, ease of implementation, and maximization of the transfer ratio. The difference between most of the proposed modulation methods like sine-triangular, SVM, and 120 - 60 - 30 Discontinuous PWM consists in the redistribution of the time-length applied for the zero voltage vectors during a fundamental frequency period. This paper presents a unified analytical equation for determining the theoretical spectra components for all the carrier based PWM methods with redistributed zero space vector time-length using the double Fourier integral analysis. The proposed unified equation can also be used for determination of the phase and line-to-line voltage spectra when the modulator works in over-modulation region. Moreover, the effect of the DC-link voltage ripple on the line-to-line voltage spectra is also considered. The experimental results show a very good agreement with the theoretically calculated spectra.

Mathe, Laszlo; Cornean, Horia

2011-01-01

114

Three-phase power supply, output 60v and 100a, with unit power factor and low RFI level  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a three-phase rectifier, unit power factor, non-dissipative commutation in DC-DC converter and synchronized control in frequency, working with 89% of global efficiency and low level do RFI. The proposed structure allows the operation with high switching frequency. The output voltage is controlled by PWM with a constant frequency. The operation principle, theoretical analysis from DC converter, relevant equations, current balance control technique and experimental results, are shown in this paper.

Carlos Henrique Gonçalves Treviso; Adriano Alves Pereira; Lúcio dos Reis Barbosa; Luiz Carlos de Freitas; João Batista Vieira Júnior

2003-01-01

115

Novos algoritmos de limitação para inversores de tensão PWM a quatro braços utilizando modulação space vector  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este artigo propõe dois novos algoritmos de limitação para inversores de tensão trifásicos a quatro braços. Estes baseiam-se na limitação do vetor de comando dentro da região de operação linear do inversor. O primeiro algoritmo utiliza um elipsóide inscrito no dodecaedro definido pelas extremidades dos possíveis vetores de comutação do inversor, e o segundo é baseado nos planos limites desse poliedro. Uma descrição detalhada, abordando os principais pont (more) os requeridos para a implementação digital, da modulação space vector e dos algoritmos de limitação são apresentados. Ainda, as tensões de saída e as correntes nos indutores são dinamicamente reguladas, por meio de servo controladores MIMO em eixos síncronos dq0. Estes controladores são projetados usando a técnica do regulador linear quadrático discreto de regime permanente, o qual assegura estabilidade para o sistema em toda a faixa de operação. Além disso, para prover transições suaves entre os diferentes modos de operação do inversor, são propostos algoritmos MIMO não lineares para limitar a sobrecarga da ação integral, quando o vetor de comando for limitado, e atualizar dinamicamente as variáveis dos servo controladores. Finalmente, são apresentados resultados experimentais obtidos de um protótipo de 15 kVA, totalmente controlado por um DSP TMS320F241, para validar os algoritmos propostos e demostrar o desempenho do sistema como um todo. Abstract in english This paper proposes two novel limiting algorithms for three-phase four-leg voltage source inverters to constrain the command vector inside the dodecahedron defined by the boundaries of the inverter linear operating range. The first algorithm uses an inscribed ellipsoid on the dodecahedron, and the second one is based on the polyhedron boundary planes. A detailed description, with the key points required for a digital implementation of space vector and limiting algorithms, (more) is given. In addition, the output voltages and the inductors currents are dynamically regulated by means of MIMO servo controller in dq0 coordinates. These controllers are designed using optimal discrete linear quadratic regulator technique, which ensures stability for the system at all operating conditions. In order to provide smooth transitions among the different modes of operation, nonlinear MIMO anti-windup algorithms are proposed to dynamically update the controllers servo variables. Finally, experimental results on a 15 kVA PWM inverter fully controlled by a DSP controller, TMS320F241, has been used to validate the feasibility of the proposed algorithm and to demonstrate the performance of the overall system.

Camargo, Robinson F. de; Botterón, Fernando; Pinheiro, Humberto; Pinheiro, José R.; Gründling, Hilton; Hey, Hélio

2004-09-01

116

A multilevel voltage-source converter system with balanced dc voltages  

Energy Technology Data Exchange (ETDEWEB)

A multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as large induction motor drives, back-to-back interconnected power systems, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the dc capacitors. The problem may be solved by use of additional voltage regulators or separate dc sources. However, these solutions are found not to be practicable for most applications. The proposed converter system can solve the voltage unbalance problem of the conventional multilevel voltage-source converters, without using any additional voltage balance circuits or separate voltage sources. Mechanism of the voltage unbalance problem is analyzed theoretically in this paper. The validity of the new converter system is demonstrated by simulation and experiment.

Peng, Fang Zheng [Tennessee Univ., Knoxville, TN (United States); Lai, Jih-Sheng; McKeever, J.; VanCoevering, J. [Oak Ridge National Lab., TN (United States)

1995-04-01

117

Shunt active filter algorithms for a three phase system fed to adjustable speed drive  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the simulation of Shunt Active Power filter by using two different control schemes, Indirect current control technique and Synchronous detection technique by using ANN. These two control techniques are working under both balanced and unbalanced three phase voltage source conditions and it is feeding to aadjustable speed drive the torque speed characteristics of a motor is presented. Indirect current control technique is implemented under dynamic load condition and load balanced condition. The equal current distribution method of synchronous detection theory is used here to calculate the three phase compensating currents to be provided by the active filter. For calculating sequence currents neural network is used. Neural network is used for estimation of distorted waves, delay less harmonic filtering.

Sujatha.CH; Sravanthi.Kusam; Dr. K.Chandra shek

2011-01-01

118

Elimination of a Common Mode Voltage Pulse in Converter/Inverter System Modifying Space-Vector PWM Method  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a common-mode voltage reduction method base on SVPWM(Space-Vector Pulsewidth Modulation) in three phase PWM converter/inverter system. By shifting the active voltage vector of inverter and aligning this to the active voltage vector of converter, it is possible to eliminate a common-mode voltage pulse in one control period. Since the proposed PWM method maintains the active voltage vector, it does not affect the control performance of PWM converter/inverter system. Without ant extra hardware, overall common mode voltage dv/dt and corresponding leakage current can be reduced to two-third of the conventional three phase symmetric SVPWM scheme. (author). 13 refs., 10 figs., 3 tabs.

Lee, Hyeoun Dong; Lee, Young Mine; Sul, Seung Ki [Seoul National University (Korea, Republic of)

1999-02-01

119

Analysis of voltage control for a self-excited induction generator using a current-controlled voltage source inverter (CC-VSI)  

Energy Technology Data Exchange (ETDEWEB)

The analysed results of both voltage regulation and current-harmonic suppression of a self- excited induction generator (SEIG), under unbalanced and/or nonlinear loading conditions using a current-controlled voltage source inverter (CC-VSI) are presented. A hybrid induction-machine model based on the three-phase a-b-c and the d-q frames of reference is employed to describe the dynamic performance of the studied system. The three-phase a-b-c induction-machine model is employed to derive dynamic equations of the SEIG under nonlinear loading conditions. The synchronously rotating reference frame based on a d-q axis model is used to decompose three-phase load currents into active and reactive power currents. The three-phase a-b-c stator voltages of the SEIG and the DC bus voltage of the inverter are simultaneously controlled by a proportional-integral (PI) voltage controller and a harmonic compensator. The simulated results show that the performance of the SEIG under unbalanced and/or nonlinear loading conditions has been effectively improved by the proposed compensating scheme. (Author)

Kuo, S. -C.; Wang, L. [Department of Electrical Engineering, National Cheng Kung University, 1 University Road, Tainan, Taiwan 70101 (China)

2001-09-01

120

Assessment of the impact that individual voltage source has on a generator’s stability  

DEFF Research Database (Denmark)

This paper presents an approach for splitting equivalent Thevenin voltage into components induced by each voltage source in the reduced grid. Thevenin equivalent representation of the system is sometimes used for stability assessment of a given generator, where the Thevenin voltage is one of the key variables affecting the stability conditions. Thevenin voltage is formed by components induced by each voltage source in the grid, while depending on topology and system parameters, the impact of these components on the equivalent Thevenin voltage Eth might vary considerably. This paper demonstrates how the impact of individual voltage source to the Eth might be defined utilizing system admittance matrix. Knowledge about alternation of Eth while applying changes to either admittance matrix or generators’ excitation and torque gives promising perspective for determination of effective countermeasures aimed on instability prevention. Suggested approach for Eth decomposition is applied to the IEEE 30 bus test system.

Dmitrova, Evgeniya; Jóhannsson, Hjörtur

2012-01-01

 
 
 
 
121

Improving separation of three-phase mixtures  

Energy Technology Data Exchange (ETDEWEB)

To lower the loss of glycol with condensate during drying of petroleum gas in lab. conditioins, tests were carried out on porous coalescing elements from metal/ceramics and fiberglass and their combinations for separating the three-phase mixture: gas - unstable condensate - glycol. Criteria: chemical inertness, effectiveness of mixture separation after passing the element, and permeable capacity during pressure fluctuations on the element of up 20 CPa. Glycol content in condensate was determined by titration. Results derived by VNIIPIGAZPererabotka in conjunction with TsKBN were developed into ''Recommendations for reconstructing three-phase separator at the Nizhnevartovskiy gas production plant''.

Boyko, S.I.; Mil' shteyn, L.M.; Molokanov, Yu.K.; Ziberg, G.K.

1980-01-01

122

CONCEPTUAL THREE PHASE ITERATIVE MODEL OF KDD  

Directory of Open Access Journals (Sweden)

Full Text Available KDD process includes how data is stored and accessed, how andwhat algorithms can apply to large amount of data efficiently,how results can be interpreted and visualized. KDD is theprocess of identifying valid, interesting and understandablepatterns in data. In this paper we will describe conceptual threePhase Iterative Model of KDD. The main layers of this purposedmodel are: Philosophy Layer, Technique Layer and ApplicationLayer. We will also perform the comparison of Tradition KDDModel with Three Phase Iterative Model.

Simmi Bagga; Dr. G. N. Singh

2012-01-01

123

Inverted sine carrier for fundamental fortification in PWM inverters and FPGA based implementations  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with a novel natural sampled pulse width modulation (PWM) switching strategy for voltage source inverter through carrier modification. The proposed inverted sine carrier PWM (ISCPWM) method, which uses the conventional sinusoidal reference signal and an inverted sine carrier, has a better spectral quality and a higher fundamental component compared to the conventional sinusoidal PWM (SPWM) without any pulse dropping. The ISCPWM strategy enhances the fundamental output voltage particularly at lower modulation index ranges while keeping the total harmonic distortion (THD) lower without involving changes in device switching losses. The presented mathematical preliminaries for both SPWM and ISCPWM give a conceptual understanding and a comparison of the strategies. The detailed comparison of the harmonic content and fundamental component of the ISCPWM output for different values of modulation index with the results obtained for the SPWM is also presented. Finally, the proposed modulator has been implemented in field programmable gate array (FPGA- Xilinx Spartan 3) and tested with the proto-type inverter.

Jeevananthan S.; Nandhakumar R.; Dananjayan P.

2007-01-01

124

Three-Phase Shunt Active Power Filter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Active power filters have been widely used for harmonic elimination. The performance of a conventional three-phase shunt Active Power Filter (APF) using Synchronous Detection Method (SDM) has been compared with Nonlinear Autoregressive-Moving Average (NARMA)-L2 based APF. The novelty of this study l...

Moleykutty George; Kartik P. Basu

125

Selective Harmonic Virtual Impedance for Voltage Source Inverters with LCL filter in Microgrids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a new control approach for voltage source inverters ended with LCL filters for microgrid applications. The control approach consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop. The virtual impedance is adde...

Savaghebi, Mehdi; Vasquez, Juan Carlos; Jalilian, Alireza Jalilian; Guerrero, Josep M.; Lee, Tzung-Lin

126

Cross connected multilevel voltage source inverter topologies for medium voltage applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multilevel voltage source inverters where first introduced in the early 1980s. Since then, they have been continuously developed, offering a wide new research area in power electronics. The popularity of multilevel solutions come from the advantages that they offer: improved output quality, voltage ...

Chaudhuri, Toufann

127

Design and Analysis of Adaptive Neural Controller for Voltage Source Converter for STATCOM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Usually a STATCOM is installed to support power system networks that have a poor power factor and often poor voltage regulation. It is based on a power electronics voltagesource converter. Various PWM techniques make selective harmonic elimination possible, which effectively control the harmonic con...

Ganesh, Aman; Singh, G. K.; Dahiya, Ratna

128

Sliding mode Control using 3D-SVM for Three-phase Four-Leg Shunt Active Filter  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a sliding mode control strategy for a three-phase shunt active power filter. The SAPF consists of four-leg voltage source inverter bridge. The SAPF ensures full compensation for harmonic phase currents, harmonic neutral current, reactive power compensation and unbalanced nonlinear load currents. The modulation task can be carried out with three dimensional space vector modulation, which operate under a constant switching frequency. The simulation results show that the performance of the four-leg SAPF with the proposed control algorithm – compared with PI controller - is found considerably effective and adequate to compensate harmonics, reactive power, neutral current and balance load currents.

Bouzidi Mansour; Benaissa Abdelkader; Barkat Said

2013-01-01

129

UNIVERSAL THREE-PHASE FERRORESONANCE STABILIZERS  

Directory of Open Access Journals (Sweden)

Full Text Available A comparative analysis has been carried out on two options of three-phase parametric current sources (inductive-capacitive stabilizers). Their capacities to operate in voltage stabilizer mode have been studied. Such capacities were proven and their conditions were defined. Theoretical results were experimentally checked and confirmed with satisfactory accuracy. Based on theoretical and experimental studies it was proven that the considered systems can operate in both modes-as current and voltage stabilizers.

GEORGI GEORGIEV; NADEZHDA EVSTATIEVA

2013-01-01

130

Three phase extraction in the trace analysis  

International Nuclear Information System (INIS)

[en] Three-phase extraction method was used for the determination of impurities in pure TeO2 and NiSO4. Microamounts of Co, Cd, Cu, Fe, Pd, Zn, were determined, which were extracted into lower organic phase in the form of complexes with diethyldithiocarbamate. The best results on isolation of impurities contained in TeO2 are obtained at pH 10. 3 refs.; 1 fig.; 3 tabs

1988-01-01

131

Control of direct three-phase to single-phase converters under balanced and unbalanced operations  

International Nuclear Information System (INIS)

[en] In this paper, a new control method based on pulse width modulation (PWM) technique is presented for direct three-phase to single-phase converters. This control method can be easily developed to direct three-phase to n-phase converters based on the exact principle of operation. The results of the proposed control method have been presented for two conventional topologies of direct three-phase to single-phase converters with four and six power switches. The suggested control method does not depend on the balanced or unbalanced input voltages. In balanced operation, the maximum output/input voltage transfer ratios are 0.5 and 1.5 for converters with four and six power switches, respectively. Also, the proposed method has no restrictions in frequency transformation. Another advantage of the proposed control method in comparison with the conventional control methods is dv/dt reduction in switches and loads. The operation and performance of the proposed control method has been verified by the simulation and experimental results.

2011-01-01

132

Control of direct three-phase to single-phase converters under balanced and unbalanced operations  

Energy Technology Data Exchange (ETDEWEB)

In this paper, a new control method based on pulse width modulation (PWM) technique is presented for direct three-phase to single-phase converters. This control method can be easily developed to direct three-phase to n-phase converters based on the exact principle of operation. The results of the proposed control method have been presented for two conventional topologies of direct three-phase to single-phase converters with four and six power switches. The suggested control method does not depend on the balanced or unbalanced input voltages. In balanced operation, the maximum output/input voltage transfer ratios are 0.5 and 1.5 for converters with four and six power switches, respectively. Also, the proposed method has no restrictions in frequency transformation. Another advantage of the proposed control method in comparison with the conventional control methods is dv/dt reduction in switches and loads. The operation and performance of the proposed control method has been verified by the simulation and experimental results.

Babaei, Ebrahim, E-mail: babaeiebrahim@yahoo.co [Faculty of Electrical and Computer Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

2011-01-15

133

A new three-phase AC-DC zero-voltage-switching isolated converter operating in DCM  

Energy Technology Data Exchange (ETDEWEB)

As an alternative to two-stage cascaded AC-DC converters, the paper presents a single-stage three-phase rectifier with input/output isolation. The rectifier contains five active devices driven by a simple PWM controller. The proposed converter operates in DCM and provides improved input current spectrum. Zero-voltage switching for all active devices and diodes is implemented in the suggested converter with low effort. Operational principle and design, as well as experimental results obtained from a 5 kW prototype, are discussed.

Panov, Y.V.; Lee, F.C.; Cho, J.G. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)

1995-12-31

134

PWM Inverter control and the application thereof within electric vehicles  

Energy Technology Data Exchange (ETDEWEB)

An inverter (34) which provides power to an A.C. machine (28) is controlled by a circuit (36) employing PWM control strategy whereby A.C. power is supplied to the machine at a preselectable frequency and preselectable voltage. This is accomplished by the technique of waveform notching in which the shapes of the notches are varied to determine the average energy content of the overall waveform. Through this arrangement, the operational efficiency of the A.C. machine is optimized. The control circuit includes a micro-computer and memory element which receive various parametric inputs and calculate optimized machine control data signals therefrom. The control data is asynchronously loaded into the inverter through an intermediate buffer (38). In its preferred embodiment, the present invention is incorporated within an electric vehicle (10) employing a 144 VDC battery pack (32) and a three-phase induction motor (18).

Geppert, Steven (Bloomfield Hills, MI)

1982-01-01

135

Performance Evaluation of Three Phase Bridge Module Type Diode Clamped Multilevel Inverter  

Directory of Open Access Journals (Sweden)

Full Text Available This work proposes three phase five level Bridge module type Diode Clamped Multilevel Inverter (DCMLI) using various modulating techniques for induction motor load. These Pulse Width Modulating (PWM) techniques include Carrier Overlapping (CO) strategy, Variable Frequency (VF) strategy, Phase Shift (PS) strategy and Sub-Harmonic Pulse Width Modulation (SHPWM) i.e. Phase Disposition (PD) strategy, Phase Opposition Disposition (POD) strategy and Alternate Phase Opposition Disposition (APOD) strategy. The Total Harmonic Distortion (THD), VRMS (fundamental), crest factor, form factor and distortion factor are evaluated for various modulation indices. Simulation is performed using MATLAB-SIMULINK. It is observed thatPODPWM/PSPWM methods provide output with relatively low distortion for R Load. It is also observed that PSPWM method provides output with relatively low distortion for IM load. COPWM is also found to perform better since it provides relatively higher fundamental RMS output voltage for Induction Motor (IM) load and R load.

C.R. Balamurugan, S. P. Natarajan, R.Bensraj

2012-01-01

136

High-frequency, three-phase current controller implementation in an FPGA  

Energy Technology Data Exchange (ETDEWEB)

Three phase rectifiers with switching frequencies of 500 kHz or more require high speed current controllers. At such high switching frequencies analog controllers as well as high speed digital signal processing (DSP) systems have limited performance. In this paper, two high speed current controller implementations using two different field-programmable gate arrays (FPGA) - one for switching frequencies up to 1 MHz and one for switching frequencies beyond 1 MHz - are presented to overcome this performance limitation. Starting with the digital system design all the blocks of the signal chain, containing analog-to-digital (A/D) interface, digital controller implementation using HW-multipliers and implementation of a novel high speed, high resolution pulse width modulation (PWM) are discussed and compared. Final measurements verify the performance of the controllers. (author)

Hartmann, M.; Round, S. D.; Kolar, J. W.

2008-07-01

137

Elimination of the waveform distortions in the voltage-source-converter type matrix converter  

Energy Technology Data Exchange (ETDEWEB)

The recently reported voltage-source-converter type matrix converter offers advantages in terms of employing the well-known and proven technology of the 3-phase voltage-source converters, bypassing the switching difficulties associated with the bidirectional switches in the conventional 9-switch matrix converter topology, and reduction in the conduction losses. The new matrix converter topology is capable of establishing the dual condition of Unity Displacement Power Factor on the utility-side and Field Vector Control on the motor load-side. However, because of the special structure of the transformation matrix and the presence of dc components in the side-2 voltages, the branch currents on side-1 and the ac voltages on side-2 contain some unwanted components resulting in additional losses and waveform distortions. This paper addresses the above problem and proposes a novel technique for the elimination of the unwanted components. Experimental results are used to verify the correctness of the theoretical expectations.

Ooi, B.T.; Kazerani, M. [McGill Univ., Montreal, Quebec (Canada). Dept. of Electrical Engineering

1995-12-31

138

Dynamic Modeling of UPFC by Two Shunt Voltage- Source Converters and a Series Capacitor  

Directory of Open Access Journals (Sweden)

Full Text Available The unified power flow controller (UPFC) is one of the FACTS devices vastly applied in power systems. This paper presents the modeling of a new structure of UPFC consists of two shunt voltage-source converters and a series capacitor. Through the presented modeling, the transient and steady states responses of UPFC are well investigated. The results of the investigation are presented for the transient and steady states by simulating proposed system in MATLAB changing each system parameter.

Farzad Mohammadzadeh Shahir; Ebrahim Babaei

2013-01-01

139

Performance Analysis of a Voltage Source Converter (VSC) based HVDC Transmission System under Faulted Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Voltage Source Converter (VSC) based HVDC transmission technology hasbeen selected as the basis for several recent projects due to its controllability,compact modular design, ease of system interface, and low environmentalimpact. This paper investigates the dynamic performance of a 200MW,±100kV VSC-HVDC transmission system under some faulted conditionsusing MATLAB/Simulink. Simulation results confirm the satisfactoryperformance of the proposed system under active and reactive powervariations and fault conditions.

Khatir MOHAMED; Zidi Sid AHMED; Hadjeri SAMIR; Fellah Mohammed KARIM; Amiri RABIE

2009-01-01

140

Novel passive lossless turn-on snubber for voltage source inverters  

Energy Technology Data Exchange (ETDEWEB)

A novel passive lossless turn-on snubber with a soft clamped turn-off snubber circuit for voltage source inverters is proposed. The energy trapped in the snubber is recovered into the dc supply and load without any active devices, associated control circuitry, or resistors. The overshoot voltage on the switches is clamped, and the peak switch current is low, making this snubber suitable for use in high-power insulated gate bipolar transistor (IGBT) inverters.

He, X.; Qian, Z.M. [Zhejiang Univ., Hangzhou (China). Dept. of Electrical Engineering; Finney, S.J.; Williams, B.W. [Heriot-Watt Univ., Edinburgh (United Kingdom). Dept. of Computing and Electrical Engineering

1997-01-01

 
 
 
 
141

Variable speed wind turbine generator system with current controlled voltage source inverter  

International Nuclear Information System (INIS)

[en] highlights: ? Current controlled voltage source inverter scheme for wind power application. ? Low voltage ride through of wind farm. ? Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

2011-01-01

142

Low-cost PWM speed controller for an electric mini-baja type vehicle  

Directory of Open Access Journals (Sweden)

Full Text Available This paperwork presents a Pulse Width Modulation (PWM) speed controller for an electric mini-baja-type car. A battery-fed 1-kW three-phase induction motor provides the electric vehicle traction. The open-loop speed control is implemented with an equal voltage/frequency ratio, in order to maintain a constant amount of torque on all velocities. The PWM is implemented by a low-cost 8-bit microcontroller provided with optimized ROM charts for distinct speed value implementations, synchronized transition between different charts and reduced odd harmonics generation. This technique was implemented using a single passenger mini-baja vehicle, and the essays have shown that its application resulted on reduced current consumption, besides eliminating mechanical parts.

Samuel Euzédice de Lucena; Márcio Abud Marcelino; Francisco José Grandinetti

2007-01-01

143

Low-cost PWM speed controller for an electric mini-baja type vehicle  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english This paperwork presents a Pulse Width Modulation (PWM) speed controller for an electric mini-baja-type car. A battery-fed 1-kW three-phase induction motor provides the electric vehicle traction. The open-loop speed control is implemented with an equal voltage/frequency ratio, in order to maintain a constant amount of torque on all velocities. The PWM is implemented by a low-cost 8-bit microcontroller provided with optimized ROM charts for distinct speed value implementati (more) ons, synchronized transition between different charts and reduced odd harmonics generation. This technique was implemented using a single passenger mini-baja vehicle, and the essays have shown that its application resulted on reduced current consumption, besides eliminating mechanical parts.

Lucena, Samuel Euzédice de; Marcelino, Márcio Abud; Grandinetti, Francisco José

2007-03-01

144

Three-phase partitioning of hydrolyzed levan.  

UK PubMed Central (United Kingdom)

During the fructose and polymerization to synthesize levan, smaller fructooligosaccharide (FOS) molecules are produced. FOS can also be obtained by levan hydrolysis. Three-phase partitioning (TPP) is a separation technique that has been used for polysaccharide precipitation and gathers t-butanol and ammonium sulphate to exclude the polymer from the aqueous solution. In this work TPP was tested to separate levan and FOS from aqueous solution. The FOS used was obtained from Zymomonas mobilis levan acid hydrolysis and fractionation with ethanol. The yield of low TPP fractions was higher than those obtained from the native levan. The F-90 exhibited a higher yield than other fractions. However, when applying the TPP technique to lightest fraction not precipitated by ethanol at 90% (F>90), the intermediate phase was not possible to be visualize. These results have potential application because they show that by using the levan TPP separation it is possible to separate low-molecular weight sugar.

Coimbra CG; Lopes CE; Calazans GM

2010-06-01

145

Three-phase partitioning of hydrolyzed levan.  

Science.gov (United States)

During the fructose and polymerization to synthesize levan, smaller fructooligosaccharide (FOS) molecules are produced. FOS can also be obtained by levan hydrolysis. Three-phase partitioning (TPP) is a separation technique that has been used for polysaccharide precipitation and gathers t-butanol and ammonium sulphate to exclude the polymer from the aqueous solution. In this work TPP was tested to separate levan and FOS from aqueous solution. The FOS used was obtained from Zymomonas mobilis levan acid hydrolysis and fractionation with ethanol. The yield of low TPP fractions was higher than those obtained from the native levan. The F-90 exhibited a higher yield than other fractions. However, when applying the TPP technique to lightest fraction not precipitated by ethanol at 90% (F>90), the intermediate phase was not possible to be visualize. These results have potential application because they show that by using the levan TPP separation it is possible to separate low-molecular weight sugar. PMID:20163956

Coimbra, Cynthia Gisele de Oliveira; Lopes, Carlos Edison; Calazans, Glícia Maria Torres

2010-02-16

146

Three Phase Active Conditioner for Harmonics Mitigation  

Directory of Open Access Journals (Sweden)

Full Text Available The Shunt Active Power Filter is a very essential tool to remove harmonic currents and to reimburse reactive power for nonlinear loads. The fundamental standard of process of a Shunt Active Power Filter is to introduce an appropriate non-sinusoidal current (compensating current) into the system at the point of common coupling. This research work focuses on the time-domain approach for three-phase Shunt Active Power Filters through an effective algorithm. A fundamental outline and evaluation of the performance of existing improved algorithms for active power filters are presented. An enhanced approach based on time domain technique is proposed based on various complicated power quality problems and various compensation functions. It is observed that the proposed algorithm provides has shorter response time delay when compared with the conventional approaches. Therefore, the proposed approach can accurately attain various compensating current references.

P.M. Balasubramaniam; G. Gurusamy

2012-01-01

147

Three-Phase Shunt Active Power Filter  

Directory of Open Access Journals (Sweden)

Full Text Available Active power filters have been widely used for harmonic elimination. The performance of a conventional three-phase shunt Active Power Filter (APF) using Synchronous Detection Method (SDM) has been compared with Nonlinear Autoregressive-Moving Average (NARMA)-L2 based APF. The novelty of this study lies in the application of NARMA-L2 control to generate the amplitude of the reference supply current required by the APF circuit and the successful implementation of the APF system for harmonic elimination. The entire system has been modeled using MATLAB 6.1 toolbox. Simulation results demonstrate the applicability of NARMA-L2 controller for the control of APF.

Moleykutty George; Kartik P. Basu

2008-01-01

148

Metodologia de projeto de filtros de segunda ordem para inversores de tensão com modulação PWM digital  

Directory of Open Access Journals (Sweden)

Full Text Available Este artigo apresenta uma metodologia sistematizada de projeto de filtros de saída de segunda ordem para inversores que sintetizam tensões senoidais através de modulação por largura de pulso (PWM) digital. O propósito desta metodologia é o de determinar os parâmetros do filtro que assegure a especificação da máxima taxa de distorção harmônica total (THD) admissível nas tensões de saída do inversor PWM, para cargas lineares e não-lineares. A metodologia proposta é discutida em detalhes, incluindo a descrição das etapas necessárias para a derivação do procedimento de projeto para diferentes topologias de inversores de tensão e o procedimento para obtenção das curvas necessárias para o projeto. Finalizando, são apresentados alguns exemplos de projeto para topologias de inversores monofásicos e trifásicos com saída a três fios e a quatro fios. Resultados experimentais são apresentados para demonstrar a validade da metodologia de projeto proposta.This paper presents a systematized methodology of second-order output filter for inverters that synthesize sinusoidal voltage waveforms through digital pulse-width modulation (PWM). The objective of this methodology is to determine the largest corner frequency of the filter that ensure the specification of the maximum total harmonic distortion (THD) admissible in the output voltages of the PWM inverter, for linear and non-linear loads. The proposed methodology is discussed in detail, including the description of the required steps for the derivation of the design procedure for different topologies of voltage inverters and the procedure to obtain the design curve. Finally, it is presented some design examples for single-phase, three-phase three-wire and three-phase four-wire filters topologies. Experimental results have been provided to demonstrate the validity of the proposed design methodology.

Leandro Michels; Robinson F. de Camargo; Fernando Botterón; Humberto Pinheiro

2005-01-01

149

Metodologia de projeto de filtros de segunda ordem para inversores de tensão com modulação PWM digital  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este artigo apresenta uma metodologia sistematizada de projeto de filtros de saída de segunda ordem para inversores que sintetizam tensões senoidais através de modulação por largura de pulso (PWM) digital. O propósito desta metodologia é o de determinar os parâmetros do filtro que assegure a especificação da máxima taxa de distorção harmônica total (THD) admissível nas tensões de saída do inversor PWM, para cargas lineares e não-lineares. A metodologia p (more) roposta é discutida em detalhes, incluindo a descrição das etapas necessárias para a derivação do procedimento de projeto para diferentes topologias de inversores de tensão e o procedimento para obtenção das curvas necessárias para o projeto. Finalizando, são apresentados alguns exemplos de projeto para topologias de inversores monofásicos e trifásicos com saída a três fios e a quatro fios. Resultados experimentais são apresentados para demonstrar a validade da metodologia de projeto proposta. Abstract in english This paper presents a systematized methodology of second-order output filter for inverters that synthesize sinusoidal voltage waveforms through digital pulse-width modulation (PWM). The objective of this methodology is to determine the largest corner frequency of the filter that ensure the specification of the maximum total harmonic distortion (THD) admissible in the output voltages of the PWM inverter, for linear and non-linear loads. The proposed methodology is discusse (more) d in detail, including the description of the required steps for the derivation of the design procedure for different topologies of voltage inverters and the procedure to obtain the design curve. Finally, it is presented some design examples for single-phase, three-phase three-wire and three-phase four-wire filters topologies. Experimental results have been provided to demonstrate the validity of the proposed design methodology.

Michels, Leandro; Camargo, Robinson F. de; Botterón, Fernando; Pinheiro, Humberto

2005-06-01

150

A computer-aided analysis and design approach for static voltage source inverters  

Energy Technology Data Exchange (ETDEWEB)

The relative success of the ''cut and try'' method has made the design of static power converters more of an art than a science. As a result, no comprehensive analysis approach is available today that can be used to design static converters with a good degree of confidence. Some important aspects of this problem - concerning mainly static voltage source inverters - are treated in this paper within the framework of a generalized analysis and design method. The subject approach utilizes the switching function concept to derive relevant analytical expressions, and digital simulation to obtain relevant design data.

Ziogas, P.D.; Stefanovic, V.R.; Weichmann, E.P.

1985-09-01

151

Análise e implementação de retificadores PWM trifásicos com resposta de tempo mínimo utilizando desacoplamento por retroação de estados  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este trabalho desenvolve um procedimento de projeto sistemático para o controle das correntes de entrada e da tensão de saída de retificadores PWM trifásicos. Primeiramente é apresentado o modelo discreto em eixos síncronos dq do retificador PWM trifásico com filtro de entrada L, o qual leva em conta o tempo de processamento necessário para a implementação em tempo real. A operação do retificador com resposta de tempo mínimo é obtida utilizando o método de (more) desacoplamento por retroação de estados no domínio discreto, sem a necessidade de um controlador de corrente adicional no eixo d. Além disso, são desenvolvidos servos controladores de corrente e tensão a fim de garantir fator de deslocamento unitário e regulação de tensão no barramento CC respectivamente. Finalmente, resultados experimentais são apresentados, a fim de validar o procedimento proposto e verificar o desempenho do retificador PWM trifásico. Abstract in english This paper develops a systematic design procedure based on discrete decoupling by state feedback applied to three-phase PWM rectifiers. A discrete model for synchronous frame is developed for three-phase PWM rectifier with an L filter. This model takes into account the computational delays presents in the discrete implementation. Deadbeat response is obtaining without the requirement of a current controller in the axis d. Moreover, discrete servo controllers to ensure uni (more) t displacement power factor and regulated DC link voltage are developed. Finally, experimental results are presented to demonstrate the feasibility of the proposed procedure, algorithms and the performance of the overall system.

Camargo, Robinson F. de; Botterón, Fernando; Duarte, Marcelo Hey; Marques, Jéferson; Pinheiro, Humberto

2005-12-01

152

A Novel and Simple Current Controller for Three-Phase IGBT PWM Power Inverters - A Comparative Study  

UK PubMed Central (United Kingdom)

A new feedback current controller for three-phasepulse width modulated power inverters is presented. To achieverobustness against load parameter variation, fast dynamicalresponse, reduced switching frequency and simple hardwareimplementation, a three-level hysteresis sliding mode controlleris used. The voltage vectors applied to the load are accuratelyselected in order to minimise the current error. Controllerstructure based on simple analog-digital hardware is shown andexperimental results are presented. The results of a comparativestudy ilustrate the performance of the proposed controller withother known controllers.I. INTRODUCTIONVariable speed drives (Fig. 1), equipped with squirrel-cageinduction machines, play a key role in modern industrialapplications. The benefits of using this type of machine --high reliability and low maintenance -- make it widely usedthrough various industrial processes, with growingperformance demands.Elaborated control methods [1,2] ac...

J. F. Martins; A. J. Pires; J. F. Silva

153

Selective Harmonic Virtual Impedance for Voltage Source Inverters with LCL filter in Microgrids  

DEFF Research Database (Denmark)

This paper presents a new control approach for voltage source inverters ended with LCL filters for microgrid applications. The control approach consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop. The virtual impedance is added in order to mitigate the voltage distortion after the output inductor and improve the load sharing among parallel inverters. A general case with a combined voltage harmonic and unbalance distortion is considered. In such a case, voltage distortion is mitigated by inserting capacitive virtual impedance for negative sequence of fundamental component as well as positive and negative sequences of main harmonic components. Furthermore, resistive virtual impedances are added at these components in order to provide a proper load sharing and make the overall system more damped. Simulation results are presented to demonstrate the effectiveness of the proposed control approach.

Savaghebi, Mehdi; Vasquez, Juan Carlos

2012-01-01

154

A multilevel voltage-source inverter with separate dc sources for static var generation  

Energy Technology Data Exchange (ETDEWEB)

A new multilevel voltage-source inverter with a separate dc sources is proposed for high-voltage, high-power applications, such as flexible ac transmission systems (FACTS) including static var generation (SVG), power line conditioning, series compensation, phase shifting, voltage balancing, fuel cell and photovoltaic utility systems interfacing, etc. The new M-level inverter consists of (M-1)/2 single phase full bridges in which each bridge has its own separate dc source. This inverter can generate almost sinusoidal waveform voltage with only one time switching per cycle as the number of levels increases. It can solve the problems of conventional transformer-based multipulse inverters and the problems of the multilevel diode-clamped inverter and the multilevel flying capacitor inverter. To demonstrate the superiority of the new inverter, a SVG system using the new inverter topology is discussed through analysis, simulation and experiment.

Peng, Fang Zheng [Tennessee Univ., Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States); Lai, Jih-Sheng; McKeever, J.; VanCoevering, J. [Oak Ridge National Lab., TN (United States)

1995-09-01

155

A Consideration of Stable Operating Power Limits of HVDC System Composed of Voltage Source Converters  

Science.gov (United States)

The stable operating power limits of a small scale HVDC system composed of voltage source converters (VSC-HVDC system) are analyzed with a simple model. The VSC-HVDC system could operate where the AC system must be somewhat larger in capacity than the VSC-HVDC system capacity. The stable operating power limits were between one and two times the SCR (short circuit ratio). When the inverter of the VSC-HVDC system was operated with lead reactive (capacitive) power control conditions, the stable operating limits were increased through AC voltage stabilization. When the inverter was a STATCOM operation, it could operate regardless of the SCR but regions within allowable AC voltage variations.

Konishi, Hiroo; Takahashi, Choei; Kishibe, Hideto; Sato, Hiromichi

156

Powering the flagellar motor of Escherichia coli with an external voltage source.  

UK PubMed Central (United Kingdom)

Rotary motors of bacterial flagella are driven by ions that move across the cytoplasmic membrane down an electrochemical gradient. For Escherichia coli, the ions are protons, and the maximum work per unit charge that they can do is the protonmotive force. To test whether motor efficiency is limited by proton leakage or mechanical nonlinearities, we measured torque as a function of protonmotive force. Filamentous cells were drawn into micropipettes and energized with an external voltage source. Torque was proportional to protonmotive force up to -150 mV, twice the span accessible by earlier techniques. This is consistent with a mechanism in which a fixed number of protons, working at unit efficiency, carry the motor through each revolution. We also found that individual torque-generating elements inactivate at low potentials or potentials of reverse sign. When normal potentials are restored, they reactivate sequentially.

Fung DC; Berg HC

1995-06-01

157

Influence of current limitation on voltage stability with voltage sourced converter HVDC  

DEFF Research Database (Denmark)

A first study of voltage stability with relevant amount of Voltage Sourced Converter based High Voltage Direct Current (VSC-HVDC) transmission is presented, with particular focus on the converters’ behaviour when reaching their rated current. The detrimental effect of entering the current limitation on the Power-Voltage (PV) curves at a load bus is exemplified on a three-bus system, proposing a method to model the converters in current limiting mode through ideal current sources. The influence of the current magnitude and angle on the reduced stability margin is analysed and results show that, when the current limit is reached, despite the detrimental effect brought about by an increased equivalent transmission impedance, the loss of stability margin can be minimised by proper control of the converter.

Zeni, Lorenzo; Jóhannsson, Hjörtur

2013-01-01

158

Connecting fast switching voltage-source converters to the grid - Harmonic distortion and its reduction  

Energy Technology Data Exchange (ETDEWEB)

In this paper, harmonic distortion of fast switching pulse width modulated (PWM) converters connected to the grid is addressed. The origin of harmonic distortion and methods to reduce it are presented. Due to high voltage derivatives, Electro Magnetic Interference (EMI) and insulation stress on the transformer connected to the converter occur. To reduce the distortion, a third order LCL-filter is proposed. It is compared with a first order L-filter. A major advantage of the LCL-filter compared with the L-filter is that the switching frequency of the converter can be significantly decreased. This facilitates reduction of the switching speed of the semiconductor valves, such a step reduces voltage derivatives. In addition, if the plant is to be used for Static Var Compensation (SVC), the system cost can be decreased. 5 refs, 14 figs

Lindgren, M.; Svensson, Jan [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Electrical Machines and Power Electronics

1995-12-31

159

PWM Switching Strategy for Torque Ripple Minimization in BLDC Motor  

Science.gov (United States)

This paper describes a new PWM switching strategy to minimize the torque ripples in BLDC motor which is based on sensored rotor position control. The scheme has been implemented using a PIC microcontroller to generate a modified Pulse Width Modulation (PWM) signals for driving power inverter bridge. The modified PWM signals are successfully applied to the next up-coming phase current such that its current rise is slightly delayed during the commutation instant. Experimental results show that the current waveforms of the modified PWM are smoother than that in conventional PWM technique. Hence, the output torque exhibits lower ripple contents.

Salah, Wael A.; Ishak, Dahaman; Hammadi, Khaleel J.

2011-05-01

160

A COMPARATIVE STUDY OF PROPORTIONAL INTEGRAL CONTROLLER AND FUZZY LOGIC CONTROLLER IN SCALAR SPEED CONTROL OF THREE PHASE INDUCTION MOTOR  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a performance study of the proportionalintegral controller andthe fuzzy logic controller in scalar speed control of three phase squirrel cage induction motor drive. Here the speed control is possible by varying supply frequencyusing a voltage source inverter while keeping voltage to frequency ratio as a constant. Speed error is given as inputto the proportional integral controller, and speed error and change in speed error are given as input to the fuzzy logic controller.The controller output controls the reference of sinusoidal pulse width modulation. Hence, the fundamental frequency and fundamental voltage of inverter output can be varied to control the motor speed.The performance of proportional integral controller and fuzzy logic controller underload torqueand reference speed variationisevaluated by simulation results in Simulink.

SAFDAR FASAL T K, UNNIKRISHNAN L

2013-01-01

 
 
 
 
161

A New Topology of Three-Phase Four-Wire UPQC with a Simplified Control Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a simplified control algorithm based on unit vector template generation (UVTG) is proposed for a star-delta supported three-phase four-wire (3P-4W) unified power quality conditioner (UPQC) topology for the improvement of different power quality problems. Different topologies reported in literature for 3P-4W UPQC use active compensation for the mitigation of source neutral current along with other power quality (PQ) problems, while the uses of passive elements for the mitigation of source neutral current are advantageous over the active compensation due to ruggedness and less complexity of control. Hence, in this paper a star-delta transformer is connected in shunt near the load for mitigation of source neutral current, while three-leg voltage source inverters (VSIs) based shunt and series active power filters (APFs) of 3P-4W UPQC mitigate the current and voltage based distortions, respectively. A simple control algorithm based on Unit Vector Template Generation (UVTG) is used as a control strategy of UPQC for mitigation of different PQ problems. In this control scheme, the current/voltage control is applied over the fundamental supply currents/load voltages instead of fast changing APFs currents/voltages, thereby reducing the effects of computational delay and the required sensors. The performance of the proposed topology of UPQC is analyzed through simulations results using MATLAB software with its Simulink and Power System Block set toolboxes.

Yash Pal; A. Swarup; B. Singh

2012-01-01

162

Integrated modeling and control of a PEM fuel cell power system with a PWM DC/DC converter  

Energy Technology Data Exchange (ETDEWEB)

A fuel cell powered system is regarded as a high current and low voltage source. To boost the output voltage of a fuel cell, a DC/DC converter is employed. Since these two systems show different dynamics, they need to be coordinated to meet the demand of a load. This paper proposes models for the two systems with associated controls, which take into account a PEM fuel cell stack with air supply and thermal systems, and a PWM DC/DC converter. The integrated simulation facilitates optimization of the power control strategy, and analyses of interrelated effects between the electric load and the temperature of cell components. In addition, the results show that the proposed power control can coordinate the two sources with improved dynamics and efficiency at a given dynamic load. (author)

Choe, Song-Yul; Ahn, Jong-Woo [Mechanical Engineering Department, Auburn University, Auburn, AL 36848 (United States); Lee, Jung-Gi [Electrical Engineering Department, Pohang University of Science and Technology, Pohang (Korea); Baek, Soo-Hyun [Electrical Engineering Department, Dong-guk University, Seoul (Korea)

2007-02-10

163

Rotor cage fault diagnosis in three-phase induction motors based on a current and virtual flux approach  

Energy Technology Data Exchange (ETDEWEB)

This paper focuses on the detection of a rotor cage fault in a three-phase PWM feed induction motor. In inverter-fed machines there are some difficulties for the detection of a rotor cage fault. These difficulties are due to the fault signature that will be contained in the currents or voltages applied to the machine. In this way, a new approach based on the current and a virtual flux is proposed. The use of the virtual flux allows the improving of the signal to noise ratio. This approach also allows the identification of a rotor cage fault independently of the type of control used in the ac drive. The theoretical principle of this method is discussed. Simulation and experimental results are presented in order to show the effectiveness of the proposed approach. (author)

Pires, Dulce F. [Escola Sup. Tecnologia Setubal/Inst. Politecnico Setubal, Setubal (Portugal); Pires, V. Fernao [Escola Sup. Tecnologia Setubal/Inst. Politecnico Setubal, Setubal (Portugal)]|[LabSEI - Laboratorio de Sistemas Electricos Industriais, Setubal (Portugal); Martins, J.F. [CTS, Faculdade de Ciencias e Tecnologia/UNL, Lisboa (Portugal); Pires, A.J. [Escola Sup. Tecnologia Setubal/Inst. Politecnico Setubal, Setubal (Portugal)]|[LabSEI - Laboratorio de Sistemas Electricos Industriais, Setubal (Portugal)]|[CTS, Faculdade de Ciencias e Tecnologia/UNL, Lisboa (Portugal)

2009-04-15

164

Three Phase Two Leg Neutral Point Clamped Converter with output DC Voltage Regulation and Input Power Factor Correction  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a three-phase two leg neutral point clamped (NPC) converter is presented for power factor correction and dc-link voltage regulation. The adopted converter has simpler circuit configuration and less number of power switches compared to three-level PWM converter. In this circuit configuration, only eight power switches and four clamping diodes with voltage stress of half the dc bus voltage are used. A simplified space vector pulse width modulation scheme (SVPWM) is also adopted to track the line current commands. A reference voltage vector is generated on the ac terminal for drawing the sinusoidal line currents with unity power factor. This algorithm reduces the time required to calculate the switching time durations of voltage vectors. The simulation results have been presented to verify the validity and effectiveness of the proposed control strategy.

Bogimi Sirisha; P. Satish Kumar; N. Susheela

2012-01-01

165

Simulation analysis of three-phase current type AC-to-DC converter with high power factor  

Energy Technology Data Exchange (ETDEWEB)

A new three-phase current type AC-to-DC converter has been developed by the authors. This paper describes the principle of the circuit operation and the circuit configuration of the AC-to-DC converter controlled by PWM. Simulation analysis of each waveform, such as AC and DC voltages and currents, are calculated by Euler`s method. The simulated values of the total power factor agreed with the measured values within the difference of 5.8% on the condition of full load, 10kW. When the AC side voltage is unbalanced, it is found by simulation that the total harmonic distortion controlled by both feedforward control and AC side current feedback control (proportion gain, k{sub 4} = 1) is restrained at only 38% compared with only feedforward control (k{sub 4} = 0).

Okui, Yoshiaki; Yamada, Hajime [Shinshu Univ., Wakasato, Nagano (Japan). Faculty of Engineering

1997-03-01

166

Physicochemical aspects of manufacture of three-phase colloidal fuels  

Energy Technology Data Exchange (ETDEWEB)

The basic physicochemical characteristics of fabrication of three-phase colloidal fuels were analyzed. The effect of the nature and content of solid and liquid phases, type of chemical additives (plasticizers, emulsifiers, and stabilizers), and the basic methods of obtaining three-phase systems from bituminous coals and brown coals were examined.

Khil' ko, S.L.; Titov, E.V.

2007-01-15

167

An electronic solution for the direct connection of a three-phase induction generator to a single-phase feeder  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The power flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results.Este artigo propõe uma solução para a conexão direta de geradores de indução trifásicos em uma rede monofásica com regulação de vazão o que faz com que, a velocidade do gerador de indução se mantenha acima de sua velocidade síncrona. Para que a conexão entre gerador e rede monofásica seja satisfatória e para que os critérios de qualidade de energia sejam preservados, o controle do fluxo de energia, entre a rede monofásica e o conversor PWM trifásico, é realizado empregando a idéia de sistema interligado ajustando a defasagem e amplitude da tensão sintetizada pelo conversor em relação a tensão da rede monofásica de forma que o fator de potência na rede monofásica seja unitário. Em relação ao conversor de potência, espera-se que o mesmo produza tensões senoidais, com freqüência e amplitude fixas para que o gerador de indução opere balanceado. O artigo descreve a estratégia de controle do inversor, o critério de projeto dos controladores e apresenta alguns resultados experimentais.

Ricardo Q. Machado; Amílcar F. Q. Gonçalves; Simone Buso; José A. Pomilio

2009-01-01

168

An electronic solution for the direct connection of a three-phase induction generator to a single-phase feeder  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este artigo propõe uma solução para a conexão direta de geradores de indução trifásicos em uma rede monofásica com regulação de vazão o que faz com que, a velocidade do gerador de indução se mantenha acima de sua velocidade síncrona. Para que a conexão entre gerador e rede monofásica seja satisfatória e para que os critérios de qualidade de energia sejam preservados, o controle do fluxo de energia, entre a rede monofásica e o conversor PWM trifásico, ? (more) ? realizado empregando a idéia de sistema interligado ajustando a defasagem e amplitude da tensão sintetizada pelo conversor em relação a tensão da rede monofásica de forma que o fator de potência na rede monofásica seja unitário. Em relação ao conversor de potência, espera-se que o mesmo produza tensões senoidais, com freqüência e amplitude fixas para que o gerador de indução opere balanceado. O artigo descreve a estratégia de controle do inversor, o critério de projeto dos controladores e apresenta alguns resultados experimentais. Abstract in english This paper proposes a solution for the direct connection of a three-phase induction generator to a single-phase feeder. This high power quality system is intended to be used in micro-hydro power plants applications with control of the water flow. It is employed to maintain the speed of the induction generator greater than its synchronous value. The difference between the generated power and the power consumed by the local load flows through the single-phase feeder. The po (more) wer flow control is provided by a three-phase PWM inverter that additionally guarantees the local power quality. A system with good power quality must have sinusoidal and constant amplitude voltages, fixed frequency operation, balanced induction generator voltages and currents, harmonics and reactive power compensation. The paper describes the inverter control strategy, presents design criteria of the controllers, and shows experimental results.

Machado, Ricardo Q.; Gonçalves, Amílcar F. Q.; Buso, Simone; Pomilio, José A.

2009-09-01

169

Design and Implementation of Three Phase Unbalanced Voltage Motor Controller  

Directory of Open Access Journals (Sweden)

Full Text Available A state-of-the-art-technology was used to design the unbalanced three phase motor controller. The fluctuation of line voltage has been questioned in recent times due to the use of heavy powered machine with three phases. This paper is focused on deriving a control scheme to drive a three phase motor that could be used in industry or households. The very simple circuitry has been employed in this design. To do this, extensive MATLAB analysis and PSpice software was conducted in order to optimize the control system and finally the results are practically verified.

M. A. A. Mashud; S. C. Barman; M. R. A. Bhuiyan; Md. Serajul Islam

2013-01-01

170

Powerful diesel locomotives with three-phase drive system  

Energy Technology Data Exchange (ETDEWEB)

The Danish State Railways and the Norwegian State Railways have modernized their rolling stock and extended it by powerful Thyssen-Henschel diesel locomotives with BBC three-phase drive system. The diesel engine/alternator set feeds three-phase traction induction motors via inverters with variable voltage and frequency. The motors accelerate the vehicles up to a maximum speed of 140 or 160 km/h.

Teich, W.

1982-01-01

171

Low-frequency characterization of PWM converters  

Science.gov (United States)

Low-frequency components of states or outputs in PWM dc and ac converters can be characterized by differential equations called describing equations. These equations are derived by inspection of converter topology and use of switching functions and duty ratios. Their steady-state and small-signal dynamic solution shows how energy-storage elements in a converter/load system shape the frequency response of conversion functions established by the switches.

Ngo, K. D. T.

172

Neural network-based voltage regulator for an isolated asynchronous generator supplying three-phase four-wire loads  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with a neural network-based solid state voltage controller for an isolated asynchronous generator (IAG) driven by constant speed prime mover like diesel engine, bio-gas or gasoline engine and supplying three-phase four-wire loads. The proposed control scheme uses an indirect current control and a fast adaptive linear element (adaline) based neural network reference current extractor, which extracts the real positive sequence current component without any phase shift. The neutral current of the source is also compensated by using three single-phase bridge configuration of IGBT (insulated gate bipolar junction transistor) based voltage source converter (VSC) along-with single-phase transformer having self-supported dc bus. The proposed controller provides the functions as a voltage regulator, a harmonic eliminator, a neutral current compensator, and a load balancer. The proposed isolated electrical system with its controller is modeled and simulated in MATLAB along with Simulink and PSB (Power System Block set) toolboxes. The simulated results are presented to demonstrate the capability of an isolated asynchronous generating system driven by a constant speed prime mover for feeding three-phase four-wire loads. (author)

Singh, Bhim; Kasal, Gaurav Kumar [Department of Electrical Engineering, Indian Institute of Technology, Delhi, Hauz-Khas, New Delhi 110016 (India)

2008-06-15

173

Matlab/Simulink Based Analysis of Voltage Source Inverter With Space Vector Modulation  

Directory of Open Access Journals (Sweden)

Full Text Available Space vector modulation (SVM) is the best modulation technique to drive 3-phase load such as 3-phase induction motor. In this paper, the pulse width modulation strategy with SVM is analyzed in detail. The modulation strategy uses switching time calculator to calculate the timing of voltage vector applied to the three-phase balanced-load. The principle of the space vector modulation strategy is performed using Matlab/Simulink. The simulation result indicates that this algorithm is flexible and suitable to use for advance vector control. The strategy of the switching minimizes the distortion of load current as well as loss due to minimize number of commutations in the inverter.

Auzani Jidin; Tole Sutikno

2009-01-01

174

Multilevel voltage source inverters with phase shift SPWM and their applications in STATCOM and power line conditioner  

Science.gov (United States)

Reactive power compensation and harmonic reduction are two relevant research problems that exist in modern electric power systems. With the advancement of modern power electronics technology in both circuits and devices, new and better solutions are being proposed and applied to solve these two problems. To compensate reactive power, a cascading voltage source inverter with a Phase-Shift, Unipolar SPWM switching scheme is proposed. The main circuit of this inverter is composed of several identical voltage source H-bridge inverters connected in cascade form. Advantages of this scheme include use of identically rated storage capacitors, similarly rated switches and diodes, quick system response to load changes, and easily achievable redundancy. To solve the harmonic reduction problem, the flying capacitor multilevel voltage source inverter is adopted to construct a novel power line conditioner. The Phase Shift SPWM switching scheme is also employed to operate the switches of this inverter. As a result, it is possible to extend the new power line conditioner to distribution systems or industrial applications where voltage usually ranges from 4.16kV to 13.8kV. It is shown that the proposed power line conditioner not only balances the unbalanced load, but simultaneously compensates the reactive power as well.

Liang, Yiqiao

175

Three-phase relative permeability of Asphalt Ridge tar sand  

Energy Technology Data Exchange (ETDEWEB)

Two-phase relative permeabilities for Asphalt Ridge tar sand have been measured at 350/degree/F (177/degree/C). This temperature was chosen to obtain data appropriate for simulating high temperature operation. A modified equation of Stone (1973) was then used to calculate three-phase relative permeability from the measured two-phase relative permeability data. The measured two-phase relative permeability data show lower values than were predicted using typical tar sand properties. The estimated three-phase relative permeability values calculated from the measured two-phase data are lower than those values determined from estimated two-phase values. Simulations of the wet-forward tar sand combustion model, using the new three-phase relative permeability values, were compared with previous simulations and experimental data. The new three-phase relative permeability values improved the model's ability to predict experimental results. More experimental data, using three-phase relative permeability at different temperatures, may further improve model results. 5 refs., 18 figs., 5 tabs.

Sullivan, S.; Vaughn, P.

1988-08-01

176

Research on coordinate transformation of the three-phase circuit  

Directory of Open Access Journals (Sweden)

Full Text Available The different three-phase circuit coordinate transformation matrixes are given in relevant literatures , which may cause some difficulties to understand and apply the coordinate transformation. The paper presents a general expression of the coordinate transformation matrixes in three-phase circuit and points out that the coordinate transformation matrixes having different specific expressions are due to existing the parameters which can be selected in the general expression. On this basis, the three often used expressions of coordinate transformation matrixes rotating at arbitrary speed are obtained through selecting these different parameters, which are Park transformation, orthogonal transformation and the coordinate transformation in the theory of instantaneous power. The paper further points out that, through particularly choosing coordinate rotation speed ,it can get commonly used special coordinate transformation matrixes between the three-phase stationary coordinate systems, and between the stationary coordinate system and synchronous rotating coordinate system by matrix general expression. The work of this paper shows that the three-phase circuit coordinate transformation matrixes are essentially uniformed, though their forms and practical applications are different, which is helpful to further understanding and correctly using the coordinate transformation theory of three-phase circuit.

Tian Ming Xing; yan hong; Yuan Dong Sheng

2013-01-01

177

An improved fault-tolerant control scheme for PWM inverter-fed induction motor-based EVs.  

UK PubMed Central (United Kingdom)

This paper proposes an improved fault-tolerant control scheme for PWM inverter-fed induction motor-based electric vehicles. The proposed strategy deals with power switch (IGBTs) failures mitigation within a reconfigurable induction motor control. To increase the vehicle powertrain reliability regarding IGBT open-circuit failures, 4-wire and 4-leg PWM inverter topologies are investigated and their performances discussed in a vehicle context. The proposed fault-tolerant topologies require only minimum hardware modifications to the conventional off-the-shelf six-switch three-phase drive, mitigating the IGBTs failures by specific inverter control. Indeed, the two topologies exploit the induction motor neutral accessibility for fault-tolerant purposes. The 4-wire topology uses then classical hysteresis controllers to account for the IGBT failures. The 4-leg topology, meanwhile, uses a specific 3D space vector PWM to handle vehicle requirements in terms of size (DC bus capacitors) and cost (IGBTs number). Experiments on an induction motor drive and simulations on an electric vehicle are carried-out using a European urban driving cycle to show that the proposed fault-tolerant control approach is effective and provides a simple configuration with high performance in terms of speed and torque responses.

Tabbache B; Benbouzid M; Kheloui A; Bourgeot JM; Mamoune A

2013-08-01

178

General three-phase relative permeability model for Prudhoe Bay  

Energy Technology Data Exchange (ETDEWEB)

This paper describes two- and three-phase relative permeability concepts important for Prudhoe Bay. It includes a three-phase relative permeability correlation that incorporates hysteresis in gas, oil, and water relative permeability as well as the dependence of relative permeability on composition and gas/oil interfacial tension (IFT). The functional forms chosen to correlate the relative permeability data were based on interpretation of the pore-level mechanisms that determine fluid flow. The three-phase correlation reduces to traditional models in various limits and is more consistent with available data and trends in the literature than previous correlations. Although this correlation was developed for Prudhoe Bay, it can be and has been applied to other mixed-wet reservoirs with changes in the input parameters. The correlation is particularly useful in situations where both compositional effects and hysteresis are important.

Jerauld, G.R. [Arco E and P Technology (United States)

1997-11-01

179

PERFORMANCE ANALYSIS OF SENSORLESS BLDC MOTOR DRIVE SYSTEM USING ASYMMETRIC PWM CONTROL TECHNIQUE  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the simulation model for four-switch three-phase (FSTP) brushless dc (BLDC) motor drives using novel voltage PWM technique. In this paper a back EMF based sensor less scheme is clearly explained with the help of MATLABSIMULINK models. The low cost BLDC driver is achieved by the reduction of switch device count, cost down of control, and saving of hall sensors for commercial applications. Field programmable gate array was chosen as the hardware platform because of its benefits like high operating frequency and parallel processing capabilities. Asymmetric pulse width modulation scheme is developed to drive FSTP BLDC motors with the desired dynamic and static speed–torque characteristics. The simulation analysis of the back EMF based sensor less BLDC driver will be discussed and the performance using novel schemes will be evaluated.

S.Sella Kumar; Dr.M.Sasikumar; R.Meenakshi

2012-01-01

180

A 6.6-kV Transformerless Cascade PWM STATCOM  

Science.gov (United States)

This paper deals with a 6.6-kV transformerless STATCOM cascading multiple single-phase H-bridge PWM converters in each phase. The ac voltage of the STATCOM is almost sinusoidal, so that it requires no harmonic filter. Each converter is equipped with a capacitor and a voltage sensor on the dc side, which are electrically isolated from each other. The STATCOM has the capability of self-starting and voltage-balancing without any external power supply or equipment. Experiment by a three-phase 200-V, 10-kVA laboratry system, along with computer simulation, is carried out to confirm the viability and effectiveness of the STATCOM.

Yoshii, Tsurugi; Inoue, Shigenori; Akagi, Hirofumi

 
 
 
 
181

Three-phase flow measurement in the petroleum industry  

Science.gov (United States)

The problem of how to accurately measure the flowrate of oil-gas-water mixtures in a pipeline remains one of the key challenges in the petroleum industry. This paper discusses why three-phase flow measurement is still important and why it remains a difficult problem to solve. The measurement strategies and principal base technologies currently used by commercial manufacturers are described, and research developments that could influence future flowmeter design are considered. Finally, future issues, which will need to be addressed by manufacturers and users of three-phase flowmeters, are discussed.

Thorn, R.; Johansen, G. A.; Hjertaker, B. T.

2013-01-01

182

Self oscillating PWM modulators, a topological comparison  

DEFF Research Database (Denmark)

High precision control of the output voltage or current of a switch mode converter with fast response is required for a number of applications. Dependent on the type of application, the desired precision and transient response can be difficult, if not impossible, to achieve with standard PWM control caused by limitations in dynamic capabilities which often limits fast tracking of a reference signal, or fast settling during load steps due to too small achievable control loop bandwidth. Achievable open loop bandwidth for standard voltage and current mode PWM modulators is typical in the fs/10 or fs/ð range respectively, where fs is the switching frequency of the converter. For some applications this will require unacceptable high switching frequency to achieve enough control loop bandwidth for the desired dynamic performance. With self oscillating modulators, the open loop bandwidth is equal to fs which makes this type of modulators an excellent choice for a wide range of applications. Self oscillating PWM modulators can be made in a number of ways, either as voltage or current mode modulators, and the self oscillating behavior can be achieved either by using hysteresis control or by shaping the open loop function of the modulator so its gain and phase response causes a closed loop natural oscillation. The two main types of self oscillating modulators have many similarities, but differences in dynamic performance and linearity are present. The work presented is related to the author's work with switch mode audio power amplifiers, where linear tracking of the reference signal is of major importance. Use of the modulator topologies presented are not limited to this kind of equipment, but can be used in a very wide range of applications from very low to very high power levels.

Poulsen, SØren; Andersen, Michael Andreas E.

2004-01-01

183

Investigation of waveform distortion and transient oscillation of input current in current type PWM rectifiers; Denryugata PWM seiryu kairo ni okeru nyuryoku denryu hizumi to kato shindo ni kansuru ichikosatsu  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the following matters on the result of an analysis (including a computerized simulation) on steady-state distortion and transient oscillation in AC input current in a current type PWM rectifier (using a three-phase bridge circuit consisting of a self-arc extinguishing element as a main circuit). In order to reduce the effect of harmonic multiplying action in an LC filter on the input current under a steady state, it is effective to set its resonant frequency in the vicinity of three times of the odd number multiplication; the frequency for transient oscillation agrees with the resonant frequency in the LC filter, and can be a non-integer multiplication of the power source frequency; the phases in the three-phase transient oscillation agree with each other, and their amplitudes are determined by the phase of the current at the moment the transient variation is generated, the determination being different by each phase; and the conventional open loop methods such as use of higher switching frequencies and optimization of the PWM patterns are not effective to suppress the oscillation in the input current in the transient condition. 10 refs., 8 figs., 1 tab.

Sato, Y.; Kataoka , T. [Tokyo Institute of Technology, Tokyo (Japan)

1994-11-20

184

A new current controller for PWM converters  

Energy Technology Data Exchange (ETDEWEB)

From the cost-effective product point of view, it is very important to design a new current controller with the highest utilization factor of current capacity of power devices. This paper deals with a state-deadbeat current controller for PWM converters, which shows the fastest current control response without overshoot irrespective of the saturation of control voltage. No-overshoot control response means that the current capacity could be fully utilized in the control sense. Simulation results done by Matlab`s Simulink show good current control characteristics. (author). 2 refs., 4 figs., 1 tab.

Lee, J.W.; Min, J.J.; Baek, S.K.; Kang, B.H. [Samsung Advanced Institute of Technology (Korea, Republic of)

1995-07-01

185

REDUCED-PARTS THREE-PHASE UNINTERRUPTIBLE POWER SUPPLY  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a three-phase on-lineuninterruptible power supply with reducednumber of switches topology is presented. The newtopology has less number of power electronicdevices as well as control functions. Differentoperating modes of the system are investigated aswell. Simulation and experimental results arepresented, which show the viability of the proposedtopology.

DANIEL ALBU; DR?GHICIU NICOLAE; R?ZVAN DANIEL ALBU

2008-01-01

186

A cascaded three-phase symmetrical multistage voltage multiplier  

Energy Technology Data Exchange (ETDEWEB)

A cascaded three-phase symmetrical multistage Cockcroft-Walton voltage multiplier (CW-VM) is proposed in this report. It consists of three single-phase symmetrical voltage multipliers, which are connected in series at their smoothing columns like string of batteries and are driven by three-phase ac power source. The smoothing column of each voltage multiplier is charged twice every cycle independently by respective oscillating columns and discharged in series through load. The charging discharging process completes six times a cycle and therefore the output voltage ripple's frequency is of sixth order of the drive signal frequency. Thus the proposed approach eliminates the first five harmonic components of load generated voltage ripples and sixth harmonic is the major ripple component. The proposed cascaded three-phase symmetrical voltage multiplier has less than half the voltage ripple, and three times larger output voltage and output power than the conventional single-phase symmetrical CW-VM. Experimental and simulation results of the laboratory prototype are given to show the feasibility of proposed cascaded three-phase symmetrical CW-VM.

Iqbal, Shahid [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia); Singh, G K [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia); Besar, R [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia); Muhammad, G [Faculty of Information Science and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2006-10-15

187

Ac loss calorimeter for three-phase cable  

Energy Technology Data Exchange (ETDEWEB)

A calorimeter for measuring ac losses in meter-long lengths of HTS superconducting power transmission line cables is described. The calorimeter, which is based on a temperature difference technique, has a precision of 1 mW and measures single, two-phase (coupling), and three-phase losses. The measurements show significant coupling losses between phases.

Daney, D.E.; Boenig, H.J.; Maley, M.P.; McMurry, D.E.; DeBlanc, B.G. [Los Alamos National Lab., NM (United States). Superconductivity Technology Center

1996-10-01

188

Switch-Off Behaviour of 6.5 kV IGBT Modules in Two-Level Voltage Source Inverter  

Science.gov (United States)

This paper presents an analysis of the switch-off process of 6.5 kV/200 A IGBT modules in a two-level half-bridge voltage source inverter. During experiments, it was stated that real switching process is far from ideal switch-off since parasitic inductance and capacitance in the circuit cause voltage spikes and high frequency oscillations during transition processes. Operation states of the inverter are described and analyzed. Experimental and simulation results are compared, the main transients are analyzed and mathematically expressed and possible problems and solutions are discussed.

Blinov, Andrei; Jalakas, Tanel; Vinnikov, Dmitri; Janson, Kuno

2010-01-01

189

Approaches to Suppressing Shaft Voltage in Brushless DC Motor Driven by PWM Inverter Based on Ungrounded Common-Mode Equivalent Circuit  

Science.gov (United States)

This paper describes an ungrounded common-mode equivalent circuit for a motor driven by a voltage-source PWM inverter. When the capacitance of the rotor was is small, the reversal of the polarities of the common-mode voltage and shaft voltage is observed. In order to model this reversal, a bridge-type equivalent circuit is proposed. On the basis of calculations and experiment, it is found the values and polarity of the shaft voltage can be are accurately determined with the proposed equivalent circuit. Furthermore, the capacitance value of the insulated rotor required to make the shaft voltage equal to or less than the dielectric breakdown voltage of the bearing grease is obtained.

Maetani, Tatsuo; Isomura, Yoshinori; Watanabe, Akihiko; Iimori, Kenichi; Morimoto, Shigeo

190

Flow coupling during three-phase gravity drainage.  

UK PubMed Central (United Kingdom)

We measure the three-phase oil relative permeability k(ro) by conducting unsteady-state drainage experiments in a 0.8 m water-wet sand pack. We find that when starting from capillary-trapped oil, k(ro) shows a strong dependence on both the flow of water and the water saturation and a weak dependence on oil saturation, contrary to most models. The observed flow coupling between water and oil is stronger in three-phase flow than two-phase flow, and cannot be observed in steady-state measurements. The results suggest that the oil is transported through moving gas-oil-water interfaces (form drag) or momentum transport across stationary interfaces (friction drag). We present a simple model of friction drag which compares favorably to the experimental data.

Dehghanpour H; Aminzadeh B; Mirzaei M; DiCarlo DA

2011-06-01

191

The relationship between overpotential and the three phase boundary length  

Energy Technology Data Exchange (ETDEWEB)

Porous La{sub 0.81}Sr{sub 0.09}MnO{sub 3} and LSM-YSZ composite electrodes of the solid oxide fuel cell (SOFC) were made, and the relationship between the overpotential and the three phase boundary (TPB) length was investigated by constructing a model. Three-dimensional distribution of TPB for the composite cathode was suggested. The effective thickness of it was observed to be less than 20 {mu}m

Fukunaga, Hiroshi; Ihara, Manabu; Sakaki, Keiji; Yamada, Koichi [Department of Chemical System Engineering, University of Tokyo, Tokyo (Japan)

1996-07-20

192

Pancreatic adenocarcinoma : usefulness of two and three phase spiral CT  

International Nuclear Information System (INIS)

To evaluate the efficacy of each phases in two and three phase spiral CT in the detection of pancreatic adenocarcinoma. Two phase spiral CT images of 18 patients and three phase spiral CT images of 12 patients with pathologically-proven pancreatic ductal adenocarcinoma were retrospectively compared. Using a single spiral scan, images of early and delayed phases were obtained at 43 seconds and 2?3minutes respectively initiating the after administration of 100-120cc of contrast material (2?3cc/sec), Images of arterial, portal and delayed phases were also obtained at 25 and 60 seconds, and 3?4minutes, respectively, by the use of a double spiral scan. CT scans were performed with 10mm collimation at 1:1 pitch table speed. Contrast between the tumor and adjacent pancreatic parenchyma were compared and graded and enhancement pattern of the tumor were analysed together. In 12 patients (66.7%), images of the early phase were superior to those of the delayed phase. images of the portal phase were superior to those of the arterial phase. Enhancement of tumor was seen in four patients;all tumors were less than 3cm in size. The early phase of two phase spiral CT is superior to the delayed phase and the portal phase of three phase spiral CT is superior to the arterial phase. Both arterial and portal phases are superior to the delayed phase.

1996-01-01

193

A Novel Fuzzy—Adaptive Hysteresis Controller Based Three Phase Four Wire-Four Leg Shunt Active Filter for Harmonic and Reactive Power Compensation  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fuzzy-adaptive hysteresis band technique is applied for the current control to derive the switching signals for the voltage source inverter. A fuzzy logic controller is developed to control the voltage of the DC capacitor. Computer simulations are carried out on a sample power system to demonstrate the suitability of the proposed control strategy, for harmonic reduction under three different conditions namely, ideal, unbalance, unbalance and distorted source voltage conditions. The proposed control strategy is found to be effective to reduce the harmonics and compensate reactive power and neutral current and balance load currents under ideal and non-ideal source voltage conditions.

P. Rathika; D. Devaraj

2011-01-01

194

Three-phase Series-Connected Hybrid Converter System  

Science.gov (United States)

In this paper, a 3-phase series-connected hybrid converter system is introduced. The converter system is constructed by a GTO converter and an IGBT converter connected in series by two output transformers aiming at a high voltage high efficiency converter. The GTO converter operates in a square-wave switching mode at the same switching rate as a reference output voltage in order to minimize the device switching losses. The IGBT converter is built in an NPC (neutral-point-clamped) arrangement and operates in a PWM switching mode at a high switching rate. The former produces a base part of the total output voltage. The latter not only produces an additional part of the total output, but also offsets the harmonic components generated by the GTO converter. The control strategy for the system is proposed, and the experiment on an inverter, rectifier and STATCOM operation is demonstrated using the proposed hybrid converter. The experimental results verified the validity of the proposed hybrid configuration and its control strategy.

Li, Dongsheng; Fukuda, Shoji; Kubo, Yusuke; Kitano, Masayuki

195

Evolutionary Computing Based Area Integration PWM Technique for Multilevel Inverters  

Directory of Open Access Journals (Sweden)

Full Text Available The existing multilevel carrier-based pulse width modulation (PWM) strategies have no special provisions to offer quality output, besides lower order harmonics are introduced in the spectrum, especially at low switching frequencies. This paper proposes a novel multilevel PWM strategy to corner the advantages of low frequency switching and reduced total harmonic distortion (THD). The basic idea of the proposed area integration PWM (AIPWM) method is that the area of the required sinusoidal (fundamental) output and the total area of the output pulses are made equal. An attempt is made to incorporate two soft computing techniques namely evolutionary programming (EP) and genetic algorithm (GA) in the generation and placement of switching pulses. The results of a prototype seven-level cascaded inverter experimented with the novel PWM strategies are presented.

S. Jeevananthan

2007-01-01

196

A Three-phase to three-phase matrix converter prototype/ Protótipo do conversor em matriz trifásico para trifásico  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este trabalho apresenta aspectos relacionados a implementação experimental de um conversor trifásico em matriz. As chaves bidirecionais empregadas na construção do protótipo foram construídas com a utilização de componentes discretos como IGBT's e diodos rápidos. Aspectos relacionados a proteção contra sobre tensão e curto circuito, processo de comutação das chaves bidirecionais e filtro de entrada são apresentados neste trabalho juntamente com resultados experimentais da operação do conversor. Abstract in english This paper presents some implementation details of a three-phase to three-phase matrix converter prototype. The bidirectional semiconductor switches were built using discrete IGBTs and fast diodes. Design aspects such as protection against overvoltage and short-circuit, commutation process of bi-directional switches, and input filter are addressed in this paper.

Oliveira Filho, Milton E. de; Sguarezi Filho, Alfeu J.; Ruppert, Ernesto

2012-06-01

197

A Three-phase to three-phase matrix converter prototype Protótipo do conversor em matriz trifásico para trifásico  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents some implementation details of a three-phase to three-phase matrix converter prototype. The bidirectional semiconductor switches were built using discrete IGBTs and fast diodes. Design aspects such as protection against overvoltage and short-circuit, commutation process of bi-directional switches, and input filter are addressed in this paper.Este trabalho apresenta aspectos relacionados a implementação experimental de um conversor trifásico em matriz. As chaves bidirecionais empregadas na construção do protótipo foram construídas com a utilização de componentes discretos como IGBT's e diodos rápidos. Aspectos relacionados a proteção contra sobre tensão e curto circuito, processo de comutação das chaves bidirecionais e filtro de entrada são apresentados neste trabalho juntamente com resultados experimentais da operação do conversor.

Milton E. de Oliveira Filho; Alfeu J. Sguarezi Filho; Ernesto Ruppert

2012-01-01

198

Three phase AC-DC load and harmonic flows  

Energy Technology Data Exchange (ETDEWEB)

The validity of assuming fundamental frequency load flow conditions of ac - dc. conversion plant to be unaffected by the presence of harmonics is questioned, and an algorithm is derived which is capable of determining the true load flow conditions in the presence of harmonics. The algorithm is unique in its three phase approach to the problem, which is essential if normally unfiltered uncharacteristic harmonics are to be represented. Results of a realistic and relevant test system are used to demonstrate the interaction which exists between the fundamental and harmonic frequencies in the converter.

Arrillage, J.; Callaghan, C.D. (Canterbury Univ., Christchurch (New Zealand))

1991-01-01

199

Transient three-phases three-component flow. Pt. 1  

International Nuclear Information System (INIS)

[en] Starting from the conservation principles a nonconservative form of a system of 18 quasilinear partial differential equations describing the three-phase three-component flow is obtained. The flow is described using the three-velocity field approach. Each of the flow-fields consists of one inert and one noninert component. Full thermodynamical and mechanical nonequilibrium between the fields is modelled. The simplest possible concentration and entropy equations are obtained, without any simplifying assumptions. Also the definition of the Mach number, the critical mass flow rate, and the criticality condition for this physical system is obtained. (orig.)

1985-01-01

200

A new equivalent circuit for three-phase induction motors  

Energy Technology Data Exchange (ETDEWEB)

A new equivalent circuit for three-phase induction motors is presented in this paper. The equivalent circuit parameters are calculated within the design process of the machine utilising the finite element method. The behaviour study of the motor is accomplished utilising two-dimensional planar models. The results obtained, by means of the calculation method and equivalent circuit proposed, are good if compared with those measured in the laboratory once the machine has been built. The proposed method constitutes an industrial application to the design and modelling of this type of electric machines. (orig.)

Gueemes, J.A.; Hoyo, J.I. del [The University of the Basque Country, Departamento de Ingenieria Electrica, E.U. Ingenieria Tecnica Industrial, Bilbao (Spain)

2000-08-01

 
 
 
 
201

Possibilities by using a self-commutated voltage source inverter connected to a weak grid in wind parks  

Energy Technology Data Exchange (ETDEWEB)

In this paper the hybrid wind farm connected to a weak grid is investigated. By combining different electrical wind power plant systems a cost-efficient solution is obtained. The point of common connection voltage level can be controlled by injecting reactive power from a phase-compensating capacitor battery and a voltage source inverter (VSI). If the short-circuit impedance ratio is lower than 1, the demanded reactive power injection to keep the voltage at nominal level is unrealistic. For short-circuit impedance ratios of 2 or higher the demanded reactive power level is acceptable. When using both induction generators and thyristor inverters the reactive power injector VSI size should be about 0.2 pu. If the hybrid farm consists of THYs, IGs and VSIs and the active power is equally shared between the systems, the VSI had to be scaled up by 5% to handle both active and reactive power. 7 refs, 10 figs, 2 tabs

Svensson, Jan [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Electric Power Engineering

1996-12-01

202

Experimental dynamic evaluation of three-phase reactors  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The hydrodynamic parameters were determined for two different three-phase systems (fluidized-bed and trickle-bed) through the experimental evaluation of the dynamic residence time distribution in the gas or liquid phase. For different fluid phase flow rates the fluidized-bed system was operated with a tracer in the gas phase and in the trickle-bed with a tracer in the liquid phase. The analysis of the processes was achieved through the application of different models repr (more) esenting the dynamic behavior of tracers present in the gas and liquid phases with a simulation of experimental operations of the three-phase reactors. The transfer functions developed for the two systems made it possible to estimate the hydrodynamic parameters providing the gas holdup (2.22 x 10-2 to 8.42 x 10-2) and the gas phase Peclet number (54.18 to 41.20) for the fluidized-bed and the liquid holdup (0.16 to 0.25), the liquid phase Peclet number (20.37 to 4.52) and wetting efficiency (0.34 to 0.56) for the trickle-bed.

Sales, F. G.; Maranhão, L. C. A.; Pereira, J. A. F. R.; Abreu, C. A. M.

2005-09-01

203

Three phase skeletal scintigraphy for evaluation of composite tissue grafts  

International Nuclear Information System (INIS)

[en] Three phase skeletal scintigraphy consisting of a radionuclide angiogram, and early post-injection ''blood pool'' image, and images obtained three to four hours after injection was performed in five patients to evaluate the viability of free composite tissue grafts of the tensor fascha lata or the lattissimus dorsi. In four of five patients who showed normal perfusion pattern during the radionuclide angiogram and normal soft tissue distribution of tracer during the ''blood pool'' image viabiliy of the graft was correctly determined. The one patient who showed a normal perfusion pattern in the radionuclide angiogram with absence of tissue perfusion seen in the ''blood pool'' image went on to develop gangrene and infection of the composite tissue graft. Normal metabolic bone activity was shown in the delayed images of those patients who had successful grafts which included bony structures. Three phase radionuclide imaging therefore appears to be of value in evaluating composite tissue grafts and has predictive value in assessing post-operative graft viability

1982-09-02

204

Enhanced conversion via three-phase methanol synthesis  

Energy Technology Data Exchange (ETDEWEB)

A three-phase methanol process has been envisaged to enhance the single pass conversion of hydrogen and carbon monoxide. The use of an inert, high boiling solvent that preferentially absorbs the methanol as soon as it is formed, helps lower product inhibition of the forward reaction, increases conversion and virtually eliminates the need for recycle of unconverted reactants. The solvent also removes carbon dioxide to an appreciable extent. This suggests that two pre-synthesis steps might be eliminated resulting in additional savings. The proposed process involves simultaneous reaction and phase equilibria. Pertinent VLE data involving syngas, methanol, water and solvent have been obtained experimentally in the temperature range of 200-240{sup 0}C and pressure range of 50-100 atmospheres and checked against the Modified Soave-Redlich-Kwong equation of state. Indications are that the desired partitioning of the species, is attainable. CSTR simulation of the process using known vapor phase kinetics has shown that conversions as high as 90% can be achieved in a single stage. Semibatch three phase reactions have been carried out in an internal recycle reactor using copper catalyst. Conversions greater than 90% were achieved verifying the single stage simulation results.

Elliott, J.R.; Berty, J.M.; Chandrasekhar, K.; Rastogi, R.; Khosla, P. (Akron Univ., OH (USA). Dept. of Chemical Engineering)

1988-01-01

205

Three-phase bone scintigraphy of Kienboeck disease  

International Nuclear Information System (INIS)

Thirty-three joints in 31 patients with Kienboeck disease were evaluated with three-phase bone scintigraphy. Follow-up studies were performed in 19 cases of them. The patients with increased ulnar blood flow on arterial phase and ample perfusion on venous phase in angiograms showed good clinical prognosis. This ample ulnar blood flow and perfusion might be essential for the recovery of this disease. Although staging was possible using static images alone, blood pool images provided more information about the present condition of lesions, such as hyperemic state and remodeling reactions. Blood pool image was indispensable for staging and analyzing lesions and evaluating post-operative course. Increased lunate perfusion in venous phase of angiograms and localized lunate uptake in blood pool images were the favorable signs, which were shown in most cases with good prognosis. It is concluded that three-phase bone scintigraphy gives useful information for evaluating Kienboeck disease which can not be obtained by conventional bone scintigraphy. (author).

1992-01-01

206

Experimental dynamic evaluation of three-phase reactors  

Directory of Open Access Journals (Sweden)

Full Text Available The hydrodynamic parameters were determined for two different three-phase systems (fluidized-bed and trickle-bed) through the experimental evaluation of the dynamic residence time distribution in the gas or liquid phase. For different fluid phase flow rates the fluidized-bed system was operated with a tracer in the gas phase and in the trickle-bed with a tracer in the liquid phase. The analysis of the processes was achieved through the application of different models representing the dynamic behavior of tracers present in the gas and liquid phases with a simulation of experimental operations of the three-phase reactors. The transfer functions developed for the two systems made it possible to estimate the hydrodynamic parameters providing the gas holdup (2.22 x 10-2 to 8.42 x 10-2) and the gas phase Peclet number (54.18 to 41.20) for the fluidized-bed and the liquid holdup (0.16 to 0.25), the liquid phase Peclet number (20.37 to 4.52) and wetting efficiency (0.34 to 0.56) for the trickle-bed.

F. G. Sales; L. C. A. Maranhão; J. A. F. R. Pereira; C. A. M. Abreu

2005-01-01

207

Efficient evaluation of three-phase coexistence lines  

Science.gov (United States)

The Gibbs-Duhem integration method is a means for evaluating phase diagrams by molecular simulation. Starting from a state of known phase coexistence, one applies the Clapeyron equation to trace out subsequent points on the saturation line. Each simulation yields a coexistence state, and particle exchanges are not invoked to insure equality of fugacities. We describe and demonstrate here the extension of this method to three-phase coexistence, namely, among a solid, a liquid, and a gas. In one application, we compute the saturation pressure and temperature as a function of composition (more accurately, as a function of fugacity fraction) for six Lennard-Jones two-component mixtures. In a second study, we traverse a mutation pathway; that is, we evaluate three-phase equilibria as a function of the intermolecular potential. In particular, we define a path that transforms the Lennard-Jones model into a square well, and thus in our calculations we quantify the effect of the shape of the repulsive and attractive portions of the potential on the triple point. In the end we have what is, to our knowledge, the First estimate of a state of solid-fluid coexistence for a square well model. In both applications we assume that the fee crystal structure represents the thermodynamically stable solid phase.

Agrawal, R.; Mehta, M.; Kofke, D. A.

1994-11-01

208

Characteristics of the three phase AC plasma jet  

Energy Technology Data Exchange (ETDEWEB)

The report describes general characteristics of the three phase ac plasma jet which was generated by the three electrode type plasma jet generator with three radial electrodes in the constrictor section of a nozzle. The measurements of the restriking voltage and the duration time of the arc of each electrode gap at each half cycle indicated that the polarity of the arc and the arc operating parameters (arc current, gas flow rate) had little influence on the restriking characteristics. Also, it was indicated that the arc was always ignited in two electrode gaps according to the phase rotation of the three phase ac power source. The arc voltage-current characteristics were of drooping type and the thermal efficiency range was 68% to 75%. The plasma jet was stable, for all the arc restriked at 360 Hz, and its length, which was elongated in comparison with that of the single phase ac plasma jet, ranged from 17.0 mm to 19.9 mm at gas flow rate of 20 l/min.

Saeki, S.; Osaki, K.

1980-01-01

209

Novel three-phase SMR converter. Shinhoshiki sanso SMR converter  

Energy Technology Data Exchange (ETDEWEB)

The novel three-phase SMR (switch mode rectifier) converter for industrial use power supply was proposed on the basis of a direct frequency changing technology to solve several problems of the conventional SMR converter which requires an AC snubber circuit and a complicated circuit for regeneration of snubber energy. The novel converter adopted the new frequency changer with no bilateral switch, and was featured by that both ends of a switching element can be DC-clumped in direct frequency changing. The novel converter required no complicated circuit for regeneration of snubber energy and no discharge resistance, because the snubber circuit was composed of only one capacity and snubber energy was regenerated to load through the primary winding of a high frequency transformer. The prototype large-scale industrial use DC power supply facility of 400 V AC three-phase input and 100 V/100 kW DC output was developed to test its performance, and the converting efficiency over 90% was obtained successfully in a range from light load to rated one. 5 refs., 21 figs., 1 tab.

Okuma, Y.; Igarashi, S.; Kuroki, K. (Fuji Electric Corporate Research and Development, Ltd., Tokyo (Japan))

1994-05-20

210

Advanced computational model for three-phase slurry reactors  

International Nuclear Information System (INIS)

[en] In the second year of the project, the Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column is further developed. The approach uses an Eulerian analysis of liquid flows in the bubble column, and makes use of the Lagrangian trajectory analysis for the bubbles and particle motions. An experimental set for studying a two-dimensional bubble column is also developed. The operation of the bubble column is being tested and diagnostic methodology for quantitative measurements is being developed. An Eulerian computational model for the flow condition in the two-dimensional bubble column is also being developed. The liquid and bubble motions are being analyzed and the results are being compared with the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures is also being studied. Further progress was also made in developing a thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion. The balance laws are obtained and the constitutive laws are being developed. Progress was also made in measuring concentration and velocity of particles of different sizes near a wall in a duct flow. The technique of Phase-Doppler anemometry was used in these studies. The general objective of this project is to provide the needed fundamental understanding of three-phase slurry reactors in Fischer-Tropsch (F-T) liquid fuel synthesis. The other main goal is to develop a computational capability for predicting the transport and processing of three-phase coal slurries. The specific objectives are: (1) To develop a thermodynamically consistent rate-dependent anisotropic model for multiphase slurry flows with and without chemical reaction for application to coal liquefaction. Also establish the material parameters of the model. (2) To provide experimental data for phasic fluctuation and mean velocities, as well as the solid volume fraction in the shear flow devices. (3) To develop an accurate computational capability incorporating the new rate-dependent and anisotropic model for analyzing reacting and nonreacting slurry flows, and to solve a number of technologically important problems related to Fischer-Tropsch (F-T) liquid fuel production processes. (4) To verify the validity of the developed model by comparing the predicted results with the performed and the available experimental data under idealized conditions

2001-01-01

211

Three-Phase Unbalanced Load Flow Tool for Distribution Networks  

DEFF Research Database (Denmark)

This work develops a three-phase unbalanced load flow tool tailored for radial distribution networks based on Matlab®. The tool can be used to assess steady-state voltage variations, thermal limits of grid components and power losses in radial MV-LV networks with photovoltaic (PV) generators where most of the systems are single phase. New ancillary service such as static reactive power support by PV inverters can be also merged together with the load flow solution tool and thus, the impact of the various reactive power control strategies on the steady-state grid operation can be simply investigated. Performance of the load flow solution tool in the sense of resulting bus voltage magnitudes is compared and validated with IEEE 13-bus test feeder.

Demirok, Erhan; Kjær, SØren BækhØj

2012-01-01

212

Mass transfer in three-phase fluidized beds  

International Nuclear Information System (INIS)

[en] The effects of superficial liquid and gas velocity, particle diameter, liquid viscosity, and column diameter on liquid dispersion (E/sub L) and mass transfer (K/sub L/a) in three-phase fluidized beds were investigated using a water--glycerol/oxygen--nitrogen (or oxygen--argon)/glass-bead system. Overall mass transfer coefficients were calculated based on plug flow, dispersed plug flow, and continuously stirred tank models. k/sub L/a was found to increase with gas velocity and particle diameter, but no correlation of K/sub L/a with liquid velocity was observed. At low liquid velocities, K/sub L/a was lower for the more viscous liquid; the reverse was true at high liquid flow rates. E/sub L/ increased rapidly for liquid flow rates at two to three times the minimum fluidization velocity

1978-01-01

213

Mucormycosis and bone scintillography of three phases. Case description  

International Nuclear Information System (INIS)

The purpose of presenting this work, besides the interest that shows the mucormycosis pathology not so frequent, it is to carry out a clinical correlation photographic with the imagenology, particularly with the bone scintillography. In the Nuclear Medicine Service it is carried out bone scintillography of three phases previous endovenous administration of 30 mCi (1110 MBq) of 99m Tc-MDP. The images are obtained with a gamma camera model Elscint APEX SPX, first each 2 seconds during the first minute, then early image to the 5 minutes and finally the late ones to the 3 hs. The bone scintillography in the phases 2 and 3 detects bigger radioactive density in left hemi side, with increment of the osteoblast activity mainly in the medial border and the floor of the orbit, in the malar bone and a little more tenuous in the superior maxillary. (Author)

2007-01-01

214

Three-phase radionuclide bone imaging in sports medicine  

International Nuclear Information System (INIS)

Three-phase radionuclide bone (TPB) imaging was performed on 238 patients with sports-related injuries. A wide variety of lesions was encountered, but the most frequent lesions seen were stress fractures of the lower part of the leg at the junction of the middle and distal thirds of the posterior tibial cortex (42 of 79 lesions). There were no differences in the type, location, or distribution of lesions between males and females or between competitive and noncompetitive athletes. In 110 cases, bone stress lesions were often diagnosed when radiographs were normal, whereas subacute or chronic soft-tissue abnormalities had few specific scintigraphic features. TPB imaging provides significant early diagnostic information about bone stress lesions. Normal examination results (53 cases) exclude underlying osseous pathologic conditions

1985-01-01

215

Three phase pipe flow imaging using a capacitance tomography system  

Energy Technology Data Exchange (ETDEWEB)

Several tomography systems for pipe flow imaging have been developed in the past decade. Many of them are based on capacitance sensors measuring the permittivity of the flowing components. So far the systems have mostly been tested on two-phase flow, and mainly for oil/gas pipe flow. Several reconstruction techniques for reconstructing the measured capacitances have been developed. The most commonly used reconstruction algorithm is the linear back projection algorithm (LBP), which is fast and fairly crude. This paper shows that in using the LBP algorithm one must be very careful in interpreting the results. Methods for using a capacitance tomography system based on the LBP algorithm for three-phase oil/water/gas pipe flow imaging are outlined and preliminary results are presented. 4 refs., 7 figs.

Isaksen, Oe.

1996-04-01

216

Three-phase radionuclide bone imaging in sports medicine  

Energy Technology Data Exchange (ETDEWEB)

Three-phase radionuclide bone (TPB) imaging was performed on 238 patients with sports-related injuries. A wide variety of lesions was encountered, but the most frequent lesions seen were stress fractures of the lower part of the leg at the junction of the middle and distal thirds of the posterior tibial cortex (42 of 79 lesions). There were no differences in the type, location, or distribution of lesions between males and females or between competitive and noncompetitive athletes. In 110 cases, bone stress lesions were often diagnosed when radiographs were normal, whereas subacute or chronic soft-tissue abnormalities had few specific scintigraphic features. TPB imaging provides significant early diagnostic information about bone stress lesions. Normal examination results (53 cases) exclude underlying osseous pathologic conditions.

Rupani, H.D.; Holder, L.E.; Espinola, D.A.; Engin, S.I.

1985-07-01

217

Evaluation of Three-Phase Transformerless Photovoltaic Inverter Topologies  

DEFF Research Database (Denmark)

This paper analyzes and compares three transformerless photovoltaic inverter topologies for three-phase grid connection with the main focus on the safety issues that result from the lack of galvanic isolation. A common-mode model, valid at frequencies lower than 50 kHz, is adopted to study the leakage current paths. The model is validated by both simulation and experimental results. These will be used to compare the selected topologies, and to explain the influence of system unbalance and the neutral conductor inductance on the leakage current. It will be demonstrated that the later has a crucial influence. Finally, a comparison of the selected topologies is carried out, based on the adopted modulation, connection of the neutral and its inductance, effects of unbalance conditions, component ratings, output voltage levels, and filter size. Udgivelsesdato: September

Kerekes, Tamas; Liserre, Marco

2009-01-01

218

Tuning permeabilization of microbial cells by three-phase partitioning.  

UK PubMed Central (United Kingdom)

Three-phase partitioning of cells was carried out by mixing t-butanol and ammonium sulfate with aqueous suspension of cells. Permeabilized cells formed the interface between aqueous and alcohol layers. A preincubation step in which cells were exposed to just t-butanol was found to tune the selectivity of permeabilized cells of Thermus thermophilus,Saccharomyces cerevisiae, and Escherichia coli. Smaller proteins (green fluorescent protein and lipase with molecular weights of 29 and 34 kDa, respectively) were released with preincubation of 15 min, and penicillin G acylase ( approximately 85 kDa) was released with preincubation of 30 min. The high-molecular-weight proteins (alcohol dehydrogenase from S. cerevisiae and T. thermophilus with molecular weights of 150 and 170 kDa, respectively) were retained even after preincubation of 60 min. The specific activities and electrophoretic analysis of some of the proteins obtained reflected their high purity.

Raghava S; Gupta MN

2009-02-01

219

Three-phase unbalanced load flow tool for distribution networks  

Energy Technology Data Exchange (ETDEWEB)

This work develops a three-phase unbalanced load flow tool tailored for radial distribution networks based on Matlab {sup registered}. The tool can be used to assess steady-state voltage variations, thermal limits of grid components and power losses in radial MV-LV networks with photovoltaic (PV) generators where most of the system are single phase. New ancillary service such as static reactive power support by PV inverters can be also merged together with the load flow solution tool and thus, the impact of the various reactive power control strategies on the steady-state grid operation can be simply investigated. Performance of the load flow solutions tool in the sense of resulting bus voltage magnitudes is compared and validated with IEEE 13-bus test feeder. (orig.)

Demirok, Erhan; Sera, Dezso; Teodorescu, Remus [Aalborg Univ. (Denmark). Dept. of Energy Technology; Kjaer, Soeren B. [Danfoss Solar Inverters A/S, Sonderborg (Denmark)

2012-07-01

220

EMC Increasing of PWM Rectifier in Comparison with Classical Rectifier  

Directory of Open Access Journals (Sweden)

Full Text Available Pulse width modulated rectifier is a very popular topic nowadays. The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage is its capability of energy recuperation. The PWM rectifier can assert itself for its good behavior in many applications, for example as an input rectifier in indirect frequency converter, or in traction. Traction vehicles equipped with PWM rectifier do not consume reactive power, do not load the supply network with higher harmonics, and the recuperation is possible. The paper deals with the PWM rectifier functional model realization and examination. Electromagnetic compatibility of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

J. Lettl; R. Dolecek

2008-01-01

 
 
 
 
221

Non-traditional method-based solution for elimination of lower order harmonics in voltage source inverter feeding an induction motor drive  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents an efficient and reliable Genetic Algorithm-based solution for Specific Harmonic Elimination (SHE) switching pattern. This method eliminates considerable amount of lower order line voltage harmonics in Pulse Width Modulation (PWM) inverter. The determination of pulse pattern for the elimination of some lower order harmonics of a PWM inverter necessitates solving a system of nonlinear transcendental equations. Genetic Algorithm is used to solve nonlinear transcendental equations for PWM-SHE. In this proposed method, harmonics up to 17th are eliminated using Genetic Algorithm without using Dual transformer. Simulations using Matlab 7.0 and PSIM 6.1 are carried out so as to validate the solution.

Vargese Jegathesan; Jovitha Jerome

2008-01-01

222

An NPC/H-bridge modular photovoltaic grid connected inverter with new-phase shifted PWM technique  

Energy Technology Data Exchange (ETDEWEB)

The commonly used topologies for converting direct current power generated by solar panels to high quality alternating current power at the interface to the grid are the high- frequency and line frequency voltage source grid interface system. These topologies utilize transformers which come with negative features such as increase in cost, size and weight of the whole inverter. In addition, the efficiency and reliability of the system is reduced. A novel option for inverters is the multilevel concept as it is based on low frequency switching and provides voltage or current of low sharing between the power semiconductors. The key topologies which have been suggested for multilevel converters are diode clamped or neutral point clamped (NPC); capacitor clamped of flying capacitors (FC); and cascaded H-bridge inverters with separate direct current sources. The cascaded H-bridge converter demonstrates superior qualities among the multilevel converter topologies as a result of its modularity and flexibility. This paper investigated the operating principle of a cascaded NPC/H-bridge inverter for photovoltaic-grid application. The superior characteristics of the model were analyzed using the state space techniques and double Fourier principle. A new and improved phase sifted PWM technique was proposed and its performance was compared. The main system configuration, mathematical modeling, and simulation model were presented. The state space equation showed that the model has 8 different operating modes which can be utilized to realize 5 level voltages per cell. 13 refs., 1 tab., 6 figs.

Wanjekeche, T.; Nicolae, D.V.; Jimoh, A.A. [Tshwane Univ. of Technology, Pretoria (South Africa). Dept. of Electrical Engineering

2010-08-13

223

Carrier Based Pulse Width Modulation Control of a Non-Square Direct Matrix Converter with Seven-phase Input and Three-phase Output  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents pulse width modulation technique for a direct ac-ac converter. The converter has seven-phase input supply and three-phase output. The input supply may be obtained from a seven-phase wind energy generation system with variable output voltage magnitude and frequency. The output of the proposed converter topology may be fed to the three-phase stiff grid system. Thus the requirement of the modulation of the ac-ac converter is to produce fixed voltage and fixed frequency output while the input can be variable. Additionally the output voltage gain should be high. Simple carrier-based PWM technique is suggested and harmonic injection scheme is proposed to enhance the output voltage magnitude. The output voltage reaches 90% of the input supply voltage with the proposed technique. An additional control block is used to stabilize the output voltage and frequency of the converter. Simulation results are shown in the paper for the verification of the proposed scheme.

Sk Moin Ahmed; Haitham Abu-Rub; Zainal Salam

2013-01-01

224

Mitigating Balanced and Unbalanced Voltage Sag Via Shunt-Connected Voltage Source Convertor (VSC) by using Double Vector Controller  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents a shunt-Connected Voltage Source Convertor (VSC) to mitigate balanced and unbalanced voltage sag and regulate the grid voltage at a fixed level by inserting required reactive power at the Point of Common Coupling (PCC). Moreover, an inner Vector Current-Controller (VCC) and outer voltage controller (VVC) are applied together to calculates the current references for the VCC. Furthermore, an inductor/ capacitor/inductor (LCL) filter is replaced with the simple L-filter in between the VSC and the network and it is constructed to reduce the voltage sag. Likewise, to make up for the unbalanced dips, the positive and negative sequence components related to the grid voltage should be managed distinctly. The positive and negative sequence components related to the grid voltage should be managed distinctly. This is achieved through the application of two independent controllers for the two sequences with an identical cascade structure which has been explicated above. Simulation results designate proper functioning of the control system which has been proposed.

Abdollah Shokri; Hussain Shareef; Azah Mohamed; Shervin Shokri

2013-01-01

225

Mathematical modeling of a three-phase trickle bed reactor  

Directory of Open Access Journals (Sweden)

Full Text Available The transient behavior in a three-phase trickle bed reactor system (N2/H2O-KCl/activated carbon, 298 K, 1.01 bar) was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 x 10-6 m³ s-1 and the liquid phase flow (Q L) varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ s-1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.

J. D. Silva; C. A. M. Abreu

2012-01-01

226

Three-phase-boundary dynamics at Pt/YSZ microelectrodes  

Energy Technology Data Exchange (ETDEWEB)

Strong electrode activation, inductive hysteresis and non-linearity are well-known phenomena on model Pt-YSZ cathodes, and recently also a regular current fluctuation pattern have been reported. The oxygen electrode reaction with YSZ as electrolyte is studied at Pt microelectrodes prepared by electrochemical etching of platinum wire. The result is a well-defined contact area of {proportional_to} 25 {mu}m in diameter. Due to the small size and a favourable ratio between the three-phase-boundary (TPB) length and the contact area, microelectrodes should have an increased sensitivity to local events at the TPB compared to larger point electrodes normally applied. The electrode processes are studied by potential sweep, step and impedance techniques. Investigation of the YSZ and Pt surfaces afterwards reveals the growth of dendrite-like Pt structures from the TPB. The formation of these structures can explain the observed regular current fluctuation pattern and contributes to the explanation of the activation phenomena of the model Pt-YSZ and SOFC cathodes. (author)

Nielsen, J.; Jacobsen, T. [Department of Chemistry, Technical University of Denmark, DK-2800 (Denmark)

2007-05-31

227

Reduction of harmonic losses in three phase fluorescent lighting circuits  

Energy Technology Data Exchange (ETDEWEB)

There is increasing concern by supply authorities with harmonic distortion in power systems and it is anticipated that regulations similar to the European standard will be introduced into Australia in the future. The origin of this distortion can be attributed to non-linear loads of which there are many examples in industry related to applications of power electronic circuits. The fluorescent lamp is an example of a common load with non-linear characteristics. This paper describes a new method for reducing the harmonic losses associated with three phase fluorescent lighting installations. The characteristics of the harmonic distortions for both line and neutral currents in these installations have been investigated using laboratory tests, and the Thevenin equivalent circuit for the system derived. Various filter configurations have been simulated and tested showing that the new scheme leads to significant harmonic attenuation in both the neutral current and the phase current. This approach is used to reduce harmonic losses in the neutral currents and improve the line current wave-forms. (author). 5 figs., 3 refs.

Szczepanik, J. [Monash Univ., Clayton, VIC (Australia); Lawrance, W. [Curtin Univ. of Technology, Bentley, WA (Australia); Mielczarski, W. [Monash Univ., Clayton, VIC (Australia)

1995-12-31

228

Control of grid integrated voltage source converters under unbalanced conditions: development of an on-line frequency-adaptive virtual flux-based approach  

Energy Technology Data Exchange (ETDEWEB)

Three-Phase Voltage Source Converters (VSCs) are finding widespread applications in grid integrated power conversion systems. The control systems of such VSCs are in an increasing number of these applications required to operate during voltage disturbances and unbalanced conditions. Control systems designed for grid side voltagesensor-less operation are at the same time becoming attractive due to the continuous drive for cost reduction and increased reliability of VSCs, but are not commonly applied for operation during unbalanced conditions. Methods for voltage-sensor-less grid synchronization and control of VSCs under unbalanced grid voltage conditions will therefore be the main focus of this Thesis. Estimation methods based on the concept of Virtual Flux, considering the integral of the converter voltage in analogy to the flux of an electric machine, are among the simplest and most well known techniques for achieving voltage-sensor-less grid synchronization. Most of the established techniques for Virtual Flux estimation are, however, either sensitive to grid frequency variations or they are not easily adaptable for operation under unbalanced grid voltage conditions. This Thesis addresses both these issues by proposing a simple approach for Virtual Flux estimation by utilizing a frequency-adaptive filter based on a Second Order Generalized Integrator (SOGI). The proposed approach can be used to achieve on-line frequency-adaptive varieties of conventional strategies for Virtual Flux estimation. The main advantage is, however, that the SOGI-based Virtual Flux estimation can be arranged in a structure that achieves inherent symmetrical component sequence separation under unbalanced conditions. The proposed method for Virtual Flux estimation can be used as a general basis for voltage-sensor-less grid synchronization and control during unbalanced conditions. In this Thesis, the estimated Virtual Flux signals are used to develop a flexible strategy for control of active and reactive power flow, formulated as generalized equations for current reference calculation. A simple, but general, implementation is therefore achieved, where the control objective and the power flow characteristics can be selected according to the requirements of any particular application. Thus, the same control structure can be used to achieve for instance balanced sinusoidal currents or elimination of double frequency active power oscillations during unbalanced conditions. In case of voltage sags, current references corresponding to a specified active or reactive power flow might exceed the current capability of the converter. The limits for active and reactive power transfer during unbalanced conditions have therefore been analyzed, and generalized strategies for current reference calculation when operating under current limitations have been derived. The specified objectives for active and reactive power flow characteristics can therefore be maintained during unbalanced grid conditions, while the average active and reactive power flow is limited to keep the current references within safe values. All concepts and techniques proposed in this Thesis have been verified by simulations and laboratory experiments. The SOGI-based method for Virtual Flux estimation and the strategies for active and reactive power control with current limitation can also be easily adapted for a wide range of applications and can be combined with various types of inner loop control structures. Therefore, the proposed approach can potentially be used as a general basis for Virtual Flux-based voltage-sensor-less operation of VSCs under unbalanced grid voltage conditions.(Author)

Suul, Jon Are

2012-03-15

229

ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS  

International Nuclear Information System (INIS)

In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established.

2004-01-01

230

ADVANCED COMPUTATIONAL MODEL FOR THREE-PHASE SLURRY REACTORS  

Energy Technology Data Exchange (ETDEWEB)

In this project, an Eulerian-Lagrangian formulation for analyzing three-phase slurry flows in a bubble column was developed. The approach used an Eulerian analysis of liquid flows in the bubble column, and made use of the Lagrangian trajectory analysis for the bubbles and particle motions. The bubble-bubble and particle-particle collisions are included the model. The model predictions are compared with the experimental data and good agreement was found An experimental setup for studying two-dimensional bubble columns was developed. The multiphase flow conditions in the bubble column were measured using optical image processing and Particle Image Velocimetry techniques (PIV). A simple shear flow device for bubble motion in a constant shear flow field was also developed. The flow conditions in simple shear flow device were studied using PIV method. Concentration and velocity of particles of different sizes near a wall in a duct flow was also measured. The technique of Phase-Doppler anemometry was used in these studies. An Eulerian volume of fluid (VOF) computational model for the flow condition in the two-dimensional bubble column was also developed. The liquid and bubble motions were analyzed and the results were compared with observed flow patterns in the experimental setup. Solid-fluid mixture flows in ducts and passages at different angle of orientations were also analyzed. The model predictions were compared with the experimental data and good agreement was found. Gravity chute flows of solid-liquid mixtures were also studied. The simulation results were compared with the experimental data and discussed A thermodynamically consistent model for multiphase slurry flows with and without chemical reaction in a state of turbulent motion was developed. The balance laws were obtained and the constitutive laws established.

Goodarz Ahmadi

2004-10-01

231

Simulation of Single-Phase Cascade Multilevel PWM Inverters  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents simulation of a single –phase cascade multilevel PWM inverter topology.Solution is based on series connection of 3 level diodeclamped inverters modules and flying capacitor invertermodules, which gives possibility for flexible operation ofinverter at various high voltage.

Adrian ?chiop; Felicia ?chiop

2008-01-01

232

A new Zero-Current-Transition PWM switching cell  

Energy Technology Data Exchange (ETDEWEB)

In this paper a new Zero-Current-Transition (ZCT) PWM switching cell is presented. The proposed switching cell is composed of the normal hard-switched PWM cell (consisting of one active switch and one passive switch), plus as auxiliary circuit. The auxiliary circuit is inactive during the ON ad OFF intervals of the switches in the normal PWM switch. The transitions between the two states are controlled by the auxiliary circuit. Prior to turn-off, the current through the active switch in the PWM cell is forced to zero, thus the turn-off losses of the active switch are practically eliminated. At turn-on the auxiliary circuit slows down the growing rate of the current through the main switch. Thus, turn-on losses are also very much reduced. The active switch operates under ZCT conditions, the passive switch (diode) has a controlled reverse recovery, while the switch in the auxiliary circuit operates under Zero-Current-Switching (ZCS) conditions. (orig.) 3 refs.

Grigore, V. [Electronics and Telecommunications Faculty, `Politechnica` University Bucharest (Romania); Kyyrae, J. [Helsinki University of Technology, Otaniemi (Finland): Institute of Intelligent Power Electronics

1997-12-31

233

A new Zero-Voltage-Transition PWM switching cell  

Energy Technology Data Exchange (ETDEWEB)

In this paper a new Zero-Voltage-Transition (ZVT) PWM switching cell is presented. The proposed switching cell is composed of the normal hard-switched PWM cell (consisting of one active switch and one passive switch), plus an auxiliary circuit (consisting of one active switch and some reactive components). The auxiliary circuit is inactive during the ON and OFF intervals of the switches in the normal PWM switch. However, the transitions between the two states are controlled by the auxiliary circuit. Prior to turn-on, the voltage across the active switch in the PWM cell is forced to zero, thus the turn-on losses of the active switch are practically eliminated. At turn-off the auxiliary circuit behaves like a non-dissipative passive snubber reducing the turn-off losses to a great extent. Zero-Voltage-Transition switching technique almost eliminates switching losses. The active switch operates under ZVT conditions, the passive switch (diode) has a controlled reverse recovery, and the switch in the auxiliary circuit operates under Zero-Current-Switching (ZCS) conditions. (orig.) 6 refs.

Grigore, V. [Electronics and Telecommunications Faculty `Politebuica` University Bucharest (Romania); Kyyrae, J. [Helsinki University of Technology, Otaniemi (Finland): Institute of Intelligent Power Electronics

1997-12-31

234

A chaotic PWM motor drive for electric propulsion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, a chaotic Pulse width modulation (PWM) closed-loop induction motor drive is proposed and implemented to improve the electromagnetic compatibility (EMC) for electric propulsion. The key is to propose a chaotically amplitude-modulated frequency modulator (CAFM) to modulate the space vec...

Wang, Z; Chau, KT; Cheng, M

235

HVDC with voltage source converters and extruded cables for up to {+-}300 kV and 1000 MW  

Energy Technology Data Exchange (ETDEWEB)

Recent developments in voltage source converter and high voltage direct current (VSC HVDC) systems were discussed. VSC HVDC systems allow connections in or between networks via low-weight extruded cables. Connections can be made at costs comparable to overhead AC transmission lines. VSC HVDC systems can prevent fault propagation, increase low frequency stability, reduce network losses, and increase voltage stability. New research has meant that the system's maximum power handling has been increased to at least 1000 MWs. This paper explored new research developments in 4 key areas: (1) IGBT valves, (2) DC cable systems, (3) main circuit of converter stations, and (4) control systems. It was noted that the VSC valves now have improved current handling, lower losses, better cooling and better voltage sharing. A larger presspack IGBT gives higher converter current handling. The cable system has been expanded in both voltage capacity and laying depth. Both flexible and stiff joints have now been developed for the polymeric extruded cables. Testing of the cable system has verified a 300 kVdc capability and a laying depth larger than 2000 m. Converter main circuits have been modified for improved cost and lower losses. The control system has been optimized with a new black-start control which can provide full support during grid restoration processes. As a result of the modifications, the range of possible applications for VSC HVDC can be expanded to large scale transmission. The system is able to transmit large amount of power long-distance, and can also be used to add new transmission lines where restrictions concerning right-of-way have caused difficulties. It was concluded that VSC HVDC provides full power flow control in both directions, voltage stabilization via continuous reactive power control, and minimized disturbances due to fault propagation. 16 refs., 3 tabs., 6 figs.

Jacobson, B.; Jiang-Hafner, Y.; Rey, P.; Asplund, G. [ABB Power Technologies, Ludvika (Sweden); Jeroense, M.; Gustafsson, A.; Bergkvist, M. [ABB Power Technologies, Karlskrona (Sweden); Trinh, T.N. [ABB Inc., Montreal, PQ (Canada)

2006-07-01

236

Analysis of Dither in PWM Control on Electro-hydraulic Proportional Valve  

Directory of Open Access Journals (Sweden)

Full Text Available Plus with modulation (PWM) is widely used in proporational control systems for it is efficient, flexible and anti-interference. Due to the friction and hysteresis of electromagnet, hysteresis exists when hydraulic valve in steady-state, and hysteresis influences the dynamic characteristics of the valve seriously,the hysteresis can be improved by superimposing dithers with certain frequency and amplitude to the valve coil. Aiming at the character of anti-unloading power driver circuit ,this paper analyzed the parasitic dither which exists in ±24V PWM control?besides?the experiment shows that in a high frequency PWM, dither with independent frequency and amplitude can be generated by changing the frequency of the PWM, in this way, the dithers  and average current of coil  can be adjusted separately by changing PWM frequency and PWM duty cycle.  

Guoping LIU; Wuxing XIA; Dawei QI; Ronghua HU

2013-01-01

237

Research on a New Control Strategy of Three Phase Inverter for Unbalanced Loads  

Directory of Open Access Journals (Sweden)

Full Text Available One of the very important functions of three-phase inverter is to maintain the symmetric three-phase output voltage when the three-phase loads are unbalanced. Although the traditional symmetrical component decomposing and superimpose theory can keep the voltage balance through compensating the positive-, negative- and zero-sequence components of the output voltage of inverter, however, this method is time-consuming and not suitable for control. Aiming at high power medium frequency inverter source, a P+Resonant (Proportion and Resonant) controller which ensured a balanced three phase output voltage under unbalanced load is proposed in this paper. The regulator was proved to be applicable to both three-phase three-wire system and three-phase four-wire system and developed two methods of realization. The simulation results verified that this method can suppressed effectively the output voltage distorted caused by the unbalanced load and attained a high quality voltage waveforms.

Wenhua HU; Weiming Ma; Chunxi LIU

2010-01-01

238

Controlling DC Motor using Microcontroller (PIC16F72) with PWM  

Directory of Open Access Journals (Sweden)

Full Text Available Motion control plays a vital role in industrial atomization. Different types of motors AC, DC, SERVO or stepper are used depending upon the application; of these DC motors are widely used because of easier controlling. Among the different control methods for DC motor armature voltage control method using pulse width modulation (PWM) is best one. We can realize the PWM using H-bridge built with IGBT switches or transistors. Togenerate PWM signals we use PIC16F72 microcontroller.

Shruti Shrivastava, Jageshwar Rawat, Amit Agrawal

2012-01-01

239

Prediction of power losses in silicon iron sheets under PWM voltage supply  

Energy Technology Data Exchange (ETDEWEB)

The behavior of iron losses in silicon iron steels submitted to a PWM voltage is studied. The influence of modulation parameters (the depth of modulation and the number of eliminated harmonics) is clarified. In particular, the idea of an equivalent alternating pulse voltage that gives the same iron losses as the PWM voltage is established. An estimation formula for iron losses under the PWM voltage is developed based on the loss separation model and the voltage form factor. ((orig.))

Amar, M. (Service Electrotechnique et Electronique Industrielle, SUPELEC 91192, Gif-Sur-Yvette (France)); Kaczmarek, R. (Service Electrotechnique et Electronique Industrielle, SUPELEC 91192, Gif-Sur-Yvette (France)); Protat, F. (Service Electrotechnique et Electronique Industrielle, SUPELEC 91192, Gif-Sur-Yvette (France))

1994-05-01

240

Generalisation of Helmholtz-Thevenin theorem to three-phase electrical circuits  

CERN Multimedia

The scope of this paper is to determine the generalized form for equivalent tension generator theorem (Helmholtz-Thevenin theorem) for three-phase electrical circuit. Any complicated electrical power systems we can reduce depending on any three-phase electrical consumer to a three-phase electrical generator that has certain internal impedance. Starting with this assumption, we have demonstrated the way to obtain the electromotive voltages for an equivalent generator and its internal impedances.

Mihai, Gheorghe

2009-01-01

 
 
 
 
241

Three-phase gas-liquid-liquid flows in the steady and transient states  

International Nuclear Information System (INIS)

Three-phase (gas-liquid-liquid) flows are important in a number of industrial contexts. The manifestations and nature of three-phase flows are discussed and recent work at Imperial College is reviewed. Flow patterns in three-phase flows are complex and vary considerably from system to system. Time average values of pressure drop and hold-up show characteristic peaks as a function of 'water cut' (fraction by volume of water in the liquid phase). Measurements on stratified and slug flows are reviewed and cases of transient flows (where the input flow is changed suddenly) are described. Finally, predictions methods for three-phase flows are reviewed.

2005-01-01

242

Analysis and Design of a Higher Current ZVS-PWM Converter for Industrial Applications  

Directory of Open Access Journals (Sweden)

Full Text Available A new auxiliary circuit that can be implemented in DC-DC and AC-DC ZVS-PWM converters is proposed in the paper. The circuit is for ZVS-PWM converters used in applications where high-frequency operation is needed and the load current is higher than that of typical ZVS-PWM converters. In the paper, the operation of a new ZVS-PWM converter is described, its steady-state operation is analyzed, and a procedure for its design is derived and then demonstrated. The feasibility of the new converter is confirmed by experimental results obtained from a prototype.

Navid Golbon; Gerry Moschopoulos

2013-01-01

243

Investigation of iron loss under PWM voltage excitation in various size strip-wound toroidal cores  

Energy Technology Data Exchange (ETDEWEB)

The PWM inverters are widely used when variable speed and UPS are required. Due to distortion in PWM flux waveform extra power losses occur in magnetic cores. The iron loss of three types of grain-oriented 3% Si-Fe toroidal cores was measured by a highly accurate measurement system under PWM and sinusoidal voltage excitation at different flux densities. The loss increase under PWM excitation was found higher at high flux densities due to higher harmonic distortion and different magnetisation process. (orig.)

Tutkun, N. [Karaelmas Univ., Faculty of Engineering, Div. of Electrical and Electronic, Zonguldak (Turkey); Kockar, H. [Balikesir Univ., Faculty of Science, Balikesir (Turkey); Demirci, R. [Abant Izzet Baysal Univ., Faculty of Technical Education, Electrical and Electronic Dept., Duzce (Turkey)

2000-08-01

244

Effects of 60Co ?-rays on PWM and LPS induced lymphocytes  

International Nuclear Information System (INIS)

[en] The relationship between lymphocytes induced by PWM and LPS was investigated by means of 3H-TdR and 14C-UR incorporation. The study showed that in votro, PWM-induced cells were able to promote the stimulating effect of LPS to B lymphocyte. The stimulating effect of PWM-induced cells was obviously weakened after PWM cells being irradiated with ?-rays. When PWM-induced cells and LPS-induced cells were incubated together, with one kind of cells exposed to 60Co ?-rays, incorporation value of 3H-TdR became much smaller and the synergetic function disappeared, especially, when PWM-induced cells were irradiated. For patients suffering from carcinoma of nasopharynx, when treated with 60Co ?-rays, the incorporation value in LPS-induced cells approached normal level, while the incorporation value in PWM-induced cells reduced significantly and the stimulating effect of PWM-induced cells on LPS-induced cells became much weaker. The fact described above demonstrated that PWM-induced cells have the function of T-helper cells and play a more important role in the synergy than LPS induced cells

1987-01-01

245

Hysteresis modeling of synchronous reluctance motor considering PWM input voltage  

Science.gov (United States)

This paper deals with the hysteresis characteristics analysis in PWM fed synchronous reluctance motor (SynRM) using a coupled finite element method (FEM) and Preisach's modeling, which is presented to analyze the characteristics under the effect of saturation and hysteresis loss. With regard to the PWM characteristics, a vector control inverter is combined with an analysis tool. Also, a moving mesh technique is used with regard to rotation due to velocity. The focus of this paper is the applied method of Preisach modeling for rotating machines and the characteristics analysis of a SynRM using the proposed method of analysis. For the propriety of proposed method of analysis, TMS320C31 DSP-installed experimental devices are used. And then, computer simulation and experimental result for the /i-? loci, speed, current response, show the propriety of the proposed method. The characteristic analysis is performed in relation to the maximum efficiency condition for a SynRM in simulation and experiment.

Lee, J. H.; Kim, J. C.; Hyun, D. S.

2000-01-01

246

Soft Switched Multi-Output PWM DC-DC Converter  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a new soft switched cell that overcomes most of the drawbacks of the normal "hard switched-pulse width modulation" converter is proposed to contrive a new family of soft switched PWM converters. All of the semiconductor devices in this converter are turned on and off under exact or near zero voltage switching (ZVS) and/or zero current switching (ZCS). No additional voltage and current stresses on the main switch and main diode occur. A push-pull converter equipped with the proposed snubber cell is analyzed in detail. The predicted operation principles and theoretical analysis of the presented converter are verified with a prototype of a 50W PWM push-pull multi-output converter with insulated MOSFET and for regulation of slave outputs magnetic amplifier post regulators are considered as post regulators. Moreover; this multioutput converter has a simple structure, low cost, and ease of control circuitry.

Rashmi Sharma

2013-01-01

247

Dynamics of IGBT based PWM Converter A Case Study  

Directory of Open Access Journals (Sweden)

Full Text Available Optimizing the efficiency and dynamics of power converters is a critical tradeoff in power electronics. The increase of switching frequency can improve the dynamics of power converters, but theefficiency may be degraded as well as the switching losses. As power semiconductor devices like diodes, MOSFETS, IGBTs, Thyristors, BJTs have their own characterstics and dynamic responses. It is desired toanalyze and observe the dynamics of different semiconductor devices before they actually employed in the model. Inclusion of different PWM techniques help in the removal of power line interferences like harmonic losses, unwanted ripples, chopped frequencies, spikes. In this paper, we have studied and analyzed the dynamics of IGBT based PWM converter with subjected to different conditions like transient state, steady state feeding the RLC load. Snubber circuits are used to reduce the switching losses. The IGBT based PWM converter reflects the better dynamics with improved efficiency and reduced harmonics as compared to some other power semiconductor devices when FFT is performed and subjected to standard parameterized RLC load understeady state and transient analysis.

Navpreet Singh Tung; Amit Bhardwaj; Tarun Mittal; Vijay Shukla

2012-01-01

248

Effect of Implementing Three-Phase Flow Characteristics and Capillary Pressure in Simulation of Immiscible WAG  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of including a three-phase representation of the flow parameters and capillary pressure has been investigated using a black oil simulator. The simulation approaches include the complexity of three-phase flow, relative permeability hysteresis, dynamic phase trapping functions and capillary...

Dale, Elisabeth Iren; Skauge, Arne

249

Three-phase region of D2-DT-T2  

International Nuclear Information System (INIS)

Analogous to the triple point of a pure substance are a binary mixture's triple line and a ternary mixture's three-phase surface, where pressure, temperature, and composition must all be considered. The first three-phase study on a ternary hydrogen system, D2-DT-T2, is reported

1977-08-05

250

PWM-switching pattern-based diagnosis scheme for single and multiple open-switch damages in VSI-fed induction motor drives.  

Science.gov (United States)

This paper deals with a fault detection technique for insulated-gate bipolar transistors (IGBTs) open-circuit faults in voltage source inverter (VSI)-fed induction motor drives. The novelty of this idea consists in analyzing the pulse-width modulation (PWM) switching signals and the line-to-line voltage levels during the switching times, under both healthy and faulty operating conditions. The proposed method requires line-to-line voltage measurement, which provides information about switching states and is not affected by the load. The fault diagnosis scheme is achieved using simple hardware and can be included in the existing inverter system without any difficulty. In addition, it allows not only accurate single and multiple faults diagnosis but also minimization of the fault detection time to a maximum of one switching period (T(c)). Simulated and experimental results on a 3-kW squirrel-cage induction motor drive are displayed to validate the feasibility and the effectiveness of the proposed strategy. PMID:22153956

Trabelsi, Mohamed; Boussak, Mohamed; Gossa, Moncef

2011-12-06

251

Multicarrier trapezoidal PWM strategies based on control freedom degree for MSMI  

Directory of Open Access Journals (Sweden)

Full Text Available This work proposes an additional clew for the carrier based PWM methods on control of multilevel inverters which is based on the combination of the Control Freedom Degree (CFD) and novel carrier/reference signals for multilevel cascaded inverter. The significance of the proposed CFD clew on multilevel PWM techniques are verified and well demonstrated by simulation for chosen five level inverter. This paper presents a novel approach for controlling the harmonics of output voltage of chosen Cascaded MultiLevel Inverter (CMLI) employing trapezoidal PWM switching strategies. Sub Harmonic PWM (SHPWM), Phase Shift PWM (PSPWM), Variable Frequency PWM (VFPWM) and Carrier Overlapping PWM (COPWM) techniques employed are evaluated for various modulation indices using spectrum of the output voltage and other performance measures such as crest factor, form factor etc and the use of inverter state redundancies to perform additional application specific control tasks. This paper focusses on MultiCarrier Trapezoidal PWM (MCTPWM) techniques with Phase Disposition (PD), Phase Shift (PS), Variable Frequency (VF) and Carrier Overlapping (CO) of carrier for the chosen CMLI. Simulations are performed using MATLAB/SIMULINK. It is observed that PD and CO methods provide output with relatively low distortion. It is also observed that CO is found to perform better since it provides relatively higher fundamental RMS output voltage and relatively lower stress on the devices.

R. Bensraj; S. P. Natarajan; V. Padmathilagam

2010-01-01

252

High flexibility and low cost digital implementation for modern PWM strategies  

DEFF Research Database (Denmark)

In this paper a new low cost technique for PWM strategy implementation is presented. The proposed technique does not require dedicated hardware PWM units, thus offering higher flexibility of use. Furthermore, the aforementioned method eases the digital implementation of modern modulation methods like AZSPWM, NSPWM, or ACRPWM. By using a conventional PWM unit from a microcontroller, these modern modulation techniques are often difficult, or even impossible, to implement. The proposed method can be used to implement PWM strategies even for those microcontrollers which are not equipped with hardware PWM unit. The experimental results show that this new technique is suitable to replace traditional implementation methods with minimum computational overhead, with the benefit of high flexibility, lower cost and faster code development.

Mathe, Laszlo; Sera, Dezso

2011-01-01

253

Three-phase flow in field-scale simulations of gas and WAG  

Energy Technology Data Exchange (ETDEWEB)

Dimensionless scaling groups for three-dimensional three-phase flow in porous media were developed. The scaling groups were used to design simulations at various conditions of gravity, viscous and capillary force interactions. In addition, several simulations were made to determine the uncertainty of the results due to the model for three-phase relative permeabilities. The results of this study show that there is a significant uncertainty associated with the selection of the three-phase relative permeability model for field scale simulations of gas and WAG injections. This uncertainty is translated into doubtful simulation results in terms of distribution of the fluids inside large volumes of the reservoir, total oil recovery, and fluids production rates. It is shown that additional oil recovery due to gas injection after a waterflood can be different by a factor of two depending on the model for three-phase relative permeability. It is also shown that the producing gas oil ratio (GOR) varies considerably depending on the model for three-phase relative permeabilities. Accurate predictions of oil recovery in processes that exhibit three-phase flow need more rigorous models for three-phase relative permeability.

Guzman, R.E.; Aziz, K. [Stanford Univ., CA (United States); Giordano, D.; Fayers, F.J.; Godi, A.

1994-12-31

254

Instantaneous Power Compensation in Three-Phase Systems by Using p-q-r Theory  

DEFF Research Database (Denmark)

Three linearly independent instantaneous powers have been defined in the time domain in three-phase four-wire systems with the use of p-q-r theory. Any three-phase circuit can be transformed into three single-phase circuits by the p-q-r transformation Thus the instantaneous powers in any three-phase systems can be analysed as the same way of instantaneous power in single-phase systems.This paper analyses the instantaneous powers spectrally in the frequency domain for single-phase systems and three-phase systems. Each instantaneous power in three-phase systems has its own spectral pattern that is characterized by the spectral distribution of the system voltages and currents. The instantaneous power in single-phase systems has its own spectral pattern different from that of three-phase systems.From the spectral analysis of the instantaneous powers, powers are newly defined in the frequency domain. The definition of the powers is consistent through single-phase systems and three-phase systems and is well agreed with the traditional definition of powers in sinusoidal single-phase systems. Based on the defined powers, some useful power quality factors are defined to evaluate power qualities for various circuit conditions.

Kim, Hyosung; Blaabjerg, Frede

2002-01-01

255

Three-phase multi-pulse converter StatCom analysis  

Energy Technology Data Exchange (ETDEWEB)

This paper is aimed to present the analysis of operating characteristics of the static synchronous compensator (Statcom) based on a multi-pulse voltage-source inverter (VSI). A detailed analysis of voltages and currents on both 6- and 12-pulses is presented and equations describing the performance of each circuit are derived. Finally a comparison between digital simulations using the EMTDC/PSCAD and analytical results is shown, verifying the validity of the derived expressions. The device is now being implemented in the laboratory, based on IGBT's. (Author)

Davalos M, Ricardo; Ramirez, Juan M.; Tapia O, Ruben [Unidad Guadalajara, CINVESTAV-I.P.N., Guadalajara (Mexico)

2005-01-01

256

The Investigation of Sinusoidal Single Phase Voltage Source Inverter Output Filter Iš?jimo filtro tyrimas vienfazio inverterio sinusinei ?tampai formuoti  

Directory of Open Access Journals (Sweden)

Full Text Available The results of output filter investigation of single phase sine voltage source inverter (VSI) are presented. The operating principle, construction and a most widely used topology of single phase voltage source inverter is discussed. The results obtained using modeling and experimental investigation are presented. The Total Harmonic Distortion of the inverter output voltage and maximal current of the output capacitor were analyzed using Matlab Simulink software. The 1 kW inverter prototype was built for experimental investigation. The inverter switches are realized using IGBT transistors. The toroidal iron powder core with distributed air gap was used as the core of the inductor. The experimental investigation of inductor core losses and maximal current of output filter capacitor were performed.Article in LithuanianPateikti vienfazio inverterio sinusinei ?tampai formuoti iš?jimo filtro tyrimo rezultatai. Išnagrin?tas inverteri? principas, valdom?j? signal? formavimo b?dai bei inverterio sandara ir labiausiai paplitusi topologija. Atlikti modeliavimo ir eksperimentiniai tyrimai. Modeliuojant nustatytos inverterio iš?jimo ?tampos harmoninio iškraipymo (angl. THD – Total Harmonic Distortion) ribos pasirinktiems inverterio ir iš?jimo filtro parametrams bei maksimali srov?, kuri teka per iš?jimo filtro kondensatori?. Eksperimentiniam tyrimui sumontuotas iki 1 kW galios inverterio su iš?jimo filtru maketas, kurio galios laipsn? sudar? raktai su IGBT tranzistoriais. Ištirti filtro droselio šerdies nuostoliai ir maksimali filtro kondensatoriaus srov?.Straipsnis lietuvi? kalba

Andrius Platakis; Vytautas Bleizgys; Tadas Lipinskis

2011-01-01

257

Design and Implementation of a PWM Inverter for Reluctance Motors  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with aspects regarding the simulation, implementation and testing of a PWM inverter for reluctance motors. The main objectives is to present the simulation stage using the SLPS interface between Orcad PSpice® electric circuit simulator and Matlab Simulink® system simulator. SLPS interface developed by Cybernet Systems offer the possibility to integrate the real outputs of an circuit obtained with PSpice simulator and the ideal model or mathematical Simulink model, thus enabling the designers to identify and correct integration issues of electronics within a system[3].

MARGINEAN Calin; MARGINEAN Ana-Maria; VESE Ioana; TRIFA Viorel; TRIFU Emil

2012-01-01

258

Fast controller for a unity-power-factor PWM rectifier  

Energy Technology Data Exchange (ETDEWEB)

This paper presents an analog implementation of a fast controller for a unity-power-factor (UPF) PWM rectifier. The best settling times of many popular controllers for this type of converter are on the order of a few line cycles, corresponding to bandwidths under 20 Hz. The fast controller demonstrated in this paper can exercise control action at a rate comparable to the switching frequency rather than the line frequency. In order to accomplish this while maintaining unity power factor during steady-state operation, the fast controller employs a ripple-feedback cancellation scheme.

Eissa, M.O.; Leeb, S.B.; Verghese, G.C. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Lab. for Electromagnetic and Electronic Systems; Stankovic, A.M. [Northeastern Univ., Boston, MA (United States)

1996-01-01

259

A family of PWM soft-single-switched converters  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new family of PWM soft-single-switched converters, which having only a single active switch, is able to operate with soft switching in a pulse with modulation way. In addition such converters can work in high switching frequencies for wide range of load without duty cycle limitations. In order to illustrate the operating principle of these new converters a detailed study, including simulations and experimental test is carried out. the validity of these new converters is guaranteed by the obtained results. (author) 3 refs., 6 figs., 1 tab.

Vilela, M.S.; Coelho, E.A.A.; Vieira Junior, J.B.; Freitas, L.C. de; Farias, V.J. [Uberlandia Univ., MG (Brazil). Dept. de Engenharia Eletrica

1995-12-31

260

Spread Spectrum Modulation by Using Asymmetric-Carrier Random PWM  

DEFF Research Database (Denmark)

This paper presents a new fixed carrier frequency random PWM method, where a new type of carrier wave is proposed for modulation. Based on simulations and experimental measurements, it is shown that the spread effect of the discrete components from the motor current spectra and acoustic spectra is very effective and is independent from the modulation index. The flat motor current spectrum generates an acoustical noise close to the white noise, which improves the acoustical performance of the drive. The new carrier wave is easy to implement digitally, without employing any external circuits. The modulation method can be used in both open and closed loop motor control applications.

Mathe, Laszlo; Lungeanu, Florin

2012-01-01

 
 
 
 
261

An active resonant snubber for high frequency PWM converters  

Science.gov (United States)

An active resonant snubber circuit that provides a zero current turn-on transition and a zero voltage turned-off transition for continuous current constant frequency PWM (pulse width modulation) converters is described. The circuit avoids the series found in the primary current path of some passive LC dissipationless snubbers. The energy which otherwise would have appeared as primary switching power losses is transferred to the load via the snubber circuitry. Analysis and modeling results of the circuit are presented. A description of an experimental circuit demonstrating switching power loss reductions is also presented.

Wittenbreder, E.

262

The effects of viscous forces on three-phase relative permeability  

Energy Technology Data Exchange (ETDEWEB)

The overall objective of Three-Phase Relative Permeability Project (BE9) is to develop guidelines for improving the accuracy of three-phase relative permeability determinations. This report summarizes previous studies and explains the progress made at NIPER on studying the effect of variations in viscous forces on three-phase relative permeabilities by changing the viscosity of both wetting and nonwetting phases. Significant changes were observed due to viscosity variations. An increase in oil viscosity reduced the relative permeability to gas; an increase in brine/(wetting-phase) viscosity reduced the relative permeability to brine. A slight increase in gas relative permeability was also observed. These observations suggest that the viscosities of both oil and water influence three-phase permeability data. During this study, data scatter was sometimes encountered which was comparable to that of published results. The causes of this scatter are outlined in this report and remedial attempts are discussed. 20 refs., 16 figs., 5 tabs.

Maloney, D.R.; Mahmood, S.M.; Honarpour, M.M.

1989-04-01

263

Three-phase gas-liquid-liquid flows in the steady and transient states  

Energy Technology Data Exchange (ETDEWEB)

Three-phase (gas-liquid-liquid) flows are important in a number of industrial contexts. The manifestations and nature of three-phase flows are discussed and recent work at Imperial College is reviewed. Flow patterns in three-phase flows are complex and vary considerably from system to system. Time average values of pressure drop and hold-up show characteristic peaks as a function of 'water cut' (fraction by volume of water in the liquid phase). Measurements on stratified and slug flows are reviewed and cases of transient flows (where the input flow is changed suddenly) are described. Finally, predictions methods for three-phase flows are reviewed.

Hewitt, G.F. [Department of Chemical Engineering and Chemical Technology, Imperial College, Prince Consort Road, London SW7 2BY (United Kingdom)]. E-mail: g.hewitt@imperial.ac.uk

2005-05-01

264

Refolding of urea denatured ovalbumin with three phase partitioning generates many conformational variants.  

Science.gov (United States)

Three phase partitioning is a process in which mixing t-butanol with ammonium sulphate with a protein solution leads to the formation of three phases. Generally, the interfacial protein precipitate (formed between upper t-butanol rich and lower aqueous phase) can be easily dissolved back in aqueous buffers. In case of ovalbumin, this led to a precipitate which was insoluble in aqueous buffers. This precipitate when solubilized with 8M urea and subjected to three phase partitioning under various conditions led to many refolded soluble conformational variants of ovalbumin. One of these showed trypsin inhibitory activity, had marginally higher ?-sheet content and had higher surface hydrophobicity (both with respect to native ovalbumin). Scanning electron microscopy and Atomic force microscopy of this preparation showed a thread like structure characteristic of amyloid fibrils. The behaviour of ovalbumin during three phase partitioning makes it a valuable system for gaining further understanding of protein aggregation. PMID:23777710

Rather, Gulam Mohmad; Gupta, Munishwar Nath

2013-06-15

265

Efficiency analysis on a two-level three-phase quasi-soft-switching inverter  

DEFF Research Database (Denmark)

When designing an inverter, an engineer often needs to select and predict the efficiency beforehand. For the standard inverters, plenty of researches are analyzing the power losses and also many software tools are being used for efficiency calculation. In this paper, the efficiency calculation for non-conventional inverters with special shoot-through state is introduced and illustrated through the analysis on a special two-level three-phase quasi-soft-switching inverter. Efficiency comparison between the classical two-stage two-level three-phase inverter and the two-level three-phase quasi-soft-switching inverter is carried out. A 10 kW/380 V prototype is constructed to verify the analysis. The experimental results show that the efficiency of the new inverter is higher than that of the traditional two-stage two- level three-phase inverter.

Geng, Pan; Wu, Weimin

2013-01-01

266

Refolding of urea denatured ovalbumin with three phase partitioning generates many conformational variants.  

UK PubMed Central (United Kingdom)

Three phase partitioning is a process in which mixing t-butanol with ammonium sulphate with a protein solution leads to the formation of three phases. Generally, the interfacial protein precipitate (formed between upper t-butanol rich and lower aqueous phase) can be easily dissolved back in aqueous buffers. In case of ovalbumin, this led to a precipitate which was insoluble in aqueous buffers. This precipitate when solubilized with 8 M urea and subjected to three phase partitioning under various conditions led to many refolded soluble conformational variants of ovalbumin. One of these showed trypsin inhibitory activity, had marginally higher ?-sheet content and had higher surface hydrophobicity (both with respect to native ovalbumin). Scanning electron microscopy and Atomic force microscopy of this preparation showed a thread like structure characteristic of amyloid fibrils. The behaviour of ovalbumin during three phase partitioning makes it a valuable system for gaining further understanding of protein aggregation.

Rather GM; Gupta MN

2013-09-01

267

A Three-Phase Bidirectional DC-DC Converter for Automotive Applications  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a three-phase soft-switching, bidirectional dc-dc converter for high-power automotive applications. The converter employs dual three-phase active bridges and operates with a novel asymmetrical but fixed duty cycle for the top and bottom switches of each phase leg. Simulation and experimental data on a 6-kW prototype are included to verify the novel operating and power flow control principles.

Su, Gui-Jia [ORNL; Tang, Lixin [ORNL

2008-01-01

268

Comparisons between the three-phase current injection method and the forward/backward sweep method  

Energy Technology Data Exchange (ETDEWEB)

This paper presents comparisons of two power flow methodologies for distribution system analysis: the three-phase current injection method - TCIM and the forward/backward sweep - FBS. These techniques were applied for large scale three-phase distribution systems, the advantages and drawbacks are emphasized and their computational performances are presented. The results presented in this work can be helpful to decide which one of the tested methods is the most suitable to solve a particular electrical system. (author)

Araujo, Leandro Ramos de; Penido, Debora Rosana Ribeiro; Pereira, Jose Luiz Rezende; Garcia, Paulo Augusto Nepomuceno [Department of Electrical Engineering, Federal University of Juiz de Fora, Juiz de Fora, MG (Brazil); Junior, Sandoval Carneiro [Department of Electrical Engineering, Federal University of Rio de Janeiro, Postal Box 68504, Rio de Janeiro, RJ (Brazil)

2010-09-15

269

Modeling and control of a three-phase isolated grid-connected converter for photovoltaic applications/ Modelagem e controle de um conversor trifásico conectado à rede para aplicações fotovoltáica  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este artigo descreve a modelagem e o controle de um conversor trifásico conectado à rede alimentado por um conjunto fotovoltaico. O conversor é composto de um estágio CC-CC isolado um estágio CC-CA. São obtidas funções de transferência com as quais são projetados três sistemas de controle em malha fechada: um para a tensão de entrada do arranjo de painéis solares, um para a tensão do do barramento de tensão contínua e outro para as correntes trifásicas de saída. Abstract in english This paper describes the modeling and control of a three-phase grid-connected converter fed by a photovoltaic array. The converter is composed of an isolated DC-DC converter and a three-phase DC-AC voltage source inverter The converters are modeled in order to obtain small-signal transfer functions that are used in the design of three closed-loop controllers: for the output voltage of the PV array, the DC link voltage and the output currents. Simulated and experimental results are presented.

Villalva, Marcelo Gradella; Espindola, Marcos Fernando; Siqueira, Thais Gama de; Ruppert, Ernesto

2011-06-01

270

Modeling and control of a three-phase isolated grid-connected converter for photovoltaic applications Modelagem e controle de um conversor trifásico conectado à rede para aplicações fotovoltáica  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the modeling and control of a three-phase grid-connected converter fed by a photovoltaic array. The converter is composed of an isolated DC-DC converter and a three-phase DC-AC voltage source inverter The converters are modeled in order to obtain small-signal transfer functions that are used in the design of three closed-loop controllers: for the output voltage of the PV array, the DC link voltage and the output currents. Simulated and experimental results are presented.Este artigo descreve a modelagem e o controle de um conversor trifásico conectado à rede alimentado por um conjunto fotovoltaico. O conversor é composto de um estágio CC-CC isolado um estágio CC-CA. São obtidas funções de transferência com as quais são projetados três sistemas de controle em malha fechada: um para a tensão de entrada do arranjo de painéis solares, um para a tensão do do barramento de tensão contínua e outro para as correntes trifásicas de saída.

Marcelo Gradella Villalva; Marcos Fernando Espindola; Thais Gama de Siqueira; Ernesto Ruppert

2011-01-01

271

Efficiency optimal control for AC drives with PWM inverters  

Energy Technology Data Exchange (ETDEWEB)

For electrical drives using pulsewidth modulation (PWM) inverters and ac motors, methods for efficiency optimal control (EOC) have been developed. They are based on the most complete motor models, including such features as rotor skin effect. Furthermore, new solutions for selected harmonic elimination (SHE) are given. These new solutions come close to EOC. Also, it has been found that EOC solutions (although basically load-dependent as opposed to SHE) do not vary much with the motor used or the motor model applied. Even using a simple R-L series circuit as motor model does not change the solutions much. It is found that using the solutions gained from such a simple model is not more than two points off the real optimum based on a very complete motor model. (For this definition, the absolute harmonic loss minimum is given as zero points, the overall maximum as 100 points with a linear scale in between.) Therefore, one can use one EOC solution for all motors with sufficient accuracy, or, as second best solution, the new form of SHE. Therefore, the EOC solution can be judged load-independent. The implementation by microprocessor-based systems is as easy for other PWM methods. EOC for three and five switching angles per quarter period is discussed, as well as the new solutions for SHE for up to nine angles.

Zach, F.C.; Ertl, H.

1985-07-01

272

A new method for the experimental determination of three-phase relative permeabilities  

International Nuclear Information System (INIS)

Petroleum reservoirs under primary, secondary or tertiary recovery processes usually experience simultaneous flow of three fluids phases (oil, water and gas). Reports on some mathematical models for calculating three-phase relative permeability are available in the Literature. Nevertheless, many of these models were designed based on certain experimental conditions and reservoir rocks and fluids. Therefore, special care has to be taken when applying them to specific reservoirs. At the laboratory level, three-phase relative permeability can be calculated using experimental unsteady-state or steady state methodologies. This paper proposes an unsteady-state methodology to evaluate three-phase relative permeability using the equipment available at the petrophysical analysis Laboratory of the Instituto Colombiano del Petroleo (ICP) of Ecopetrol S.A. Improvements to the equipment were effected in order to achieve accuracy in the unsteady-state measurement of three-phase relative permeability. The target of improvements was directed toward to the attainment of two objectives:1) the modification of the equipment to obtain more reliable experimental data and 2) the appropriate interpretation of the data obtained. Special attention was given to the differential pressure and uncertainty measurement in the determination of fluid saturation in the rock samples. Three experiments for three-phase relative permeability were conducted using a sample A and reservoir rock from the Colombian Foothills. Fluid tests included the utilization of synthetic brine, mineral oil, reservoir crude oil and nitrogen. Two runs were conducted at the laboratory conditions while one run was conducted at reservoir conditions. Experimental results of these tests were compared using 16 mathematical models of three-phase relative permeability. For the three-phase relative permeability to oil, the best correlations between experimental data and tests using Blunt, Hustad Hasen, and Baker's models were obtained at oil saturations between 40% and 70%.

2008-01-01

273

Selection of a conventional power distribution transformer as a voltage source for saline chambers; Seleccion de un transformador de distribucion convencional como fuente de voltaje en camaras salinas  

Energy Technology Data Exchange (ETDEWEB)

In the Mexico`s Gulf Coast and in the North East part of the country there are severe pollution problems on the electric distribution power systems insulators. To solve this problem, in specialized laboratories are reproduced the pollution conditions for their quantitative and qualitative analyses. In general terms, for this purpose special voltage transformers have been used that, for being imported, are very expensive; furthermore there is no defined selection criterion that allows the voltage source to supply the current recommended by the IEC (International Electrotechnical Commission). In this article, a proposal is presented to select a transformer that fulfills the IEC requirements. This equipment, because of its acquisition easiness and economy, permits that any teaching or research institution have a voltage source that allows the experimentation of the pollution phenomena at a minimum cost. [Espanol] En la costa del Golfo de Mexico y en el noroeste del pais hay severos problemas de contaminacion en los aisladores de los sistemas electricos de distribucion. Para solucionar este problema, se reproducen, en laboratorios especializados, las condiciones de contaminacion para su analisis cualitativo y cuantitativo. En general, con este proposito se han utilizado transformadores especiales de voltaje que por ser de importacion son muy costosos; ademas, no existe un criterio definido de seleccion que permita suministrar a la fuente de voltaje la corriente recomendada por el IEC (International Electrotechnical Commission). En este articulo se presenta una propuesta para seleccionar un transformador que cumpla con los requerimientos del IEC. Esta, por su facilidad de adquisicion y economia, permite que cualquier institucion docente o de investigacion cuente con una fuente de voltaje que permita la experimentacion de los fenomenos contaminantes con un costo minimo.

Garza Macias, Anibal [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

1988-12-31

274

A new PWM based control method for forced commutated cycloconverters  

International Nuclear Information System (INIS)

[en] Highlights: ? A new control method is proposed for three-phase to single-phase cycloconverters from balanced and unbalanced input voltages. ? The proposed method has no limitation on frequency conversion and is independent of the load. ? In proposed method, the low order harmonics are not generated in the input and output quantities. ? The proposed method can be easily extended to three-phase to n-phase cycloconverters. ? We demonstrate real experimental results of the power converter. - Abstract: In this paper, a new control method is proposed for three-phase to single-phase cycloconverters for synthesizing the desired output voltage from balanced and unbalanced input voltages. The theoretical analysis of the proposed control method is given for both of the conventional topologies of three-phase to single-phase cycloconverters. Using the proposed control method, the maximum output/input voltage transfer ratios are 0.5 and 1.5 for conventional cycloconverters that consist of three and six bidirectional switches, respectively. The proposed control method has no limitation on frequency conversion and is independent of the load. In other words, using the proposed control method, the three-phase to single-phase cycloconverter can operate as a generalized transformer. Using the proposed control method, the low order harmonics are not generated in the input and output quantities. As a result, the size of the required filters is decreased. The proposed control method can be easily extended to three-phase to n-phase cycloconverters based on the same principle of the operation. The simulation and experimental results verify the operation and performance of the proposed control method.

2012-01-01

275

Fast asymmetrical three-phase load flow based on symmetrical component  

International Nuclear Information System (INIS)

This paper deals with the three-phase asymmetrical load-flow problem. It presents a solution of this problem in the sequence domain, which is more efficient than standard solutions in both the phase and the sequence domain. It specially copes with asymmetrical states of unbalanced power systems. The efficiency is achieved by introducing the following basic advancements of the standard asymmetrical load-flow calculations: 1 - Elimination of phase-shifts from the sequence circuits of three-phase transformers; 2 - Enhancement of the standard classification of power systems buses to provide a correct treatment of Q limits enforcement; 3 - Synthesizing of buses of the generators and step-up transformers in the transformers high voltage buses; thus, reducing the form of the three-phase asymmetrical load-flow models to the form of symmetrical models. The efficiency of the presented solution in memory, CPU time and robustness is confirmed on the basis of several examples. (Original)

2001-01-01

276

Three-phase bone scan in osteomyelitis and other musculoskeletal disorders.  

UK PubMed Central (United Kingdom)

The three-phase bone scan is very sensitive and is the study of choice in the evaluation of patients with suspected osteomyelitis and normal radiographs. If the underlying bone pathology, such as a healing fracture or degenerative disease, is detected on radiographs of the bone, the indium-111-labeled autologous leukocyte scan is the most cost-effective second study. When fracture of the long bones is clinically suspected but radiographs are normal and a delay in definitive diagnosis is acceptable, it is practical and economical to take follow-up films in 10 to 14 days. In cases requiring prompt diagnosis or when follow-up radiographic films are not diagnostic, the three-phase bone scan is the most cost-effective study. The three-phase bone scan is also used in the evaluation of occupational and sports injuries, including shin splints, stress and occult fractures, enthesiopathies and reflex sympathetic dystrophy.

Sutter CW; Shelton DK

1996-10-01

277

Three-phase bone scan in osteomyelitis and other musculoskeletal disorders.  

Science.gov (United States)

The three-phase bone scan is very sensitive and is the study of choice in the evaluation of patients with suspected osteomyelitis and normal radiographs. If the underlying bone pathology, such as a healing fracture or degenerative disease, is detected on radiographs of the bone, the indium-111-labeled autologous leukocyte scan is the most cost-effective second study. When fracture of the long bones is clinically suspected but radiographs are normal and a delay in definitive diagnosis is acceptable, it is practical and economical to take follow-up films in 10 to 14 days. In cases requiring prompt diagnosis or when follow-up radiographic films are not diagnostic, the three-phase bone scan is the most cost-effective study. The three-phase bone scan is also used in the evaluation of occupational and sports injuries, including shin splints, stress and occult fractures, enthesiopathies and reflex sympathetic dystrophy. PMID:8857786

Sutter, C W; Shelton, D K

1996-10-01

278

A Novel Unit Power Factor Rectifier Based on Three-phase Digital PLL  

Directory of Open Access Journals (Sweden)

Full Text Available A novel three-phase phase-locked loop solution is proposed based on D-Q transformation aiming at the AC-DC rectifier with high efficiency and high power factor. The phase-locked loop is implemented digitally using the Xilinx blockset integrated with Matlab/Simulink. The three-phase digital phase-locked loop (TDPLL) is elaborately designed with the parameters defined in detail. The AC-DC converter (rectifier) model with the TDPLL is built and simulated in the high-speed VHS-ADC simulation platform from Canada. The simulation and test results show the TDPLL is locked right after the different three-phase voltage disturbances and very suitable for control of the rectifier with high parallelism through space vector pulse width modulation (SVPWM).  

Xuegui Zhu; Zhihong Fu; Xiangfeng Su

2013-01-01

279

Harmonics reduction of three-phase boost rectifier by modulating duty ratio  

Energy Technology Data Exchange (ETDEWEB)

Line currents of three-phase diode bridge rectifier suffer from high THD. This THD is higher than IEEE standards. Injection of six harmonic components from the DC bus back to the duty ratio of the boost converter connected to the three-phase diode bridge rectifier reduces the THD of the utility line current. In this study a sine wave and a triangle wave with six times the fundamental frequency is presented. The analysis has been carried out to reduce THD of the utility line current of three-phase boost rectifier. The THD of the utility line currents depends on the amplitude and phase-shift of the six-order component injected to the duty ratio of the boost converter. A complete mathematical and simulation analysis of the injection technique has been carried out. The mathematical analysis and simulation results of 6 kW prototype system show the superiority of the proposed injection technique. (author)

Eltamaly, Ali M. [Electrical Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421 (Saudi Arabia)

2007-08-15

280

Chaotic Recurrence Analysis of Oil-Gas-Water Three-phase Flow in Vertical Upward Pipe  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the conductance fluctuating signals of oil/gas/water were analyzed by using nonlinear chaotic recurrence, were obtained four kinds of recurrence quantification indicator, recurrence rate, determinism, average length of diagonal segment, entropy which got the transition law of the oil/gas/water three-phase flow patterns in vertical upward pipe. Specific process was: Firstly the C-C algorithm was used to determine phase space embedding dimension and time delay of nonlinear time series, then the method of using the time series data generated by the Lorenz equation to verify the sensitivity of recurrence quantification analysis was presented, finally the chaotic recurrence analysis method was used to identify three-phase flow patterns. The results show that: the texture of chaotic recurrence plot can reflect the oil/gas/water three-phase flow pattern evolution, the recurrence quantification indicator with the phase flow are more sensitive.

Ying-Wei Li; Na Xie; Ling-Fu Kong

2011-01-01

 
 
 
 
281

Note: A simple correlation to locate the three phase coexistence line in methane-hydrate simulations  

Science.gov (United States)

In this Note, the three phases coexistence (hydrate-water-methane) temperature is determined by using direct coexistence simulations for a force field in which methane is described by a single Lennard-Jones site, and water is described by either SPC or SPC/E models. Results were obtained for two pressures: 100 and 400 bars. The results of this note along with those obtained in our previous work [M. M. Conde and C. Vega, J. Chem. Phys. 133, 064507 (2010)] allow to present the three phases coexistence line for a number of water models: SPC, SPC/E, TIP4P, TIP4P/2005, and TIP4P/Ice. A correlation between the three phases coexistence temperature T3 of the methane hydrate and the melting point of ice at normal pressure Tm of the water model is found. Models with a good prediction of the melting temperature of ice Ih, have also good predictions of the three phases coexistence line. Models with a bad prediction of the melting temperature of ice Ih, provide poor estimates of T3. As a rule of thumb, the three phase coexistence line of the methane hydrate at 100 bars for a water-methane force field is located approximately at about 15(7) K above the melting temperature of ice Ih of the considered water model. In summary, when modeling the methane-hydrate, if you are looking for a three phases coexistence line in good agreement with experiment, you need first a water model that describes accurately the melting temperature of ice Ih.

Conde, M. M.; Vega, C.

2013-02-01

282

Area Based Approach for Three Phase Power Quality Assessment in Clarke Plane  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents an area-based approach for electric power quality analysis. Some specific reference signals have been defined and areas formed by the real power system data with the reference signal have been calculated wherefrom contributions of fundamental waveform and harmonic components have been assessed separately. Active power, reactive power and total harmonic distortion factors have been measured. Clarke transformation technique has been used for analysis in three-phase system, which has reduced the computational effort to a great extent. Distortion factors of individual phase of a three-phase system have also been assessed.

S. CHATTOPADHYAY; M. MITRA; S. SENGUPTA

2008-01-01

283

Fuzzy Logic Closed Loop Control of 5 level MLI Driven Three phase Induction motor  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals about fuzzy logic control of closed loop controlled five level Multi Level Inverter (MLI) driven three phase induction motor. Three phase Induction motor is most widely used drive in Industries, so needs proper control of speed. Induction motor is fed from five level multilevel inverter which is controlled by fuzzy logic. The closed loop consists of two loops. First inner loop is current loop and second outer loop is speed loop. The torque is varied at different times and corresponding change in speed and Total Harmonic Distortion (THD) is observed. The MLI is controlled by Sinusoidal Pulse Width Modulation (SPWM) Technique

Mulukutla Venkata Subramanyam; P.V.N. Prasad; G.Poornachandra Rao

2013-01-01

284

A new method for redundancy analysis of measurements applied to three-phase state estimation  

Energy Technology Data Exchange (ETDEWEB)

In this paper, a new method based on the properties of the Gram matrix is proposed to verify the redundancy of measurements in three-phase state estimation. The Gram matrix is constructed using rows of the measurement Jacobian matrix as vectors. The method can be used for measurement systems planning or updating of three-phase networks so that the overall system remain observable even under possible branch contingencies and loss of measurements. It is a fast and robust numerical method based on the Gram matrix factorization that is easy to implement. A small numerical example that shows the application of the method is presented. (author)

de Almeida, Madson C.; Garcia, Ariovaldo V. [Av. Albert Einstein, 400, 13083-852 Campinas, SP (Brazil); Asada, Eduardo N. [Av. Trabalhador Sao-carlense, 400, 13566-590 Sao Carlos, SP (Brazil)

2009-01-15

285

Juvenile Dermatomyositis Diagnosed by 99mTc-HDP Three-phase Bone Scintigraphy  

International Nuclear Information System (INIS)

[en] Juvenile dermatomyositis is a common inflammatory muscle disease of childhood, characterized by weakness in proximal muscles and specific skin rash. In case of juvenile dermatomyositis without characteristic clinical features, non-invasive imaging tools such as 99mTc-HDP three-phase bone scan are very helpful in diagnostic workup of myopathies. We report a case of 13-year old female with juvenile dermatomyositis, in which 99mTc-HDP three-phase bone scan was useful in diagnosis and assessing therapy response

2009-01-01

286

Juvenile Dermatomyositis Diagnosed by {sup 99m}Tc-HDP Three-phase Bone Scintigraphy  

Energy Technology Data Exchange (ETDEWEB)

Juvenile dermatomyositis is a common inflammatory muscle disease of childhood, characterized by weakness in proximal muscles and specific skin rash. In case of juvenile dermatomyositis without characteristic clinical features, non-invasive imaging tools such as {sup 99m}Tc-HDP three-phase bone scan are very helpful in diagnostic workup of myopathies. We report a case of 13-year old female with juvenile dermatomyositis, in which {sup 99m}Tc-HDP three-phase bone scan was useful in diagnosis and assessing therapy response.

Kim, Ja Hye; Song, Ho Chun; Yoo, Su Ung; Ha, Jung Min; Chong, A Ri; Oh, Jong Ryool; Min, Jung Joon; Bom, Hee Seung; Jeong, Eun Hui; Lee, Min Chul [Chonnam National University Hospital, Gwangju (Korea, Republic of)

2009-12-15

287

Three-Phase Modulated Pole Machine Topologies Utilizing Mutual Flux Paths  

DEFF Research Database (Denmark)

This paper discusses three-phase topologies for modulated pole machines (MPMs). The authors introduce a new threephase topology, which takes advantage of mutual flux paths; this is analyzed using 3-D finite-element methods and compared to a three-phase topology using three single-phase units stacked axially. The results show that the new “combined-phase MPM” exhibits a greater torque density, while offering a reduction in the number of components. The results obtained from two prototypes are also presented to verify the concept; the results show that the “combined-phase” machine could provide both performance and constructional benefits over prior MPM topologies.

Washington, Jamie G.; Atkinson, Glynn J.

2012-01-01

288

Voltage angle lock loop control of the boost type PWM converter for HVDC application  

Energy Technology Data Exchange (ETDEWEB)

High voltage direct current (HVDC) transmission is based on line-commutated technologies. The advent of high power, high frequency, solid-state switches with fast, gate turn-off capabilities suggests that pulsewidth modulated (PWM) techniques can soon be introduced to HVDC applications. A boost type PWM converter with voltage angle lock control that is tailored to the utility environment is described. Experimental results from 1-kVA size models show that the advantages are substantial.

Ooi, B.T.; Wang, X. (McGill Univ., Montreal, PQ (Canada). Dept. of Electrical Engineering)

1990-04-01

289

HIGH EFFICIENCY BRIDGELESS PWM CUK CONVERTER WITH SOFT SWITCHING TECHNIQUE  

Directory of Open Access Journals (Sweden)

Full Text Available High efficiency bridgeless single-phase ac-dc PWM cuk converter with soft-switching (ZVS) technique is proposed. This paper emphasizes more on the converter efficiency. The conduction losses and input current harmonics of the proposed converter is very less due to the absence of the input diode bridge and also during each switching cycle, only two semiconductor switches are present in the current path unlike other conventional Cuk converters. Soft switching (ZVS)technique is applied by using an auxiliary circuit to improve the efficiency of the proposed converter. Output voltage regulating control technique is provided to regulate the output which also ultimately improves the efficiency. Power factor is almost unity due to less input current harmonics. The circuit configuration, principle of operation, design procedure and simulation results are presented.

ANJAN KUMAR SAHOO, SARIKA KALRA, NITIN SINGH

2013-01-01

290

Voltage Control of Variable Speed Induction Generator Using PWM Converter  

Directory of Open Access Journals (Sweden)

Full Text Available The paper describes a simple control structure for astand-alone Induction Generator (IG) used to operate undervariable speeds. Fuzzy Logic Control (FLC) has been developed toautomatically vary the duty-cycle of the PWM converter such thatto maintain the DC-link voltage constant. The required reactivepower for the variable-speed IG is supplied by means of the PWMconverter and a capacitor bank to build up the voltage of the IGwithout the need for a battery and to reduce the rating of the PWMconverter with the need for only three sensors. This proposedscheme has been used efficiently for variable speed wind or hydroenergy conversion systems. The measurements of the IG system atvarious speeds and loads are given and show that this proposedsystem is capable of good DC voltages regulation. The proposedsystem has been simulated using MATLAB-SIMULINK softwareand verified the theoretical analysis.

Sivakami.P; Karthigaivel.R; Selvakumaran.S

2013-01-01

291

CARRIER OVERLAPPING PWM METHODS FOR ASYMMETRICAL MULTILEVEL INVERTER  

Directory of Open Access Journals (Sweden)

Full Text Available Multilevel inverter has gained attention in recent years due to its high power capability associated with lower output harmonics. Several multilevel topologies have been reported in the literature and thispaper focuses on asymmetric cascaded multilevel inverter employing Carrier Overlapping PWM (COPWM) technique. This technique provides reduced harmonics in the output voltage and significantly improves the root mean square value of the output voltage compared to the conventional Sinusoidal Pulse Width Modulation (SPWM). A detailed study of the proposed modulation technique is carried out throughMATLAB/SIMULINK for Total Harmonic Distortion (THD). An experimental seven-level inverter test rig has been built to implement the proposed algorithm. Gating signals are generated using PIC microcontroller. The performance of the inverter has been analyzed and compared with the result obtained from theory and simulation.

DR.R.SEYEZHAI

2011-01-01

292

Soft-switching PWM DC-DC converter with reduced circulating current; Junkan denryu wo teigenshita soft switching PWM DC-DC converter  

Energy Technology Data Exchange (ETDEWEB)

Soft-switching phase-shifted PWM converters have been attracted much attention because of their low switching losses, constant frequency operation and simple control. However, a circulating current flows through the transformer and the primary bridge circuit during the freewheeling interval, resulting in relatively high current stresses for the transformer and switching devices compared with those of conventional hard-switching PWM converters. This paper presents an improved soft-switching PWM DC-DC converter which can substantially reduce the circulating current by employing a tapped inductor for output low-pass filter. The principle of operation and the role of the tapped inductor are illustrated. The effectiveness of the tapped inductor is evaluated through simulating analysis. Moreover, a 500W-100kHz prototype converter is implemented to demonstrate the excellent performances of both low switching and low conduction losses. 11 refs., 12 figs.

Hamada, S. [Sansha Electric Mfg. Co. Ltd., Osaka (Japan)

1996-01-20

293

Advances in modeling and applications of three-phase power converters  

Energy Technology Data Exchange (ETDEWEB)

In open power markets, power transmission and distribution must be reliable, flexible and economical. These objectives can be achieved with Flexible AC Transmission Systems (FACTS). However, FACTS technology relies on accurate information regarding the topology, modeling and control of power converters. This thesis presents a new modeling approach based on nonlinear transformation to derive linear models for 3-phase PWM power converters which are independent of the operating point. Linear controllers were designed for quick and decoupled control during operation. New topologies for FACTS controllers were also proposed for current-source converters. These new modeling and control approaches were applied to the Static Synchronous compensator (STATCOM) along with other techniques to verify the validity and performance of the current-source converter-based STATCOM and the Static Synchronous Series Compensator.

Ye, Y.

2002-07-01

294

A New parallel Resonant DC-Link Inverter for Soft Switched PWM  

Energy Technology Data Exchange (ETDEWEB)

A novel soft switching PWM converter for high frequency AC/DC power conversion is presented by using a new parallel resonant dc-link(PRDCL) and by adopting single phase soft switching(SPSS) technique. The new PRDCL provides variable link pulse position as well as variable link pulse width, which is quite different feature from the other resonant dc-links and thus the PWM capability can be remarkably increased. The SPSS technique is also adopted for further enhancement of PWM capability. Moderate combination of two soft switching operations enables the conventional space vector PWM technique to be used. Due to distinctive advantages including true PWM capability, minimum device voltage stresses(all Vs) and reasonable additional device count(3 devices), the proposed converter can be operated in a wide power range(20-200 KW). Operational principles, analyses and the realization of a space vector PWM of the proposed converter are presented. Simulation results are also shown to verify the operational principle. (author). 15 refs., 14 figs.

Cho, J.G.; Kim, H.S.; Cho, G.H. [Korea Advanced Energy Research Inst., Daeduk-Danji (Korea, Republic of). Korea Nuclear Safety Center

1993-03-01

295

Modeling and Control of Three-Phase Shunt Active Power Filter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this research the performance of a three-phase shunt active power filter (APF) using Model Reference Controller (MRC) has been compared with that using instantaneous active and reactive (p-q) theory. The novelty of this research lies in the application of MRC to generate the amplitude of the refe...

Moleykutty George; Kartik P. Basu

296

Three-Phase Boost Active Power Factor Correction for Diode Rectifiers.  

Science.gov (United States)

This report documents an investigation and implementation of a 3 kW active power factor correction (pfc) design used to enable a diode rectifier to draw sinusoidal line currents with nearly unity power factor from a three-phase utility grid. The design ut...

J. G. Nairus

1996-01-01

297

Three-phase scintigraphy in epicondylitis of the lateral lower humerus  

International Nuclear Information System (INIS)

Ten patients with tennis elbow were examined by three-phase scintigraphy, using sup(99m)Tc-MDP. In agreement with the histological findings of H. Schneider (14), there was no uptake during the perfusion and soft tissue phase. In the phase, there was focal bone uptake in one patient only. (orig.)

1982-01-01

298

A Protection Scheme for Three-Phase Induction Motor from Incipient Faults Using Embedded Controller  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study presents a protection scheme for three-phase induction motor from incipient faults using embedded microcontroller. The induction motor experiences several types of electrical faults like over/under voltage, over load, phase reversing, unbalanced voltage, single phasing and earth fault. Du...

M. Sudha; P. Anbalagan

299

Three-phase Single Switch Power Factor Correction Circuit with Harmonic Reduction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A harmonic injection technique, which reduces the line frequency harmonics of the single switch three-phase boost rectifier, has been implemented. In this method, a periodic voltage is injected in the control circuit to vary the duty cycle of the rectifier switch within a line cycle so that the fift...

S.M. Bashi; N. Mariun; S.B. Noor; H.S. Athab

300

Analysis of a Three Phase Induction Motor Directly from Maxwell's Equations  

CERN Multimedia

The torque developed in a three phase AC squirrel cage motor is usually expressed in terms of resistances and reactances of the stator, the rotor, and the motor as a whole. We use Maxwell's equations to find the torque in terms of geometrical parameters. This allows us to estimate the torque developed by a motor without knowing the details of its circuitry.

Bhattacharjee, Shayak

2011-01-01

 
 
 
 
301

Harmonic Wave Analysis and Suppression Research on Three-phase SPWM Inverter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The output voltage of the Sinusoidal Pulse Width Modulation (SPWM) inverter contains various ultra harmonics. It increases the system’s power consumption and generates the harmonic interference. By establishing the mathematical model of the three-phase inverter and doing the FFT transformation o...

Hui Xie; Hongbing Li; Heping Liu; Qiang Chen

302

Field Performance of Three-Phase Amorphous Metal Core Distribution Transformers at Pearl Harbor, Hawaii.  

Science.gov (United States)

As part of a 3-year project sponsored by the Naval Facilities Engineering Command (NAVFAC) and Office of Naval Research (ONR), eight prototype three-phase amorphous metal core distribution transformers (three 75-k and five 150-kVA units) were installed at...

J. Franchi

1990-01-01

303

Verification of Buckley-Leverett three-phase theory using computerized tomography  

Energy Technology Data Exchange (ETDEWEB)

The mathematical extension of the Buckley-Leverett (B-L) theory to three immiscible fluids was presented by Grader and O`Meara (1988). However, the three-phase flow extension of the theory has not previously been experimentally demonstrated. Fluid flow experiments are conducted through uniform glass bead packs using three immiscible liquids: water, benzyl alcohol and decane. In some experiments decane is injected into a core saturated with water and benzyl alcohol and in other experiments water is injected into a core saturated with all three phases. The recovered fluid volumes are used to calculate the in-situ saturations by applying the three-phase extension of the B-L theory. These saturations are then compared against in-situ saturations determined using X-ray computerized tomography (CT). The results show good agreement between the phase saturations determined by these two independent methods even for cases when double shocks are formed during the displacement process. They also show that the measurement of three-phase relative permeabilities using the extension of the B-L theory has both sound theoretical and experimental bases

Siddiqui, S.; Hicks, P.J.; Grader, A.S. [Pennsylvania State University, Petroleum Engineering Department, University Park, PA (United States)

1996-07-20

304

Measurements of communication signal propagation on three phase power distribution lines  

Energy Technology Data Exchange (ETDEWEB)

In this paper measurements of voltages and currents for distribution line carrier signals on a three phase power distribution network are presented. Both symmetric and asymmetric lines are used under loaded and unloaded conditions. Conclusions are drawn from the resulting standing wave patterns about carrier signal propagation over such lines.

Suh, J.D.; Hardy, M.E.; Ardalan, S.; O' Neal, J.B. Jr. (North Carolina State Univ., Raleigh, NC (United States)); Shuey, K.C. (Westinghouse Electric Corp., Raleigh, NC (United States)); Gale, L.J. (Carolina Power and Light Co., Raleigh, NC (United States))

1991-07-01

305

A model for communication signal propagation on three phase power distribution lines  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this paper is to describe a theoretical model for determining the signal strength of communication signals on three phase power distribution lines. This model has been implemented in software. The model is used to compute voltage and current as functions of the distance from the signal source for several different power line configurations. The data so generated are compared with measurements.

Hardy, M.E.; Ardalan, S.; O' Neal, J.B. Jr. (North Carolina State Univ., Raleigh, NC (United States)); Gale, L.J. (Carolina Power and Light Co., Raleigh, NC (United States)); Shuey, K.C. (Westinghouse Electric Corp., Raleigh, NC (United States))

1991-07-01

306

Adaptive RBF Neural Network Control for Three-Phase Active Power Filter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An adaptive radial basis function (RBF) neural network control system for three?phase active power filter (APF) is proposed to eliminate harmonics. Compensation current is generated to track command current so as to eliminate the harmonic current of non?linear load and improve the quality of the pow...

Juntao Fei; Zhe Wang

307

Numerical Dosimetry of Induced Phenomena in the Human Body by a Three-Phase Power Line  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We computed by finite element the fields induced in an heterogeneous model of the human body by both the electric and magnetic field generated by a three-phase power line. Results were partially validated and analyzed by comparison with existing data with uniform magnetic field. Induced currents due...

Hoang, Le Ha; Scorretti, Riccardo; Burais, Noël; Voyer, Damien

308

Fibrous structured catalytic beds for three-phase reaction engineering Hydrodynamics study in staged bubble columns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Woven fibrous materials are proposed as structured catalysts for three-phase catalytic reactors. The design of a catalytic bed arranged as a plate bubble column is discussed. The hydrodynamic parameters, like pressure drop and liq. hold-up were found to depend on the woven structure of the fibrous l...

Holler, V.; Wegricht, D.; Kiwi-Minsker, L.; Renken, A.

309

Three-phase drive for a DT3 motor-coach of the Hamburger Hochbahn AG  

Energy Technology Data Exchange (ETDEWEB)

BBC equipped a three-car underground railway vehicle of the Hamburger Hochbahn AG with a static inverter and rugged three-phase squirrel-cage motors. Compared with conventional drive systems, the new drive concept features a high degree of reliability, energy savings and low maintenance costs. This article contains information on the drive equipment and proves its suitability for the drive system.

Gemmeke, K.; Mueller, E.; Runge, W.; Schulze, H.; Steimel, A.

1980-01-01

310

The fuel properties of three-phase emulsions as an alternative fuel for diesel engines  

Energy Technology Data Exchange (ETDEWEB)

The pollutants emitted from diesel engines (in particular nitrogen oxides and particulate matter) are detrimental to the health of living beings and ecological environment have been recognized as the major air pollution source in metropolitan areas and have thus attracted much research interest. Although diesel oil emulsion has been considered as a possible approach to reduce diesel engine pollutants, previous relevant applications were restricted to two-phase emulsions. Three-phase emulsions such as oil-in-water-in-oil briefly denoted as O/W/O emulsions and water-in-oil-in-water, denoted as W/O/W, have not been used as an alternative fuel for any combustion equipment. Studies on the properties of three-phase emulsion as fuel have not been found in the literature. The emulsification properties of an O/W/O three-phase diesel fuel emulsion were investigated in this experimental study. The results show that the mean drop size of the O/W/O emulsion was reduced significantly with increasing homogenizing machine revolution speed. An increase in inner phase proportion of the O/W/O emulsion resulted in increasing the emulsion viscosity. The viscosity of O/W/O emulsion is greater than that for water-in-oil (denoted briefly as W/O emulsion) for the same water content. More stable emulsion turbidity appeared for three-phase O/W/O diesel emulsions added with emulsifier with HLB values ranging from 6 to 8. In addition, three-phase O/W/O emulsions with greater water content will form a larger number of liquid droplets, leading to a faster formation rate and greater emulsion turbidity at the beginning but a faster descending rate of emulsion turbidity afterwards. The potential for using O/W/O emulsions as an alternative fuel for diesel engines was also evaluated. 15 refs., 11 figs., 7 tabs.

Cherng-Yuan Lin; Kuo-Hua Wang [National Taiwan Ocean University, Keelung (Taiwan). Department of Marine Engineering

2003-07-01

311

Dynamic modeling of PWM and single-switch single-stage power factor correction converters  

Science.gov (United States)

The concept of averaging has been used extensively in the modeling of power electronic circuits to overcome their inherent time-variant nature. Among various methods, the PWM switch modeling approach is most widely accepted in the study of closed-loop stability and transient response because of its accuracy and simplicity. However, a non-ideal PWM switch model considering conduction losses is not available except for converters operating in continuous conduction mode (CCM) and under small ripple conditions. Modeling of conduction losses under large ripple conditions has not been reported in the open literature, especially when the converter operates in discontinuous conduction mode (DCM). In this dissertation, new models are developed to include conduction losses in the non-ideal PWM switch model under CCM and DCM conditions. The developed model is verified through two converter examples and the effect of conduction losses on the steady state and dynamic responses of the converter is also studied. Another major constraint of the PWM switch modeling approach is that it heavily relies on finding the three-terminal PWM switch. This requirement severely limits its application in modeling single-switch single-stage power factor correction (PFC) converters, where more complex topological structures and switching actions are often encountered. In this work, we developed a new modeling approach which extends the PWM switch concept by identifying the charging and discharging voltages applied to the inductors. The new method can be easily applied to derive large-signal models for a large group of PFC converters and the procedure is elaborated through a specific example. Finally, analytical results regarding harmonic contents and power factors of various PWM converters in PFC applications are also presented here.

Zhu, Guangyong

312

Fracture healing: Quantitative three-phase bone scintigraphy as a prognostic factor  

International Nuclear Information System (INIS)

Aim: Careful clinical examination and conventional radiography, together with other standard methods for evaluation of bone fracture healing, are frequently inconclusive. Furthermore, it is difficult to predict the complications of healing on the basis of clinical and radiographic findings only. Bone scintigraphy plays an important role in detecting bone fractures. This method is very sensitive, but not enough specific. The aim of this work was to evaluate the role of three-phase bone scintigraphy in the healing prognosis of long bone fractures. Material and Methods: We evaluated the three elements (perfusion, blood pool and static image) of three-phase bone scintigraphy in early prognosis of the course of fracture healing in patients with fractures of femur or tibia. Three-phase bone scintigraphy was performed in 73 patients. The patients were divided into 4 groups according to X-ray and clinical examination: 1) Non operated patients with stable fracture, 2) Operated patients with unstable fracture (infection), 3) Fractures with delayed union, 4) Patients with pseudoarthrosis. Using region of interest (ROI) method we compared the activity on the site of fracture with the activity on the symmetrical place in the healthy bone. The relative indices for each group of patients and for each element of three-bone scintigraphy were calculated in order to make possible the follow up of the fracture healing and to obtain data for prognosis and evaluation of possible complications. Results: The most valuable results were obtained by quantitative analysis of perfusion data immediately after trauma and 2-3 weeks later. Our results show a high diagnostic accuracy in identifying infection by perfusion scintigrams immediately after trauma. The perfusion indices obtained immediately and after 2-3 weeks could predict delayed union after the trauma. Quantitative analysis of blood pool phase gave no data of clinical significance in distinguishing various pathologies. Conclusion: Our results indicate that the three-phase bone scintigraphy is a useful method when complications of fracture healing are expected. In these cases radiography gives only a partial insight into the state of bone union, but no information about the healing process. So, the increasing use of three-phase bone scintigraphy is quite understandable. Nevertheless, as most of the fractures heal regularly, we would not advise the three-phase bone scintigraphy as a routine procedure.

2002-10-02

313

Existence of three-phase interlines on a cerium dioxide surface  

CERN Document Server

The three-phase interline described by a statistical continuum limit (i.e. quasi-boundary) has been postulated to gain a deeper insight into the reduction of CeO2 to CeO1.940 in a LiCl-KCl eutectic melt. Fabrication of a CeO2 superstructure by a condensed-phase method provided a CeO2 (111) surface at the nanoscale, which allowed the three-phase interline to be identified given previously reported quantum confinement effects in quasi-stoichiometric CeO2 nanoparticles. Also, the CeO2 superstructure displays the same crystal lattice planes as a bulk CeO2 grain but the triply degenerate Raman-active peak of the grain is higher by a factor of ~ 2.5 with a wider full width at half maximum.

Osarinmwian, Charles

2013-01-01

314

99mTc-gluconate three-phase imaging for diagnosis of lung cancer  

International Nuclear Information System (INIS)

99mTc-gluconate lung imagings were performed in 121 cases which included 55 of lung cancers, 49 of benign lesions and 17 of normal controls. In 78 cases of them, three-phase lung imaging was performed and the uptake ratio (UR) and cancer index (LCI) were calculated. Using the values higher than the mean UR + 2SD in healthy persons as a criterion of positive uptake, the percentages of postive uptake in lung cancers and in benign lesions were 98.2% and 61.2% respectively. The difference between them was statistically significant (P99mTc-gluconate three-phase lung imaging is a valuable detecting method for patients with suspected lung cancer.

1989-01-01

315

Transient analysis of three-phase induction machine using different reference frames  

Directory of Open Access Journals (Sweden)

Full Text Available Three-phase induction machines are generally used as motors for many industrial applications and all this is due to its simple construction and other advantages in contrast to other machines. Popularity of these motors has resulted into a lot of research including the transient behavior of the machine. Literature survey reveals that most of the researchers adopted only a single reference frame to estimate transient behavior of the machine. In this paper qd axis based modeling is proposed to analyze the transient performance of three-phase squirrel cage induction motor using stationary reference frame, rotor reference frame and synchronously rotating reference frame. Simulated results have been compared and verified with experimental results on a test machine. A close agreement between the simulated and experimental results proves the validity of proposed modeling. The proposed system has been developed using MATLAB/SIMULINK.

Vivek Pahwa; K.S. Sandhu

2009-01-01

316

Performance Comparison of Three-Phase Shunt Active Power Filter Algorithms  

Directory of Open Access Journals (Sweden)

Full Text Available The usage of parallel converters is ever increasing. However, the voltage and current harmonics, zero-sequence and negative- sequence components of voltage and current and reactive power present in parallel converters give an alarming signal to power system and power electronic engineers. This research discusses performance of three-phase shunt active power filter (APF) system using three different control techniques namely synchronous detection algorithm (SDM), instantaneous active and reactive (p-q) theory and instantaneous direct and quadrature (d-q) current method for the control of zero and negative sequence components, reactive power and harmonics. The novelty of this research lies in the successful application of SDM based APF and (d-q) current method APF for the control of reactive power, harmonics and negative and zero sequence currents resulted by the use of parallel three-phase converters. MATLAB 6.1 toolbox is used to model the systems.

Moleykutty George; Kartik P. Basu

2008-01-01

317

Application of Generalized Instantaneous Reactive Power Theory for Three-Phase Four-Wire System  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a concept of generalized theory of instantaneous imaginary power is proposed for a three-phase four-wire system. Unlike instantaneous reactive power theory in which a complexmathematical transformation is used for controlling action of shunt active power filters. The proposed control strategy is simple and further to reduced its complexity the line current vector is decomposed into two orthogonal components without mathematical transformations. The developed control strategy has been tested for three-phase four-wire system feeding non-linear load. The obtained results show satisfactory performance for a number of actual system conditions such as load changing of non-linear load. The THD (total harmonic distortion) on supply side with shunt active power filter complies with IEEE harmonic standard, which validates the satisfactory implementation of proposed theory.

Ajay Kumar Maurya; Yogesh K Chauhan

2012-01-01

318

Unified Constant-frequency Integration Control of Three-phase Standard Bridge Boost Rectifier  

UK PubMed Central (United Kingdom)

In this paper, a three-phase six-switch standard boostrectifier with unity-power-factor-correction is investigated. Ageneral equation is derived that relates input phase voltage andduty ratios of switches in continuous conduction mode. Based onone of solutions and using One-Cycle Control, a UnifiedConstant-frequency Integration (UCI) controller for powerfactor-correction (PFC) is proposed. For the standard bridgeboost rectifier, unity-power-factor and low total-harmonicdistortion(THD) can be realized in all three phases with asimple circuit that is composed of one integrator with resetalong with several flips-flops, comparators, and some logic andlinear components. It does not require multipliers and threephasevoltage sensors, which are used in many other controlapproaches. In addition, it employs constant switchingfrequency modulation that is desirable for industrialapplications. The proposed control approach is simple andreliable. Theoretical analysis is verified by simulation andexperimental results.

Chongming Qiao; Keyue M. Smedley

319

Modeling and control of three phase rectifier with electronic smoothing inductor  

DEFF Research Database (Denmark)

This paper presents a simple, direct method for deriving the approximate, small-signal, average model and control strategy for three-phase diode bridge rectifier operating with electronic smoothing technique. Electronic smoothing inductor (ESI) performs the function of an inductor that has controlled variable impedance. This increases power factor (PF) and reduces total harmonic distortions (THDs) in mains current. The ESI based rectifier enables compact and cost effective design of three phase electric drive as size of passive components is reduced significantly. In order to carry out stability and voltage regulation studies, the average, small-signal, dynamic model and control strategy of the ESI is developed and validated by simulation and laboratory measurements.

Singh, Yash Veer; Rasmussen, Peter Omand

2011-01-01

320

Axial dispersion of the liquid phase in a three-phase Karr reciprocating plate column  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of the gas flow rate and vibration intensity in the presence of the solid phase (polypropylene spheres) on axial mixing of the liquid phase in a three phase (gas-liquid-solid) Karr reciprocating plate column (RPC) was investigated. Assuming that the dispersion model of liquid flow could be used for the real situation inside the column, the dispersion coefficient of the liquid phase was determined as a function of different operating parameters. For a two-phase liquid-solid RPC the following correlation was derived: DL = 1.26(Af)1.42 UL0.51 eS0.23 and a similar equation could be applied with ± 30 % confidence for the calculation of axial dispersion in the case of a three-phase RPC: DL = 1.30(Af)0.47 UL0.42 UG0.03eS-0.23.

LJUBISA B. NIKOLIC; VESNA D. NIKOLIC; VLADA B. VELJKOVIC; MIODRAG L. LAZIC; DEJAN U. SKALA

2004-01-01

 
 
 
 
321

Diesel-electric MaK locomotive DE 501 with three-phase AC power transmission  

Energy Technology Data Exchange (ETDEWEB)

Krupp MaK Maschinenbau GmbH, Kiel, has developed a new diesel electric standard locomotive with BBC three-phase AC power transmission. The three-axle locomotive with a driving engine output of 500 kW is destined for heavy shunting service with industrial and connecting railways, where working and economical advantages are to be expected by the special features of the three-phase AC technique. Out of the first series of 20 locomotives some are already brought into operation with different clients on the home market and in foreign countries. In completion of the new diesel electric standard programme a bogie locomotive having a driving engine capacity of 1120 kW is under construction.

Ditting, G.

1981-05-01

322

Dynamic\tmodelling of catalytic three-phase reactors for hydrogenation and oxidation processes  

Directory of Open Access Journals (Sweden)

Full Text Available The dynamic modelling principles for typical catalytic three-phase reactors, batch autoclaves and fixed (trickle) beds were described. The models consist of balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. Rate equations, transport models and mass balances were coupled to generalized heterogeneous models which were solved with respect to time and space with algorithms suitable for stiff differential equations. The aspects of numerical solution strategies were discussed and the procedure was illustrated with three case studies: hydrogenation of aromatics, hydrogenation of aldehydes and oxidation of ferrosulphate. The case studies revealed the importance of mass transfer resistance inside the catalyst pallets as well as the dynamics of the different phases being present in the reactor. Reliable three-phase reactor simulation and scale-up should be based on dynamic heterogeneous models.

Salmi T.; Wärnå J.; Toppinen S.; Rönnholm M.; Mikkola J.P.

2000-01-01

323

Improvement the Capacity of Cockcroft-Walton High Voltage Source from 300 kV/20 mA to 500 kV/20 mA for Accelerating Voltage of Electron Beam Machine  

International Nuclear Information System (INIS)

[en] The improvement capacity of Cockcroft-Walton high voltage source from 300 kV/20 mA to 500 kV/mA has been carrying out. To improve the capacity of high voltage source was done by means of increasing the stage number of voltage multiplier from 11 to 18 and its output voltage measuring resistance. Each stage of voltage multiplier consists of 2 capacitors and 2 circuits of high voltage diode. This voltage multiplier is constructed using main components of high voltage capacitor and high voltage diode each of 0.22 ?F/50 kV and UF 5408 respectively. To avoid stray discharge and corona it was provided with high voltage electrode and corona ring. The test result indicated that the output voltage obtained from 16 stages was 350 kV according to operating condition of 25 M? resistive load and first stage voltage of 28.5 kV with oscillator frequency of 24 Hz. That condition requires anode voltage and current of 5.5 kV and 2.5 A respectively. The no load test for 16 stages indicates 400 kV of output voltage and 28.5 kV first stage voltage. Efficiency of high voltage source was 48 % at 6.75 kW of output power. The expected test of 500 kV with 18 stages of voltage multiplier can not be carried out because of some restrictive of loading system. From the test result can be predicted that the output voltage of 500 kV with 18 stages of voltage multiplier requires 31.2 kV of first stage voltage. Then the expected high voltage source of Cockcroft-Walton is capable as accelerating voltage source for Electron Beam Machine with energy of 500 kV. (author)

2002-06-27

324

Computer Modeling of Three-Phase to Single-Phase Matrix Converter Using MATLAB  

Directory of Open Access Journals (Sweden)

Full Text Available A three-phase to single-phase matrix converter is modeled and investigated in the MATLAB environment in the present paper. Based on the state matrix vector, a mathematical analysis of the converter is performed giving the relation between the sinusoidal line voltage (current) and the output voltage (current). The results of the investigation are confirmed using computer simulation of the converter by the program product MATLAB.

Georgi Kunov; Mihail Antchev; Elissaveta Gadjeva

2010-01-01

325

Performance Analysis of three phases three wire Series Active Power Filter  

Directory of Open Access Journals (Sweden)

Full Text Available the aim of this paper is to investigate and study the performance analysis of the three phase three wire series active power filter. Auto-tuned filters give a better performance for harmonic mitigation, reactive power compensation and power factor correction as compared to the classic filters. This paper presents the simulation analysis to reduce the harmonic in the output voltage to improve the power quality.

As,ma Fatma Arif,; Dr.Jyoti Shrivastava,

2013-01-01

326

Transient analysis of a three phase induction motor with single phase supply  

Energy Technology Data Exchange (ETDEWEB)

The transient behaviour of a three phase induction motor operating with single phase supply and using capacitors as phase converter is considered. Instantaneous symmetrical components are used in modeling the motor with different stator connections, including the external capacitor. Digital simulation studies have been carried out for the system considered and the results are presented and discussed. The results presented include transient current and torque patterns under run-up conditions. Considerable oscillations in torque occur during run-up.

Murthy, S.S.; Berg, G.J.; Jha, C.S.; Singh, B.; Singh, B.P.

1983-01-01

327

Three Phase Induction Motor Faults Detection by Using Radial Basis Function Neural Network  

Directory of Open Access Journals (Sweden)

Full Text Available In the present study the Artificial Neural Network (ANN) technique for the detection of (bearing and stator inter turn faults) incipient faults in an induction motor bas been explored. Radial basis function approach has been used for ANN Training and test. Three phase instantaneous currents and angular velocity depending on rotor speed are utilized in proposed approach. An experimental setup is used to implement an online fault defector

Ahmed N. Abd Alla

2006-01-01

328

Study and updating of three phase separators of the gas-condensate-glycol mixture  

Energy Technology Data Exchange (ETDEWEB)

Results are presented of examination of the gravitational separators of gas-condensate-glycol. It is indicated that the losses of glycol from the apparatus are mainly due to its ablation with condensate. The previously developed technique for predicting the effectiveness of gravitational separators was corrected. In order to reduce the losses of glycol, a three phase separator was developed with coalescing stage made of porous adapters, as a result of which the ablation of glycol with condensate was reduced several times.

1983-01-01

329

Electronic and optical properties of three phases of titanium dioxide: Rutile, anatase, and brookite  

Energy Technology Data Exchange (ETDEWEB)

Using the self-consistent orthogonalized linear-combination-of-atomic-orbitals method in the local-density approximation, the electronic structure and the optical properties of three phases of titanium dioxide have been studied. For rutile, the calculated band structure, equilibrium lattice constant, and bulk modulus are in good agreement with other recent calculations and with experimental data. The results on the ground-state properties of anatase and brookite are reported. Compared with the rutile phase, anatase has similar ground-state properties except for a larger band gap, whereas brookite has relatively smaller bulk modulus. The optical properties of these three phases are also calculated using the band-structure results and compared with the available measurements. For the rutile phase, the anisotropic properties of the dielectric function are in good agreement with the reflectance spectroscopy. For the anatase phase, there are very limited experimental optical data for comparison. For the brookite phase, no experimental data are available. Our calculations show subtle differences in the optical properties of these three phases.

Mo, S.; Ching, W.Y. [Department of Physics, University of Missouri-Kansas City, Kansas City, Missouri 64110 (United States)

1995-05-15

330

Measurement of Reactive Power in Three-Phase Electric Power Systems by Use of Walsh Functions  

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 false false false MicrosoftInternetExplorer4 Normal 0 false false false MicrosoftInternetExplorer4 Normal 0 false false false MicrosoftInternetExplorer4 This paper presents a new method for measuring of three-phase reactive power (RP) in three-phase systems. Extraction of three-phase reactive power RP from entire instantaneous power signal is achieved by multiplication the phase instantaneous powers with the Walsh function(WF). This method simplifies the multiplication procedure required for the evaluation the tree-phase reactive power components due to the use of the peculiar properties of the WF. In contrast to the existing methods involving phase shift operation between the input voltage  and current signals  proposed measurement approach  does not require the phase shift  of the phase current signals to the 90 degrees with respect to the voltage signals. Limitations and proposals for future performance enhancements of the suggested method are also discussed.  Validity and effectiveness of the suggested method have been tested by use of a simulation tools developed on the base of “Matlab 6.5”. The results obtained demonstrate that the computational demands can be substantially reduced by using the proposed method.  

Adalet Abiyev

2010-01-01

331

A Simple and Direct Approach for Unbalanced Radial Distribution System three phase Load Flow Solution  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the study is to develop a simple and direct approach for unbalanced radial distribution system three-phase load flow solution .The special topological characteristics of unbalanced radial distribution networks have been fully utilized to make the direct three phase load flow solution possible. Two developed matrices-the node-injection to line section-current matrix and the line section-current to node-voltage matrix - and a simple matrix multiplication are used to obtain the three phase load flow solution. Due to the distinctive solution techniques of the proposed method, the time-consuming Lower Upper decomposition and forwardbackward substitution of the Jacobian matrix or admittance matrix required in the traditional load flow methods became not necessary. Therefore, the proposed method is observed as robust and time-efficient. Results obtained on 8 node and IEEE 13 node test systems demonstrate the validity of the proposed method. The proposed method has got good potential for the usage in distribution automation applications.

J.B.V. Subrahmanyam; C. Radhakrishna; K. Pandukumar

2010-01-01

332

Half bridge ZVS DC-DC converter with DCS PWM active clamp technique  

Directory of Open Access Journals (Sweden)

Full Text Available Half bridge (HB) dc–dc converter is an attractive topology for middle power level applications owing to its simplicity. This paper presents a new control scheme, to be known as duty-cycle shifted PWM (DCS PWM) control, is proposed and applied to the conventional HB dc–dc converters to achieve ZVS for one of the two switches without adding extra components and without adding asymmetric penalties of the complementary control. The concept of this new control scheme is shifting one of the two symmetric PWM driving signals close to the other, such that ZVS may be achieved for the lagging switch due to the shortened resonant interval. Moreover, based on the DCS PWM control, an active clamp branch comprising an auxiliary switch and a diode is added across the isolation transformer primary winding in the half bridge converter to achieve ZVS for the other main switch by utilizing energy stored in the transformer leakage inductance. Moreover, the auxiliary switch also operates at ZVS and ZCS conditions. In addition, the proposed topology with DCS PWM control eliminates the ringing resulting from the oscillation between the transformer leakage inductance and the switches junction capacitances during the off-time period. Therefore, the proposed converter has a potential to operate at higher efficiencies and switching frequencies.

JANAPATI SIVAVARA PRASAD

2012-01-01

333

DEVELOPMENT OF DIRECT TORQUE CONTROL MODELWITH USING SVI FOR THREE PHASE INDUCTION MOTOR  

Directory of Open Access Journals (Sweden)

Full Text Available Direct torque control method is one of the best control strategies which allow a torque control in steady state and transient operation of induction motor. The main aim of direct torque control strategies is to effectively control the torque and flux of induction motor. Direct torque control method made the motor more accurate and fasttorque control, high dynamic speed response and simple to control. This paper present the principle of the direct torque control for voltage source inverter fed induction motor drive, and switching table, amplitude selection of the hysterics band of torque and flux. and also this method based on space vector modulation And its considered as an alternative to field oriented control technique. direct torque control methods is the first technology to control the ‘real’ motor control variable of torque and flux. and its has also more advantage such as it not required a feedback device and also not need external excitation. The performance of direct torque controlmethod has been demonstrated by simulation using a simulation package in matlab.

MUKESH KUMAR ARYA; DR. SULOCHANA WADHWANI

2011-01-01

334

Performance Analysis of Fuzzy Flatness Based Speed Control of Three Phase Induction Motor  

Directory of Open Access Journals (Sweden)

Full Text Available Induction motor plays a vital role in engineering and industry. Induction motor offer a convenient means for controlling the operation of different equipment used in industry. Induction motor input supply will give from the voltage source inverter for its speed control purpose. If we connect induction motor directly to the AC supply its speed control will not applicable, so that we go inverter fed induction motor speed control. Gate pulse has been given by using FPGA processor. Fuzzy flatness program has been flashed in the FPGA processor for generating the gate pulse for VSI inverter. FPGA processor is directly fed to opto-coupler and the driver circuit and then it has given to VSI inverter. Her closed loop control has been achieved by using inductive type proximity sensor. In closed loop control when input voltage has been changed but speed of the induction motor has maintained constant. Fuzzy flatness based control is applied in the speed controller of induction motor. This method gives better efficiency of induction motor speed control. Fuzzy flatness controller method for induction motor gives better performance and reduces tracking error and reduces the torque ripple.

C.SASIKUMAR, DR. C.MUNIRAJ

2013-01-01

335

PWM-Statcom system additionally having active filter function  

Energy Technology Data Exchange (ETDEWEB)

The harmonic characteristics of static synchronous compensators (Statcom) were discussed with particular reference to the difference between symmetrical and asymmetrical modulation strategies that influence a quality of output waveform. The asymmetrical modulation strategy is the better approach in higher power factor applications such as alternating current (AC) motor drives. It was noted that in cases requiring a passive filter with a very large scale Statcom, a symmetrical modulation strategy is superior. Therefore, in this study, a symmetrical modulation was preferred for a neutral point clamped (NPC) pulse width modulation (PWM) inverter. Due to switching in a limited narrow frequency band, such output harmonics can be eliminated using a simple passive filter and harmonics such as the fifth and the seventh, can be suppressed using the proposed Statcom scheme in which the feedback signals for the fifth and seventh harmonics are injected into the Statcom. Using these feedback signals, the harmonics in the power system were significantly reduced. This result was also confirmed by simulation. It was concluded that, in addition to the proper operation of the Statcom, it is possible to perform an active filtering function . 10 refs., 1 tab., 9 figs.

Matsui, K.; Kojima, H.; Yamamoto, I.; Hasegawa, M. [Chubu Univ., Kasugai Aichi (Japan); Ando, K. [Nitto Kogyo Corp., Nagakute, Aichi (Japan)

2006-07-01

336

Design High Efficiency PWM Boost Converter for Wind Power Generation  

Directory of Open Access Journals (Sweden)

Full Text Available The uses of renewable power source toprovide electric power as an alternative become amajor consideration than the costly classical powersources. However, due to research on very lowmaintenancedesigns, small wind turbines becomingmore popularity than economical ways to bring thebenefits of power production to home.The efficiency, size, and cost are the primaryadvantages of switching DC-DC boost powerconverters; it is offer high efficiency performance andprovides power management circuit designers with theability to approach a broad range of designapplications with flexible and easy-to-implementsolutions in wind power generation systems.This paper presents a design method of boostingDC voltage from 7 Volts to 12 Volts, by using a highefficiency PWM DC-DC switching boost converter inthe wind power generation system for 5kW singlefamily home appliances.PowerSim simulation program is used to validateand improve the aggregate boost converter design andobtaining measurements. Results showed excellentresults regarding system behavior of higher efficiency,lower ripple voltage, and verifies the operation of theproposed drive system when applied to eitherresidential wind home applications.

SULAIMAN R. Diary; MUHAMMAD A. Aree

2010-01-01

337

A new control strategy to improve the performance of a PWM ac to dc converter under unbalanced operating conditions  

Energy Technology Data Exchange (ETDEWEB)

Abnormal harmonics of significant magnitude are generated at the output and input terminals of a PWM ac to dc converter under unbalanced operating conditions. A new control strategy is presented here to selectively cancel the generated lower order abnormal harmonics at the output and input terminals and thereby to preserve the high performance features of a PWM ac to dc converter. The proposed technique essentially involves computing the sequence components of the unbalanced input supply and suitably counter-unbalances the PWM gating signals of the converter switches to cancel the generated abnormal harmonics. The technique is essentially a feed forward approach and is suitable for higher power G.T.O. type PWM ac to dc converters. A procedure for implementing this technique in real time is discussed. Finally selected results are verified experimentally on a prototype PWM ac to dc converter.

Enjeti, P.N.; Choudhury, S.A. [Texas A and M Univ., College Station, TX (United States). Dept. of Electrical Engineering

1993-10-01

338

Isolated PDM and PWM DC-AC SICAMs[Pulse Density Modulated; Pulse Width Modulated  

Energy Technology Data Exchange (ETDEWEB)

In this report a class of isolated PDM and PWM DC-AC SICAMs is described, which introduce the audio reference only in the output stage. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitor. Isolation from the AC mains is achieved using a high frequency (HF) transformer, receiving the HF voltage pulses from the input 'inverter' stage and transferring them to the output 'rectifier+inverter' stage, which can use either PDM or PWM. The latter stage is then interfaced to the load using an output low-pass filter. Each of the dedicated stages is discussed in detail. Measurements on the master/slave PWM DC-AC SICAM prototype are presented to help benchmarking the performance of this class of SICAMs and identify the advantages and drawbacks. (au)

Ljusev, P.

2004-03-15

339

Synthesis of PWM and quasi-resonant DC-to-DC power converters  

Energy Technology Data Exchange (ETDEWEB)

Synthesis procedures for systematic construction of switched-mode DC-to-DC converter topologies in the two largest families-PWM (square-wave) and Quasi-Resonant (QR) - are developed in this thesis. The proposed synthesis procedure for PWM converter is based on a matrix representation of the converter topology and on general properties of PWM networks. The properties derived in the thesis include a constraint on the number of switches, a constraint on the number of reactances, and relations between the network complexity and attainable DC conversion ratios. The synthesis procedure starts with a set of desired specifications, which may include the DC conversion ratio, features of non-pulsating terminal currents and possible coupling of inductors, the number of reactances, the number of switches and, in particular, the number of active, transistor switches. Outputs of the procedure are all possible PWM converters that satisfy the required specifications. Quasi-Resonant converters - a family of DC-to-DC converters featuring zero-voltage or zero-current switching - are derived by adding two or more resonant elements to a two-switch PWM converter. Systematic synthesis of QR converters is based on extraction of all topologically distinct positions of resonant elements within a PWM converter. Addition of two resonant elements yields six classes of QR converters, two of which have not been identified before. Subject to different switch realizations and control timing, QR converters can exhibit vastly different behavior and properties. In particular, it is shown that a controllable rectifier can be used to achieve constant-frequency control in all QR converters. Unified DC analyses are completed for QR classes and operating modes of most practical interest.

Maksimovic, D.

1989-01-01

340

A three-phase microfluidic chip for rapid sample clean-up of alkaloids from plant extracts  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A three-phase microchip was developed for the rapid and efficient small-scale purification of alkaloids from plant extracts. As part of the development of such a three-phase microchip, first a two-phase microchip with two channels (3.2 cm and 9.3 cm) was used to study the extraction efficiency of st...

Tetala, K.K.R.; Swarts, J.W.; Chen, B.; Janssen, A.E.M.; Beek, T.A., van

 
 
 
 
341

Elimination of output voltage oscillations in DC-DC converter using PWM with PI controller  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper the SIMULINK model of a PWM controlled DC-DC converter is modeled using switching function concept to control the speed of the DC motor. The presence of the voltage oscillation cycles due to higher switching frequency in the DC-DC converter is identified. The effect of these oscillations on the output voltage of the converter, Armature current, Developed torque and Speed of the DC motor is analyzed. In order to minimize the oscillation cycles the PI controller is proposed in the PWM controller.

Sreenivasappa Veeranna Bhupasandra; Udaykumar Yaragatti

2010-01-01

342

A QRC-ZCS-PWM buck converter using a non-linear resonant inductor  

Energy Technology Data Exchange (ETDEWEB)

This paper shows a loss-less commutation cell that uses a non-linear resonant inductor. The principle of the non-linear resonant inductor is applied to a QRC-ZCS-PWM buck converter with objective of reducing the peak current in the main switch, maintaining the ZCS characteristics of the QRC-ZCS-PWM buck converter. This is achieved by un-saturating the core of the non-linear resonant inductor limiting its peak value. Mathematical equations, circuit operation and experimental results are also presented 4 refs., 16 figs., 1 tab.

Paiva, Elcio Precioso de; Freitas, Luiz Carlos de; Farias, Valdeir Jose; Coelho, Ernane Antonio Alves; Vieira Junior, Joao Batista [Uberlandia Univ., MG (Brazil). Dept. de Engenharia Eletrica

1995-12-31

343

Analysis of RF conducted emission due to PWM and resonant DC-DC converters  

Energy Technology Data Exchange (ETDEWEB)

Analysis and modeling of common mode conducted ElectroMagnetic Interference (EMI) in the Radio Frequency (RF) range (10 KHZ--30MHZ) of a ZVT (DC-DC boost Zero Voltage Transition) PWM converter and a conventional PWM (DC-DC boost) converter are compared. Noise signal measurement is carried out by means of a LISN (Line Impedance Stabilization Network). To compute the noise spectrum of LISN output in RF range, direct simulation of equivalent noise circuits is implemented as well as an analysis in the frequency domain.

Mahdavi, J. [Sharif Univ. of Technology, Tehran (Iran, Islamic Republic of). Dept. of Electrical Engineering; Shahintabe, A. [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Dept. of Electrical Engineering; Farhadi, A. [Electric Power Research Center, Tehran (Iran, Islamic Republic of). Dept. of Electronics

1995-12-31

344

Soft Switching Full-Bridge PWM DC/DC Converter Using Secondary Snubber  

Directory of Open Access Journals (Sweden)

Full Text Available A novel full-bridge PWM DC/DCconverter with controlled secondary side rectifier usingsecondary snubber is presented in this paper.Limitation of the circulating current as well as softswitching for all power switches of the inverter isachieved for full load range from no-load to shortcircuit by using controlled rectifier and snubber on thesecondary side. Phase shift PWM control strategy isused for the converter. The principle of operation isexplained and analyzed and the experimental resultson a 1kW, 50 kHz laboratory model of the converterare presented.

Jaroslav Dudrik; Vladimír Ruš?in; Marcel Bodor; Daniel Nistor Trip; Pavol Špánik

2009-01-01

345

Parallel implementation of DNA sequences matching algorithms using PWM on GPU architecture.  

UK PubMed Central (United Kingdom)

Positional Weight Matrices (PWMs) are widely used in representation and detection of Transcription Factor Of Binding Sites (TFBSs) on DNA. We implement online PWM search algorithm over parallel architecture. A large PWM data can be processed on Graphic Processing Unit (GPU) systems in parallel which can help in matching sequences at a faster rate. Our method employs extensive usage of highly multithreaded architecture and shared memory of multi-cored GPU. An efficient use of shared memory is required to optimise parallel reduction in CUDA. Our optimised method has a speedup of 230-280x over linear implementation on GPU named GeForce GTX 280.

Sharma R; Gupta N; Narang V; Mittal A

2011-01-01

346

Three-phase contact force equilibrium of liquid drops at hydrophilic and superhydrophobic surfaces.  

UK PubMed Central (United Kingdom)

Hydrophilic and superhydrophobic surfaces were obtained by modifying a dendritic Au surface with carboxyl- or methyl-terminated self-assembled monolayers, respectively. The hydrophilic surface generates capillary forces which induce water flow through the grooves defined by the dendritic structure, resulting in a halo structure; the superhydrophobic surface on the other hand completely repels water drops. The contrasting behaviors exhibited by the two surfaces with nominally identical morphology but different surface chemistry are explained semi-quantitatively in terms of the equilibrium of surface forces developing at the three-phase (air-solid-water) contact lines.

Zhu J; Zangari G; Reed ML

2013-08-01

347

Transient one-dimensional equilibrium three-phase, three-component flow  

Energy Technology Data Exchange (ETDEWEB)

A mathematical model of transient one-dimensional nonhomogeneous three-phase flow consisting of liquid, its steam, noncondensable gas and solid phase homogeneously dispersed in the liquid is described under the condition of thermodynamic equilibrium. The set of five equations is transformed into a nonconservative form. From the steady state system an expression defining the local critical mass flow rate is found. For the homogeneous case the set of five equations is transformed into canonical form. For both cases good agreement is obtained with existing theories for the limiting cases of a missing phase or component.

Kolev, N.I.

1985-01-01

348

Improving Output Voltage of the Three Phase Six-Switch Inverters  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a simple method for selecting the best conductive angle based on power factor of load in three phase six-switch inverters is proposed. Conductive angle from 120 to 180, and power factor from 0 to 1 are changed for lead and lag loads. Then RMS and THD values of the output voltage are studied. Simulation results show that a special conductive angle for each specific power factor has to be used to improve the mentioned indices and applying conventional conductive angles 120, 180 and 150 in some power factors increases THD and decreases RMS of output voltage.

Ebrahim Babaei; Mehdi Mahaei

2011-01-01

349

Hydraulic conductance and viscous coupling of three-phase layers in angular capillaries.  

UK PubMed Central (United Kingdom)

Predicting three-phase relative permeability by network models requires reliable models for hydraulic conductance of films and layers stabilized by capillary forces at the pore level. We solve the creeping flow approximation of the Navier-Stokes equation for stable wetting and intermediate layers in the corner of angular capillaries by using a continuity boundary condition at the layer interface. We find significant coupling between the condensed phases and calculate the generalized mobilities by solving cocurrent and countercurrent flow of wetting and intermediate layers. Finally, we present a simple heuristic model for the generalized mobilities as a function of the geometry and viscosity ratio.

Dehghanpour H; Aminzadeh B; DiCarlo DA

2011-06-01

350

Modeling and Control of Three-Phase Shunt Active Power Filter  

Directory of Open Access Journals (Sweden)

Full Text Available In this research the performance of a three-phase shunt active power filter (APF) using Model Reference Controller (MRC) has been compared with that using instantaneous active and reactive (p-q) theory. The novelty of this research lies in the application of MRC to generate the amplitude of the reference supply current required by the APF circuit and the successful implementation of the APF system for harmonic elimination. The entire system has been modeled using MATLAB 6.1 toolbox. Simulation results demonstrate the applicability of MRC for the control of APF.

Moleykutty George; Kartik P. Basu

2008-01-01

351

Simulation of the Double-closed Loop Three-phase Asynchronous Variable Voltage Control System  

Directory of Open Access Journals (Sweden)

Full Text Available When controlling the voltage and speed of the asynchronous motor, to expand the speed control range and reduce the speed fluctuation, the speed control system adopts two feedback control loops, i.e. the speed feedback control loop and the current feedback control loop. The principle and components of the double-closed loop three-phase asynchronous variable voltage control system are studied, and the simulation model and the test result based on MATLAB/Simulink are provided in this article through the system modeling and the parameter setup of the main circuit and the control circuit.

Shuhua Jiang

2011-01-01

352

Design and sub-beam phase measurement of Dammann grating with three-phase array output.  

UK PubMed Central (United Kingdom)

An improved type of Dammann grating (DG) that could generate an equal-intensity spot array which has only three phases is proposed. Numerical solutions of 1×4 and 1×5 such DGs are given. A 4×4 two-phase DG manufactured by very-large-scale integration (VLSI) techniques is presented. A phase-shift-interferometry-based technique that measures the intensity and sub-beam phases of beam splitting gratings is proposed. The performance measurements of the manufactured 4×4 two-phase DG using the proposed technique is carried out.

Li B; Zhi Y; Sun J; Zhang N; Zhou Y; Wang L; Hou P; Liu L

2013-08-01

353

Design and sub-beam phase measurement of Dammann grating with three-phase array output.  

Science.gov (United States)

An improved type of Dammann grating (DG) that could generate an equal-intensity spot array which has only three phases is proposed. Numerical solutions of 1×4 and 1×5 such DGs are given. A 4×4 two-phase DG manufactured by very-large-scale integration (VLSI) techniques is presented. A phase-shift-interferometry-based technique that measures the intensity and sub-beam phases of beam splitting gratings is proposed. The performance measurements of the manufactured 4×4 two-phase DG using the proposed technique is carried out. PMID:23903105

Li, Bing; Zhi, Ya'nan; Sun, Jianfeng; Zhang, Ning; Zhou, Yu; Wang, Lijuan; Hou, Peipei; Liu, Liren

2013-08-01

354

Three phase fluidized bed reactors: hydrodynamic characteristics and mixing of particles  

Energy Technology Data Exchange (ETDEWEB)

The hydrodynamic characteristics, i.e. fluidization minimum velocity, retentions of the various phases, and expansion rates, of a large three phase fluidized bed are determined. The variable parameters are the standing-by bed height, the superficial velocity of fluids, and the solid particle characteristics (density, dimension and shape). The fluids utilized are cyclohexane and nitrogen and the particles are industrial catalyst holders such as balls and alumina extrudates. This study is based on an electromagnetic measuring method of particle concentration which are traced at various levels in the column.

Fortin, Y.

1984-07-01

355

Direct torque control of six-phase induction motors using three-phase matrix converter  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new direct torque control (DTC) method for six-phase induction motor (SPIM). In the proposed method, direct torque and flux control are applied to the SPIM using matrix converter with the conventional three-phase source as its input. The new DTC scheme for SPIM benefits the advantages of both DTC and matrix converter, such as unity power factor and absence of dc-link. The simulation results show the effectiveness of the proposed method in both dynamic and steady state response.

Talaeizadeh, V., E-mail: valitalaeezadeh@yahoo.co [Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Kianinezhad, R.; Seyfossadat, S.G. [Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Shayanfar, H.A. [The Center of Excellence for Power System Automation and Operation, Department of Electrical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

2010-12-15

356

Modelling of droplet entrainment in annular two-fluid three-phase dispersed flow  

International Nuclear Information System (INIS)

[en] This paper deals with the derivation of a two-fluid three-phase model describing the mass and momentum conservation for each phase with the Population Balance framework replacing the mass conservation equation for the dispersed phase. The mass transfer phenomena due to droplet entrainment and deposition is successfully modelled and coupled with droplet drag effects, gas-film shear and wall friction. The traditional size-averaged droplet velocity was replaced by a velocity distribution. The complete model was solved using the least squares spectral method which solves all the equations simultaneously, yielding a faster convergence rate. (author)

2009-10-02

357

A laboratory grid simulator based on three-phase four-leg inverter : Design and implementation  

DEFF Research Database (Denmark)

This paper presents the design and implementation of a laboratory grid simulator which is used to test the grid-connected devices according to the strict standards. Three-phase four-leg inverter with direct voltage control in Natural Frame is adopted in this grid simulator, which significantly reduces the computing and realizing complexities. Proportional and resonant controller is utilized to regulate the output voltage. Furthermore, various feedback variables in the inner control loop are discussed and compared. The capacitor current feedback was identified to guarantee better stability and power quality. Experimental results verify the functionality and performances of the designed grid simulator.

Li, Fei; Wang, Xiongfei

2011-01-01

358

A Digital Phase Locked Loop Speed Control of Three Phase Induction Motor Drive: Performances Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with performance analysis and implementation of a three phase inverter fed induction motor (IM) drive system. The closed loop control scheme of the drive utilizes the Digital Phase Locked Loop (DPLL). The DPLL is safely implemented all around the well known integrated circuit DPLL 4046. An ex-perimental verification is carried out on one kw scalar controlled IM system drives for a wide range of speeds and loads appliance. This presents a simple and high performance solution for industrial applications.

Ben Hamed Mouna; Sbita Lassaâd

2011-01-01

359

Three-phase heaters with common overburden sections for heating subsurface formations  

Energy Technology Data Exchange (ETDEWEB)

A heating system for a subsurface formation is described. The heating system includes three substantially u-shaped heaters with first end portions of the heaters being electrically coupled to a single, three-phase wye transformer and second end portions of the heaters being electrically coupled to each other and/or to ground. The three heaters may enter the formation through a first common wellbore and exit the formation through a second common wellbore so that the magnetic fields of the three heaters at least partially cancel out in the common wellbores.

Vinegar, Harold J. (Bellaire, TX)

2012-02-14

360

Three-phase contact force equilibrium of liquid drops at hydrophilic and superhydrophobic surfaces.  

Science.gov (United States)

Hydrophilic and superhydrophobic surfaces were obtained by modifying a dendritic Au surface with carboxyl- or methyl-terminated self-assembled monolayers, respectively. The hydrophilic surface generates capillary forces which induce water flow through the grooves defined by the dendritic structure, resulting in a halo structure; the superhydrophobic surface on the other hand completely repels water drops. The contrasting behaviors exhibited by the two surfaces with nominally identical morphology but different surface chemistry are explained semi-quantitatively in terms of the equilibrium of surface forces developing at the three-phase (air-solid-water) contact lines. PMID:23726384

Zhu, Jianzhong; Zangari, Giovanni; Reed, Michael L

2013-05-06

 
 
 
 
361

Transient one-dimensional equilibrium three-phase, three-component flow  

International Nuclear Information System (INIS)

[en] A mathematical model of transient one-dimensional nonhomogeneous three-phase flow consisting of liquid, its steam, noncondensable gas and solid phase homogeneously dispersed in the liquid is described under the condition of thermodynamic equilibrium. The set of five equations is transformed into a nonconservative form. From the steady state system an expression defining the local critical mass flow rate is found. For the homogeneous case the set of five equations is transformed into canonical form. For both cases good agreement is obtained with existing theories for the limiting cases of a missing phase or component. (orig.)

1985-01-01

362

The effective conductivity of three-phase composite materials with circular cylindrical inclusions  

Energy Technology Data Exchange (ETDEWEB)

We extend the Rayleigh method for the calculation of the effective conductivity to three-phase composite materials. The materials under study consist of two types of circular cylinders in a periodic arrangement embedded in a matrix. Highly accurate values for lattice sums were obtained using algorithms which have been recently developed. A series of explicit formulations, which are used to facilitate the calculation of the effective conductivity of the composites under study, are reported. We also perform a series of numerical calculations to study the behaviour of these composites.

Moosavi, A; Sarkomaa, P [Department of Energy and Environmental Technology, Lappeenranta University of Technology, PO Box 20, Fin-53851, Lappeenranta (Finland)

2003-07-07

363

Three-Phase Buck Rectifier Using Snubber Energy Recovery Bridge Legs  

Science.gov (United States)

Three-phase buck rectifier using snubber energy recovery bridge legs is studied. The snubber capacitors assembled into the bridge legs are mainly charged and discharged under the resonance and the energy stored in them is transferred to the load circuit. Also, the currents flowing through power semiconductor devices are always limited to the dc current. The experimental prototype employing insulated-gate bipolar transistors is implemented to investigate the operation under the pulse-width modulation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor.

Itoh, Ryozo; Ishizaka, Kouichi

364

Instantaneous Active and Reactive Power Measuring Method in Three Phase Power System  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes an electronic means of measuring the instantaneous active and reactive power absorbed by any electrical equipment. The measurements are based on the Clark (a-b) and Park (d-q) transformations. The system is useful to teach electrical machines in Park’s coordinates and it allows also the study and control of some power electronics converters that are connected to three phase power network, such as static VAR compensator. The principle of the measuring method of the active and reactive power is described, and analyzed for different tests. The effectiveness of the proposed measuring method is confirmed by experimental investigation employing a test system.

A. TAHRI; Azeddine DRAOU

2005-01-01

365

Saturable reactor assisted soft-switching PWM DC-DC converter. Kahowa reactor hojo soft switching PWM DC-DC converter  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a new soft-switching PWM (pulse width modulation) full-bridge DC-DC converter which can overcome some of drawbacks by utilizing a small saturable reactor. The principle of operation and steady-state characteristics are presented. A role of the saturable reactor is also discussed. Moreover, the voltage and current stresses for active and passive components are mentioned. In order to verify the results, key experiments were conducted using a 350W, 500kHz prototype converter. Consequently, it was demonstrated that the converter achieves soft-switching in a wide load range without substantial increase in voltage and current stresses for active and passive components. From the merits and drawbacks of the present circuit system, this converter was found to have features of both conventional PWM converter and resonance type converter. 11 refs., 12 figs., 3 tabs.

Hamada, S. (Sansha Electric Mfg. Co. Ltd., Osaka (Japan)); Ogino, Y. (Osaka Institute of Technology, Osaka (Japan)); Nakaoka, M. (Kobe University, Kobe (Japan))

1992-12-20

366

Fuzzy Logic Controller Based Three-phase Shunt Active Filter for Line Harmonics Reduction  

Directory of Open Access Journals (Sweden)

Full Text Available Harmonic distortion is a form of electrical noise. It is a superposition of signals, which are of multiples of fundamental frequency. Proliferation of large power electronic systems results in increased harmonic distortion. Harmonic distortion results in reduction of power quality and system stability. This paper presents fuzzy control applicable for active power filter for three-phase systems, which are comprised of nonlinear loads. The active filter is based on a three-phase inverter with six controllable switches. The AC side of the inverter is connected in parallel with the other nonlinear loads through a filter inductance. The DC side of the inverter is connected to a filter capacitor. The Fuzzy Controller (FC) is used to shape the current through the filter inductor such that the line current is in phase with and of the same shape as the input voltage. The results of the computer simulation prove that the injected harmonics are greatly reduced, system efficiency and power factor are improved.

C. Sharmeela; M. R. Mohan; G. Uma; J. Baskaran

2007-01-01

367

Control Strategy of Three Phase Shunt Active Power Filter for Power Quality Improvement  

Directory of Open Access Journals (Sweden)

Full Text Available The increasing use of power electronics-based loads (adjustable speed drives, switch mode power supplies, etc.) to improve system efficiency and controllability is increasing the concern forharmonic distortion levels in end use facilities and overall power system. The application of passive tuned filters creates new system resonances which are dependent on specific system conditions. In addition, passive filters often need to be significantly over-rated to account for possible harmonic absorption from the power system.Passive filter ratings must be coordinated with reactive power requirements of the loads. Parallel (or shunt) active filters have been recognized as a valid solution to current harmonic and reactive power compensation of non-linear loads. The basic principle of Shunt Active Power filter is that it generates a current equal andopposite in polarity to the harmonic current drawn by the load and injects it to the point of coupling thereby forcing the source current to be pure sinusoidal. The control strategy is Synchronous Detection Algorithm. This technique relies in the fact that the three phase currents are balanced. The average power is calculated anddivided equally between the three phases. The signal is then synchronized relative to the mains voltage for each phase. Then the desired reference current is evaluated.

Angit Kumar.G; Ramesh Babu.U

2012-01-01

368

Hydrogen production with immobilized sewage sludge in three-phase fluidized-bed bioreactors.  

UK PubMed Central (United Kingdom)

Municipal sewage sludge was immobilized with a modified alginate gel entrapment method, and the immobilized cells were used to produce hydrogen gas in a three-phase fluidized bed. The hydrogen-producing fluidized beds were operated at different liquid velocity (U(0)) and hydraulic retention time (HRT). The results show that in response to operating liquid velocities, the fluidized-bed system had three flow regimes, namely, plug flow, slug flow, and free bubbling. Pressure fluctuation analysis was used to analyze the hydrodynamic properties in this three-phase fluidized bed when it was under a steady-state production of biogas. With a steady-state biogas production rate (U(g)) of 0.196 mL/s/L, a transition state occurred at a liquid velocity (U(0)) of 0.85 cm/s. As U(0) < 0.85 cm/s, the system was basically a nonhomogeneous fluidized bed, whereas the bed became homogeneous when U(0) was higher than 0.85 cm/s. The fluidized bed can be stably carried out at high loading rates (HRT as low as 2 h). Hydrogen fermentation results show that the maximal hydrogen production rate was 0.93 L/h/L and the best yield (Y(H)2(/sucrose)) was 2.67 mol H(2)/mol sucrose.

Wu SY; Lin CN; Chang JS

2003-05-01

369

Prediction of Riser Gas Holdup in Three- Phase External Loop Air Lift Fluidized Bed Reactor  

Directory of Open Access Journals (Sweden)

Full Text Available Hydrodynamics is an important issue for design and development of three phase external-loop airlift fluidized bed. This paper deals on the experimental investigations on the effect of superficial gas and liquid velocities and properties of solids on the riser gas holdup of a three phase external-loop airlift fluidized bed reactor and it was characterized using Newtonian and non Newtonian systems. Water, 65% and 85% of glycerol and n-butanol were used as Newtonian liquids and different concentration of Carboxyl Methyl Cellulose (CMC) i.e., 0.2%, 0.5% and 1% were used as non Newtonian liquids. Spherical glass beads, bearl saddles and rasching rings of different sizes were used as solid phase. The phase flow rates and properties of solid particle had significant effect on the hydrodynamic characteristics of the external-loop airlift fluidized bed reactor such as riser gas holdup. Unified correlations have been developed to estimate the riser gas holdup as a function of superficial phase velocities, properties of solid particle and physical properties of both Newtonian and Non-Newtonian liquid systems. The predicting ability of the correlations were tested with the experimental data and found to be good fit with an absolute average relative error (AARD) of ± 9.7 % for riser gas holdup.

Sivakumar Venkatachalam; Kannan Kandasamy; Akilamudhan Palaniappan

2010-01-01

370

Genetic Algorithm based Steady-State Analysis of Three-Phase Self-Excited Induction Generators  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a genetic algorithm based steady-state analysis of a three-phase self-excited induction generator (SEIG) for wind energy conversion. A generalized mathematical model based on inspection is developed for a three-phase induction generator for steady-state analysis. The proposed mathematical model is quite general in nature and can be implemented for any type of load such as resistive or reactive load. The proposed model completely avoids the tedious work of segregating real and imaginary components of the complex impedance of the equivalent circuit. Also, any equivalent circuit component can be easily included or eliminated from the model, if required. To carry out the steady-state analysis of SEIG, a genetic algorithm approach is used to find the unknown variables using the proposed model. The parameter sensitivity analysis of the generator is also carried out. The computed performance characteristics of the machine are compared with the experimentally obtained values on a laboratory machine, and a good correlation is observed.

S. Singaravelu,; S. Sasikumar

2012-01-01

371

Strictly hyperbolic models of co-current three-phase flow withgravity  

Energy Technology Data Exchange (ETDEWEB)

We study the character of the equations in the traditional formulation of one-dimensional immiscible three-phase flow with gravity, in the limit of negligible capillarity. We restrict our analysis to co-current flow required for a displacement process; in cases of mixed co-current and counter-current flow, capillarity effects cannot be dropped from the formulation. The model makes use of the classical multiphase extension of Darcy's equation. It is well known that, if relative permeabilities are taken as fixed functions of saturations, the model yields regions in the saturation space where the system of equations is locally elliptic. We regard elliptic behavior as a nonphysical artifact of an incomplete formulation, and derive conditions on the relative permeabilities that ensure strict hyperbolicity of the governing equations. The key point is to acknowledge that a Darcy-type formulation is insufficient to capture all the physics of three-phase flow and that, consequently, the relative permeabilities are functionals that depend on the fluid viscosity ratio and the gravity number. The derived conditions are consistent with the type of displacements that take place in porous media. By means of an illustrative example, we show how elliptic behavior can be removed, even when using simplistic relative permeability models.

Juanes, Ruben; Patzek, Tadeusz W.

2002-11-18

372

Alcohol vapour detection at the three phase interface using enzyme-conducting polymer composites.  

UK PubMed Central (United Kingdom)

Immobilisation of enzymes on a breathable electrode can be useful for various applications where the three-phase interface between gas or chemical vapour, electrolyte and electrode is crucial for the reaction. In this paper, we report the further development of the breathable electrode concept by immobilisation of alcohol dehydrogenase into vapour-phase polymerised poly(3,4-ethylene dioxythiophene) that has been coated onto a breathable membrane. Typical alcohol sensing, whereby the coenzyme ?-Nicotinamide adenine dinucleotide (NADH) is employed as a redox-mediator, was successfully used as a model reaction for the oxidation of ethanol. This indicates that the ethanol vapour from the backside of the membrane has access to the active enzyme embedded in the electrode. The detecting range of the sensor is suitable for the detection of ethanol in fruit juices and for the baseline breath ethanol concentration of drunken driving. After continuous operation for 4.5h the system only showed a 20% decrease in the current output. The electrodes maintained 62% in current output after being refrigerated for 76 days. This work is continuing the progress of the immobilisation of specific enzymes for certain electrochemical reactions whereby the three-phase interface has to be maintained and/or the simultaneous separation of gas from liquid is required.

Winther-Jensen O; Kerr R; Winther-Jensen B

2013-08-01

373

Design and Development of Gas-Liquid Cylindrical Cyclone Compact Separators for Three-Phase Flow  

Energy Technology Data Exchange (ETDEWEB)

The objective of this five-year project (October 1997--September 2002) was to expand the current research activities of Tulsa University Separation Technology Projects (TUSTP) to multiphase oil/water/gas separation. This project was executed in two phases. Phase I (1997--2000) focused on the investigations of the complex multiphase hydrodynamic flow behavior in a three-phase Gas-Liquid Cylindrical Cyclone (GLCC) Separator. The activities of this phase included the development of a mechanistic model, a computational fluid dynamics (CFD) simulator, and detailed experimentation on the three-phase GLCC. The experimental and CFD simulation results will be suitably integrated with the mechanistic model. In Phase II (2000--2002), the developed GLCC separator will be tested under high pressure and real crude conditions. This is crucial for validating the GLCC design for field application and facilitating easy and rapid technology deployment. Design criteria for industrial applications will be developed based on these results and will be incorporated into the mechanistic model by TUSTP.

Mohan, R.S.; Shoham, O.

2001-01-10

374

Perfect wetting along a three-phase line: Theory and molecular dynamics simulations  

Science.gov (United States)

Wetting behavior along a three-phase equilibrium has been obtained by density gradient theory (DGT) and molecular dynamics simulations for a type-II equal size Lennard-Jones mixture. In order to perform a consistent comparison between both methodologies, the molecular parameters of this type of mixture were defined from the global phase diagram of equal size Lennard-Jones mixtures. We have found excellent agreement between predictions from the DGT (coupled to a Lennard-Jones equation for the bulk phases) and simulations results for both the phase and interface behavior, in the whole temperature, pressure, and concentration ranges. For all conditions explored in this work, this type-II mixture shows a three-phase equilibrium composed by a bulk immiscible liquid phase (L1) and a bulk gas phase (G) separated by a second immiscible liquid phase (L2). A similar phase distribution is obtained from the interfacial concentration profile in the whole range of conditions used in this work. This type of structure is a clear evidence that L2 completely wets the GL1 interface. The wetting behavior is also confirmed by the values and evolution of the interfacial tensions. In summary, this kind of type-II mixture does not show wetting transitions and exhibits a permanent perfect wetting in all the thermodynamic conditions explored here.

Mejía, Andrés; Vega, Lourdes F.

2006-06-01

375

The utility of three-phase bone scintigraphy in the assessment of fractured carpal scaphoid  

Energy Technology Data Exchange (ETDEWEB)

Thirty-seven joints in 36 patients with a fractured carpal scaphoid were evaluated by three-phase bone scintigraphy. They were classified into two groups according to their progress. Some were in good clinical condition and some in a non-union condition. Increased blood flow in the radial arteries and ample perfusion on and around the scaphoid bones on blood flow images suggested a good clinical course. The activity and the effectiveness of remodeling correlated well with the degree of scaphoid uptake on blood pool images taken more than seven days after injury. Scaphoid uptake was more localized or there was almost none on blood pool images in cases with nearly complete recovery while it was amply visualized on static images. Blood pool images were indispensable for analyzing lesions and evaluating the clinical course. Two typical findings of scaphoid fractures were found on both blood pool and static images. One was diffusely increased scaphoid uptake seen in cases with a good clinical course, and the other was decreased uptake at proximal fragments seen in cases with non-union. It is concluded that three-phase bone scintigraphy provides useful information for evaluating the process of scaphoid fractures which cannot be obtained by means of conventional bone scintigraphy. (author).

Makino, Naoki; Takamatsu, Koichi (Toyota Memorial Hospital, Aichi (Japan)); Ishigaki, Takeo; Tsunoda, Kenji; Imaeda, Toshihiko; Nakamura, Ryogo

1993-09-01

376

Clinical study on three-phase bone scintigraphy of Kienboeck`s disease  

Energy Technology Data Exchange (ETDEWEB)

Three-phase bone scintigraphy was performed on 52 joints in 49 patients with Kienboeck`s disease. They were analyzed by Lichtman`s classification and by the prognosis made after radial wedge osteotomy. Radionuclide angiograms of 78 percent patients in good clinical prognosis after osteotomy showed increased ulnar blood flow, and 70 percent showed obvious perfusion of lunate. These findigns were not seen in fair or poor cases. This flow and perfusion were considered to be necessary for recovery from the disease. On blood-pool images, the intensity of the uptake area adjacent to lunate reflected the severity of the clinical condition of Kienboeck`s disease: that is, the degree and the extent of the uptake increased in proportion to the aggravation of the disease. That found in good cases of postoperative progress decreased significantly. Therefore, we believe that blood-pool image was indispensable for evaluating the prognosis of Kienboeck`s disease which couldn`t be demonstrated by plain radiography. Static images assisted us in defining osteoarthritis of the carpus, radius and ulna in degenerative cases. It is concluded that three-phase bone scintigraphy provides significant information to evaluate the pathology and the prognosis of Kienboeck`s disease. (author).

Nakao, Etsuhiro; Nakamura, Tatego; Imaeda, Toshihiko; Tsunoda, Kenji [Nagoya Univ. (Japan). Hospital; Makino, Naoki

1995-02-01

377

The utility of three-phase bone scintigraphy in the assessment of fractured carpal scaphoid  

International Nuclear Information System (INIS)

Thirty-seven joints in 36 patients with a fractured carpal scaphoid were evaluated by three-phase bone scintigraphy. They were classified into two groups according to their progress. Some were in good clinical condition and some in a non-union condition. Increased blood flow in the radial arteries and ample perfusion on and around the scaphoid bones on blood flow images suggested a good clinical course. The activity and the effectiveness of remodeling correlated well with the degree of scaphoid uptake on blood pool images taken more than seven days after injury. Scaphoid uptake was more localized or there was almost none on blood pool images in cases with nearly complete recovery while it was amply visualized on static images. Blood pool images were indispensable for analyzing lesions and evaluating the clinical course. Two typical findings of scaphoid fractures were found on both blood pool and static images. One was diffusely increased scaphoid uptake seen in cases with a good clinical course, and the other was decreased uptake at proximal fragments seen in cases with non-union. It is concluded that three-phase bone scintigraphy provides useful information for evaluating the process of scaphoid fractures which cannot be obtained by means of conventional bone scintigraphy. (author).

1993-01-01

378

Clinical study on three-phase bone scintigraphy of Kienboeck's disease  

International Nuclear Information System (INIS)

Three-phase bone scintigraphy was performed on 52 joints in 49 patients with Kienboeck's disease. They were analyzed by Lichtman's classification and by the prognosis made after radial wedge osteotomy. Radionuclide angiograms of 78 percent patients in good clinical prognosis after osteotomy showed increased ulnar blood flow, and 70 percent showed obvious perfusion of lunate. These findigns were not seen in fair or poor cases. This flow and perfusion were considered to be necessary for recovery from the disease. On blood-pool images, the intensity of the uptake area adjacent to lunate reflected the severity of the clinical condition of Kienboeck's disease: that is, the degree and the extent of the uptake increased in proportion to the aggravation of the disease. That found in good cases of postoperative progress decreased significantly. Therefore, we believe that blood-pool image was indispensable for evaluating the prognosis of Kienboeck's disease which couldn't be demonstrated by plain radiography. Static images assisted us in defining osteoarthritis of the carpus, radius and ulna in degenerative cases. It is concluded that three-phase bone scintigraphy provides significant information to evaluate the pathology and the prognosis of Kienboeck's disease. (author).

1995-01-01

379

Artificial neural network backpropagation model with three-phase annealing developed for the building energy predictor shootout  

Energy Technology Data Exchange (ETDEWEB)

An artificial neural network back propagation model with three-phase annealing was used for the first building energy prediction competition held by the American Society of Heating, Refrigerating and Air Conditioning Engineers in 1993. Three-phase annealing is an empirical method to gradually reduce the learning rate during the training period in order to improve accuracy in a relatively short time. In this paper, the preprocessing of the competition data, methods of back propagation training (including three phase annealing), modeling guidelines for the network, and results of the prediction are presented and discussed.

Kawashima, Minoru [Shimizu Corp., Tokyo (Japan). Inst. of Technology

1994-12-31

380

A comperative study on quality changes in positive, negative and combined switching strategies in control of three Phase Matrix Converter  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper has used positive, negative and combined switching strategies for three phase ac/ac matrix converter.the author compares these strategies. The performance comparison of these three strategies is made under balanced operation. The simulation of three phase matrix converter feeding a three phase load was accomplished by means of the matlab/simulink software. After the simulation the comparison of the waveforms THD in three switching sequence is done. It must be mentioned that the duty cycle of the whole switches in the converter is according to Venturini switching algorithm.

Mohammad Sarvi, Iman Soltani; Hossein Faramarzi

2013-01-01

 
 
 
 
381

The comparison of radiosensitivity of human lymphocytes stimulated with PHA Con A and PWM  

International Nuclear Information System (INIS)

The transformation, DNA strand breaks and its repair ability in human peripheral blood lymphocytes stimulated with PHA, Con A and PWM were respectively assessed following exposure to 60Co gamma rays by 3H-thymidine uptake and hydroxylapatite chromatography. It was showed the transformation of lymphocytes stimulated with PHA, Con A and PWM were suppressed by gamma rays and the dose-effect curves were biphase within the range of 0?8 Gy. The lymphocytes stimulated with PWM was the most resistant to gamma rays. The extent of DNA strand breaks in lymphocytes induced by gamma rays was linearly related to the dose within the range of 0?30 Gy and was identical in three kinds of lymphocytes. After post-irradiation incubation of 37 deg C, the DNA strand breaks could be repaired incompletely and after maxium repair the strand breaks were observed again. The repair ratio of strand breaks in the lymphocytes stimulated with PWM was the highest in the cells with three mitogens. The results showed that the difference of radiation effect on the transformation is probably related to the repair ability of DNA strand breaks.

1989-01-01

382

Propulsion system for Kwachon line of Korean National Railways (application of PWM converter to commuter car)  

Energy Technology Data Exchange (ETDEWEB)

With the development of the Korean economy and the population concentration in metropolitan areas, metropolitan Seoul is suffering from heavy traffic jams and needs to urgently expand its railway network as a mass transit system. In connection with this, the Kwachon Line is to be constructed to connect the Korean National Railways (KNR) line and Seoul Subway (SMSC) Line No. 4, and new dual-voltage electric multiple units (EMU) have been produced to offer a run-through service to the KNR line having an aerial power line of 25 kV AC and 60 Hz and the SMSC line having an aerial power line of 1500 V DC. This dual-voltage electric car is the first commuter-train adopting a PWM power converter-PWM inverter method to provide high frequency and power factor and to reduce high frequency. A reverse conducting GTO is adopted for the main circuit switching elements to miniaturize and reduce the number of components. Since this system is the first PWM power converter-PWM inverter method in Korea, it is structured with particular attention to its maintenance and handling. This paper introduces the outline and characteristics of this system.

Akiyama, Y.; Miyazaki, A. [Kanagawa Inst. of Tech. (Japan)

1994-12-31

383

The PWM auto-control circuit of neutron tube atmospheric pressure  

International Nuclear Information System (INIS)

[en] Ion source atmospheric pressure auto-control circuit for C/O logging neutron generator is introduced. The pulse circuit of ion source adopts zero-voltage quasi-resonant switch technique and the heating circuit for replenisher adopts PWM converter

1997-01-01

384

Active and reactive power control of a current-source PWM-rectifier using space vectors  

Energy Technology Data Exchange (ETDEWEB)

In this paper the current-source PWM-rectifier with active and reactive power control is presented. The control system is realized using space vector methods. Also, compensation of the reactive power drawn by the line filter is discussed. Some simulation results are shown. (orig.) 8 refs.

Salo, M.; Tuusa, H. [Tampere University of Technology (Finland). Department of Electrical Engineering, Power Electronics

1997-12-31

385

PWM-digital control of hydraulic actuator utilizing 2-way solenoid valves  

Energy Technology Data Exchange (ETDEWEB)

The objet of this study was to propose a mathematical model for the PWM-actuator system, to control digitally each types of hydraulic systems. This PWM hydraulic actuator system was made up of two 2-way solenoid valves operated in the PWM (pulse width modulation)-digital mode by a personal computer, a hydraulic actuator and pipes. The static and dynamic characteristics of the system were verified in comparison with experimental results, simulating numerically based on the proposed model. Main results were as follows: Representing the relationship between the valve displacement and the input voltage to the solenoid as a linear function with time lage existing between the input and output signals of the valves, the behavior of the on/off action of the solenoid valves were rationally described; hydraulic transient in the pipes connected with the solenoid valve could not be ignored while the valve were operated with high speed on/off action. It is necessary to attach importance to the natural frequency decreasing caused by existing of the element of pipes in the system on the view point of the resonance oscillation at PWM-digital control system. 8 references, 8 figures, 2 tables.

Muto, Takayoshi; Yamada, Hironao; Suematsu, Yoshikazu

1988-07-15

386

Double Two Switch Forward Soft Switching PWM DC-DC Converter  

Science.gov (United States)

A novel prototype of a double two-switch forward transformer linked zero-voltage and zero-current mode soft-switching (ZVZCS) pulse width modulation (PWM) DC-DC power converter using IGBTs for high power applications is presented. Based on a conventional two-switch forward transformer linked PWM DC-DC converter topology, this converter circuit configuration doesn't include any complex auxiliary resonant circuit. Combining two identical two-switch forward type DC-DC power conversion circuits with a tapped-inductor type DC smoothing filter into a power DC-DC conversion system makes it possible to achieve soft-switching conditions for the active power switches with aid of lossless snubber capacitors and transformer parasitic inductors. Lowered peak voltage across the power switching devices and their related peak current stresses, no transformer saturation effect, reducing of idle and circulating currents through circuit components are practically attained for this converter. This soft-switching PWM DC-DC power converter has some unique advantages such as better power conversion efficiency, lowered output DC ripple current, high power density, constant frequency PWM control scheme, cost effective and wide soft-switching operation range under load variations and PWM regulation settings for high power utilizations. The basic operating principle of the new soft switching power converter treated here is illustrated with approximate periodic steady-state circuit analysis for each mode equivalent circuit. The practical effectiveness of the proposed soft-switching DC-DC power converter is confirmed by the simulation results and is experimentally evaluated on basis of 500W-100kHz breadboard setup using the fast switching IGBTs.

Hamada, Satoshi; Moisseev, Serguei; Koudriavtsev, Oleg; Nakaoka, Mutsuo

387

Absorption in a three-phase fluidized bed I: Hydrodynamic investigations  

Directory of Open Access Journals (Sweden)

Full Text Available The hydrodynamic properties of a three phase fluidized bed with low density inert spherical packing, fluidized by the interaction of a gas flowing upwards and a liquid flowing downwards through the column, were investigated. It was found that the pressure drop, liquid hold up and dynamic bed height increase with both increasing liquid and gas flow rate. While the dynamic bed height and minimum fluidization velocity remain unchanged, both the pressure drop and liquid hold up increase with increasing density of the packing. Therefore, an increase in packing density causes more intensive mass transfer between the fluid phases than packed columns. It was shown that increase of the liquid flow rate causes an increase of both the effective liquid and gas velocity through the fluidized bed, which may also improve mass transfer.

Pejanovi? Sr?an M.

2003-01-01

388

Magnetoelectric effect of three-phase core-shell-matrix particulate multiferroic composites  

Science.gov (United States)

This paper studies the magnetoelectricity of a core-shell-matrix three-phase particulate composite made of piezoelectric (PE) and piezomagnetic (PM) phases. We propose a micromechanical model, the two-level recursive scheme in conjunction with Mori-Tanaka's method, to investigate the effective magnetoelectric coupling coefficients of the composite. We compare this micromechanical solution with those predicted by finite element analysis, which provides the benchmark results for a periodic array of inclusions. Both the magnitudes and trends between them are in good agreement. Based on this micromechanical approach, we show that, for the case of PE/PM/PM (core/shell/matrix) multiferroic composite, with a coating appropriate for the inhomogeneity, the effective magnetoelectric coupling can be enhanced many-fold as compared to the noncoated counterpart. Further, useful design principles are proposed for engineering magnetoelectric composites.

Kuo, Hsin-Yi; Wu, Tzu-Sheng

2012-03-01

389

Measurement and prediction of saturation-pressure relationships in three-phase porous media systems  

Energy Technology Data Exchange (ETDEWEB)

Scaled multiphase versions of the Brooks-Corey and van Genuchten retention functions were used to describe saturation-capillary pressure curves measured in air-water, air-organic liquid and organic liquid-water systems in a sandy porous medium for four organic liquids during monotonic wetting phase drainage. Scaling was achieved by a linear transformation of capillary pressures using scaling coefficients which are shown to be closely predicted by ratios of measured interfacial tensions, providing that the latter are measured on fluids having contacted the porous media system. The multiphase version for the van Genuchten function described the experimental data with slightly greater precision than the Brooks-Corey function for all four organic liquid systems. A technique is introduced to ensure that when two-phase saturation-capillary pressure measurements are used to predict fluid behavior in three-phase systems, the estimated parameters imply an invariate pore geometry pertinent to the description of a rigid porous medium.

Lenhard, R.J.; Parker, J.C.

1987-01-01

390

Design and Research on the LCL Filter in Three-Phase PV Grid-Connected Inverters  

Directory of Open Access Journals (Sweden)

Full Text Available Aiming at the problem of filtering in the three-phase PV grid-connected inverters, the mathematics models for L filter and LCL filter are established. The values of capacitances and inductances are calculated by analyzing the related constraint conditions for the main parameters of LCL filter. There are two ways to increase the value of damping resistor of the filter capacitor. The impacts on the stability and filtering property, in both ways, are analyzed. The simulation result indicated that the LCL filter achieve the best performance than L filter and LC filter. Under the prerequisite of increasing system stability, parallel resistor is even more advantageous than series resistor. And the validity of theoretical results is confirmed.

Xu Renzhong; Xia Lie; Zhang Junjun; Ding Jie

2013-01-01

391

Modeling of a three-phase reactor for bitumen-derived gas oil hydrotreating  

International Nuclear Information System (INIS)

[en] A three-phase reactor model for describing the hydrotreating reactions of bitumen-derived gas oil was developed. The model incorporates the mass-transfer resistance at the gas-liquid and liquid-solid interfaces and a kinetic rate expression based on a Langmuir-Hinshelwood-type model. We derived three correlations for determining the solubility of hydrogen (H2), hydrogen sulfide (H2S) and ammonia (NH3) in hydrocarbon mixtures and the calculation of the catalyst effectiveness factor was included. Experimental data taken from the literature were used to determine the kinetic parameters (stoichiometric coefficients, reaction orders, reaction rate and adsorption constants for hydrodesulfuration (HDS) and hydrodenitrogenation (HDN)) and to validate the model under various operating conditions. Finally, we studied the effect of operating conditions such as pressure, temperature, LHSV, H2/feed ratio and the inhibiting effect of H2S on HDS and NH3 on HDN. (author)

2012-01-01

392

Modeling and analysis of input characteristics of three phase inverter fed permanent magnet synchronous motor drive  

Energy Technology Data Exchange (ETDEWEB)

This paper models and analyzes a three phase permanent magnet synchronous motor (PMSM) used as a load in a distributed DC power system. The DC bus is supplied by a switching regulator which forms a source subsystem. The PMSM drive forms a load subsystem in order to analyze the interaction of the two subsystems at their interface, the output impedance of the source subsystem and input impedance of the load subsystem are very important. The input impedance characteristics of a motor working as a load subsystem are studied for the first time in this paper with a permanent magnet synchronous motor. Two commonly used operating modes of the motor are considered. Characteristics that are unique in nature are reported. Whether these characteristics can lead to interaction problems is analyzed.

Shrivathsan, M.S.P.; Lee, F.C.; Cho, B.H. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)

1995-12-31

393

Neuro-Fuzzy based Controller for a Three- Phase Four-Wire Shunt Active Power Filter  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the application of a novel neuro-fuzzy based control strategy which is used in order to improve the Active Power Filter (APF) dynamics to minimize the harmonics for wide range of variations of load current under various conditions. To improve dynamic behavior of a three phase four-wire shunt active power filter and its robustness under range of load variations, adaptive hysteresis band with instantaneous p-q theory is used with the inclusion of neural network filter for reference current generation and fuzzy logic controller for DC voltage control. The proposed control scheme for “split-capacitor” converter topology is simple and also capable of maintaining the compensated line currents balanced, irrespective of unbalancing in the source voltages & deviation in the capacitor voltages. The results presented in MATLAB-SIMULINK software in this paper clearly reflect the effectiveness of the proposed APF to meet the IEEE-519 standard recommendations on harmonic levels.

Mridul Jha; S.P. Dubey

2011-01-01

394

Probabilistic Breakdown Phenomenon at On-Ramp Bottlenecks in Three-Phase Traffic Theory  

CERN Multimedia

A nucleation model for the breakdown phenomenon in freeway free traffic flow at an on-ramp bottleneck is presented. This model, which can explain empirical results on the breakdown phenomenon, is based on assumptions of three-phase traffic theory in which the breakdown phenomenon is related to a first-order phase transition from the "free flow" phase to the "synchronized flow" phase. The main idea of this nucleation model is that random synchronized flow nucleation occurs within a metastable inhomogeneous steady state associated with a deterministic local perturbation in free flow, which can be considered "deterministic vehicle cluster" in free flow at the bottleneck. This deterministic vehicle cluster in free flow is motionless and exists permanent at the bottleneck due to the on-ramp inflow. In the nucleation model, traffic breakdown nucleation occurs through a random increase in vehicle number within this deterministic vehicle cluster, if the amplitude of the resulting random vehicle cluster exceeds some c...

Kerner, B S; Kerner, Boris S.; Klenov, Sergey L.

2005-01-01

395

Modeling of a three-phase reactor for bitumen-derived gas oil hydrotreating  

Directory of Open Access Journals (Sweden)

Full Text Available A three-phase reactor model for describing the hydrotreating reactions of bitumen-derived gas oil was developed. The model incorporates the mass-transfer resistance at the gas-liquid and liquid-solid interfaces and a kinetic rate expression based on a Langmuir-Hinshelwood-type model. We derived three correlations for determining the solubility of hydrogen (H2), hydrogen sulfide (H2S) and ammonia (NH3) in hydrocarbon mixtures and the calculation of the catalyst effectiveness factor was included. Experimental data taken from the literature were used to determine the kinetic parameters (stoichiometric coefficients, reaction orders, reaction rate and adsorption constants for hydrodesulfuration (HDS) and hydrodenitrogenation (HDN)) and to validate the model under various operating conditions. Finally, we studied the effect of operating conditions such as pressure, temperature, LHSV, H2/feed ratio and the inhibiting effect of H2S on HDS and NH3 on HDN.

R. Chacón; A. Canale; A. Bouza; Y. Sánchez

2012-01-01

396

Power Controllability of Three-phase Converter with Unbalanced AC Source  

DEFF Research Database (Denmark)

Three-phase DC-AC power converters suffer from power oscillation and overcurrentt problems in case of unbalanced AC source voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive and negative sequence currents. In this work a new series of control strategies which utilize the zero-sequence components are proposed to enhance the power control ability under this adverse conditions. It is concluded that by introducing proper zero sequence current controls and corresponding circuit configurations, the power converter can enable more flexible control targets, achieving better performances in the delivered power and load current when suffering from unbalanced AC sources.

Ma, Ke; Liserre, Marco

2013-01-01

397

Efficient Voltage Regulation in Three Phase A.C. Transmission Lines Using Static VAR Compensator  

Directory of Open Access Journals (Sweden)

Full Text Available Due to the rapid technological progress, the consumption of electric energy increases continuously. But the transmission systems are not extended to the same extent because building of new lines is difficult for environmental as well as political reasons. Hence, the systems are driven closer to their limits resulting in congestions and critical situations endangering the system security. Power Flow Control devices such as Flexible AC Transmission Systems (FACTS) provide the opportunity to in?uence power ?ows and voltages and therefore to enhance system security, e.g. by resolving congestions and improving the voltage pro?le. From the last few years static var compensator plays an important role in voltage regulation in AC Transmission Systems. This paper deals with the designing and implementation of Static Var compensator for Efficient Voltage regulation in three phase A.C. transmission lines in MATLAB Simulink platform.

AVNEESH KUMAR VISHWAKARMA; DHANESHWARI SAHU

2013-01-01

398

Renewable Distributed Generation Models in Three-Phase Load Flow Analysis for Smart Grid  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents renewable distributed generation  (RDG) models as three-phase resource in load flow computation and analyzes their effect when they are connected in composite networks. The RDG models that have been considered comprise of photovoltaic (PV) and wind turbine generation (WTG). The voltage-controlled node and complex power injection node are used in the models. These improvement models are suitable for smart grid power system analysis. The combination of IEEE transmission and distribution data used to test and analyze the algorithm in solving balanced/unbalanced active systems. The combination of IEEE transmission data and IEEE test feeder are used to test the the algorithm for balanced and unbalanced multi-phase distribution system problem. The simulation results show that by increased number and size of RDG units have improved voltage profile and reduced system losses.

Syafii Ghazali; K. M. Nor

2013-01-01

399

Determination of three-phase relative permeability values by using an artificial neural network model  

Energy Technology Data Exchange (ETDEWEB)

In this study, an artificial neural network (ANN) tool, which uses the data obtained from a pore network (PN) model, was developed in order to obtain three-phase relative permeability values. During the development of this ANN tool, four different stages were implemented in which ANN structures were changed in order to find the best architecture that would predict the oil isoperms correctly. By using the data obtained from the PN model, training was implemented and the prediction power of that tool was tested. When the data obtained from PN and ANN tools were compared, it has been found that irrelevant variables affected the ANN model negatively as decreasing its ability to learn perfectly. Finally, it has been observed that trends of the isoperms were effectively predicted and the overall quality of predictions was improved by changing the ANN structure. (Author)

Karaman, Turker [Turkish Petroleum Corp., Ankara (Turkey); Demiral, Birol [METU, Dept. of Petroleum and Natural Gas Engineering, Ankara (Turkey)

2004-08-15

400

Estimated D2--DT--T2 phase diagram in the three-phase region  

International Nuclear Information System (INIS)

[en] A composite of experimental eH2-D2 phase-diagram data at the three-phase line is assembled from the literature. The phase diagram is a smooth cigar shape without a eutectic point, indicating complete miscibility of liquid and solid phases. Additional data is used to estimate the D2-T2, D2DT, and DT-T2 binary phase diagrams. These are assembled into the ternary D2-DT-T2 phase diagram. A surface representing the chemical equilibrium of the three species is added to the phase diagram. At chemical equilibrium, it is estimated that 50-50 liquid D-T at 19.70K is in equilibrium with 42 mole percent T vapor and 54 percent T solid. Infrared spectroscopy is suggested as a means of component analysis of liquid and solid mixtures

1975-09-30

 
 
 
 
401

A Protection Scheme for Three-Phase Induction Motor from Incipient Faults Using Embedded Controller  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents a protection scheme for three-phase induction motor from incipient faults using embedded microcontroller. The induction motor experiences several types of electrical faults like over/under voltage, over load, phase reversing, unbalanced voltage, single phasing and earth fault. Due to these electrical faults, the windings of the motor get over heated which lead to insulation failure and thus reduce the life time of the motor. To analyze the behavior of induction motor during electrical faults, the induction motor is modeled using arbitrary reference frame theory in MATLAB/Simulink environment; the faults are created and the variation of the induction motor parameters under faulty conditions are observed. Based on the analysis, embedded controller is developed to protect the motor from incipient faults.

M. Sudha; P. Anbalagan

2009-01-01

402

FPGA Based Optimized Discontinuous SVPWM Algorithm for Three Phase VSI in AC Drives  

Directory of Open Access Journals (Sweden)

Full Text Available The discontinuous space vector pulse width modulation (SVPWM) has well-known that can reduce switching losses. By simplifying the thermal management issues, the discontinuous SVPWM can potentially reduce the inverter size and cost. However, using the modulation due to different time interval equations for each sector can introduce glitches at the points when the sector is changed. The more main problem, it can increase unwanted harmonic content and current ripple. Consider the decrease in switching losses associated with discontinuous modulation allows the system to utilize a higher switching frequency, this paper present high frequency switching of optimized discontinuous SVPWM based on FPGA to overcome the problems above. The proposed SVPWM has been successfully implemented by using APEX20KE Altera FPGA to drive on a three phase inverter system with 1.5 kW induction machine as load. The results have proved that the method can reduce harmonic content and current ripple without glitches.

Tole Sutikno; Nik Rumzi Nik Idris; Auzani Jidin; Mohd Hatta Jopri

2013-01-01

403

A digital control system, using DSP, for three-phase rectifier to maximize the power factor  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the implementation of a digital control system, using a digital signal processor (DSP), to monitor and control the output voltage of a three-phase ac-dc converter. The system aims to maximize the power factor by controlling the converter output voltage. The control variable is the load dc voltage, which is adjusted by the conducting angle of three bi-directional solid state switches. The value of this angle is determined and modified by the DSP, providing power factor correction. The final result, obtained from the control system, is an ac-dc converter with high power factor and stabilized output voltage within a wide range of output power. (author) 9 refs., 10 figs.

Mohr, Hari Bruno; Mussa, Samir Ahmad [Santa Catarina Univ., Florianopolis, SC (Brazil)

1995-12-31

404

A Compact Three-Phase Single-Input/Dual-Output Matrix Converter  

DEFF Research Database (Denmark)

This paper presents a novel matrix converter with one ac input and two ac outputs. The presented topology is based on the traditional indirect matrix converter, but with its rear-end six-switch inverter replaced by a compact nine-switch inverter. With only three extra switches added, the proposed converter can produce two sets of three-phase ac outputs, whose amplitudes, frequencies, and phases can appropriately be regulated. Features such as sinusoidal input and outputs, unity input power factor and minimum commutation count are all retained by the proposed topology, despite having an additional output. Its modulation is realized by the computationally less intensive carrier-based method, whose unique carrier requirements can easily be managed within a programmable logic device. Mathematical proof for validating sinusoidal input and outputs achieved by this modulation technique is also discussed, before being verified in simulation and experimentally, together with other findings.

Liu, Xiong; Wang, Peng

2012-01-01

405

Study and analysis of catalytic sulphur dioxide oxidation in a `verlifix` three-phase reactor  

Energy Technology Data Exchange (ETDEWEB)

After a kinetic study of catalytic oxidation of sulfur dioxide in aqueous slurry of fine particles of activated carbon, dp = 20 {mu}m, we used the same chemical reaction to study the performance of a three-phase reactor formed by a jet venturi placed above a fixed-bed of crushed particles of activated carbon (dfp = 4.10{sup -3} m). Under variables operating conditions, some hydrodynamic characteristics are precised as well as the conductance of gas-liquid and liquid-solid mass transfer. Then, the sulfur dioxide oxidation is carried out in the verlifix reactor. The modelling of the reactor shows that the apparent reaction rate is strongly controlled by intraparticle diffusion. (author) 10 figs., 3 tabs., 11 refs.

Kiared, K.; Mahfud; Zoulalian, A. [Nancy Univ., Lab. du Genie des Procedes, ESSTIB, Nancy (France)

1991-12-31

406

Novel Wavelet Ann Technique To Classify Interturn Fault In Three Phase Induction Motor  

Directory of Open Access Journals (Sweden)

Full Text Available Early detection of faults in stator winding of induction motor is crucial for reliable and economical operation of induction motor in industries. Whereas major winding faults can be easily identified from supply currents, minor faults involving less than 5 % of turns are not readily discernible. The present contribution reports experimental results for monitoring of minor short circuit faults in stator winding of induction motor. Motor line current has been analyzed using modern signal processing and data reduction tool combing Park’s Transformation and Discrete Wavelet Transform (DWT). Feed Forward Artificial Neural (FFANN) based data classification tool is used for fault characterization based on DWT features extracted from Park’s Current Vector Pattern. An online algorithm is tested successfully on three phase induction motor and experimental results are presented to demonstrate the effectiveness of the proposed method.

Anjali Uday Jawadekar; Sudhir Paraskar; Gajanan Dhole

2011-01-01

407

Three-phase harmonic distortion state estimation algorithm based on evolutionary strategies  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new methodology to estimate unbalanced harmonic distortions in a power system, based on measurements of a limited number of given sites. The algorithm utilizes evolutionary strategies (ES), a development branch of evolutionary algorithms. The problem solving algorithm herein proposed makes use of data from various power quality meters, which can either be synchronized by high technology GPS devices or by using information from a fundamental frequency load flow, what makes the overall power quality monitoring system much less costly. The ES based harmonic estimation model is applied to a 14 bus network to compare its performance to a conventional Monte Carlo approach. It is also applied to a 50 bus subtransmission network in order to compare the three-phase and single-phase approaches as well as the robustness of the proposed method. (author)

Arruda, Elcio F.; Kagan, N.; Ribeiro, P.F. [Department of Electrical Engineering, University of Sao Paulo, Escola Politecnica, Av. Prof. Luciano Gualberto, travessa 3 n 380 - CEP 05508-970 - Sao Paulo (Brazil)

2010-09-15

408

Heat transfer coefficient between bed and inserted horizontal tube in a three-phase fluidized bed  

International Nuclear Information System (INIS)

[en] The heat transfer coefficient between bed and horizontal tube wall was measured in three-phase fluidized beds of 19 and 12 cm i.d. Glass spheres with different diameters (particle diameter=0.052-0.22 cm, particle density = 2.5 g.cm-3) and alumina spheres (particle diameter=0.32 cm, apparent particle density=1.62 g.cm-3) were fluidized by the fluid media of air-water or air-aqueous solution of carboxymethyl cellulose. The superficial velocities of gas and liquid were varied in the range of 2.0-16 cm . s-1 and 0.1-8.0 cm . s-1, respectively

1986-01-01

409

Numerical simulation of three-phase immiscible displacement in heterogeneous reservoirs  

Energy Technology Data Exchange (ETDEWEB)

We introduce a new method for the numerical solution of three-phase flow problems in petroleum reservoirs. The method combines techniques that have been used to solve two phase-flow equations with satisfactory results. A two-level operator splitting technique allows for the use of distinct time steps for the three problems defined by the procedure: transport, diffusion and pressure-velocity. A system of conservation laws is approximated by a non-oscillatory, second order, conservative central difference scheme in the transport step. Locally conservative mixed finite elements are used to discretize both the diffusion and pressure-velocity problems. A simulator was developed and it was shown to be accurate and efficient through a set of numerical experiments, The numerical solutions are in very good agreement with semi-analytic results available in the literature; in these numerical solutions transitional waves, which have a strong dependency upon the physical diffusion being modeled, have been captured. (author)

Abreu, Eduardo; Pereira, Felipe [Universidade do Estado, Nova Friburgo, RJ (Brazil). Dept. de Modelagem Computacional]. E-mail: eabreu@iprj.uerj.br; pereira@iprj.uerj.br

2003-07-01

410

MULTIOBJECTIVE OPTIMAL DESIGN OF THREE-PHASE INDUCTION GENERATOR USING SIMULATED ANNEALING TECHNIQUE  

Directory of Open Access Journals (Sweden)

Full Text Available Self-excited induction generators are growing in popularity due to their advantages over the conventional synchronous generators. In this paper, the task of finding optimal design of a three-phase self-excited induction generator has been formulated as a multi criterion optimization problem. Criterial functions in the example are the active material cost and capacitance required for excitation under full load conditions to maintain rated voltage. Simulated Annealing technique is used as a tool to solve the problem. The obtained results prove the effectiveness of a multi objective approach since it allows us to find a good compromise among the proposed goals, and above all it represents an efficacious tool for the designer.

R.Kannan; Dr.S.Subramanian,; Dr.R.Bhuvaneswari

2010-01-01

411

Simulation of coarsening in three-phase solid oxide fuel cell anodes  

Energy Technology Data Exchange (ETDEWEB)

Coarsening of the nickel phase is known to occur in solid oxide fuel cell (SOFC) anodes consisting of Ni and yttria-stabilized zirconia (YSZ). However, the exact nature of the coarsening process is not known, nor how it affects three-phase boundaries (TPBs) and the resulting electrochemical performance. We apply a phase-field approach to simulate the microstructural evolution of Ni-YSZ anode functional layers. An experimentally obtained three-dimensional reconstruction of a functional layer from an anode-supported SOFC is used as the initial microstructure. The evolution of the microstructure is characterized quantitatively by examining the TPB density, interfacial area per unit volume, and tortuosity versus time. The assumed TPB contact angles are found to have a strong effect on the microstructural evolution; in particular, reducing the contact angle of nickel on YSZ yields less TPB reduction. (author)

Chen, Hsun-Yi; Yu, Hui-Chia; Thornton, Katsuyo [Department of Materials Science and Engineering, University of Michigan, 2300 Hayward St., Ann Arbor, MI 48109 (United States); Scott Cronin, J.; Wilson, James R.; Barnett, Scott A. [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60201 (United States)

2011-02-01

412

Electromagnetic losses in a three-phase high temperature superconducting cable determined by calorimetric measurements  

DEFF Research Database (Denmark)

A 10 m long high temperature superconducting (HTS) cable conductor was placed in a plane three-phase arrangement. The test-bed enabled us to study the conductor losses for different separations between the phases. The superconductor was fixed symmetrically in the centre, whilst the two outer conventional phases (600 mm2 Cu) could be moved in the plane. It was possible to vary the inter-phase distance (centre to centre distance) from 9 to 48 cm. The HTS cable conductor was placed in a stainless steel cryostat and cooled with flowing liquid nitrogen (LN2). The losses were determined using a calorimetric technique where the temperature increase in the flowing LN2 was measured with a set of thermo-couples. Results indicate that the total AC loss increases significantly when the separation between the conductors is reduced.

Traeholt, C.; Veje, E.

2002-01-01

413

Insulated conductor temperature limited heater for subsurface heating coupled in a three-phase WYE configuration  

Energy Technology Data Exchange (ETDEWEB)

A heating system for a subsurface formation is described. The heating system includes a first heater, a second heater, and a third heater placed in an opening in the subsurface formation. Each heater includes: an electrical conductor; an insulation layer at least partially surrounding the electrical conductor; and an electrically conductive sheath at least partially surrounding the insulation layer. The electrical conductor is electrically coupled to the sheath at a lower end portion of the heater. The lower end portion is the portion of the heater distal from a surface of the opening. The first heater, the second heater, and the third heater are electrically coupled at the lower end portions of the heaters. The first heater, the second heater, and the third heater are configured to be electrically coupled in a three-phase wye configuration.

Vinegar, Harold J. (Bellaire, TX); Sandberg, Chester Ledlie (Palo Alto, CA)

2010-11-09

414

Three Phase Induction Motor Drive Using Igbts And Constant V/F Method  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents design and analysis of a three phase induction motor drive using IGBT?s at the inverter power stage with volts hertz control (V/F) in closed loop using dsPIC30F2010 as a controller. It is a 16 bit high-performance digital signal controller (DSC). DSC is a single chip embedded controller that integrates the controller attributes of a microcontroller with the computation and throughput capabilities of a DSP in a single core. A 1HP, 3-phase, 415V, 50Hz induction motor is used as load for the inverter. Digital Storage Oscilloscope Textronix TDS2024B is used to record and analyze the various waveforms. The experimental results for V/F control of 3-Phase induction motor using dsPIC30F2010 chip clearly shows constant volts per hertz and stable inverter line to line output voltage.

M.S.ASPALLI; ASHA.R; P.V.HUNAGUND

2013-01-01

415

Three Phase Current Measurement of Ac Drives Using Single Current Sensor & Vector Insertion  

Directory of Open Access Journals (Sweden)

Full Text Available In this thesis a technique for measuring and controlling line currents of three phase AC motors using information from a single current sensor resistor mounted in the DC-link of an inverter is presented. The principal motivation is to reduce the sensor cost, weight, and volume and also to improve the reliability of a drive system.However the basic dc link single current sensor technique poses a limitation because the duration of the active voltage vectors must be long enough to measure the dc link current reliably. To overcome this problem a new algorithm called the measurement vector insertion method is presented along with basic single current sensor technique that overcomes this problem using active voltage vectors that are applied for brief measurement intervals only when needed during each cycle of fundamental frequency.

SAMEERA KANCHWALA, Mr. AMOL BARVE

2013-01-01

416

Mitigation of Output Power Fluctuations in Utility Grid using Three Phase Distribution Generation  

Directory of Open Access Journals (Sweden)

Full Text Available Renewable electricity generation has never seen the level of investment and incentives that have been put in place by governments around the world during the last decade. However, despite the envisaged environmental and security of supply benefits that the harvesting of indigenous, renewable sources might bring about, their integration into the power system creates significant challenges to both the network operators and developers. The power quality challenges become even greater when large volumes of renewable generation capacity are connected to distribution networks, traditionally designed to be passive circuits with unidirectional power flows. This paper presents two schemes to meet the different power quality challenges in the utility grid due to Distribution Generation. In this first scheme is DSTATCOM and second is three phase Distributed Generation. This work is aimed at demonstrating, from the planning perspective, the benefits that the adoption of the different compensators might bring the system to a ‘fit and forget’ approach.

K.Sri Chandan,; T.Sandhya

2010-01-01

417

Somalia’s “Pirate Cycle”: The Three Phases of Somali Piracy  

Directory of Open Access Journals (Sweden)

Full Text Available This article provides a theoretical framework for examining Somali piracy from its origins in the 1990s to the present. This analysis provides both a detailed description of the changing nature of piracy, as well as explanations for why these changes have occurred. The increase in pirate activity off Somalia from 1991 to 2011 did not occur in a steady linear progression, but took place in three separate phases. These three phases can be viewed in terms of a “cycle of piracy,” based on a theory developed by the pirate historian Philip Gosse in 1932. By employing this framework, policy-makers in the U.S. and elsewhere would be better able to judge when counter-piracy intervention is necessary. By preventing piracy from developing into large-scale professionalized operations, as witnessed in Somalia since 2007, the international community will be able carryout more efficient and effective piracy suppression operations in future.

Edward R. Lucas

2013-01-01

418

Sliding Mode Controller for Three-Phase Hybrid Active Power Filter with Photovoltaic Application  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new three-phase hybrid active power filter configuration that interconnects a passive high-pass filter in parallel with an active power filter and a photovoltaic system. The proposed configuration can improves the filtering performance of the conventional active power filter, as well as simultaneously supply the power from the photovoltaic arrays to the load and utility. This paper will describe the proposed hybrid active power filter control using sliding mode with photovoltaic system. The proposed technique effectively filters harmonics under 1 kHz but also higher frequency to achieve wideband harmonics compensation. The THD of source current is reduced from 30.09% to 1.95%. The result indicates that the sliding mode controller can track the reference signals and have good dynamic characteristics.

Ayman Blorfan; Jean Mercklé; Damien Flieller; Patrice Wira; Guy Sturtzer

2012-01-01

419

Electrical properties of novel three-phase polymer nanocomposites with a high dielectric constant  

Science.gov (United States)

Novel three-phase poly(vinylidene fluoride) (PVDF)/lead zirconate titanate (PZT)/expanded graphite (EG) nanocomposites were prepared using the solution method followed by hot pressing. The loading of PZT powder was varied from 0 to 85 wt% (?57 vol%) in the PVDF matrix. Scanning electron microscopy revealed uniform dispersion of PZT particles in the matrix. X-ray diffraction showed the presence of ?-phase of PVDF in the nanocomposites. Dielectric constant of the 80 wt% (C-80) composites increased to approximately 57 and it was further increased to approximately 192, 237 and 842 for the C-80 nanocomposites containing additional EG content of 0.25 wt%, 0.50 wt% and 0.75 wt%, respectively. However, it decreased with increasing frequency. The electrical conductivity and dissipation factor also increased significantly with increasing content of EG. Various theoretical models were used to rationalize the dielectric behaviour of binary composites.

Goyal, R. K.; Kulkarni, A. B.

2012-11-01

420

Social cognition throughout the three phases of bipolar disorder: A state-of-the-art overview.  

UK PubMed Central (United Kingdom)

Although it is now well documented that bipolar disorder (BD) often presents with cognitive deficits and suboptimal social adjustment, the social cognitive profile of the illness throughout its three phases remains unclear. An extensive search was conducted through the online databases EBSCO, PsychInfo, PubMed, ScienceDirect, and Wiley-Blackwell, covering the period between 1990 and 2012. Fifty-one studies comparing the social cognitive performance of bipolar patients with that of healthy controls were identified. Deficits in emotion recognition and theory of mind were found in manic, depressed, and euthymic bipolar subjects. Furthermore, altered face emotion recognition and brain-related abnormalities were noted both in euthymic patients and subjects at risk for BD. The influence of clinical and neurocognitive variables on the social