Predictive Pulse Pattern Current Modulation Scheme for Harmonic Reduction in Three-Phase Multidrive Systems

DEFF Research Database (Denmark)

Davari, Pooya; Yang, Yongheng; Zare, Firuz

2016-01-01

at the rectification stage to synthesize sinusoidal input currents. The input voltage sensing is avoided in order to minimize the number of required sensors, and the grid synchronization also has been implemented based on a common Phase-Locked-Loop (PLL) using the DC-link capacitor voltage ripple. Experimental results......The majority of the industrial motor drive systems are equipped with the conventional line-commutated front-end rectifiers, and being one of the main sources of harmonics in the power line. While a parallel combination of these drive units elevates current quality issues, a proper arrangement...... of them can lead to the cancellation of specific harmonics. This paper proposes a new cost-effective harmonic mitigation solution for multi-drive systems using a predictive pulse pattern current modulation control strategy. The proposed technique applies suitable interaction among parallel drive units...

Power grid current harmonics mitigation drawn on low voltage rated switching devices with effortless control

Energy Technology Data Exchange (ETDEWEB)

Marques, Hugo S.; Anunciada, Victor; Borges, Beatriz V. [Power Electronics Group, Instituto de Telecomunicacoes, Lisbon (Portugal); Instituto Superior Tecnico - Universidade Tecnica de Lisboa, Lisbon (Portugal)

2010-01-15

The great majority of the existing hybrid active power filter solutions is normally focused in 3{phi} systems and, in general, concentrates its domain of application in specific loads with deterministic behavior. Because common use grids do not exhibit these characteristics, it is mandatory to develop solutions for more generic scenarios, encouraging the use of less classical hybrid solutions. In fact, due to the widely use of switch mode converters in a great variety of consumer electronics, the problematic of mains current harmonic mitigation is no longer an exclusive matter of 3{phi} systems. The contribution of this paper is to present a shunt hybrid active power filter topology, initially conceived to work in 1{phi} domestic grids, able to operate the inverter at a voltage rate that can be lower than 10% of the mains voltage magnitude, even under nonspecific working conditions. In addition, the results shown in this paper demonstrate that this topology can, without lack of generality, be suitable to medium voltage (1{phi} or 3{phi}) systems. A new control approach for the proposed topology is discussed in this paper. The control method exhibits an extremely simple architecture requiring single point current sensing only, with no need for any kind of reference. Its practical implementation can be fulfilled by using very few, common use, operational amplifiers. The principle of operation, design criteria, simulation predictions and experimental results are presented and discussed. (author)

Harmonic currents circulation in electrical networks simulation and analysis

Energy Technology Data Exchange (ETDEWEB)

Em-Mamlouk, W.M. [MEP, Cairo (Egypt); El-Sharkawy, M.A. [Shams Univ., Cairo (Egypt). Dept. of Electrical Power and Machines; Mostafa, H.E. [Jazan Univ., Jazan (Saudi Arabia). Electrical Dept.

2009-07-01

A detailed harmonic flow analysis for a 13-bus balanced industrial distribution system was presented. The aim of the study was to determine the influence of harmonic sources in various branches of the system on voltage and current waveforms before disruptions to the utility supply system occurred. The current harmonic contents of an adjustable speed drive (ASD) were studied under various loading conditions. The test system was simulated using a standard study test system. Harmonic effects from multiple sources were investigated, and voltage distortion on the different buses was monitored. The study demonstrated that while the harmonic loads circulated harmonic currents in all system branches, no harmonic source was directly connected to the system buses. Many of the investigated cases exceeded allowable voltage total harmonic distortion and or current total harmonic distortion standards set by the Institute of Electrical and Electronic Engineers (IEEE). It was concluded that active harmonic filters should be used to prevent the effects of harmonic current circulation at different buses on neighbouring loads within a system. 8 refs., 11 tabs., 15 figs.

Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation.

Science.gov (United States)

Mohajerin-Ariaei, Amirhossein; Ziyadi, Morteza; Chitgarha, Mohammad Reza; Almaiman, Ahmed; Cao, Yinwen; Shamee, Bishara; Yang, Jeng-Yuan; Akasaka, Youichi; Sekiya, Motoyoshi; Takasaka, Shigehiro; Sugizaki, Ryuichi; Touch, Joseph D; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

2015-07-15

We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification in the saturation regime. Phase noise reduction of ∼40% and OSNR-gain of ∼3  dB at BER 10(-3) are experimentally demonstrated for 20- and 30-Gbaud QPSK input signals.

Enhanced Phase-Shifted Current Control for Harmonic Cancellation in Three-Phase Multiple Adjustable Speed Drive Systems

DEFF Research Database (Denmark)

Yang, Yongheng; Davari, Pooya; Zare, Firuz

2017-01-01

A phase-shifted current control can be employed to mitigate certain harmonics induced by the Diode Rectifiers (DR) and Silicon-Controlled Rectifiers (SCR) as the front-ends of multiple parallel Adjustable Speed Drive (ASD) systems. However, the effectiveness of the phase-shifted control relies...... on the loading condition of each drive unit as well as the number of drives in parallel. In order to enhance the harmonic cancellation by means of the phase-shifted current control, the currents drawn by the rectifiers should be maintained almost at the same level. Thus, this paper firstly analyzes the impact...... of unequal loading among the parallel drives, and a scheme to enhance the performance is introduced to improve the quality of the total grid current, where partial loading operation should be enabled. Simulation and experimental case studies on multidrive systems have demonstrated that the enhanced phase...

Harmonics mitigation on industrial loads using series and parallel ...

African Journals Online (AJOL)

Most industrial loads are inductive in nature and therefore absorb Volts Ampere Reactance (VARs) leading to lagging power factor. Some inductive loads also produce current and voltage signals with frequencies in integer multiples of the 50 or 60 Hz fundamental frequencies called harmonics. Harmonics in power system ...

A hybrid filter to mitigate harmonics caused by nonlinear load and resonance caused by power factor correction capacitor

Science.gov (United States)

Adan, N. F.; Soomro, D. M.

2017-01-01

Power factor correction capacitor (PFCC) is commonly installed in industrial applications for power factor correction (PFC). With the expanding use of non-linear equipment such as ASDs, power converters, etc., power factor (PF) improvement has become difficult due to the presence of harmonics. The resulting capacitive impedance of the PFCC may form a resonant circuit with the source inductive reactance at a certain frequency, which is likely to coincide with one of the harmonic frequency of the load. This condition will trigger large oscillatory currents and voltages that may stress the insulation and cause subsequent damage to the PFCC and equipment connected to the power system (PS). Besides, high PF cannot be achieved due to power distortion. This paper presents the design of a three-phase hybrid filter consisting of a single tuned passive filter (STPF) and shunt active power filter (SAPF) to mitigate harmonics and resonance in the PS through simulation using PSCAD/EMTDC software. SAPF was developed using p-q theory. The hybrid filter has resulted in significant improvement on both total harmonic distortion for voltage (THDV) and total demand distortion for current (TDDI) with maximum values of 2.93% and 9.84% respectively which were within the recommended IEEE 519-2014 standard limits. Regarding PF improvement, the combined filters have achieved PF close to desired PF at 0.95 for firing angle, α values up to 40°.

Harmonic currents Compensator Grid-Connected Inverter at the Microgrid

DEFF Research Database (Denmark)

Asuhaimi Mohd Zin, A.; Naderipour, A.; Habibuddin, M.H.

2016-01-01

The main challenge associated with the grid-connected inverter in distributed generation (DG) systems is to maintain the harmonic contents in output current below the specified values and compensates for unbalanced loads even when the grid is subject to disturbances such as harmonic distortion...... and unbalanced loads. To overcome these challenges, a current control strategy for a three-phase grid-connected inverter under unbalanced and nonlinear load conditions is presented. It enables grid-connected inverter by the proposed control method to inject balanced clean currents to the grid even when the local...... loads are unbalanced and/or nonlinear and also compensate of the harmonic currents and control the active and reactive power. The main advantage and objective of this method is to effectively compensate for the harmonic currents content of the grid current and microgrid without using any compensation...

Harmonic current prediction by impedance modeling of grid-tied inverters

DEFF Research Database (Denmark)

Pereira, Heverton A.; Freijedo, Francisco D.; Silva, M. M.

2017-01-01

and harmonic voltage profiles. Results reinforce that impedance models can represent with relatively accuracy the harmonic current emitted by the PV plants at the point of common coupling (PCC). Lastly, a stress test is performed to show how a variation in the harmonic voltage phase angle impacts the PV plant...... impedance models when used in harmonic integration studies. It is aimed to estimate the harmonic current contribution as a function of the background harmonic voltages components. Time domain simulations based on detailed and average models are compared with the impedance model developed in frequency domain....... In grids with harmonic voltages, impedance models can predict the current distortion for all active power injection scenarios. Furthermore, measurements in a 1.4 MW PV plant connected in a distributed grid are used to validate the simulation based on impedance models during different power injections...

SHAF for Mitigation of Current Harmonics Using p-q Method with PI and Fuzzy Controllers

Directory of Open Access Journals (Sweden)

A. K. Panda

2011-08-01

Full Text Available Commencing with incandescent light bulb, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and response to problems caused by harmonics. Issue of Harmonics are of a greater concern to engineers, building designers and in industrial applications because they do more than distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality has become more and more serious with each passing day. As a result active power filter (APF gains much more attention due to excellent harmonic compensation. But still the performance of the active filter seems to be in contradictions with different control techniques. The main objective of this paper is to analyse shunt active filter with fuzzy and pi controllers. To carry out the analysis, we consider active and reactive power method (p-q. Extensive simulations were carried out; simulations were performed with balance, unbalanced and non sinusoidal conditions. Simulation results validate the dynamic behaviour of fuzzy logic controller over pi controller.

Mitigation of Harmonics in Grid-Connected and Islanded Microgrids via Virtual Admittances and Impedances

DEFF Research Database (Denmark)

Micallef, Alexander; Apap, Maurice; Spiteri-Staines, Cyril

2017-01-01

Optimization of the islanded and grid-connected operation of microgrids is important to achieve a high degree of reliability. In this paper, the authors consider the effect of current harmonics in single phase microgrids during both modes of operation. A detailed analysis of the effect of the out......Optimization of the islanded and grid-connected operation of microgrids is important to achieve a high degree of reliability. In this paper, the authors consider the effect of current harmonics in single phase microgrids during both modes of operation. A detailed analysis of the effect...... of the output impedance of the considered primary control loops on the harmonic output of the considered voltage source inverters is initially carried out. A virtual admittance loop is proposed to attenuate the current harmonic output in grid-connected operation that is generated due to the grid voltage...... distortion present at the point of common coupling (PCC) and due to local non-linear loads. This paper also considers the harmonic current sharing and resulting voltage harmonics at the PCC during islanded operation of the microgrid. A capacitive virtual impedance loop was implemented to improve the harmonic...

Stator Current Harmonic Control with Resonant Controller for Doubly Fed Induction Generator

DEFF Research Database (Denmark)

Liu, Changjin; Blaabjerg, Frede; Chen, Wenjie

2012-01-01

rotor current control loop for harmonic suppression. The overall control scheme is implemented in dq frame. Based on a mathematical model of the DFIG control system, the effects on system stability using the resonant controller, an analysis of the steady-state error, and the dynamic performance......, are discussed in this paper. Taking these effects into account, the parameters of the resonant controller can be designed and effectively damp the influence from the grid voltage harmonics. As a result, the impacts of the negative sequence fifth- and positive sequence seventh-order voltage harmonics...... harmonics, especially low-order harmonics. This paper proposes a stator current harmonic suppression method using a sixth-order resonant controller to eliminate negative sequence fifth- and positive sequence seventh-order current harmonics. A stator current harmonic control loop is added to the conventional...

Designing single phase Current-Programmed-Controlled rectifiers by harmonic currents

DEFF Research Database (Denmark)

Andersen, Gert Karmisholt; Blaabjerg, Frede

2002-01-01

The grid current harmonics of a Current-Programmed-Controlled (CPC) pfc rectifier strongly depends on the choice of switching frequency and switching inductance. This paper describes a new simple and vert fast method to calculate the grid current of a CPC controlled pfc converter. The method...

Reduction of Harmonics by 18-Pulse Rectifier

Directory of Open Access Journals (Sweden)

Stanislav Kocman

2008-01-01

Full Text Available Operation of such electrical devices as data processing and electronics devices, adjustable speed drives or uninterruptible power supply can cause problems by generating harmonic currents into the network, from which they are supplied. Effects of these harmonic currents are various, they can get worse the quality of supply voltage in the network or to have negative influences on devices connected to this network. There are various technical solutions for reduction of harmonics. One of them is using of multi-pulse rectifiers, whereas the 18-pulse rectifier in the structure of adjustable speed drive is briefly presented in this paper including some results of its behaviour. The examined experimental measurements confirmed its very good efficiency in the harmonic mitigation.

Three-Phase Harmonic Analysis Method for Unbalanced Distribution Systems

Directory of Open Access Journals (Sweden)

Jen-Hao Teng

2014-01-01

Full Text Available Due to the unbalanced features of distribution systems, a three-phase harmonic analysis method is essential to accurately analyze the harmonic impact on distribution systems. Moreover, harmonic analysis is the basic tool for harmonic filter design and harmonic resonance mitigation; therefore, the computational performance should also be efficient. An accurate and efficient three-phase harmonic analysis method for unbalanced distribution systems is proposed in this paper. The variations of bus voltages, bus current injections and branch currents affected by harmonic current injections can be analyzed by two relationship matrices developed from the topological characteristics of distribution systems. Some useful formulas are then derived to solve the three-phase harmonic propagation problem. After the harmonic propagation for each harmonic order is calculated, the total harmonic distortion (THD for bus voltages can be calculated accordingly. The proposed method has better computational performance, since the time-consuming full admittance matrix inverse employed by the commonly-used harmonic analysis methods is not necessary in the solution procedure. In addition, the proposed method can provide novel viewpoints in calculating the branch currents and bus voltages under harmonic pollution which are vital for harmonic filter design. Test results demonstrate the effectiveness and efficiency of the proposed method.

Harmonic Analysis and Mitigation of Low- Frequency Switching Voltage Source Inverter with Auxiliary VSI

DEFF Research Database (Denmark)

Bai, Haofeng; Wang, Xiongfei; Blaabjerg, Frede

2018-01-01

The output currents of high-power Voltage Source Inverters (VSIs) are distorted by the switching harmonics and the background harmonics in the grid voltage. This paper presents an active harmonic filtering scheme for high-power, low-frequency switching VSIs with an additional auxiliary VSI. In th...

Current controller considering harmonics compensation for grid connected converter in DPGS applications

DEFF Research Database (Denmark)

Barote, L.; Marinescu, C.; Teodorescu, Remus

2012-01-01

This paper deals with the design and implementation of PR current control method in the αβ stationary reference frame for the grid side converter in Distributed Power Generation Systems (DPGS) applications. The goals of this paper are to implement a control technique for the grid side inverter...... including a LC filter, a compensation technique for low-order harmonics and to examine the grid current harmonic content with and without harmonic compensation. A comparative study in terms of current harmonic distortion between two different values of PR proportional gain running in steady state condition...

Study on UPF Harmonic Current Detection Method Based on DSP

Energy Technology Data Exchange (ETDEWEB)

Zhao, H J [Northwestern Polytechnical University, Xi' an 710072 (China); Pang, Y F [Xi' an University of Technology, Xi' an 710048 (China); Qiu, Z M [Xi' an University of Technology, Xi' an 710048 (China); Chen, M [Northwestern Polytechnical University, Xi' an 710072 (China)

2006-10-15

Unity power factor (UPF) harmonic current detection method applied to active power filter (APF) is presented in this paper. The intention of this method is to make nonlinear loads and active power filter in parallel to be an equivalent resistance. So after compensation, source current is sinusoidal, and has the same shape of source voltage. Meanwhile, there is no harmonic in source current, and the power factor becomes one. The mathematic model of proposed method and the optimum project for equivalent low pass filter in measurement are presented. Finally, the proposed detection method applied to a shunt active power filter experimental prototype based on DSP TMS320F2812 is developed. Simulation and experiment results indicate the method is simple and easy to implement, and can obtain the real-time calculation of harmonic current exactly.

Harmonic Analysis and Active Filtering in Offshore Wind Power Plants

DEFF Research Database (Denmark)

Chaudhary, Sanjay Kumar; Freijedo Fernandez, Francisco Daniel; Guerrero, Josep M.

2015-01-01

Due to presence of long high voltage cable networks, and power transformers for the grid connection, the offshore wind power plants (OWPPs) are susceptible to harmonic distortion and resonances. The grid connection of OWPP should not cause the harmonic distortion beyond the permissible limits...... at the point of common coupling (PCC). The resonance conditions should be avoided in all cases. This paper describes the harmonic analysis techniques applied on an OWPP network model. A method is proposed to estimate the harmonic current compensation from a shunt-connected active power filter to mitigate...

Microgrid Reactive and Harmonic Power Sharing Using Enhanced Virtual Impedance

DEFF Research Database (Denmark)

He, Jinwei; Wei Li, Yun; Guerrero, Josep M.

2013-01-01

To address the load sharing problem in islanding microgrids, this paper proposes an improved approach which regulates the distributed generation (DG) unit interfacing virtual impedance at fundamental and selected harmonic frequencies. In contrast to the conventional virtual impedance control where...... only a line current feed-forward term is added to the DG voltage reference, the proposed virtual impedances at fundamental and harmonic frequencies are realized using DG line current and point of common coupling (PCC) voltage feed-forward terms, respectively. With this modification, the mismatched DG...... feeder impedances can be properly compensated, resulting in accurate reactive and harmonic power sharing at the same time. In addition, this paper shows that the microgrid PCC harmonic voltages can be mitigated by reducing the magnitude of DG unit equivalent harmonic impedance. Finally, an improved...

Novel low harmonics 3-phase rectifiers for efficient motor systems; Novel low harmonics 3-phase rectifiers for efficient motor systems. Konzeptstudie - Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

Pietkiewicz, A.; Melly, S.; Tucker, A.; Haeberle, N. [Schaffner EMV AG, Luterbach (Switzerland); Biner, H.-P. [Haute Ecole Specialisee de Suisse occidentale, HES-SO Valais, Sion (Switzerland)

2010-07-15

This final report for the Swiss Federal Office of Energy (SFOE) presents the results of a concept study made concerning novel low harmonics 3-phase rectifiers for efficient motor systems. The harmonic distortions which are produced by these systems are discussed and ways of minimising them are examined. The authors discuss novel, passive, multi-pulse current splitters that are considered to be cost efficient, compact and highly-reliable harmonics mitigation concepts for three-phase loads. According to the authors, functional prototypes for a nominal load of 4 kW proved, in laboratory tests, the outstanding properties of multi-pulse current splitters with respect to harmonics cancellation and robustness against voltage asymmetry. The design process, prototype construction and application tests are discussed, as are energy-saving potentials and marketing aspects.

Flexible Compensation of Voltage and Current Unbalance and Harmonics in Microgrids

DEFF Research Database (Denmark)

Mousazadeh, Seyyed Yousef; Jalilian, Alireza; Savaghebi, Mehdi

2017-01-01

In recent years, the harmonics and unbalance problem endanger the voltage and current quality of power systems due to increasing usage of nonlinear and unbalance loads. Using DG interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method...... is proposed to compensate voltage and current unbalance and harmonics using the Distributed Generation (DG) interfacing inverters. This method is applicable to both grid-connected and islanded microgrids. In the proposed method, not only the proper control of active and reactive powers can be achieved......) frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. The results show that depending on the compensation mode, the harmonics and unbalance compensation of DGs’ output current, MG’s injected current to the grid as well...

A novel current mode controller for a static compensator utilizing Goertzel algorithm to mitigate voltage sags

International Nuclear Information System (INIS)

Najafi, E.; Yatim, A.H.M.

2011-01-01

Research highlights: → We proposed a new current control method for STATCOM. → The current control method maintains a fixed switching frequency. → It also produces fewer harmonics compared to conventional hysteresis method. → A new voltage dip (sag) detection method was used in STATCOM. → The control method can mitigate voltage sag in each phase separately. -- Abstract: Static compensator (STATCOM) has been widely proposed for power quality and network stability improvement. It is easily connected in parallel to the electric network and has many advantages for electrical grids. It can improve network stability; power factor, power transfer rating and can avoid some disturbances such as sags and swells. Most of STATCOM controllers are based on voltage controllers that are based on balanced d-q transform. However, they are not thorough solutions for network disturbances since in most cases single-phase disturbances occur in electrical networks that cannot be avoided by the conventional controllers. Voltage mode controllers are also not capable of responding fast enough to the changes expected of a network system. This paper proposes a new current mode controller to overcome the mentioned problem. The approach uses a fixed frequency current controller to maintain voltage levels in voltage sags (dips). This approach is also simple and can be easily implemented by digitally. It has superior performance over conventional methods in terms of harmonic reduction in STATCOM output current. Another important factor for STATCOM effectiveness in sag mitigation is its sag detection method. This paper also introduces a new sag detection method based on Goertzel algorithm which is both effective and simple for practical applications. The simulation results presented illustrate the superiority of the proposed controller and sag detection algorithm to be utilized in the STATCOM.

Design of PR current control with selective harmonic compensators using Matlab

Directory of Open Access Journals (Sweden)

Daniel Zammit

2017-12-01

Full Text Available This paper presents a procedure to design a Proportional Resonant (PR current controller with additional PR selective harmonic compensators for Grid Connected Photovoltaic (PV Inverters. The design of the PR current control and the harmonic compensators will be carried out using Matlab. Testing was carried out on a 3 kW Grid-Connected PV Inverter which was designed and constructed for this research. Both simulation and experimental results will be presented. Keywords: Inverters, Proportional-resonant controllers, Harmonic compensation, Photovoltaic, Matlab, SISO design tool

Mitigation of grid-current distortion for LCL-filtered grid-connected voltage-source inverter with inverter-side current control

DEFF Research Database (Denmark)

Xin, Zhen; Mattavelli, Paolo; Yao, WenLi

2017-01-01

Due to the low inductance of an LCL-filter, the grid current generated by an LCL-filtered Voltage Source Inverter (VSI) is sensitive to low-order grid-voltage harmonics. This issue is especially tough for the control system with Inverter Current Feedback (ICF), because the grid-current harmonics...... can freely flow into the filter capacitor without control. To cope with this issue, this paper develops an approach for the ICF control system to suppress the grid-current harmonics without adding extra sensors. The proposed method applies harmonic controllers and feedforward scheme simultaneously...

Harmonic and reactive behavior of the quasiparticle tunnel current in SIS junctions

Energy Technology Data Exchange (ETDEWEB)

Rashid, H., E-mail: hawal@chalmers.se; Desmaris, V.; Pavolotsky, A.; Belitsky, V. [Group for Advanced Receiver Development, Earth and Space Sciences Department, Chalmers University of Technology, Gothenburg, 412 96 (Sweden)

2016-04-15

In this paper, we show theoretically and experimentally that the reactive quasiparticle tunnel current of the superconductor tunnel junction could be directly measured at specific bias voltages for the higher harmonics of the quasiparticle tunnel current. We used the theory of quasiparticle tunneling to study the higher harmonics of the quasiparticle tunnel current in superconducting tunnel junction in the presence of rf irradiation. The impact of the reactive current on the harmonic behavior of the quasiparticle tunnel current was carefully studied by implementing a practical model with four parameters to model the dc I-V characteristics of the superconducting tunnel junction. The measured reactive current at the specific bias voltage is in good agreement with our theoretically calculated reactive current through the Kramers-Kronig transform. This study also shows that there is an excellent correspondence between the behavior of the predicted higher harmonics using the previously established theory of quasiparticle tunnel current in superconducting tunnel junctions by J.R. Tucker and M.J. Feldman and the measurements presented in this paper.

Harmonic and reactive behavior of the quasiparticle tunnel current in SIS junctions

International Nuclear Information System (INIS)

Rashid, H.; Desmaris, V.; Pavolotsky, A.; Belitsky, V.

2016-01-01

In this paper, we show theoretically and experimentally that the reactive quasiparticle tunnel current of the superconductor tunnel junction could be directly measured at specific bias voltages for the higher harmonics of the quasiparticle tunnel current. We used the theory of quasiparticle tunneling to study the higher harmonics of the quasiparticle tunnel current in superconducting tunnel junction in the presence of rf irradiation. The impact of the reactive current on the harmonic behavior of the quasiparticle tunnel current was carefully studied by implementing a practical model with four parameters to model the dc I-V characteristics of the superconducting tunnel junction. The measured reactive current at the specific bias voltage is in good agreement with our theoretically calculated reactive current through the Kramers-Kronig transform. This study also shows that there is an excellent correspondence between the behavior of the predicted higher harmonics using the previously established theory of quasiparticle tunnel current in superconducting tunnel junctions by J.R. Tucker and M.J. Feldman and the measurements presented in this paper.

Optimal Selective Harmonic Control for Power Harmonics Mitigation

DEFF Research Database (Denmark)

Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede

2015-01-01

of power harmonics. The proposed optimal SHC is of hybrid structure: all recursive SHC modules with weighted gains are connected in parallel. It bridges the real “nk+-m order RC” and the complex “parallel structure RC”. Compared to other IMP based control solutions, it offers an optimal trade-off among...

A current controller of grid-connected converter for harmonic damping in a distribution network

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2011-01-01

Harmonic resonance caused by the increased use of shunt-connected capacitors in LCL-filters and power factor correction devices may become a serious power quality challenge in electric distribution systems. A voltage-detection method based on current control is developed to damp harmonic resonances....... However, it is susceptible to the mismatch between harmonic conductance and characteristic impedance of distribution feeder. This paper proposes a current controller which allows discrete adjustment of harmonic conductance for both the characteristic harmonic and the non-characteristic harmonic voltages...

A novel harmonic current sharing control strategy for parallel-connected inverters

DEFF Research Database (Denmark)

Guan, Yajuan; Guerrero, Josep M.; Savaghebi, Mehdi

2017-01-01

A novel control strategy which enables proportional linear and nonlinear loads sharing among paralleled inverters and voltage harmonic suppression is proposed in this paper. The proposed method is based on the autonomous currents sharing controller (ACSC) instead of conventional power droop control...... to provide fast transient response, decoupling control and large stability margin. The current components at different sequences and orders are decomposed by a multi-second-order generalized integrator-based frequency locked loop (MSOGI-FLL). A harmonic-orthogonal-virtual-resistances controller (HOVR......) is used to proportionally share current components at different sequences and orders independently among the paralleled inverters. Proportional resonance controllers tuned at selected frequencies are used to suppress voltage harmonics. Simulations based on two 2.2 kW paralleled three-phase inverters...

A Method for Harmonic Sources Detection based on Harmonic Distortion Power Rate

Science.gov (United States)

Lin, Ruixing; Xu, Lin; Zheng, Xian

2018-03-01

Harmonic sources detection at the point of common coupling is an essential step for harmonic contribution determination and harmonic mitigation. The harmonic distortion power rate index is proposed for harmonic source location based on IEEE Std 1459-2010 in the paper. The method only based on harmonic distortion power is not suitable when the background harmonic is large. To solve this problem, a threshold is determined by the prior information, when the harmonic distortion power is larger than the threshold, the customer side is considered as the main harmonic source, otherwise, the utility side is. A simple model of public power system was built in MATLAB/Simulink and field test results of typical harmonic loads verified the effectiveness of proposed method.

Optimal Selective Harmonic Mitigation Technique on Variable DC Link Cascaded H-Bridge Converter to Meet Power Quality Standards

DEFF Research Database (Denmark)

Najjar, Mohammad; Moeini, Amirhossein; Dowlatabadi, Mohammadkazem Bakhshizadeh

2016-01-01

In this paper, the power quality standards such as IEC 61000-3-6, IEC 61000-2-12, EN 50160, and CIGRE WG 36-05 are fulfilled for single- and three-phase medium voltage applications by using Selective Harmonic Mitigation-PWM (SHM-PWM) in a Cascaded H-Bridge (CHB) converter. Furthermore, the ER G5/...

Harmonic current interaction at a low voltage customer's installations

NARCIS (Netherlands)

Bhattacharyya, S.; Myrzik, J.M.A.; Kling, W.L.; Cobben, J.F.G.; Casteren, van J.

2009-01-01

The increased uses of power electronics and switching devices in the electricity network have changed the operational environment of the power system. These devices have nonlinear voltage-current characteristics and produce harmonic currents, and consequently distort the voltage waveform. A low

Research on Harmonic Characteristic of Electronic Current Transformer Based on the Rogowski Coil

Science.gov (United States)

Shen, Diqiu; Hu, Bei; Wang, Xufeng; Zhu, Mingdong; Wang, Liang; Lu, Wenxing

2017-05-01

The nonlinear load present in the power system will cause the distortion of AC sine wave and generate the harmonic, which havea severe impact on the accuracy of energy metering and reliability of relay protection. Tosatisfy the requirements of energy metering and relay protection for the new generation of intelligent substation, based on the working principle of Rogowski coil current transformer, mathematical model and transfer characteristics of Rogowski coil sensors were studied in this paper, and frequency response characteristics of Rogowski coil current transformer system were analysed. Finally, the frequency response characteristics of the Rogowski coil current transformer at 2 to 13 harmonics was simulated and experimented. Simulation and experiments show that Rogowski coil current transformer couldmeet 0.2 accuracy requirements of harmonic power measurement of power system, and measure the harmonic components of the grid reliably.

Analytical Modeling Approach to Study Harmonic Mitigation in AC Grids with Active Impedance at Selective Frequencies

Directory of Open Access Journals (Sweden)

Gonzalo Abad

2018-05-01

Full Text Available This paper presents an analytical model, oriented to study harmonic mitigation aspects in AC grids. As it is well known, the presence of non-desired harmonics in AC grids can be palliated in several manners. However, in this paper, a power electronic-based active impedance at selective frequencies (ACISEF is used, due to its already proven flexibility and adaptability to the changing characteristics of AC grids. Hence, the proposed analytical model approach is specially conceived to globally consider both the model of the AC grid itself with its electric equivalent impedances, together with the power electronic-based ACISEF, including its control loops. In addition, the proposed analytical model presents practical and useful properties, as it is simple to understand and simple to use, it has low computational cost and simple adaptability to different scenarios of AC grids, and it provides an accurate enough representation of the reality. The benefits of using the proposed analytical model are shown in this paper through some examples of its usefulness, including an analysis of stability and the identification of sources of instability for a robust design, an analysis of effectiveness in harmonic mitigation, an analysis to assist in the choice of the most suitable active impedance under a given state of the AC grid, an analysis of the interaction between different compensators, and so on. To conclude, experimental validation of a 2.15 kA ACISEF in a real 33 kV AC grid is provided, in which real users (household and industry loads and crucial elements such as wind parks and HVDC systems are near inter-connected.

Current Harmonics Compensation in Microgrids Exploiting the Power Electronics Interfaces of Renewable Energy Sources

Directory of Open Access Journals (Sweden)

Ioannis Bouloumpasis

2015-03-01

Full Text Available This work presents a method of current harmonic reduction in a distorted distribution system. In order to evaluate the proposed method a grid with high-order current harmonics is assumed. The reduction of current distortion is feasible due to the pulse modulation of an active filter, which consists of a buck-boost converter connected back-to-back to a polarity swapping inverter. For a practical application, this system would be the power electronic interface of a Renewable Energy Source (RES and therefore it changes a source of harmonics to a damping harmonics system. Using the proposed method, the current Total Harmonic Distortion (THD of the grid is reduced below the acceptable limits and thus the general power quality of the system is improved. Simulations in the MATLAB/SIMULINK platform and experiments have been performed in order to verify the effectiveness of the proposed method.

Adaptive Virtual Impedance Scheme for Selective Compensation of Voltage Unbalance and Harmonics in Microgrids

DEFF Research Database (Denmark)

Savaghebi, Mehdi; Shafiee, Qobad; Vasquez, Juan Carlos

2015-01-01

and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop mainly for voltage harmonics and unbalance compensation. The virtual impedance is set by the central secondary controller to mitigate the voltage distortion at sensitive load bus (SLB). Secondary...... controller is connected to a measurement unit to obtain the data of voltage harmonics and unbalance at microgrid SLB and broadcasts the commands for adjusting the virtual impedance of each unit. A general case with a combined voltage harmonic and unbalance distortion is considered. In such a case, voltage...... distortion is mitigated by selective insertion of capacitive virtual impedances for negative sequence of fundamental component as well as positive and negative sequences of main harmonics. The values of virtual capacitances are determined based on the required voltage quality at the load bus; thus...

A Unified Voltage Harmonic Control Strategy for Coordinated Compensation with VCM and CCM Converters

DEFF Research Database (Denmark)

Zhao, Xin; Meng, Lexuan; Xie, Chuan

2018-01-01

-controlled mode (VCM) and current-controlled mode (CCM), need to cooperatively provide the compensation function. Aiming at this objective, this paper proposes a unified voltage harmonic mitigation strategy for VCM and CCM converters with high harmonic current sharing accuracy. Another advantage of the proposal......Harmonics have been considered as one of the major issues in modern power grids. Considering the high penetration level of power electronic converter interfaced distributed generators (DGs), it is of interest to provide ancillary services through DG interfacing converters, such as harmonic...... compensation. In case of that, multiple DG interfacing converters are utilized to compensate harmonics, and the compensation effort should be properly shared among these converters. However, it is rarely considered in existing literatures that converters operating in different modes, such as voltage...

Active power compensator of the current harmonics based on the instantaneous power theory

Directory of Open Access Journals (Sweden)

Marian GAICEANU

2005-12-01

Full Text Available The quality of the electrical current becomes a major concern. The proliferation of the power electronic converters, which are used extensively to control electrical apparatus in industrial and commercial applications (dc and ac variable speed motor drives, induction furnaces, power line conditioners, and industrial power supplies, is at the origin of the AC current distribution network pollution and the reactive power demand. These power electronic converters typically draw non-sinusoidal currents from the utility, causing interference with adjacent sensitive loads and limit the utilization of the available electrical supply. The quality of the electrical current thus becomes a significant concern for the distributors of energy and their customers. Recent progress as regards technology of the power electronics brings a capacity of compensation and correction of the harmonic distortion generated by the nonlinear loads. In this paper a parallel active filter prototype capable of reducing the total harmonic distortion in the supply for most current source or adjustable speed drive type loads is presented. A 33 kVA active power filter was developed for harmonic and reactive power compensation based on the instantaneous power theory. The active filter configuration requires the measurement of both the load and filter currents. Experimental results from a prototype active power filter confirm the suitability of the proposed approach. The actual 33kVA prototype converter has been built and tested in the SIEI S.p.A. (Italy laboratory under the Marie Curie Post Doctoral research. The active power compensator is controlled by a high performance DSP platform, resulting in the following active filter features: source current reduction up to the 25th harmonic, 10% THD achievable for current source type loads, efficiency above 97%, does not cause resonance with other loads, operation in the presence of unbalanced loads, reactive power and harmonics

Flexible Compensation of Voltage and Current Unbalance and Harmonics in Microgrids

Directory of Open Access Journals (Sweden)

Seyyed Yousef Mousazadeh Mousavi

2017-10-01

Full Text Available In recent years, the harmonics and unbalance problems endanger the voltage and current quality of power systems, due to increasing usage of nonlinear and unbalanced loads. Use of Distributed Generation (DG-interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method is proposed to compensate voltage and current unbalance and harmonics using the distributed generation (DG-interfacing inverters. This method is applicable to both grid-connected and islanded Microgrids (MGs. In the proposed method, not only the proper control of active and reactive powers can be achieved, but also there is flexibility in compensating the voltage or current quality problems at DG terminals or Points of Common Coupling (PCCs. This control strategy consists of active and reactive power controllers and a voltage/current quality-improvement block. The controller is designed in a stationary (αβ frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. Depending on the compensation modes, the harmonics and unbalance compensation of DG output current, MG-injected current to the grid, as well as PCC and DG voltages, can be achieved in grid-connected operation of MG while in the islanded operation, and the PCC and DG voltages compensation can be obtained through the proposed control scheme.

Assessing harmonic current source modelling and power definitions in balanced and unbalanced networks

Energy Technology Data Exchange (ETDEWEB)

Atkinson-Hope, Gary; Stemmet, W.C. [Cape Peninsula University of Technology, Cape Town Campus, Cape Town (South Africa)

2006-07-01

The purpose of this paper is to assess the DlgSILENT PowerFactory software power definitions (indices) in terms of phase and sequence components for balanced and unbalanced networks when harmonic distortion is present and to compare its results to hand calculations done, following recommendation made by the IEEE Working Group on this topic. This paper also includes the development of a flowchart for calculating power indices in balanced and unbalanced three-phase networks when non-sinusoidal voltages and currents are present. A further purpose is to determine how two industrial grade harmonic analysis software packages (DlgSILENT and ERACS) model three-phase harmonic sources used for current penetration studies and to compare their results when applied to a network. From the investigations, another objective was to develop a methodology for modelling harmonic current sources based on a spectrum obtained from measurements. Three case studies were conducted and the assessment and developed methodologies were shown to be effective. (Author)

Improving the voltage quality of an inverter via by-passing the harmonic current components

DEFF Research Database (Denmark)

Zhong, Qing-Chang; Blaabjerg, Frede; Guerrero, Josep M.

2012-01-01

In this paper, a control strategy is proposed to improve the total harmonic distortion (THD) of the output voltage of an inverter. The physical interpretation of the control strategy is to connect shunt resonant filters at harmonic frequencies to the output so that the harmonic current components...

Effect of accelerating field third harmonic on microtron steady-state conditions and limiting current

International Nuclear Information System (INIS)

Kol'tsov, A.V.; Serov, A.V.

1992-01-01

Setting the acceleration regime in a microtron with the resonator in which the third accelerating field harmonic is excited by accelerated clusters is considered. It is shown that excitation of the accelerating field third harmonic in the microtron resonator (E 011 mode) causes a 1.5 time increase of the range of field intensity values under which resonance particle acceleration is possible. Under moderate energies and accelerated currents (10-15 MeV, 50-80 mA) this leads to a reduction of requirements to the stability of power coming to the resonator and cathode temperature. Under accelerated currents of > 100 mA the third harmonic complicates the microtron transition to acceleration regime. The microtron transfers to stable autooscillation regime, but the current achieved in a single short pulse is increased. By varying the value of the resonator quality factor on the third harmonic one can change the current pulse duration and autooscillation period

Magnetization, critical current, and injection field harmonics in superconducting accelerator magnets

International Nuclear Information System (INIS)

Ghosh, A.K.; Sampson, W.B.; Wanderer, P.

1985-01-01

The very large energy ratio of machines such as the SSC dictates rather low injection field (for 6T, 20 TeV it is approximately 0.3T). Since the harmonic content at such low fields is largely determined by magnetization currents in the superconductor, the random errors depend on the uniformity of the superconducting wire. In principle the magnitude of the residual fields can be reduced indefinitely by using finer filaments, but in practice there is a lower limit of a few microns. We have compared the injection field harmonics for a number of accelerator dipoles with magnetization measurements made on samples of the conductor used to wind the coils. In addition both the magnetization and harmonics have been compared with short sample critical current measurements made at 5T. The results indicated that an accurate estimate of the variation in injection field harmonics can only be obtained from direct measurements of the magnetization of the cable. It appears feasible to use such measurements to ''shuffle'' magnets for a large accelerator by predicting the low field properties of a magnet before actually winding the coils. 10 refs., 4 figs., 2 tabs

Stator Current Harmonic Reduction in a Novel Half Quasi-Z-Source Wind Power Generation System

Directory of Open Access Journals (Sweden)

Shoudao Huang

2016-09-01

Full Text Available The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the system. This paper proposes a novel half quasi-Z-source inverter (H-qZSI for grid-connected wind power generation systems, which can reduce the generator stator current harmonics a great deal. When H-qZSI operates in the shoot-through zero state, the derivative of the generator stator current is only determined by the instantaneous value of the generator stator voltage, so the nonlinear relationship between generator stator current and stator voltage is improved compared with the traditional impedance-source inverter. Theoretically, it is indicated that the stator current harmonics can be reduced effectively by means of the proposed H-qZSI. Finally, simulation and experimental results are given to verify the theoretical analysis.

Improved control strategy for PI-R current of DFIG considering voltage and current harmonics compensation

Science.gov (United States)

Song, S. Y.; Liu, Q. H.; Zhao, Y. N.; Liu, S. Y.

2016-08-01

With the rapid development of wind power generation, the related research of wind power control and integration issues has attracted much attention, and the focus of the research are shifting away from the ideal power grid environment to the actual power grid environment. As the main stream wind turbine generator, a doubly-fed induction generator (DFIG) is connected to the power grid directly by its stator, so it is particularly sensitive to the power grid. This paper studies the improvement of DFIG control technology in the power grid harmonic environment. Based on the DFIG dynamic model considering the power grid harmonic environment, this paper introduces the shortcomings of the common control strategy of DFIG, and puts forward the enhanced method. The decoupling control of the system is realized by compensating the coupling between the rotor harmonic voltage and harmonic current, improving the control performance. In addition, the simulation experiments on PSCAD/EMTDC are carried out to verify the correctness and effectiveness of the improved scheme.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics.

Science.gov (United States)

Boedo, J A; Rudakov, D L

2017-03-01

We present a method to calculate the ion saturation current, I sat , for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat . It is noted that the I sat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e . We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

Analytical Expressions for Harmonic Distortion at Low Frequencies due to Device Mismatch in CMOS Current Mirrors

DEFF Research Database (Denmark)

Bruun, Erik

1999-01-01

One of the origins of harmonic distortion in current mirrors is the inevitable mismatch between the mirror transistors. In this brief we examine both single current mirrors and complementary class AB current mirrors and develop analytical expressions for the mismatch induced harmonic distortion. ...

Third harmonic current injection into highly saturated multi-phase machines

Directory of Open Access Journals (Sweden)

Klute Felix

2017-03-01

Full Text Available One advantage of multi-phase machines is the possibility to use the third harmonic of the rotor flux for additional torque generation. This effect can be maximised for Permanent Magnet Synchronous Machines (PMSM with a high third harmonic content in the magnet flux. This paper discusses the effects of third harmonic current injection (THCI on a five-phase PMSM with a conventional magnet shape depending on saturation. The effects of THCI in five-phase machines are shown in a 2D FEM model in Ansys Maxwell verified by measurement results. The results of the FEM model are analytically analysed using the Park model. It is shown in simulation and measurement that the torque improvement by THCI increases significantly with the saturation level, as the amplitude of the third harmonic flux linkage increases with the saturation level but the phase shift of the rotor flux linkage has to be considered. This paper gives a detailed analysis of saturation mechanisms of PMSM, which can be used for optimizing the efficiency in operating points of high saturations, without using special magnet shapes.

Harmonic current layer method for the design of superconducting quadrupole magnetic field

International Nuclear Information System (INIS)

Zizek, F.

1977-01-01

The magnetic field of a superconducting quadrupole is investigated by the method of harmonic current layers of cylindrical shape. The superconducting winding is replaced by a system of thin current layers with a harmonically distributed density of the surface current along the circumference. The effect of the outer ferromagnetic circuit with an arbitrary constant permeability over the cross section is replaced analogically. The resultant magnetic field is then given by the superposition of the contributions from the individual current layers. The calculation method can be modified for the selection of the geometry of the winding for the latter to meet the demand for the high homogeneity of the gradient of magnetic induction in the working space of the superconducting quadrupole. (author)

Measurement-based harmonic current modeling of mobile storage for power quality study in the distribution system

Directory of Open Access Journals (Sweden)

Wenge Christoph

2017-12-01

Full Text Available Electric vehicles (EVs can be utilized as mobile storages in a power system. The use of battery chargers can cause current harmonics in the supplied AC system. In order to analyze the impact of different EVs with regardto their number and their emission of current harmonics, a generic harmonic current model of EV types was built and implemented in the power system simulation tool PSS®NETOMAC. Based on the measurement data for different types of EVs three standardized harmonic EV models were developed and parametrized. Further, the identified harmonic models are used by the computation of load flow in a modeled, German power distribution system. As a benchmark, a case scenario was studied regarding a high market penetration of EVs in the year 2030 for Germany. The impact of the EV charging on the power distribution system was analyzed and evaluated with valid power quality standards.

Current Harmonics from Single-Phase Grid-Connected Inverters

DEFF Research Database (Denmark)

Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

2016-01-01

Environmental conditions and operational modes may significantly impact the distortion level of the injected current from single-phase grid-connected inverter systems, such as photovoltaic (PV) inverters, which may operate in cloudy days with a maximum power point tracking, in a non-unity power...... factor, or in the low voltage ride through mode with reactive current injection. In this paper, the mechanism of the harmonic current injection from grid-connected single-phase inverter systems is thus explored, and the analysis is conducted on single-phase PV systems. In particular, the analysis...... is focused on the impacts of the power factor and the feed-in grid current level on the quality of the feed-in grid current from single-phase inverters. As a consequence, an internal model principle based high performance current control solution is tailor-made and developed for single-phase grid-connected...

A Hierarchical Control Scheme for Reactive Power and Harmonic Current Sharing in Islanded Microgrids

DEFF Research Database (Denmark)

Lorzadeh, Iman; Firoozabadi, Mehdi Savaghebi; Askarian Abyaneh, Hossein

2015-01-01

In this paper, a hierarchical control scheme consisting of primary and secondary levels is proposed for achieving accurate reactive power and harmonic currents sharing among interface inverters of distributed generators (DGs) in islanded microgrids. Firstly, fundamental and main harmonic componen...

MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

Directory of Open Access Journals (Sweden)

Felix Weber

2016-12-01

Full Text Available This paper describes a semi-active vibration absorber (SVA concept based on a real-time controlled magnetorheological damper (MR-SVA for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD. Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.

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

DEFF Research Database (Denmark)

Savaghebi, Mehdi; Vasquez, Juan Carlos; Jalilian, Alireza Jalilian

2012-01-01

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...

A Harmonic Current Suppression Control Strategy for Droop-Controlled Inverter Connected to the Distorted Grid

DEFF Research Database (Denmark)

Wei, Feng; Sun, Kai; Guan, Yajuan

2015-01-01

currents. Therefore, the reason of generation of distorted grid-feeding current of GF-VCI under the distorted grid voltage is investigated firstly in this paper. Then, a harmonic grid-feeding current suppression control strategy for GF-VCI is proposed. Two different filters are compared and analysed before...... voltage component at the point of common coupling. As a result, the difference of harmonic voltage between PCC and GF-VCI is reduced and the THDi of grid feeding-currents is decreased. Finally, the proposed control strategy is verified through simulations and experimental results....

Development of a harmonized risk mitigation toolbox dedicated to environmental risks of pesticides in farmland in Europe: outcome of the MAgPIE workshop

Directory of Open Access Journals (Sweden)

Alix, A.

2015-11-01

Full Text Available Risk mitigation measures are a key component in designing conditions of use of pesticides in crop protection. A 2-step workshop was organized under the auspices of SETAC and the European Commission and gathered risk assessors and risk managers of 21 European countries, industry, academia and agronomical advisors/extension services, in order to provide European regulatory authorities with a toolbox of risk mitigation measures designed to reduce environmental risks of pesticides used in agriculture, and thus contribute to a better harmonization within Europe in the area. The workshop gathered an inventory of the risk mitigation tools for pesticides being implemented or in development in European countries. The inventory was discussed in order to identify the most promising tools for a harmonized toolbox in the European area. The discussions concerned the level of confidence in the technical data on which the tools identified rely, possible regulatory hurdles, expectations as regards the implementation of these tools by farmers and links with risk assessment. Finally, this workshop was a first step towards a network gathering all stakeholders, i.e. experts from national authorities, research sector, industry and farmers, to share information and further develop this toolbox. This paper presents an outline of the content of the toolbox with an emphasis on spray drift reducing techniques, in line with the discussions ongoing in the SPISE workshop.

Harmonic Damping in DG-Penetrated Distribution Network

DEFF Research Database (Denmark)

Lu, Jinghang; Savaghebi, Mehdi; Guerrero, Josep M.

2016-01-01

Grid background harmonics may be amplified, propagate through a long distribution feeder and even lead to power system instability. In this paper, harmonic propagation issue is investigated and mitigation of the harmonics is analyzed by using transmission line theory which has already been applied...... in power systems. It is demonstrated that a specific harmonic will not be amplified if the feeder’s length is less than one quarter of the harmonic wavelength meanwhile the terminal impedance is less than characteristic impedance. Besides, three scenarios will be considered in accordance...... with the relationship between the feeder’s length and harmonic wavelength. Harmonic suppression control strategies will be respectively designed considering 5th and 7th harmonics coexisting in the distribution line. Finally, a simulation study has been performed to verify the theoretical analysis and demonstrate...

Harmonics Monitoring Survey on LED Lamps

Directory of Open Access Journals (Sweden)

Abdelrahman Ahmed Akila

2017-03-01

Full Text Available Light Emitting Diode (LED lamps are being increasingly used in many applications. These LED lamps operate using a driver, which is a switching device. Hence, LED lamps will be a source of harmonics in the power system. These harmonics if not well treated, may cause severe performance and operational problems. In this paper, harmonics (amplitude and phase angles generated by both LED lamps and conventional fluorescent lamps will be studied practically. Then they will be analyzed and evaluated. Compared to each other harmonics generated by both LED and conventional florescent lamps, self mitigation may occur based on the phase angle of these harmonics. All data will be measured using power analyzer and will be done on a sample of actual lamps.

A Novel Method for the Current Harmonic Elimination of Industrial Power System Using Single Tuned Shunt Passive Filter

Directory of Open Access Journals (Sweden)

Mansoor Ahmed Soomro

2012-01-01

Full Text Available The automation of IPS (Industrial Power System has brought about several advantages of increased productivity and efficiency but it suffers from incompatible problems of overheating, noise, complexity etc, which disturb its smooth and fault tolerant implication. When the resonance condition is reached, these effects become detrimental and disturb the whole power system. The purpose of this research work is to include single tuned shunt type passive filter for harmonic elimination of the components used in industrial power system. For this purpose, MATLAB simulation using sim Power system tool has been used to analyze the effects of current harmonics. Third harmonic effects have been removed by the addition of six pulse converter technique. The simulation results show that implication of single tuned shunt (parallel connected passive filter removes effects of succeeding order current harmonics i.e. fifth, seventh and eleventh etc. which are causing substantial damage to industrial power system. The effects of current harmonics can be solved by installing without and with the application of proposed filter. Further, it is observed that these filters contribute in reduction of THD (Total Harmonic Current Distortion followed by improvement in power factor. These results are taken considering limits of IEEE 519-1992 standards.

Torque ripple reduction of brushless DC motor with harmonic current injection based on integral terminal sliding mode control

DEFF Research Database (Denmark)

Boroujeni, Mojtaba Shirvani; Markadeh, Gholamreza Arab; Soltani, Jafar

2018-01-01

Brushless Harmonic current injection to the stator windings is one of the most effective methods for torque ripple reduction of brushless DC motors. Because of multi harmonic contents of the stator currents, the conventional methods based on rotational reference frame cannot be used to calculate...

Design of six pulse bridge multiplication converter model for current harmonic elimination of three phase ac-dc converter

International Nuclear Information System (INIS)

Soomro, M.A.; Helepoto, I.A.

2014-01-01

The recent development of semiconductor technology and wide spread use of power electronic devices in power system have open the era of the power system harmonics due to increasing penetration of non-linear loads. Harmonics are widely admitted as most important issues of power quality which must be eliminated to maintain power system reliability. The tolerable THD (Total Harmonic Distortion) values must be bounded in well-defined limits recognized by IEEE-519 standard. In this work, in order to eliminate the current harmonics produced by non-linear loads, six pulse multiplication converter technique in conjunction with STSSHPE (Single Tuned Shunt Harmonic Passive Filter) is proposed. The proposed model has the capacity of harmonic cancellation of the dominant 3rd order harmonics. Besides that, the 5th and 7th order harmonics are also reduced to a diminishing level. The hardware model has been experimentally tested by PQA (Power Quality Analyzer) and simulation model is designed using MATLAB software. The acquired results have been measured by considering THD values in terms of current and voltage. Furthermore, they have been compared against IEEE-519 performance standards. The prosed model, successfully bounds the total harmonic distortion under defined limits by IEEE-519 standard. (author)

Cancellation of neutral current harmonics by using a four-branch star hybrid filter

DEFF Research Database (Denmark)

Blaabjerg, Frede; Rodriguez, Pedro; Candela, I.

2008-01-01

filtering topology to a three-phase four-wire system. An extensive evaluation using simulation and experimental results are conducted in this work to validate the good performance of the proposed solution for canceling current harmonics flowing through the neutral conductor.......This paper presents a new technique for filtering current harmonics in three-phase four-wire networks based on the usage of a four-branch star (FBS) filter topology. Based on single-phase inductors and capacitors, the specific layout of the FBS filter topology allows achieving a power filter...... is improved by integrating a power converter into its structure. This paper analyzes the FBS topology and presents fundamental concepts regarding the control of a generic FBS hybrid power filter. A neutral current hybrid power filter and var compensator is presented as an illustrative example applying the FBS...

Optimization Based Shunt APF Controller to Mitigate Reactive Power, Burden of Neutral Conductor, Current Harmonics and Improve cosɸ

Directory of Open Access Journals (Sweden)

P. Anjana

2017-03-01

Full Text Available This paper presents a Modified Gravitational Search Algorithm (MGSA to improve the performance of PI controller in varying load condition. The proposed approach is capable of mitigating reactive power, neutral current, source current THD and significant improvement in power factor nearly unity (0.997. The DC link voltage across the capacitor is controlled by PI controller which is deciding the performance of shunt APF. Hence, the robust optimization technique based integral time square error (ITSE with consideration of weight factor (α & β, maximum overshoot ((|(∆_Ve ̅〖(n〗_max | and setling time t_s-t_0, is providing the optimum solution of Kp & Ki. The robustness of proposed objective function and algorithm compared with GSA based three other error criterion techniques. The efficiency of the proposed controller has been tested over nonlinear and unbalance loading condition. The performance of ITSE based MGSA-PI controller is batter then other three error criterion techniques. The values of THD are below the mark of 5% specified in IEEE-519 standard.

Autonomous control of inverter-interfaced Distributed Generation units for harmonic current filtering and resonance damping in an islanded microgrid

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2012-01-01

Harmonic current filtering and resonance damping have become important concerns on the control of an islanded microgrids. To address these challenges, this paper proposes a control method of inverter-interfaced Distributed Generation (DG) units, which can autonomously share harmonic currents and ...

Determination of nonlinear resistance voltage-current relationships by measuring harmonics

Science.gov (United States)

Stafford, J. M.

1971-01-01

Test configuration measures harmonic signal amplitudes generated in nonlinear resistance. Vacuum-type voltmeter measures low frequency sinusoidal input signal amplitude and wave-analyzer measures amplitude of harmonic signals generated in junction. Input signal harmonics amplitude must not exceed that of harmonics generated in nonlinear resistance.

Harmonic Active Filtering and Impedance-based Stability Analysis in Offshore Wind Power Plants

DEFF Research Database (Denmark)

Dhua, Debasish; Yang, Guangya; Zhang, Zhe

2017-01-01

installation and provides effectively similar functionality as passive filters. This work is focused on harmonic propagation studies in wind power plants, power quality evaluation at the point of connection and harmonic mitigation by active filtering. Finally, an impedance-based stability analysis......Nowadays, to eliminate harmonics injected by the wind turbines in offshore wind power plants there is a need to install passive filters. Moreover, the passive filters are not adaptive to harmonic profile changes due to topology changes, grid loading etc. Therefore, active filters in wind turbines...... are proposed as a flexible harmonic mitigation measure. The motivation of this study is to explore the possibility of embedding active filtering in wind turbine grid-side converters without having to change the system electrical infrastructure. The active filtering method can prevent additional equipment...

Protection of Multi-Terminal VSC-HVDC Grids Based on the Response of the First Carrier Frequency Harmonic Current

DEFF Research Database (Denmark)

Ashouri, Mani; Khazraj, Hesam; Silva, Filipe Miguel Faria da

This paper investigates the response of first carrier frequency harmonic (FCFH) current for designing a protection algorithm for multi-terminal Voltage source converter-based HVDC (VSC-MTDC) transmission grids. This transient harmonic current has been used before, to discriminate external AC faults...... various kinds of faults with different locations and resistances. This paper will also consider half-bridge MMC instead of two-level VSCs to test the sensitivity of the FCFH based algorithm for lower harmonic values. A modified meshed version of CIGRE DC model has been used in PSCAD and the signal...

ECH power deposition at 3rd harmonic in high elongation TCV discharges sustained by 2nd harmonic current profile broadening

International Nuclear Information System (INIS)

Pochelon, A. . E-mail : Antoine.Pochelon@epfl.ch; Arnoux, G.; Camenen, Y.

2003-01-01

This paper summarises the present effort aimed at developing high elongation heated discharges and testing their confinement properties at normalised currents for which the highest ideal MHD β-limits are predicted. 2nd harmonic (X2) far off-axis ECH/CD is used to stabilise the plasma vertically at high elongation by broadening the current profile in stationary conditions (during the current flat top and over several current diffusion times). Current broadening is maximal for a power deposition in a narrow region (∼a/5), for a finite toroidal injection angle and for high plasma density using upper lateral launchers to minimise refraction. In these discharges which are twice X2 overdense in the centre, 3rd harmonic (X3) is injected from a top launcher to deposit power in the centre and increase the central pressure, simultaneously with far off-axis X2. Using modulated X3, full absorption is measured by the diamagnetic probe. Absorption higher than calculated by thermal ray tracing is occasionally found, indicating absorption on the electron bulk as well as in the suprathermal electron population sometimes with a hollow deposition profile. The high sensitivity of the power coupling to the beam angle stresses the need for developing a mirror feedback scheme to increase the coupling efficiency in transient heating scenarios. (author)

harmonics mitigation on industrial loads using series and parallel

African Journals Online (AJOL)

user

harmonics using Simulink model of the power system of NICHEMTEX, a Textile industry in Nigeria as a .... operating loss Akagi [5]. ... where he described the pros and cons of active, passive ... fluorescent lighting, computer switch mode power.

HARMONIC DRIVE SELECTION

Directory of Open Access Journals (Sweden)

Piotr FOLĘGA

2014-03-01

Full Text Available The variety of types and sizes currently in production harmonic drive is a problem in their rational choice. Properly selected harmonic drive must meet certain requirements during operation, and achieve the anticipated service life. The paper discusses the problems associated with the selection of the harmonic drive. It also presents the algorithm correct choice of harmonic drive. The main objective of this study was to develop a computer program that allows the correct choice of harmonic drive by developed algorithm.

Optimized design of resonant controller for stator current harmonic compensation in DFIG wind turbine systems

DEFF Research Database (Denmark)

Liu, Changjin; Chen, Wenjie; Blaabjerg, Frede

2012-01-01

This paper presents an analytical method to optimize the parameters of resonant controller which is used in a Doubly-Fed Induction Generator (DFIG). In the DFIG control system, the fundamental current loop is controlled by PI-controllers, and the stator harmonic current loop is controlled...

A New Control Structure for Grid-Connected LCL PV Inverters with Zero Steady-State Error and Selective Harmonic Compensation

DEFF Research Database (Denmark)

Teodorescu, Remus; Blaabjerg, Frede; Borup, Uffe

2004-01-01

disturbance rejection capability leads to the need of grid feed-forward compensation. However the imperfect compensation action of the feed-forward control results in high harmonic distortion of the current and consequently non-compliance with international standards. In this paper a new control strategy...... aimed to mitigate these problems is proposed. Stationary-frame generalized integrators are used to control the fundamental current and to compensate the grid harmonics providing disturbance rejection capability without the need of feed-forward grid compensation. Moreover the use of a grid LCL......The PI current control of a single-phase inverter has well known drawbacks: steady-state magnitude and phase-error and limited disturbance rejection capability. When the current controlled inverter is connected to the grid, the phase error results in a power factor decrement and the limited...

The harmonic distortion evolution of current in computers; A evolucao da distorcao harmonica de corrente em computadores

Energy Technology Data Exchange (ETDEWEB)

Bollen, Math; Larsson, Anders; Lundmark, Martin [Universidade de Tecnologia de Lulea (LTU) (Sweden); Wahlberg, Mats; Roennberg, Sarah [Skelleftea Kraft (Sweden)

2010-05-15

This project made feeding measurements of large group of computers during games between 2002 and 2008, including the magnitude of current in each phase and in the neutral conductor, the energy consumption and the harmonic spectrum. The presented results show that the harmonic distortion has been diminishing significantly, while the energy consumption by computer do not register important increase.

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

Science.gov (United States)

Singh, B.; Shahani, D. T.; Verma, A. K.

2015-03-01

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

Deterministic and Stochastic Study of Wind Farm Harmonic Currents

DEFF Research Database (Denmark)

Sainz, Luis; Mesas, Juan Jose; Teodorescu, Remus

2010-01-01

Wind farm harmonic emissions are a well-known power quality problem, but little data based on actual wind farm measurements are available in literature. In this paper, harmonic emissions of an 18 MW wind farm are investigated using extensive measurements, and the deterministic and stochastic char...

Harmonics and energy management

International Nuclear Information System (INIS)

Andresen, M.

1993-01-01

To summarize what this paper has presented: Voltage and current non-sinusoidal wave shapes exist in our power system. These harmonics result from the prolific use of non-linear loads. The use of these types of loads is increasing dramatically, partly due to the push to implement energy management techniques involving harmonic generating equipment. Harmonic analysis can identify specific harmonics, their frequency, magnitude, and phase shift referenced to the fundamental. Harmonic distortion forces the use of true RMS multimeters for measurement accuracy. High levels of neutral current and N-G voltages are now possible. Transformers may overheat and fail even though they are below rated capacity. Low power factors due to harmonics cannot be corrected by the installation of capacitors, and knowledge of the fundamental VARs or the displacement power factor is needed to use capacitors alone for power factor correction. The harmonic related problems presented are by no means an exhaustive list. Many other concerns arise when harmonics are involved in the power system. The critical issue behind these problems is that many of the devices being recommended from an energy management point of view are contributing to the harmonic levels, and thus to the potential for harmonic problems. We can no longer live in the sinusoidal mentality if we are to be effective in saving energy and reducing costs

Influence of load type on power factor and harmonic composition of three-phase rectifier current

Science.gov (United States)

Nikolayzin, N. V.; Vstavskaya, E. V.; Konstantinov, V. I.; Konstantinova, O. V.

2018-05-01

This article is devoted to research of the harmonic composition of the three-phase rectifier current consumed when it operates with different types of load. The results are compared with Standard requirements.

Minimizing Harmonic Distortion Impact at Distribution System with Considering Large-Scale EV Load Behaviour Using Modified Lightning Search Algorithm and Pareto-Fuzzy Approach

Directory of Open Access Journals (Sweden)

S. N. Syed Nasir

2018-01-01

Full Text Available This research is focusing on optimal placement and sizing of multiple variable passive filter (VPF to mitigate harmonic distortion due to charging station (CS at 449 bus distribution network. There are 132 units of CS which are scheduled based on user behaviour within 24 hours, with the interval of 15 minutes. By considering the varying of CS patterns and harmonic impact, Modified Lightning Search Algorithm (MLSA is used to find 22 units of VPF coordination, so that less harmonics will be injected from 415 V bus to the medium voltage network and power loss is also reduced. Power system harmonic flow, VPF, CS, battery, and the analysis will be modelled in MATLAB/m-file platform. High Performance Computing (HPC is used to make simulation faster. Pareto-Fuzzy technique is used to obtain sizing of VPF from all nondominated solutions. From the result, the optimal placements and sizes of VPF are able to reduce the maximum THD for voltage and current and also the total apparent losses up to 39.14%, 52.5%, and 2.96%, respectively. Therefore, it can be concluded that the MLSA is suitable method to mitigate harmonic and it is beneficial in minimizing the impact of aggressive CS installation at distribution network.

Evaluation of an Advanced Harmonic Filter for Adjustable Speed Drives using a Toolbox Approach

DEFF Research Database (Denmark)

Asiminoaei, Lucian; Hansen, Steffan; Blaabjerg, Frede

2004-01-01

A large diversity of solutions exists to reduce the harmonic emission of the 6-pulse Adjustable Speed Drive in order to fulfill the requirements of the international harmonic standards. Among them, new types of advanced harmonic filters recently gained an increased attention due to their good...... a combination of a pre-stored database and new interpolation techniques the toolbox can provide the harmonic data on real applications allowing comparisons between different mitigation solutions....

Two dimensional code for modeling of high ione cyclotron harmonic fast wave heating and current drive

International Nuclear Information System (INIS)

Grekov, D.; Kasilov, S.; Kernbichler, W.

2016-01-01

A two dimensional numerical code for computation of the electromagnetic field of a fast magnetosonic wave in a tokamak at high harmonics of the ion cyclotron frequency has been developed. The code computes the finite difference solution of Maxwell equations for separate toroidal harmonics making use of the toroidal symmetry of tokamak plasmas. The proper boundary conditions are prescribed at the realistic tokamak vessel. The currents in the RF antenna are specified externally and then used in Ampere law. The main poloidal tokamak magnetic field and the ''kinetic'' part of the dielectric permeability tensor are treated iteratively. The code has been verified against known analytical solutions and first calculations of current drive in the spherical torus are presented.

Detection of second harmonic of phase dependence of superconducting current in Nb/Au/YBCO heterojunctions

CERN Document Server

Komissinskij, F V; Ilichev, E V; Ivanov, Z G

2001-01-01

The results of the experimental study on the current phase dependence (CPD) of the heterotransitions, consisting of the niobium and the YBa sub 2 Cu sub 3 O sub x (YBCO) film with an additional interlayer from gold (Nb/Au/YBCO) are presented. The CPD measurement is carried out through the radiofrequency superconducting quantum interferometer. The CPD second harmonic is determined in the Nb/Au/YBCO heterotransitions. Possible causes of its appearance are discussed within the frames of the d +- s combined symmetry of the YBCO order parameter. One of the causes of the CPD second harmonic appearance is the twinning of the YBCO films (001). The second cause of existing the anomalously high critical current consists in the availability of the Nb/Au boundary with the transparence of approx 10 sup - sup 1 in the Nb/Au/YBCO

High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

Energy Technology Data Exchange (ETDEWEB)

Thomas, Alexander Roy [Univ. of Michigan, Ann Arbor, MI (United States); Krushelnick, Karl [Univ. of Michigan, Ann Arbor, MI (United States)

2016-09-08

We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactions at 10²¹ Wcm^-2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.

Modification of double vector control algorithm to filter out grid harmonics

DEFF Research Database (Denmark)

Awad, Hilmy; Blaabjerg, Frede

2005-01-01

terminals in the case of distorted grid voltage. Furthermore, a selective harmonic compensation strategy is applied to filter out the grid harmonics. The operation of the SSC under distorted utility conditions and voltage dips is discussed. The validity of the proposed controller is verified by experiments......, which have been carried out on a 10-kV SSC laboratory setup. Experimental results have shown the ability of the SSC to mitigate voltage dips and harmonics. It is also shown that the proposed controller has improved the transient performance of the SSC even under distorted utility conditions....

Simulation and RTDS Hardware Implementation of SHAF for Mitigation of Current Harmonics with p-q and Id-Iq Control Strategies Using PI Controller

Directory of Open Access Journals (Sweden)

A. K. Panda

2011-06-01

Full Text Available Control strategies for extracting the three-phase reference currents for shunt active power filters are compared, evaluating their performance under different source conditions in MATLAB/Simulink environment and also with Real Time Digital Simulator (RTDS Hardware. When the supply voltages are balanced and sinusoidal, the two control strategies are converging to the same compensation characteristics but when the supply voltages are distorted and/or un-balanced sinusoidal, these control strategies result in different degrees of compensation in harmonics. The p-q control strategy is unable to yield an adequate solution when source voltages are not ideal. Extensive Simulations are carried out with PI controller for both p-q and Id-Iq control strategies for different voltage conditions and adequate results were presented. The 3-ph 4-wire SHAF system is also implemented on RTDS Hardware to further verify its effectiveness. The detailed simulation and RTDS Hardware results are included.

Harmonic Resonances in Wind Power Plants

DEFF Research Database (Denmark)

Fernandez, Francisco Daniel Freijedo; Chaudhary, Sanjay; Teodorescu, Remus

2015-01-01

This work reviews the state-of-the-art in the field of harmonic resonance problems in Wind Power Plants (WPPs). Firstly, a generic WPP is modeled according to the equivalent circuits of its passive and active components. Main focus is put on modeling active components, i.e. the ones based on power...... converters. Subsequently, pros and cons of frequency and time domain analysis methods are outlined. The next sections are devoted to mitigation methods implemented in the power electronics converters. From the wind turbine perspective, different techniques to enhance the robustness of the controller...... are analyzed. Subsequently, the suitability for active damping of harmonics using STATCOM devices is assessed, with focus both on control techniques and power converter technologies....

Benchmark of AC and DC Active Power Decoupling Circuits for Second-Order Harmonic Mitigation in Kilowatt-Scale Single-Phase Inverters

DEFF Research Database (Denmark)

Qin, Zian; Tang, Yi; Loh, Poh Chiang

2016-01-01

efficiency and high power density is identified and comprehensively studied, and the commercially available film capacitors, the circuit topologies, and the control strategies adopted for active power decoupling are all taken into account. Then, an adaptive decoupling voltage control method is proposed...... to further improve the performance of dc decoupling in terms of efficiency and reliability. The feasibility and superiority of the identified solution for active power decoupling together with the proposed adaptive decoupling voltage control method are finally verified by both the simulation and experimental......This paper presents the benchmark study of ac and dc active power decoupling circuits for second order harmonic mitigation in kW scale single-phase inverters. First of all, a brief comparison of recently reported active power decoupling circuits is given, and the best solution that can achieve high...

Stator current harmonics evolution by neural network method based on CFE/SS algorithm for ACEC generator of Rey Power Plant

International Nuclear Information System (INIS)

Soleymani, S.; Ranjbar, A.M.; Mirabedini, H.

2001-01-01

One method for on-line fault diagnosis in synchronous generator is stator current harmonics analysis. Then artificial neural network is considered in this paper in order to evaluate stator current harmonics in different loads. Training set of artificial neural network is made ready by generator modeling, finite element method and state space model. Many points from generator capability curve are used in order to complete this set. Artificial neural network which is used in this paper is a percept ron network with a single hidden layer, Eight hidden neurons and back propagation algorithm. Results are indicated that the trained artificial neural network can identify stator current harmonics for arbitrary load from the capability curve. The error is less than 10% in comparison with values obtained directly from the CFE-SS algorithm. The rating parameters of modeled generator are 43950 (kV A), 11(KV), 3000 (rpm), 50 (H Z), (P F=0.8)

Multivariable polynomial fitting of controlled single-phase nonlinear load of input current total harmonic distortion

Science.gov (United States)

Sikora, Roman; Markiewicz, Przemysław; Pabjańczyk, Wiesława

2018-04-01

The power systems usually include a number of nonlinear receivers. Nonlinear receivers are the source of disturbances generated to the power system in the form of higher harmonics. The level of these disturbances describes the total harmonic distortion coefficient THD. Its value depends on many factors. One of them are the deformation and change in RMS value of supply voltage. A modern LED luminaire is a nonlinear receiver as well. The paper presents the results of the analysis of the influence of change in RMS value of supply voltage and the level of dimming of the tested luminaire on the value of the current THD. The analysis was made using a mathematical model based on multivariable polynomial fitting.

Enhanced Power Quality and Minimized Peak Current Control in An Inverter based Microgrid under Unbalanced Grid Faults

DEFF Research Database (Denmark)

Liu, Wenzhao; Guo, Xiaoqiang; Sulligoi, Giorgio

2016-01-01

The microgrid inverter experiences the power oscillations and current harmonics in case of the unbalanced grid voltage faults. However, there is a trade-off between power oscillations and current harmonics should be considered in three phase three wire inverter systems during the conventional fault...... ride through control. In order to solve this problem, a novel control strategy is proposed to enhance the output current quality while mitigating the active and reactive output power oscillations. Moreover, a simple current-limited control strategy can be achieved without the necessity of the voltage....../current positive/negative sequence extraction. Finally, the simulation tests of the conventional and proposed control solutions are carried out. The results verify the effectiveness of the proposed strategy....

A Voltage Feedback Based Harmonic Compensation Strategy for Current-Controlled Converters

DEFF Research Database (Denmark)

Zhao, Xin; Meng, Lexuan; Xie, Chuan

2018-01-01

Harmonics have been considered as one of the major issues in future power grids. With the increasing demand in advanced control functions, power electronic converter interfaced distributed generators (DGs) are expected to perform harmonic compensation when necessary. It has been demonstrated in a...

Steam generator degradation: Current mitigation strategies for controlling corrosion

International Nuclear Information System (INIS)

Millett, P.

1997-01-01

Steam Generator degradation has caused substantial losses of power generation, resulted in large repair and maintenance costs, and contributed to significant personnel radiation exposures in Pressurized Water Reactors (PWRs) operating throughout the world. EPRI has just published the revised Steam Generator Reference Book, which reviews all of the major forms of SG degradation. This paper discusses the types of SG degradation that have been experienced with emphasis on the mitigation strategies that have been developed and implemented in the field. SG degradation is presented from a world wide perspective as all countries operating PWRs have been effected to one degree or another. The paper is written from a US. perspective where the utility industry is currently undergoing tremendous change as a result of deregulation of the electricity marketplace. Competitive pressures are causing utilities to strive to reduce Operations and Maintenance (O ampersand M) and capital costs. SG corrosion is a major contributor to the O ampersand M costs of PWR plants, and therefore US utilities are evaluating and implementing the most cost effective solutions to their corrosion problems. Mitigation strategies developed over the past few years reflect a trend towards plant specific solutions to SG corrosion problems. Since SG degradation is in most cases an economic problem and not a safety problem, utilities can focus their mitigation strategies on their unique financial situation. Accordingly, the focus of R ampersand D has shifted from the development of more expensive, prescriptive solutions (e.g. reduced impurity limits) to corrosion problems to providing the utilities with a number of cost effective mitigation options (e.g. molar ratio control, boric acid treatment)

Virtual RC Damping of LCL-Filtered Voltage Source Converters with Extended Selective Harmonic Compensation

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

2015-01-01

Active damping and harmonic compensation are two common challenges faced by LCL-filtered voltage source converters. To manage them holistically, this paper begins by proposing a virtual RC damper in parallel with the passive filter capacitor. The virtual damper is actively inserted by feeding back...... the passive capacitor current through a high-pass filter, which indirectly, furnishes two superior features. They are the mitigation of phase lag experienced by a conventional damper and the avoidance of instability caused by the negative resistance inserted unintentionally. Moreover, with the virtual RC...

Harmonic Mitigation in Islanded Microgrids by Inverter-Interfaced Distributed Energy Resources

DEFF Research Database (Denmark)

Wang, Xiongfei

of Distributed Energy Resource (DER) for both customers and utilities. However, during islanded operations, microgrids are more sensitive to power quality disturbances, owing to the low short-circuit ratio and limited capacity of DER units. As a consequence, harmonic distortion caused by the proliferation...

Synthesis of Variable Harmonic Impedance in Inverter-Interfaced Distributed Generation Unit for Harmonic Damping Throughout a Distribution Network

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2012-01-01

This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverters in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective harmonic load current feedforward loop...... at the dominant harmonic frequencies. Thus, the harmonic voltage drop on the grid-side inductance and the harmonic resonances throughout a distribution feeder with multiple shunt-connected capacitors can be effectively attenuated. Simulation and laboratory test results validate the performance of the proposed...

Analysis of Even Harmonics Generation in an Isolated Electric Power System

Science.gov (United States)

Kanao, Norikazu; Hayashi, Yasuhiro; Matsuki, Junya

Harmonics bred from loads are mainly odd order because the current waveform has half-wave symmetry. Since the even harmonics are negligibly small, those are not generally measured in electric power systems. However, even harmonics were measured at a 500/275/154kV substation in Hokuriku Electric Power Company after removal of a transmission line fault. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as automatic supervisory signal. This paper describes the mechanism of generation of the even harmonics by comparing measured waveforms with ATP-EMTP simulation results. As a result of analysis, it is cleared that even harmonics are generated by three causes. The first cause is a magnetizing current of transformers due to flux deviation by DC component of a fault current. The second one is due to harmonic conversion of a synchronous machine which generates even harmonics when direct current component or even harmonic current flow into the machine. The third one is that increase of harmonic impedance due to an isolated power system produces harmonic voltages. The design of the input filter of protective digital relays should consider even harmonics generation in an isolated power system.

Multivariable polynomial fitting of controlled single-phase nonlinear load of input current total harmonic distortion

Directory of Open Access Journals (Sweden)

Sikora Roman

2018-04-01

Full Text Available The power systems usually include a number of nonlinear receivers. Nonlinear receivers are the source of disturbances generated to the power system in the form of higher harmonics. The level of these disturbances describes the total harmonic distortion coefficient THD. Its value depends on many factors. One of them are the deformation and change in RMS value of supply voltage. A modern LED luminaire is a nonlinear receiver as well. The paper presents the results of the analysis of the influence of change in RMS value of supply voltage and the level of dimming of the tested luminaire on the value of the current THD. The analysis was made using a mathematical model based on multivariable polynomial fitting.

Benchmark of AC and DC active power decoupling circuits for second-order harmonic mitigation in kW-scale single-phase inverters

DEFF Research Database (Denmark)

Qin, Zian; Tang, Yi; Loh, Poh Chiang

2015-01-01

studied, where the commercially available film capacitors, circuit topologies, and control strategies for active power decoupling are all taken into account. Then, an adaptive decoupling voltage control method is proposed to further improve the performance of dc decoupling in terms of efficiency...... and reliability. The feasibility and superiority of the identified solution for active power decoupling together with the proposed adaptive decoupling voltage control method are finally verified by both the experimental results obtained on a 2 kW single-phase inverter.......This paper presents the benchmark study of ac and dc active power decoupling circuits for second-order harmonic mitigation in kW-scale single-phase inverters. First of all, the best solutions of active power decoupling to achieve high efficiency and power density are identified and comprehensively...

Synthesis of variable harmonic impedance in inverter-interfaced distributed generation unit for harmonic damping throughout a distribution network

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2012-01-01

This paper proposes a harmonic impedance synthesis technique for voltage-controlled distributed generation inverter in order to damp harmonic voltage distortion on a distribution network. The approach employs a multiloop control scheme, where a selective load harmonic current feedforward loop bas...

Global Harmonic Current Rejection of Nonlinear Backstepping Control with Multivariable Adaptive Internal Model Principle for Grid-Connected Inverter under Distorted Grid Voltage

Directory of Open Access Journals (Sweden)

Yang Yu

2013-01-01

Full Text Available Based on a brief review on current harmonics generation mechanism for grid-connected inverter under distorted grid voltage, the harmonic disturbances and uncertain items are immersed into the original state-space differential equation of grid-connected inverter. A new algorithm of global current harmonic rejection based on nonlinear backstepping control with multivariable internal model principle is proposed for grid-connected inverter with exogenous disturbances and uncertainties. A type of multivariable internal model for a class of nonlinear harmonic disturbances is constructed. Based on application of backstepping control law of the nominal system, a multivariable adaptive state feedback controller combined with multivariable internal model and adaptive control law is designed to guarantee the closed-loop system globally uniformly bounded, which is proved by a constructed Lyapunov function. The presented algorithm extends rejection of nonlinear single-input systems to multivariable globally defined normal form, the correctness and effectiveness of which are verified by the simulation results.

Harmonic Distortion of Rectifier Topologies for Adjustable Speed Drives

DEFF Research Database (Denmark)

Hansen, Steffan

This thesis deals with the harmonic distortion of the diode rectifier and a number of alternative rectifier topologies for adjustable speed drives. The main intention of this thesis is to provide models and tools that allow easy prediction of the harmonic distortion of ASD’s in a given system...... rectifier are presented. The first level is an ideal model where the diode rectifier basically is treated as an independent (harmonic) current source. The second level is an empirical model, where simulated (or measured) values of the harmonic currents of the diode rectifier for different parameters......-angle of the individual harmonic currents of different diode rectifier types is analyzed. Four selected rectifier topologies with a high input power factor are presented. It is shown that using ac- or dc-coils is a very simple and efficient method to reduce the harmonic currents compared to the basic diode rectifier...

H∞ Robust Current Control for DFIG Based Wind Turbine subject to Grid Voltage Distortions

DEFF Research Database (Denmark)

Wang, Yun; Wu, Qiuwei; Gong, Wenming

2016-01-01

This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage...... distortions considered include asymmetric voltage dips and grid background harmonics. An uncertain DFIG model is developed with uncertain factors originating from distorted stator voltage, and changed generator parameters due to the flux saturation effect, the skin effect, etc. Weighting functions...... are designed to efficiently track the unbalanced current components and the 5th and 7th background harmonics. The robust stability (RS) and robust performance (RP) of the proposed controller are verified by the structured singular value µ. The performance of the H∞ robust current controller was demonstrated...

Multipole lenses with implicit poles and with harmonic distribution of current density in a coil

International Nuclear Information System (INIS)

Skachkov, V.S.

1984-01-01

General theory of the multipole lense with implicit poles is presented. The thickness of lense coil is finite. Current density distribution in the coil cross section is harmonic in the azimuth direction and arbitrary in the radial one. The calculation of yoke contribution in the lence field is given. Two particular lense variants differing from each other in the method of current density radial distribution are considered and necessary calculated relations for the lense with and without yoke ar presented. A comparative analysis of physical and technological peculiarities of these lenses is performed

Investigation on the Performance of UPQC-Q for Voltage Sag Mitigation and PQ Improvement at a Critical Load Point

OpenAIRE

Basu, Malabika; Das, S. P.; Dubey, Gopal

2008-01-01

The unified power quality conditioner (UPQC) is one of the major custom power solutions, which is capable of mitigating the effect of supply voltage sag at the load end or at the point of common coupling (PCC) in a distributed network. It also prevents the propagation of the load current harmonics to the utility and improves the input power factor of the load. The control of series compensator (SERC) of the UPQC is such that it injects voltage in quadrature advance to the supply current. Thus...

Harmonic Detection at Initialization With Kalman Filter

DEFF Research Database (Denmark)

Hussain, Dil Muhammad Akbar; Imran, Raja Muhammad; Shoro, Ghulam Mustafa

2014-01-01

Most power electronic equipment these days generate harmonic disturbances, these devices hold nonlinear voltage/current characteristic. The harmonics generated can potentially be harmful to the consumer supply. Typically, filters are integrated at the power source or utility location to filter out...... the affect of harmonics on the supply. For the detection of these harmonics various techniques are available and one of that technique is the Kalman filter. In this paper we investigate that what are the consequences when harmonic detection system based on Kalman Filtering is initialized...

Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

Science.gov (United States)

Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

2015-01-01

ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the

Detection of Harmonic Occurring using Kalman Filtering

DEFF Research Database (Denmark)

Hussain, Dil Muhammad Akbar; Shoro, Ghulam Mustafa; Imran, Raja Muhammed

2014-01-01

/current characteristic. These harmonics are not to be allowed to grow beyond a certain limit to avoid any grave consequence to the customer’s main supply. Filters can be implemented at the power source or utility location to eliminate these harmonics. In this paper we detect the instance at which these harmonics occur...

CURRENT TRENDS IN TAX HARMONIZATION AND COMPETITION WITHIN THE EUROPEAN UNION

Directory of Open Access Journals (Sweden)

Gherman Adela-Teodora

2010-12-01

Full Text Available This article treats on the fiscal harmonization process within the European Union being indispensable for assuring loyalty in the competition on its single market, given the fact that different system of taxation had direct and powerful impact on the prices level and on chosing the location for production and distribution activities. Both direct and indirect taxation distort the four fundamental freedoms of the single market. Most of the European Unions regulations regarding fiscal harmonization resemble to the Directive regarding especially the indirect taxes: VAT, Excises. The fiscal reforms from the member states have to be conceived in such a manner that they take into account the necessity of fiscal harmonization on EU level, creating a reasonable compromise between each country's sovereignty and the desideratum of removing fiscal barriers from the normal functioning of the single market.

Removal of Direct Current Link Harmonic Ripple in Single Phase Voltage Source Inverter Systems Using Supercapacitors

Science.gov (United States)

2016-09-01

Khaligh, “Optimization of sizing and battery cycle life in battery/ultracapacitor hybrid energy storage systems for electric vehicle applications...depth cycling operation in photovoltaic system ,” in 22nd International Conference “Mixed Design of Integrated Circuits and Systems ,” Toruń, Poland...CURRENT LINK HARMONIC RIPPLE IN SINGLE-PHASE VOLTAGE SOURCE INVERTER SYSTEMS USING SUPERCAPACITORS by Gabriel D. Hernandez September 2016

A Novel DBC Layout for Current Imbalance Mitigation in SiC MOSFET Multichip Power Modules

DEFF Research Database (Denmark)

Li, Helong; Munk-Nielsen, Stig; Beczkowski, Szymon

2016-01-01

This letter proposes a novel direct bonded copper (DBC) layout for mitigating the current imbalance among the paralleled SiC MOSFET dies in multichip power modules. Compared to the traditional layout, the proposed DBC layout significantly reduces the circuit mismatch and current coupling effect...

Harmonic Analysis on Torque Ripple of Brushless DC Motor Based on Advanced Commutation Control

Directory of Open Access Journals (Sweden)

Yanpeng Ji

2018-01-01

Full Text Available This paper investigates the relationship between current, back electromotive force (back-EMF, and torque for permanent-magnet brushless DC (PM BLDC motors under advanced commutation control from the perspective of harmonics. Considering that the phase current is the influencing factor of both torque and torque ripple, this paper firstly analyzes the effects of advanced commutation on phase current and current harmonics. And then, based on the harmonics of the phase current and back-EMF, the torque harmonic expressions are deduced. The expressions reveal the relationship of harmonic order between the torque, phase current, and back-EMF and highlight the different contribution of individual torque harmonic to the total torque ripple. Finally, the proposed harmonic analysis method is verified by the experiments with different speed and load conditions.

Harmonic Stability and Resonance Analysis in Large PMSG-Based Wind Power Plants

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2018-01-01

Compared to the conventional power systems, large Wind Power Plants (WPPs) present a more challenging system where the interactions between the passive elements and the wideband control systems of power converters may result in harmonic instability and new resonance frequencies. Most of researches...... system and the resonance frequencies are identified based on the element amplitudes of the MIMO matrix. An active damping controller is used to set the poles of the WPP in a desired location in order to mitigate the harmonic instability problems. Multiple case studies are provided to depict that Wind...

Harmonics in transmission power systems

DEFF Research Database (Denmark)

Wiechowski, Wojciech Tomasz

. The comparison shows that results obtained used both types of the cores are the same, so it is concluded that both cores can be used for harmonic measurements. Low-inductance resistors are introduced in the secondary circuits, in series with the metering and protective relaying. On those resistors, the harmonic......Some time ago, Energinet.dk, the Transmission System Operator of the 150 kV and 400 kV transmission network in Denmark, had experienced operational malfunctions of some of the measuring and protection equipment. Also an overloading of a harmonic filter has been reported, and therefore, a need...... end only so the ground is not used as a return path. A way to reduce the capacitive coupling is to provide shielding. Harmonic currents are measured using the conventional inductive voltage transformers. Both protective and metering cores were compared if they could be used for harmonic measurements...

Second harmonic generation and sum frequency generation

International Nuclear Information System (INIS)

Pellin, M.J.; Biwer, B.M.; Schauer, M.W.; Frye, J.M.; Gruen, D.M.

1990-01-01

Second harmonic generation and sum frequency generation are increasingly being used as in situ surface probes. These techniques are coherent and inherently surface sensitive by the nature of the mediums response to intense laser light. Here we will review these two techniques using aqueous corrosion as an example problem. Aqueous corrosion of technologically important materials such as Fe, Ni and Cr proceeds from a reduced metal surface with layer by layer growth of oxide films mitigated by compositional changes in the chemical makeup of the growing film. Passivation of the metal surface is achieved after growth of only a few tens of atomic layers of metal oxide. Surface Second Harmonic Generation and a related nonlinear laser technique, Sum Frequency Generation have demonstrated an ability to probe the surface composition of growing films even in the presence of aqueous solutions. 96 refs., 4 figs

Currents and fluctuations of quantum heat transport in harmonic chains

International Nuclear Information System (INIS)

Motz, T; Ankerhold, J; Stockburger, J T

2017-01-01

Heat transport in open quantum systems is particularly susceptible to the modeling of system–reservoir interactions. It thus requires us to consistently treat the coupling between a quantum system and its environment. While perturbative approaches are successfully used in fields like quantum optics and quantum information, they reveal deficiencies—typically in the context of thermodynamics, when it is essential to respect additional criteria such as fluctuation-dissipation theorems. We use a non-perturbative approach for quantum dissipative dynamics based on a stochastic Liouville–von Neumann equation to provide a very general and extremely efficient formalism for heat currents and their correlations in open harmonic chains. Specific results are derived not only for first- but also for second-order moments, which requires us to account for both real and imaginary parts of bath–bath correlation functions. Spatiotemporal patterns are compared with weak coupling calculations. The regime of stronger system–reservoir couplings gives rise to an intimate interplay between reservoir fluctuations and heat transfer far from equilibrium. (paper)

Methodologies for Wind Turbine and STATCOM Integration in Wind Power Plant Models for Harmonic Resonances Assessment

DEFF Research Database (Denmark)

Freijedo Fernandez, Francisco Daniel; Chaudhary, Sanjay Kumar; Guerrero, Josep M.

2015-01-01

-domain. As an alternative, a power based averaged modelling is also proposed. Type IV wind turbine harmonic signature and STATCOM active harmonic mitigation are considered for the simulation case studies. Simulation results provide a good insight of the features and limitations of the proposed methodologies.......This paper approaches modelling methodologies for integration of wind turbines and STATCOM in harmonic resonance studies. Firstly, an admittance equivalent model representing the harmonic signature of grid connected voltage source converters is provided. A simplified type IV wind turbine modelling...... is then straightforward. This linear modelling is suitable to represent the wind turbine in the range of frequencies at which harmonic interactions are likely. Even the admittance method is suitable both for frequency and time domain studies, some limitations arise in practice when implementing it in the time...

RF heating and current drive on NSTX with high harmonic fast waves

International Nuclear Information System (INIS)

Ryan, P.M.; Swain, D.W.; Rosenberg, A.L.

2003-01-01

NSTX is a small aspect ratio tokamak (R = 0.85 m, a = 0.65 m). The High Harmonic Fast Wave (HHFW) system is a 30 MHz, 12-element array capable of launching both symmetric and directional wave spectra for plasma heating and non-inductive current drive. It has delivered up to 6 MW for short pulses and has routinely operated at ∼3 MW for 100-400 ms pulses. Results include strong, centrally-peaked electron heating in both D and He plasmas for both high and low phase velocity spectra. H-modes were obtained with application of HHFW power alone, with stored energy doubling after the L-H transition. Beta poloidal as large as unity has been obtained with significant fractions (0.4) of bootstrap current. Differences in the loop voltage are observed depending on whether the array is phased to drive current in the co- or counter-current directions. A fast ion tail with energies extending up to 140 keV has been observed when HHFW interacts with 80 keV neutral beams; neutron rate and lost ion measurements, as well as modeling, indicate significant power absorption by the fast ions. Radial rf power deposition and driven current profiles have been calculated with ray tracing and kinetic full-wave codes and compared with measurements. (author)

Autonomous Control of Current and Voltage Controlled DG Interface Inverters for Reactive Power Sharing and Harmonics Compensation in Islanded Microgrids

DEFF Research Database (Denmark)

Mousazadeh, Seyyed Yousef; Jalilain, Alireza; Savaghebi, Mehdi

2018-01-01

In microgrids, Voltage Source Inverters (VSIs) interfacing Distributed Generation (DG) units can be operated in Voltage or Current Controlled Modes (VCM/CCM). In this paper, a coordinated control of CCM and VCM units for reactive power sharing and voltage harmonics compensation is proposed....... This decentralized control scheme is based on the local measurement of signals. In this way, the need for communication links is removed which results in a simpler and more reliable structure compared to the communication based control structures. To be more exact, the VCM units contribute to harmonics compensation....... Experimental and simulation studies show that the harmonics compensation is achieved by using only local measurements in presence of virtual admittance/impedance schemes of CCM/VCM units. Furthermore, it is demonstrated that the reactive power sharing among the CCM and VCM units is obtained based...

Harmonic filter design consideration for a tire-rubber factory

Energy Technology Data Exchange (ETDEWEB)

Zebardast, A. [Azad Univ., Tehran (Iran, Islamic Republic of). Abhar Branch]|[Sharif Univ., Tehran (Iran, Islamic Republic of); Mokhtari, H. [Azad Univ., Tehran (Iran, Islamic Republic of)

2005-07-01

Nonlinear loads and arc furnace loads are the main sources of harmonic currents in power distribution systems. Harmonic currents can cause reductions in system efficiency, and shorten the lifespan of transformers and capacitor banks. This paper provided details of a filter designed to attenuate harmonic currents at a tire company in Iran. The tire company was supplied by 3 distribution transformers and an emergency transformer. Main supply was through a 132 kV/20 kV transformer, which was connected to 2 A and B stations. The AC/DC drivers generated harmonics. Harmonic measurements were performed to determine the type and size of the required filters. A summary of site harmonic measurements was provided. A passive filter was placed at a medium voltage location. A sensitivity analysis was then performed in order to assess loading effects on filter performance. The analysis was performed on all possible configurations in the plant, including load change, capacitor bank step change, and transformer energization. Resonance conditions were also examined. Results showed that attention must be paid to the filter component rating in addition to potential resonant conditions. It was concluded that resonant conditions alter when system operating conditions change. 5 refs., 7 figs.

Passive wide spectrum harmonic filter for adjustable speed drives in oil and gas industry

Science.gov (United States)

Al Jaafari, Khaled Ali

Non-linear loads such as variable speed drives constitute the bulky load of oil and gas industry power systems. They are widely used in driving induction and permanent magnet motors for variable speed applications. That is because variable speed drives provide high static and dynamic performance. Moreover, they are known of their high energy efficiency and high motion quality, and high starting torque. However, these non-linear loads are main sources of current and voltage harmonics and lower the quality of electric power system. In fact, it is the six-pulse and twelve-pulse diode and thyristor rectifiers that spoil the AC power line with the dominant harmonics (5th, 7th, 11th). They provide DC voltage to the inverter of the variable speed drives. Typical problems that arise from these harmonics are Harmonic resonances', harmonic losses, interference with electronic equipment, and line voltage distortion at the Point of Common Coupling (PCC). Thus, it is necessary to find efficient, reliable, and economical harmonic filters. The passive filters have definite advantage over active filters in terms of components count, cost and reliability. Reliability and maintenance is a serious issue in drilling rigs which are located in offshore and onshore with extreme operating conditions. Passive filters are tuned to eliminate a certain frequency and therefore there is a need to equip the system with more than one passive filter to eliminate all unwanted frequencies. An alternative solution is Wide Spectrum Harmonic passive filter. The wide spectrum harmonic filters are becoming increasingly popular in these applications and found to overcome some of the limitations of conventional tuned passive filter. The most important feature of wide spectrum harmonic passive filters is that only one capacitor is required to filter a wide range of harmonics. Wide spectrum filter is essentially a low-pass filter for the harmonic at fundamental frequency. It can also be considered as a

On separating customer and supply side harmonic contributions at the pcc based on new notions suggested to power theory development

International Nuclear Information System (INIS)

Eisa, A.A.A.E

2008-01-01

Excessive use of nonlinear loads connected to electric power systems distorts the AC power current, and consequently the AC voltage drop. Thereby resulting in the flow of harmonic currents in the system. This can introduce many problems through out the system. If such problems are unavoidable, then remedy or mitigation and cost of such action should be properly accounted for as fairly as possible. Due to this reason, it is important to determine precisely the quantity and direction of energy and power for each harmonic order. This will be very useful while constructing energy billing and rate structure.This thesis concerns with this matter, which is called reverse harmonic study. It introduces a new method to determine the attributes for each harmonic order at the point of common coupling (PCC) between the supplier and the consumer.Depending on the premise that harmonics cause power flow in power systems, just as fundamental frequency does, the thesis analytically introduces a new approach to develop the power theory. The purpose of this approach is to determine an accurate, fair, practical method for measuring the harmonic power components and energy transfer.There is consensus that the present definitions used to evaluate the flow of energy and power in electric networks are not adequate for conducting studies when non-sinusoidal voltage or current are present. For that reason the thesis suggests a new notion in power theory for periodic current and voltage waveforms. The idea of this notion has been inspired from the concept of instantaneous power. This term has been defined for convenience in representing the energy content of a system, since it satisfies the law of c onservation of energy . By this new approach we have analytically introduced definitions and formulas that determine precisely proper instantaneous power components in ac power systems under sinusoidal and non-sinusoidal conditions. The rapid progression of digital sampling technology in power

The Virasoro algebra from harmonic superspace

International Nuclear Information System (INIS)

Saidi, E.H.; Zakkari, M.

1990-08-01

Using harmonic superspace techniques, we construct a new field realization of the Virasoro algebra. The main conformal objects are U(1) Cartan tensors instead of the U(1) Lorentz ones. The new conformal model, which admits moreover a d=2 (4,0) global supersymmetry is constructed out of the infinitely relaxed HST and FS hypermultiplets. The conformal current T 4+ together with the harmonic superspace OPE rules are given. The Virasoro algebra and the harmonic superspace Schwarzian derivative S 4+ are also derived. (author). 14 refs

Reducing Harmonic Instability and Resonance Problems in PMSG Based Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2018-01-01

Unlike conventional power systems where harmonic resonances are coming from passive inductive and capacitive elements, large-scale power electronic systems like wind farms present a more complex system, where the fast dynamics of the power electronic converters may present an inductive or capacit......Unlike conventional power systems where harmonic resonances are coming from passive inductive and capacitive elements, large-scale power electronic systems like wind farms present a more complex system, where the fast dynamics of the power electronic converters may present an inductive...... or capacitive behavior. Therefore, the interactions between the fast controllers of the power converters and the passive elements may lead to harmonic instability and new resonances at various frequencies. This paper presents an optimum design technique for the Wind Turbine (WT) inner controllers in a PMSG...... based wind farm in order to reduce the number of resonances and to mitigate harmonic instability. In the approach, a PMSG based wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system by modeling the high bandwidth control loops of the power converters. Resonance frequencies...

Harmonic effects of solar geomagnetically induced currents on the electrical distribution system in nuclear power plants

International Nuclear Information System (INIS)

Carroll, D.P.; Kasturi, S.; Subudhi, M.; Gunther, W.

1992-01-01

Most previous analysis on the effects of geomagnetically induced currents (GIC) on electric utility systems has steady-state phenomena, with the main interest in the generator step-up transformer and the off-site power system. This paper begins to investigate the possible effects that a GIC event might have on the power plant itself, by examining the harmonic distortion that could exist at various voltage levels in the on-site distribution system

Second harmonic inversion for ultrasound contrast harmonic imaging

Energy Technology Data Exchange (ETDEWEB)

Pasovic, Mirza; Danilouchkine, Mike; Faez, Telli; Van Neer, Paul L M J; Van der Steen, Antonius F W; De Jong, Nico [THORAXCENTER, Department of Biomedical Engineering Ee2302, Erasmus MC, Rotterdam (Netherlands); Cachard, Christian; Basset, Olivier, E-mail: mirza.pasovic@creatis.insa-lyon.fr [CREATIS-LRMN, Universite de Lyon, INSA-Lyon, Universite Lyon 1, Inserm U630, CNRS UMR 5220 (France)

2011-06-07

Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p'', of the same frequency f{sub 0} and the same amplitude P{sub 0} to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40 dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20 dB compared to standard second harmonic imaging and 13 dB of improvement in harmonic power Doppler.

Second harmonic inversion for ultrasound contrast harmonic imaging

International Nuclear Information System (INIS)

Pasovic, Mirza; Danilouchkine, Mike; Faez, Telli; Van Neer, Paul L M J; Van der Steen, Antonius F W; De Jong, Nico; Cachard, Christian; Basset, Olivier

2011-01-01

Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p'', of the same frequency f 0 and the same amplitude P 0 to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40 dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20 dB compared to standard second harmonic imaging and 13 dB of improvement in harmonic power Doppler.

[Current aspects of harmonization of classification of occupational hearing loss].

Science.gov (United States)

Pankova, V B; Sinëva, E L; Tavartkiladze, G A; Fedina, I N; Preobrazhenskaia, E A; Mukhamedova, G R

2013-01-01

The objective of the present work was to develop unified criteria for the evaluation of the severity of noise-induced hearing loss. Current approaches to taking expert decisions based on the results of medical examination of the patients with impaired hearing are substantially different due to the considerable difference between the criteria for the estimation of hearing envisaged by the international classification, occupational pathology classification, and the national system of medico-social expertise. We undertook an attempt to correct and harmonize the existing criteria for the estimation of severity of occupational hearing loss based on the integration of all the three classification in order to "reduce them to a common denominator" and thereby to ensure the basis for the unified diagnostic and expert decisions for the cases of hearing impairment of any etiology. The project proposed in this paper makes it possible to use unified criteria for the assessment of the degree of hearing loss caused by occupational noises for diagnostic purposes and expertise compatible with the internationally accepted approaches.

Current source converter based D-STATCOM for voltage sag mitigation

Directory of Open Access Journals (Sweden)

Singh Moirangthem Deben

2015-01-01

Full Text Available This paper presents a novel method of realizing one of the custom power controllers, the distribution static synchronous compensator (D-STATCOM using current source converter (CSC topology. Almost all the custom power controllers such as dynamic voltage restorer (DVR, unified power quality conditioner (UPQC including D-STATCOM are generally designed and implemented by using voltage source converters (VSC and not much research publications with CSC based approach has been reported over the last one decade. Since the D-STATCOM is a current injection device, its performance can be improved when realized by a current-source converter which can generate a controllable current directly at its output terminals and offers many advantageous features. In this paper, an attempt has been made to study the performance of a CSC based D-STATCOM suitable for use in the power distribution system in order to mitigate voltage sag and improve power quality. The proposed model uses a three leg CSC whose switching strategy is based on sinusoidal pulse width modulation (SPWM. The model has been simulated in the Matlab/Simulink environment. The results of the simulation runs under steady state and dynamic load perturbation provide excellent voltage and current waveforms that support the justification of the proposed model.

ARTIFICIAL INTELLIGENT SYSTEM FOR MEASUREMENT OF HARMONIC POWERS

Directory of Open Access Journals (Sweden)

Jovitha Jerome

2017-11-01

Full Text Available The importance of the electric power quality (PQ demands new methodologies and measurement tools in the power industry for the analysis and measurement of the basic electric magnitudes necessary. This paper presents a new measurement procedure based on neural networks for the estimation of harmonic amplitudes of current/voltage and respective harmonic powers. The measurement scheme is built with two neural network modules. The first module is an adaptive linear neuron (ADALINE that is the kernel part of estimation of complex harmonic coefficients of the current/voltage. The second module is feedforward neural network that obtains the harmonic active/reactive powers. In order to perform digital simulation the Feedforward and Adaline neural network tools were developed in LabVIEW. This measurement algorithm was tested for the practical cases and found to be robust, computationally fast and efficient.

Robust Sub-harmonic Mixer at 340 GHz Using Intrinsic Resonances of Hammer-Head Filter and Improved Diode Model

Science.gov (United States)

Wang, Cheng; He, Yue; Lu, Bin; Jiang, Jun; Miao, Li; Deng, Xian-Jin; Xiong, Yong-zhong; Zhang, Jian

2017-11-01

This paper presents a sub-harmonic mixer at 340 GHz based on anti-parallel Schottky diodes (SBDs). Intrinsic resonances in low-pass hammer-head filter have been adopted to enhance the isolation for different harmonic components, while greatly minimizing the transmission loss. The application of new DC grounding structure, impedance matching structure, and suspended micro-strip mitigates the negative influences of fabrication errors from metal cavity, quartz substrate, and micro-assembly. An improved lumped element equivalent circuit model of SBDs guarantees the accuracy of simulation, which takes current-voltage (I/V) behavior, capacitance-voltage (C/V) behavior, carrier velocity saturation, DC series resistor, plasma resonance, skin effect, and four kinds of noise generation mechanisms into consideration thoroughly. The measurement indicates that with local oscillating signal of 2 mW, the lowest double sideband conversion loss is 5.5 dB at 339 GHz; the corresponding DSB noise temperature is 757 K. The 3 dB bandwidth of conversion loss is 50 GHz from 317 to 367 GHz.

Research on the influence of driving harmonic on electromagnetic field and temperature field of permanent magnet synchronous motor

Directory of Open Access Journals (Sweden)

Qiu Hongbo

2017-06-01

Full Text Available At present, the drivers with different control methods are used in most of permanent magnet synchronous motors (PMSM. A current outputted by a driver contains a large number of harmonics that will cause the PMSM torque ripple, winding heating and rotor temperature rise too large and so on. In this paper, in order to determine the influence of the current harmonics on the motor performance, different harmonic currents were injected into the motor armature. Firstly, in order to study the influence of the current harmonic on the motor magnetic field, a novel decoupling method of the motor magnetic field was proposed. On this basis, the difference of harmonic content in an air gap magnetic field was studied, and the influence of a harmonic current on the air gap flux density was obtained. Secondly, by comparing the fluctuation of the motor torque in the fundamental and different harmonic currents, the influence of harmonic on a motor torque ripple was determined. Then, the influence of different current harmonics on the eddy current loss of the motor was compared and analyzed, and the influence of the drive harmonic on the eddy current loss was obtained. Finally, by using a finite element method (FEM, the motor temperature distribution with different harmonics was obtained.

Mitigation of current quench by runaway electrons in LHCD discharges in the HT-7 tokamak

International Nuclear Information System (INIS)

Lu, H.W.; Hu, L.Q.; Lin, S.Y.; Zhong, G.Q.

2009-01-01

Production of runaway electrons during a major disruption has been observed in HT-7 Tokamak. The runaway current plateaus, which can carry part of the pre-disruptive current, are observed in lower-hybrid current drive (LHCD) limiter discharges. It is found that the runaway current can mitigate the disruptions effectively. Detailed observations are presented on the runaway electrons generated following disruptions in the HT-7 tokamak with carbon limited discharges. The results indicate that the magnetic oscillations play an important role in the activity of runaway electrons in disruption. (author)

Current collapse imaging of Schottky gate AlGaN/GaN high electron mobility transistors by electric field-induced optical second-harmonic generation measurement

International Nuclear Information System (INIS)

Katsuno, Takashi; Ishikawa, Tsuyoshi; Ueda, Hiroyuki; Uesugi, Tsutomu; Manaka, Takaaki; Iwamoto, Mitsumasa

2014-01-01

Two-dimensional current collapse imaging of a Schottky gate AlGaN/GaN high electron mobility transistor device was achieved by optical electric field-induced second-harmonic generation (EFISHG) measurements. EFISHG measurements can detect the electric field produced by carriers trapped in the on-state of the device, which leads to current collapse. Immediately after (e.g., 1, 100, or 800 μs) the completion of drain-stress voltage (200 V) in the off-state, the second-harmonic (SH) signals appeared within 2 μm from the gate edge on the drain electrode. The SH signal intensity became weak with time, which suggests that the trapped carriers are emitted from the trap sites. The SH signal location supports the well-known virtual gate model for current collapse.

Coordinated Control of Multifunctional Inverters for Voltage Support and Harmonic Compensation in a Grid-Connected Microgrid

DEFF Research Database (Denmark)

Mousazadeh, Seyyed Yousef; Jalilian, Alireza; Savaghebi, Mehdi

2018-01-01

In this paper, a coordinated harmonic compensation and voltage support scheme is presented for distributed generations’ (DGs’) interface inverters in a resistive grid-connected microgrid. Voltage support is performed by reactive power compensation which can mitigate the over/under voltage problem...

Second harmonic generation imaging

CERN Document Server

2013-01-01

Second-harmonic generation (SHG) microscopy has shown great promise for imaging live cells and tissues, with applications in basic science, medical research, and tissue engineering. Second Harmonic Generation Imaging offers a complete guide to this optical modality, from basic principles, instrumentation, methods, and image analysis to biomedical applications. The book features contributions by experts in second-harmonic imaging, including many pioneering researchers in the field. Written for researchers at all levels, it takes an in-depth look at the current state of the art and possibilities of SHG microscopy. Organized into three sections, the book: Provides an introduction to the physics of the process, step-by-step instructions on how to build an SHG microscope, and comparisons with related imaging techniques Gives an overview of the capabilities of SHG microscopy for imaging tissues and cells—including cell membranes, muscle, collagen in tissues, and microtubules in live cells—by summarizing experi...

Photovoltaic power converter system with a controller configured to actively compensate load harmonics

Science.gov (United States)

de Rooij, Michael Andrew; Steigerwald, Robert Louis; Delgado, Eladio Clemente

2008-12-16

Photovoltaic power converter system including a controller configured to reduce load harmonics is provided. The system comprises a photovoltaic array and an inverter electrically coupled to the array to generate an output current for energizing a load connected to the inverter and to a mains grid supply voltage. The system further comprises a controller including a first circuit coupled to receive a load current to measure a harmonic current in the load current. The controller includes a second circuit to generate a fundamental reference drawn by the load. The controller further includes a third circuit for combining the measured harmonic current and the fundamental reference to generate a command output signal for generating the output current for energizing the load connected to the inverter. The photovoltaic system may be configured to compensate harmonic currents that may be drawn by the load.

Regulations for marine microalgal toxins: Towards harmonization of ...

African Journals Online (AJOL)

The World Trade Organization and the General Agreements on Tariffs and Trade encourage the harmonization of regulations on food safety requirements. The current policy on trade liberalization of seafood is presented, together with a review of the regulations for marine microalgal toxins. Activities on harmonization of ...

Assessment and mitigation of power quality problems for PUSPATI TRIGA Reactor (RTP)

Science.gov (United States)

Zakaria, Mohd Fazli; Ramachandaramurthy, Vigna K.

2017-01-01

An electrical power systems are exposed to different types of power quality disturbances. Investigation and monitoring of power quality are necessary to maintain accurate operation of sensitive equipment especially for nuclear installations. This paper will discuss the power quality problems observed at the electrical sources of PUSPATI TRIGA Reactor (RTP). Assessment of power quality requires the identification of any anomalous behavior on a power system, which adversely affects the normal operation of electrical or electronic equipment. A power quality assessment involves gathering data resources; analyzing the data (with reference to power quality standards) then, if problems exist, recommendation of mitigation techniques must be considered. Field power quality data is collected by power quality recorder and analyzed with reference to power quality standards. Normally the electrical power is supplied to the RTP via two sources in order to keep a good reliability where each of them is designed to carry the full load. The assessment of power quality during reactor operation was performed for both electrical sources. There were several disturbances such as voltage harmonics and flicker that exceeded the thresholds. To reduce these disturbances, mitigation techniques have been proposed, such as to install passive harmonic filters to reduce harmonic distortion, dynamic voltage restorer (DVR) to reduce voltage disturbances and isolate all sensitive and critical loads.

Harmonic synchronization in resistively coupled Josephson junctions

International Nuclear Information System (INIS)

Blackburn, J.A.; Gronbech-Jensen, N.; Smith, H.J.T.

1994-01-01

The oscillations of two resistively coupled Josephson junctions biased only by a single dc current source are shown to lock harmonically in a 1:2 mode over a significant range of bias current, even when the junctions are identical. The dependence of this locking on both junction and coupling parameters is examined, and it is found that, for this particular two-junction configuration, 1:1 locking can never occur, and also that a minimum coupling coefficient is needed to support harmonic locking. Some issues related to subharmonic locking are also discussed

Sequence Domain Harmonic Modeling of Type-IV Wind Turbines

DEFF Research Database (Denmark)

Guest, Emerson; Jensen, Kim Høj; Rasmussen, Tonny Wederberg

2017-01-01

-sampled pulsewidth modulation and an analysis of converter generated voltage harmonics due to compensated dead-time. The decoupling capabilities of the proposed the SD harmonic model are verified through a power quality (PQ) assessment of a 3MW Type-IV wind turbine. The assessment shows that the magnitude and phase...... of low-order odd converter generated voltage harmonics are dependent on the converter operating point and the phase of the fundamental component of converter current respectively. The SD harmonic model can be used to make PQ assessments of Type-IV wind turbines or incorporated into harmonic load flows...... for computation of PQ in wind power plants....

Adaptive Harmonic Compensation in Residential Distribution Grid by Roof-Top PV Systems

DEFF Research Database (Denmark)

Zangeneh Bighash, Esmaeil; Sadeghzadeh, Seyed Mohammad; Ebrahimzadeh, Esmaeil

2018-01-01

grid- connected roof-top PV inverters in residential distribution grid can be an opportunity to engage these systems in the power quality issues as custom power devices. By implementing a proper control for roof-top PV inverters, these systems may in addition to inject the fundamental current......, additionally act like a virtual harmonic resistance and dedicate their additional current capacity to compensate the harmonics of residential distribution grid. In this paper, each roof-top PV system is a grid harmonic supervisor, where it continually measures the PCC voltage harmonics by Sliding Discrete...

[Harmonization of TSH Measurements.

Science.gov (United States)

Takeoka, Keiko; Hidaka, Yoh; Hishinuma, Akira; Ikeda, Katsuyoshi; Okubo, Shigeo; Tsuchiya, Tatsuyuki; Hashiguchi, Teruto; Furuta, Koh; Hotta, Taeko; Matsushita, Kazuyuki; Matsumoto, Hiroyuki; Murakami, Masami; Maekawa, Masato

2016-05-01

The measured concentration of thyroid stimulating hormone (TSH) differs depending on the reagents used. Harmonization of TSH is crucial because the decision limits are described in current clinical practice guide- lines as absolute values, e.g. 2.5 mIU/L in early pregnancy. In this study, we tried to harmonize the report- ed concentrations of TSH using the all-procedure trimmed mean. TSH was measured in 146 serum samples, with values ranging from 0.01 to 18.8 mIU/L, using 4 immunoassays. The concentration of TSH was highest with E test TOSOH and lowest with LUMIPULSE. The concentrations with each reagent were recalculated with the following formulas: E test TOSOH 0.855x-0.014; ECLusys 0.993x+0.079; ARCHITECT 1.041x- 0.010; and LUMIPULSE 1.096x-0.015. Recalculation eliminated the between-assay discrepancy. These formulas may be used until harmonization of TSH is achieved by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).

Transfer functions of US transducers for harmonic imaging and bubble respons

NARCIS (Netherlands)

van Neer, Paul L.M.J.; Matte, Guillaume; Sijl, J.; Borsboom, Jerome M.G.; de Jong, N.

2007-01-01

Current medical diagnostic echo systems are mostly using harmonic imaging. This means that a fundamental frequency (e.g., 2 MHz) is transmitted and the reflected and scattered higher harmonics (e.g., 4 and 6 MHz), produced by nonlinear propagation, are recorded. The signal level of these harmonics

A Novel DBC Layout for Current Imbalance Mitigation in SiC MOSFET Multichip Power Modules

DEFF Research Database (Denmark)

Li, Helong; Munk-Nielsen, Stig; Beczkowski, Szymon

2016-01-01

This paper proposes a novel Direct Bonded Copper (DBC) layout for mitigating the current imbalance among the paralleled SiC MOSFET dies in multichip power modules. Compared to the traditional layout, the proposed DBC layout significantly reduces the circuit mismatch and current coupling effect......, which consequently improves the current sharing among the paralleled SiC MOSFET dies in power module. Mathematic analysis and circuit model of the DBC layout are presented to elaborate on the superior features of the proposed DBC layout. Simulation and experimental results further verify the theoretical...

Generation of second harmonic in off-diagonal magneto-impedance in Co-based amorphous ribbons

International Nuclear Information System (INIS)

Buznikov, N A; Yoon, S S; Jin, L; Kim, C O; Kim, C G

2006-01-01

The off-diagonal magneto-impedance in Co-based amorphous ribbons was measured using a pick-up coil wound around the sample. The ribbons were annealed in air or in vacuum in the presence of a weak magnetic field. The evolution of the first and second harmonics in the pick-up coil voltage as a function of the current amplitude was studied. At low current amplitudes, the first harmonic dominates in the frequency spectrum of the voltage, and at sufficiently high current amplitudes, the amplitude of the second harmonic becomes higher than that of the first harmonic. For air-annealed ribbons, the asymmetric two-peak behaviour of the field dependences of the harmonic amplitudes was observed, which is related to the coupling between the amorphous phase and surface crystalline layers appearing after annealing. For vacuum-annealed samples, the first harmonic has a maximum at zero external field, and the field dependence of the second harmonic exhibits symmetric two-peak behaviour. The experimental results are interpreted in terms of a quasi-static rotational model. It is shown that the appearance of the second harmonic in the pick-up coil voltage is related to the anti-symmetrical distribution of the transverse field induced by the current. The calculated dependences are in qualitative agreement with the experimental data

High-order harmonic conversion efficiency in helium

International Nuclear Information System (INIS)

Crane, J.K.

1992-01-01

Calculated results are presented for the energy, number of photons, and conversion efficiency for high-order harmonic generation in helium. The results show the maximum values that we should expect to achieve experimentally with our current apparatus and the important parameters for scaling this source to higher output. In the desired operating regime where the coherence length, given by L coh =πb/(q-1), is greater than the gas column length, l, the harmonic output can be summarized by a single equation: N q =[(π z n z b 3 τ q |d q | z )/4h]{(p/q)(2l/b) z }. N q - numbers of photons of q-th harmonic; n - atom density; b - laser confocal parameter; τ q - pulse width of harmonic radiation; q - harmonic order; p - effective order of nonlinearity. (Note the term in brackets, the phase-matching function, has been separated from the rest of the expression in order to be consistent with the relevant literature)

Electric shock and elevated EMF levels due to triplen harmonics

International Nuclear Information System (INIS)

Tran, T.Q.; Conrad, L.E.; Stallman, B.K.

1996-01-01

The increasing use of single phase rectifiers for electric power conversion in residential applications increases harmonic load on utility systems. Many papers have analyzed the effect of these loads on power quality and equipment loadability. However, there are two more critical concerns for harmonic loads served phase to neutral on multi-grounded wye systems. Triplen harmonics, particularly the third, add in the neutral and have little diversity between loads. The higher neutral currents may cause significant problems. Neutral to earth voltages will increase near the substations which could increase stray voltage complaints. The additional neutral current on three phase lines will elevate EMF levels especially in the fringe areas. This paper provides fundamental understanding of triplen harmonic influence on stray voltage and EMF related to multi-grounded wye electric distribution systems

Discrepancies in historical emissions point to a wider 2020 gap between 2 deg. C benchmarks and aggregated national mitigation pledges

International Nuclear Information System (INIS)

Rogelj, Joeri; Hare, William; Chen, Claudine; Meinshausen, Malte

2011-01-01

Aggregations of greenhouse gas mitigation pledges by countries are frequently used to indicate whether resulting global emissions in 2020 will be 'on track' to limit global temperature increase to below specific warming levels such as 1.5 or 2 deg. C. We find that historical emission levels aggregated from data that are officially reported by countries to the UNFCCC are lower than independent global emission estimates, such as the IPCC SRES scenarios. This discrepancy in historical emissions could substantially widen the gap between 2020 pledges and 2020 benchmarks, as the latter tend to be derived from scenarios that share similar historical emission levels to IPCC SRES scenarios. Three methods for resolving this discrepancy, here called 'harmonization', are presented and their influence on 'gap' estimates is discussed. Instead of a 3.4-9.2 GtCO 2 eq shortfall in emission reductions by 2020 compared with the 44 GtCO 2 eq benchmark, the actual gap might be as high as 5.4-12.5 GtCO 2 eq (a 22-88% increase of the gap) if this historical discrepancy is accounted for. Not applying this harmonization step when using 2020 emission benchmarks could lead to an underestimation of the insufficiency of current mitigation pledges.

RF heating and current drive on NSTX with high harmonic fast waves

International Nuclear Information System (INIS)

Ryan, P.M.

2002-01-01

NSTX is a small aspect ratio tokamak with a large dielectric constant (50-100); under these conditions high harmonic fast waves (HHFW) will readily damp on electrons via Landau damping and TTMP. The HHFW system is a 30 MHz, 12-element array capable of launching both symmetric and directional wave spectra for plasma heating and non-inductive current drive. It has delivered up to 6 MW for short pulses and has routinely operated at ∼3-4 MW for 100-200 ms pulses. Results include strong, centrally-peaked electron heating in both D and He plasmas, for both high and low phase velocity spectra. H-modes were obtained with application of HHFW power alone, with stored energy doubling after the L-H transition. Beta poloidal as large as unity has been obtained with large fractions (0.4) of bootstrap current. A fast ion tail with energies extending up to 140 keV has been observed when HHFW interacts with 80 keV neutral beams; neutron rate and lost ion measurements, as well as modeling, indicate significant power absorption by the fast ions. Radial power deposition profiles are being calculated with ray tracing and kinetic full-wave codes and benchmarked against measurements. (author)

Probabilistic Aspects of Harmonic Emission of Large Offshore Wind Farms

DEFF Research Database (Denmark)

Jensen, Christian Flytkjær; Bak, Claus Leth; Kocewiak, Lukasz Hubert

2011-01-01

In this article, a new probabilistic method of as-sessment of harmonic emission of large offshore wind farms is presented. Based on measurements from the British wind farm Burbo Banks, probability density functions are estimated for the dominating low order harmonic currents injected by a single...... turbine. The degree and type of dependence between the harmonic emission and the operating point of a single turbine is established. A model of Burbo Banks, suitable for harmonic load flow studies, is created in DIgSILENT Power Factory along with a DPL-script that deals with the probabilistic issues...... of the harmonic emission. The simulated harmonic distortion at the PCC is compared to measurement. This reveals some diffi-culties regarding harmonic load flow studies. The harmonic background distortion in the grid to where the wind farm is connected must be included in the study. Furthermore, a very detailed...

Harmonic statistics

International Nuclear Information System (INIS)

Eliazar, Iddo

2017-01-01

The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.

Harmonic statistics

Energy Technology Data Exchange (ETDEWEB)

Eliazar, Iddo, E-mail: eliazar@post.tau.ac.il

2017-05-15

The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.

Laser waveform control of extreme ultraviolet high harmonics from solids.

Science.gov (United States)

You, Yong Sing; Wu, Mengxi; Yin, Yanchun; Chew, Andrew; Ren, Xiaoming; Gholam-Mirzaei, Shima; Browne, Dana A; Chini, Michael; Chang, Zenghu; Schafer, Kenneth J; Gaarde, Mette B; Ghimire, Shambhu

2017-05-01

Solid-state high-harmonic sources offer the possibility of compact, high-repetition-rate attosecond light emitters. However, the time structure of high harmonics must be characterized at the sub-cycle level. We use strong two-cycle laser pulses to directly control the time-dependent nonlinear current in single-crystal MgO, leading to the generation of extreme ultraviolet harmonics. We find that harmonics are delayed with respect to each other, yielding an atto-chirp, the value of which depends on the laser field strength. Our results provide the foundation for attosecond pulse metrology based on solid-state harmonics and a new approach to studying sub-cycle dynamics in solids.

Analysis of Expediency to Apply LCL Model with Source of Higher Harmonics of Current While Investigating Resonance Condition of Power Supply Network

OpenAIRE

M. Pavlovsky; A. Shimansky; Z. Fialkovsky

2004-01-01

The paper considers a power system model of a plant with one capacitor bank and with one current source of higher harmonics for higher power factor. The laboratory research results of this system and practical application of the proposed model are given in the paper.

Secondary magnetic field harmonics dependence on vacuum beam chamber geometry

Directory of Open Access Journals (Sweden)

S. Y. Shim

2013-08-01

Full Text Available The harmonic magnetic field properties due to eddy currents have been studied with respect to the geometry of the vacuum beam chamber. We derived a generalized formula enabling the precise prediction of any field harmonics generated by eddy currents in beam tubes with different cross-sectional geometries. Applying our model to study the properties of field harmonics in beam tubes with linear dipole magnetic field ramping clearly proved that the circular cross section tube generates only a dipole field from eddy currents. The elliptic tube showed noticeable magnitudes of sextupole and dipole fields. We demonstrate theoretically that it is feasible to suppress the generation of the sextupole field component by appropriately varying the tube wall thickness as a function of angle around the tube circumference. This result indicates that it is possible to design an elliptical-shaped beam tube that generates a dipole field component with zero magnitude of sextupole. In a rectangular-shaped beam tube, one of the selected harmonic fields can be prevented if an appropriate wall thickness ratio between the horizontal and vertical tube walls is properly chosen. Our generalized formalism can be used for optimization of arbitrarily complex-shaped beam tubes, with respect to suppression of detrimental field harmonics.

MREIT experiments with 200 µA injected currents: a feasibility study using two reconstruction algorithms, SMM and harmonic BZ

International Nuclear Information System (INIS)

Arpinar, V E; Muftuler, L T; Hamamura, M J; Degirmenci, E

2012-01-01

Magnetic resonance electrical impedance tomography (MREIT) is a technique that produces images of conductivity in tissues and phantoms. In this technique, electrical currents are applied to an object and the resulting magnetic flux density is measured using magnetic resonance imaging (MRI) and the conductivity distribution is reconstructed using these MRI data. Currently, the technique is used in research environments, primarily studying phantoms and animals. In order to translate MREIT to clinical applications, strict safety standards need to be established, especially for safe current limits. However, there are currently no standards for safe current limits specific to MREIT. Until such standards are established, human MREIT applications need to conform to existing electrical safety standards in medical instrumentation, such as IEC601. This protocol limits patient auxiliary currents to 100 µA for low frequencies. However, published MREIT studies have utilized currents 10–400 times larger than this limit, bringing into question whether the clinical applications of MREIT are attainable under current standards. In this study, we investigated the feasibility of MREIT to accurately reconstruct the relative conductivity of a simple agarose phantom using 200 µA total injected current and tested the performance of two MREIT reconstruction algorithms. These reconstruction algorithms used are the iterative sensitivity matrix method (SMM) by Ider and Birgul (1998 Elektrik 6 215–25) with Tikhonov regularization and the harmonic B Z proposed by Oh et al (2003 Magn. Reason. Med. 50 875–8). The reconstruction techniques were tested at both 200 µA and 5 mA injected currents to investigate their noise sensitivity at low and high current conditions. It should be noted that 200 µA total injected current into a cylindrical phantom generates only 14.7 µA current in imaging slice. Similarly, 5 mA total injected current results in 367 µA in imaging slice. Total acquisition

Probabilistic aspects of harmonic emission of large offshore wind farms

Energy Technology Data Exchange (ETDEWEB)

Jensen, Christian F. [Energinet.dk, Fredericia (Denmark); Bak, Claus L. [Aalborg Univ. (Denmark). Dept. of Energy Technology; Kocewiak, Lukasz; Hjerrild, Jesper [DONG Energy, Skaerbaek (Denmark); Berthelsen, Kasper K. [Aalborg Univ. (Denmark). Dept. of Mathematical Sciences

2011-07-01

In this article, a new probabilistic method of assessment of harmonic emission of large offshore wind farms is presented. Based on measurements from the British wind farm Burbo Banks, probability density functions are estimated for the dominating low order harmonic currents injected by a single turbine. The degree and type of dependence between the harmonic emission and the operating point of a single turbine is established. A model of Burbo Banks, suitable for harmonic load flow studies, is created in DIgSILENT Power Factory along with a DPL-script that deals with the probabilistic issues of the harmonic emission. The simulated harmonic distortion at the PCC is compared to measurement. This reveals some difficulties regarding harmonic load flow studies. The harmonic background distortion in the grid to where the wind farms is connected must be included in the study. Furthermore, a very detailed representation of the frequency dependent short circuit impedance must be used before sufficiently accurate results can be obtained from the model. (orig.)

Effect of Frequency and Spatial-Harmonics on Rotary and Linear Induction Motor Characteristics

Science.gov (United States)

1972-03-01

A computer analysis is made of the effect of current and MMF airgap harmonics on the output characteristics of rotary and linear induction motors. The current harmonics accompanying thyristor-control operation are evaluated by Fourier analyzing the p...

Harmonic reduction by using single-tuned passive filter in plastic processing industry

Science.gov (United States)

Fahmi, M. I.; Baafai, U.; Hazmi, A.; Nasution, T. H.

2018-02-01

The using of non-linear loads generated by industrial machines may result inconsistent harmonics that do not reach the IEEE 519 - 1992 standards. This study discusses the use of single-tuned passive filters in reducing harmonics in the plastics processing industry. The system modeling using matlab / simulink simulation resulted in total harmonic distortion (THD) of 15.55%, can be reduced to 4.77% harmonics in accordance with IEEE 519 - 1992 standards. From the simulation results also seen that single-tuned passive filter can reduce the harmonics of the current 82.23% harmonic that wants to be reduced and also can reduce other orders harmonics between 7% to 8%.

Math Model and Calculation Analysis of Inter-harmonic of Double PWM Speed Control System in Distribution Network

Directory of Open Access Journals (Sweden)

Yang Wen-Huan

2014-11-01

Full Text Available Aiming at the problem that the distribution network voltage will fluctuate because of the inter-harmonic currents injected into the network by double PWM speed control system when regulating the speed of the asynchronous motor, we established the inter-harmonic current math model of double PWM speed control system according to switching function based on a real bridge crane. The distribution law of the inter-harmonic is got by calculating the grid-side currents and their spectrum while letting the motor run at different quadrants and frequencies. The result which is verified by simulation and experiment shows that the content of the inter harmonic currents is more than that of harmonic currents in double PWM speed control system, the frequency of the inter harmonics of the grid-side current mainly focus on the scope lower than the fundamental frequency, and when the motor runs at low frequencies, the THD of the grid-side current is high. The result has verified the reason why the voltage of a bridge crane distribution system of a deepwater port in Shanghai flickers.

Harmonics in large offshore wind farms

DEFF Research Database (Denmark)

Kocewiak, Lukasz Hubert

and nature of various harmonic components. A comprehensive comparison of harmonic voltages and currents based on probability distribution estimation and appropriate statistics calculation (mean, variance, probability density function, etc.) is applied. Such approach gives a better overview and comparison...... and analysis, and ϐinally ending up on modelling and models application. Different aspects of validation in time domain, frequency domain, and by application of statistical methods are mentioned in relation to respective problems. Measurements constitute a core part in industry-oriented research. Due...... that it is of great importance to know the nature of generated harmonics in large offshore wind farms in order to apply the most suitable data processing technique. Time-frequency analysis based on multiresolution wavelet transform is used in order to perform time-frequency domain analysis helpful to distinguish...

Evaluation of Harmonics Impact on Digital Relays

Directory of Open Access Journals (Sweden)

Kinan Wannous

2018-04-01

Full Text Available This paper presents the concept of the impact of harmonic distortion on a digital protection relay. The aim is to verify and determine the reasons of a mal-trip or failure to trip the protection relays; the suggested solution of the harmonic distortion is explained by a mathematical model in the Matlab Simulink programming environment. The digital relays have been tested under harmonic distortions in order to verify the function of the relays algorithm under abnormal conditions. The comparison between the protection relay algorithm under abnormal conditions and a mathematical model in the Matlab Simulink programming environment based on injected harmonics of high values is provided. The test is separated into different levels; the first level is based on the harmonic effect of an individual harmonic and mixed harmonics. The test includes the effect of the harmonics in the location of the fault point into distance protection zones. This paper is a new proposal in the signal processing of power quality disturbances using Matlab Simulink and the power quality impact on the measurements of the power system quantities; the test simulates the function of protection in power systems in terms of calculating the current and voltage values of short circuits and their faults. The paper includes several tests: frequency variations and decomposition of voltage waveforms with Fourier transforms (model and commercial relay, the effect of the power factor on the location of fault points, the relation between the tripping time and the total harmonic distortion (THD levels in a commercial relay, and a comparison of the THD capture between the commercial relay and the model.

Analysis of Expediency to Apply LCL Model with Source of Higher Harmonics of Current While Investigating Resonance Condition of Power Supply Network

Directory of Open Access Journals (Sweden)

M. Pavlovsky

2004-01-01

Full Text Available The paper considers a power system model of a plant with one capacitor bank and with one current source of higher harmonics for higher power factor. The laboratory research results of this system and practical application of the proposed model are given in the paper.

Research on Harmonic Characteristics Influence for Distribution Network with Renewable Energy

Directory of Open Access Journals (Sweden)

Huang Wei

2016-01-01

Full Text Available In order to study the influence on harmonic characteristics of distribution network with renewable energy, a simplified model of distribution network is established to analyse theory while considering the influence of cable on the system capacitive current. Establishing an actual distribution network model by Digsilent to research the harmonic characteristics impact when photovoltaic power with PV incorporated the distribution network in a variety of different access , while using constant current source model as harmonic source model which often been used in engineering practices. The simulation results show that: optimizing the access location and dispersion of PV can decrease the waveform distortion levels in distribution network and a certain number of high-order harmonic will magnify by a specific grid structure, deteriorating the distribution network power quality.

Polarization-Resolved Study of High Harmonics from Bulk Semiconductors

Science.gov (United States)

Kaneshima, Keisuke; Shinohara, Yasushi; Takeuchi, Kengo; Ishii, Nobuhisa; Imasaka, Kotaro; Kaji, Tomohiro; Ashihara, Satoshi; Ishikawa, Kenichi L.; Itatani, Jiro

2018-06-01

The polarization property of high harmonics from gallium selenide is investigated using linearly polarized midinfrared laser pulses. With a high electric field, the perpendicular polarization component of the odd harmonics emerges, which is not present with a low electric field and cannot be explained by the perturbative nonlinear optics. A two-dimensional single-band model is developed to show that the anisotropic curvature of an energy band of solids, which is pronounced in an outer part of the Brillouin zone, induces the generation of the perpendicular odd harmonics. This model is validated by three-dimensional quantum mechanical simulations, which reproduce the orientation dependence of the odd-order harmonics. The quantum mechanical simulations also reveal that the odd- and even-order harmonics are produced predominantly by the intraband current and interband polarization, respectively. These experimental and theoretical demonstrations clearly show a strong link between the band structure of a solid and the polarization property of the odd-order harmonics.

The current biodiversity extinction event: scenarios for mitigation and recovery.

Science.gov (United States)

Novacek, M J; Cleland, E E

2001-05-08

The current massive degradation of habitat and extinction of species is taking place on a catastrophically short timescale, and their effects will fundamentally reset the future evolution of the planet's biota. The fossil record suggests that recovery of global ecosystems has required millions or even tens of millions of years. Thus, intervention by humans, the very agents of the current environmental crisis, is required for any possibility of short-term recovery or maintenance of the biota. Many current recovery efforts have deficiencies, including insufficient information on the diversity and distribution of species, ecological processes, and magnitude and interaction of threats to biodiversity (pollution, overharvesting, climate change, disruption of biogeochemical cycles, introduced or invasive species, habitat loss and fragmentation through land use, disruption of community structure in habitats, and others). A much greater and more urgently applied investment to address these deficiencies is obviously warranted. Conservation and restoration in human-dominated ecosystems must strengthen connections between human activities, such as agricultural or harvesting practices, and relevant research generated in the biological, earth, and atmospheric sciences. Certain threats to biodiversity require intensive international cooperation and input from the scientific community to mitigate their harmful effects, including climate change and alteration of global biogeochemical cycles. In a world already transformed by human activity, the connection between humans and the ecosystems they depend on must frame any strategy for the recovery of the biota.

One dimension harmonic oscillator

International Nuclear Information System (INIS)

Cohen-Tannoudji, Claude; Diu, Bernard; Laloe, Franck.

1977-01-01

The importance of harmonic oscillator in classical and quantum physics, eigenvalues and eigenstates of hamiltonian operator are discussed. In complement are presented: study of some physical examples of harmonic oscillators; study of stationnary states in the /x> representation; Hermite polynomials; resolution of eigenvalue equation of harmonic oscillator by polynomial method; isotope harmonic oscillator with three dimensions; charged harmonic oscillator in uniform electric field; quasi classical coherent states of harmonic oscillator; eigenmodes of vibration of two coupled harmonic oscillators; vibration modus of a continuous physical system (application to radiation: photons); vibration modus of indefinite linear chain of coupled harmonic oscillators (phonons); one-dimensional harmonic oscillator in thermodynamic equilibrium at temperature T [fr

Harmonics Suppression for Single-Phase Grid-Connected Photovoltaic Systems in Different Operation Modes

DEFF Research Database (Denmark)

Yang, Yongheng; Zhou, Keliang; Blaabjerg, Frede

2013-01-01

-connected PV inverters may be severely affected in different operation modes. In this paper, a detailed analysis is conducted to reveal the relationship between the harmonics level with the power factor and the current level in the PV systems. A current control solution which employs an Internal Model...... Principle (IMP) is proposed to suppress the harmonic currents injected into the grid. Experiments are carried out to verify the analysis and the performance of the proposed control method. It is demonstrated that the proposed method presents an effective solution to harmonics suppression for single......-phase grid-connected PV systems in different operation modes. Especially, it can remove higher order harmonics effectively leading to a better power quality compared to the Proportional plus Multi-Resonant Controller, and it has less computational burden....

Effects of external magnetic field on harmonics generated in laser interaction with underdense plasma

International Nuclear Information System (INIS)

Faghihi-Nik, M.; Ghorbanalilu, M.; Shokri, B.

2010-01-01

Complete text of publication follows. Generation of harmonic radiation is an important subject of laser plasma interaction and attracts great attention due to a wide range of applications. It has been seen that intense electromagnetic and quasi-static transverse magnetic fields are generated in laser plasma interaction. An extremely intense magnetic field (up to hundreds of MG) has been observed by experimental measurements in interaction of short laser pulses with plasma. These self-generated or applied magnetic fields affect the propagation of the laser pulses. In most laser interactions with homogeneous plasma, odd harmonics of laser frequency are generated. In this paper, we point out the possibility of even harmonics generation when a linearly polarized laser beam propagates in homogeneous plasma in the presence of a transverse magnetic field. It is shown that applying external field induces a transverse current density oscillating twice of the laser field which leds to generation of second harmonic radiation. This current density is derived using the perturbation method, and the steady state amplitude of the second harmonic obtained by solution of the wave equation. By the same procedure the current density and then the steady state amplitude of higher order harmonics are calculated. The efficiency of harmonic generation (the ratio of harmonic power to incident power) is a drastically function of the strength of external magnetic field. It is found that the efficiency of even harmonics is zero in the absence of magnetic field and increases as the magnetic field is increased. For odd harmonics, applying the external magnetic field enhances the generated harmonics as well. The conversion efficiency also increases with increase in plasma density and intensity of the laser beam.

Highlighting the harmonic regime generated by electric locomotives equipped with DC motors

Science.gov (United States)

Baciu, I.; Cunţan, C. D.

2018-01-01

The paper presents the results of measurements made using the C.A. 8334 power quality analyzer on an electric locomotive equipped with DC motors. We carried out determinations of the current-voltage regime using a locomotive motor. The harmonic regime of the other motors being identical to the analysed one, we could easily deduce the effects caused by the entire locomotive. The data measured with the analyzer were firstly transferred into a computer system using the Qualistar software, followed by data processing in Excel, enabling therefore a graphical representation of the characteristic parameters of power quality. Based on the acquired data, we determined the power factor, as well as the active, reactive and apparent power. The measurements revealed high values of the current harmonics, fact that required some measures to be taken for reducing the values of these harmonics. For this, we ran a simulation using the PSCAD/EMTDC software, by introducing LC filters in tune with the harmonic frequencies. The result was a significant reduction in the harmonic regime, either in the harmonics values or the power factor and reactive power.

Static harmonization of dynamically harmonized Fourier transform ion cyclotron resonance cell.

Science.gov (United States)

Zhdanova, Ekaterina; Kostyukevich, Yury; Nikolaev, Eugene

2017-08-01

Static harmonization in the Fourier transform ion cyclotron resonance cell improves the resolving power of the cell and prevents dephasing of the ion cloud in the case of any trajectory of the charged particle, not necessarily axisymmetric cyclotron (as opposed to dynamic harmonization). We reveal that the Fourier transform ion cyclotron resonance cell with dynamic harmonization (paracell) is proved to be statically harmonized. The volume of the statically harmonized potential distribution increases with an increase in the number of trap segments.

Deliberately dispatched SCR firing angles for harmonic mitigation in three-phase multi-drive systems without communication

DEFF Research Database (Denmark)

Yang, Yongheng; Davari, Pooya; Zare, Firuz

2016-01-01

Adjustable Speed Drives (ASDs) are widely used in threephase multi-drive applications in industry, where low-cost Diode Rectifiers (DRs) or Silicon-Controlled Rectifiers (SCRs) are still employed as the front-ends in practice, also for simplicity. However, the associated harmonics are produced...

Simulation model of harmonics reduction technique using shunt active filter by cascade multilevel inverter method

Science.gov (United States)

Andreh, Angga Muhamad; Subiyanto, Sunardiyo, Said

2017-01-01

Development of non-linear loading in the application of industry and distribution system and also harmonic compensation becomes important. Harmonic pollution is an urgent problem in increasing power quality. The main contribution of the study is the modeling approach used to design a shunt active filter and the application of the cascade multilevel inverter topology to improve the power quality of electrical energy. In this study, shunt active filter was aimed to eliminate dominant harmonic component by injecting opposite currents with the harmonic component system. The active filter was designed by shunt configuration with cascaded multilevel inverter method controlled by PID controller and SPWM. With this shunt active filter, the harmonic current can be reduced so that the current wave pattern of the source is approximately sinusoidal. Design and simulation were conducted by using Power Simulator (PSIM) software. Shunt active filter performance experiment was conducted on the IEEE four bus test system. The result of shunt active filter installation on the system (IEEE four bus) could reduce THD current from 28.68% to 3.09%. With this result, the active filter can be applied as an effective method to reduce harmonics.

Harmonic Effects on Electromechanical Overcurrent Relays = Harmoniklerin Elektromekanik Aşırı Akım Röleleri Üzerindeki Etkileri

Directory of Open Access Journals (Sweden)

Altuğ BOZKURT

2005-06-01

Full Text Available The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay (ITOCR were examined. Not common in existing studies, the behaviour of ITOCR was analysed with laboratory experiments for distorted waveforms. A type of induction disc relay was used as an electromechanical ITOCR in the experiments. The non-sinusoidal load currents that consist of different harmonic spectra were applied to ITOCR and these nonlinear-load currents were processed by a data acquisition card and a harmonic analysis programme in the computer environment. According to the experiment results, the pick up current and the operating time of the ITOCR increase proportionally to the total harmonic distortion (THD value of the non-sinusoidal current. It is concluded that, this type of relay cannot protect the system reliably due to the harmonic components of current.

A modular spherical harmonics approach to the neutron transport equation

International Nuclear Information System (INIS)

Inanc, F.; Rohach, A.F.

1989-01-01

A modular nodal method was developed for solving the neutron transport equation in 2-D xy coordinates. The spherical harmonic expansion was used for approximating the second-order even-parity form of the neutron transport equation. The boundary conditions of the spherical harmonics approximation were derived in a form to have forms analogous to the partial currents in the neutron diffusion equation. Relations were developed for generating both the second-order spherical harmonic equations and the boundary conditions in an automated computational algorithm. Nodes using different orders of the spherical harmonics approximation to the transport equation were interfaced through mixed-type boundary conditions. The determination of spherical harmonic orders implemented in the nodes were determined by the scheme in an automated manner. Results of the method compared favorably to benchmark problems. (author)

Mitigation of Traffic-Induced Ground Vibration by Inclined Wave Barriers

DEFF Research Database (Denmark)

Andersen, Lars; Augustesen, Anders Hust

2009-01-01

Double sheet pile walls can be used as wave barriers in order to mitigate ground vibrations from railways. The present analysis concerns the efficiency of such barriers, especially with regard to the influence of the barrier inclination and the backfill between the walls. Thus, the screening capa...... of reference following the load. This allows a computation of the steady state response to a harmonically varying point source moving at different speeds typical for a train....

Three-dimensional analysis of harmonic generation in high-gain free-electron lasers

International Nuclear Information System (INIS)

Huang, Zhirong; Kim, Kwang-Je

2000-01-01

In a high-gain free-electron laser (FEL) employing a planar undulator, strong bunching at the fundamental wavelength can drive substantial bunching and power levels at the harmonic frequencies. In this paper we investigate the three-dimensional evolution of harmonic radiation based on the coupled Maxwell-Klimontovich equations that take into account nonlinear harmonic interactions. Each harmonic field is a sum of a linear amplification term and a term driven by nonlinear harmonic interactions. After a certain stage of exponential growth, the dominant nonlinear term is determined by interactions of the lower nonlinear harmonics and the fundamental radiation. As a result, the gain length, transverse profile, and temporal structure of the first few harmonics are eventually governed by those of the fundamental. Transversely coherent third-harmonic radiation power is found to approach 1% of the fundamental power level for current high-gain FEL projects

The Technology of Suppressing Harmonics with Complex Neural Network is Applied to Microgrid

Science.gov (United States)

Zhang, Jing; Li, Zhan-Ying; Wang, Yan-ping; Li, Yang; Zong, Ke-yong

2018-03-01

According to the traits of harmonics in microgrid, a new CANN controller which combines BP and RBF neural network is proposed to control APF to detect and suppress harmonics. This controller has the function of current prediction. By simulation in Matlab / Simulink, this design can shorten the delay time nearly 0.02s (a power supply current cycle) in comparison with the traditional controller based on ip-iq method. The new controller also has higher compensation accuracy and better dynamic tracking traits, it can greatly suppress the harmonics and improve the power quality.

WAVEMOTH-FAST SPHERICAL HARMONIC TRANSFORMS BY BUTTERFLY MATRIX COMPRESSION

International Nuclear Information System (INIS)

Seljebotn, D. S.

2012-01-01

We present Wavemoth, an experimental open source code for computing scalar spherical harmonic transforms (SHTs). Such transforms are ubiquitous in astronomical data analysis. Our code performs substantially better than existing publicly available codes owing to improvements on two fronts. First, the computational core is made more efficient by using small amounts of pre-computed data, as well as paying attention to CPU instruction pipelining and cache usage. Second, Wavemoth makes use of a fast and numerically stable algorithm based on compressing a set of linear operators in a pre-computation step. The resulting SHT scales as O(L 2 log 2 L) for the resolution range of practical interest, where L denotes the spherical harmonic truncation degree. For low- and medium-range resolutions, Wavemoth tends to be twice as fast as libpsht, which is the current state-of-the-art implementation for the HEALPix grid. At the resolution of the Planck experiment, L ∼ 4000, Wavemoth is between three and six times faster than libpsht, depending on the computer architecture and the required precision. Because of the experimental nature of the project, only spherical harmonic synthesis is currently supported, although adding support for spherical harmonic analysis should be trivial.

Automated detection and characterization of harmonic tremor in continuous seismic data

Science.gov (United States)

Roman, Diana C.

2017-06-01

Harmonic tremor is a common feature of volcanic, hydrothermal, and ice sheet seismicity and is thus an important proxy for monitoring changes in these systems. However, no automated methods for detecting harmonic tremor currently exist. Because harmonic tremor shares characteristics with speech and music, digital signal processing techniques for analyzing these signals can be adapted. I develop a novel pitch-detection-based algorithm to automatically identify occurrences of harmonic tremor and characterize their frequency content. The algorithm is applied to seismic data from Popocatepetl Volcano, Mexico, and benchmarked against a monthlong manually detected catalog of harmonic tremor events. During a period of heightened eruptive activity from December 2014 to May 2015, the algorithm detects 1465 min of harmonic tremor, which generally precede periods of heightened explosive activity. These results demonstrate the algorithm's ability to accurately characterize harmonic tremor while highlighting the need for additional work to understand its causes and implications at restless volcanoes.

Promoting interactions between local climate change mitigation, sustainable energy development, and rural development policies in Lithuania

International Nuclear Information System (INIS)

Streimikiene, Dalia; Baležentis, Tomas; Kriščiukaitienė, Irena

2012-01-01

Lithuania has developed several important climate change mitigation policy documents however there are no attempts in Lithuania to develop local climate change mitigation policies or to decentralize climate change mitigation policy. Seeking to achieve harmonization and decentralization of climate change mitigation and energy policies in Lithuania the framework for local climate change mitigation strategy need to be developed taking into account requirements, targets and measures set in national climate change mitigation and energy policy documents. The paper will describe how national climate change mitigation and energy policies can be implemented via local energy and climate change mitigation plans. The aim of the paper is to analyze the climate change mitigation policy and its relationship with policies promoting sustainable energy development in Lithuania and to present a framework for local approaches to climate change mitigation in Lithuania, in the context of the existing national and supra-national energy, climate change, and rural development policies. - Highlights: ► The framework for local energy action plans is offered. ► The structural support possibilities are assessed with respect to the Lithuanian legal base. ► The proposals are given for further promotion of sustainable energy at the local level.

Apparatus and Methods for Mitigating Electromagnetic Emissions

Science.gov (United States)

Geng, Steven M. (Inventor); Niedra, Janis M. (Inventor)

2016-01-01

Apparatus, methods, and other embodiments associated with mitigation of magnetic fields are described herein. In an embodiment, a method for mitigating an electromagnetic field includes positioning a mitigating coil around a linear alternator of linear motor so that the mitigating coil is coaxially located with an alternator coil; arranging the mitigating coil to generate a field to mitigate an electromagnetic field generated by the alternator coil; and passing an induced current from the alternator coil through the mitigating coil.

Investigation of voltage swell mitigation using STATCOM

International Nuclear Information System (INIS)

Razak, N A Abdul; Jaafar, S; Hussain, I S

2013-01-01

STATCOM is one of the best applications of a self commutated FACTS device to control power quality problems in the distribution system. This project proposed a STATCOM model with voltage control mechanism. DQ transformation was implemented in the controller system to achieve better estimation. Then, the model was used to investigate and analyse voltage swell problem in distribution system. The simulation results show that voltage swell could contaminate distribution network with unwanted harmonic frequencies. Negative sequence frequencies give harmful effects to the network. System connected with proposed STATCOM model illustrates that it could mitigate this problems efficiently.

A Transformerless Hybrid Active Filter Capable of Complying with Harmonic Guidelines for Medium-Voltage Motor Drives

Science.gov (United States)

Kondo, Ryota; Akagi, Hirofumi

This paper presents a transformerless hybrid active filter that is integrated into medium-voltage adjustable-speed motor drives for fans, pumps, and compressors without regenerative braking. The authors have designed and constructed a three-phase experimental system rated at 400V and 15kW, which is a downscaled model from a feasible 6.6-kV 1-MW motor drive system. This system consists of the hybrid filter connecting a passive filter tuned to the 7th harmonic filter in series with an active filter that is based on a three-level diode-clamped PWM converter, as well as an adjustable-speed motor drive in which a diode rectifier is used as the front end. The hybrid filter is installed on the ac side of the diode rectifier with no line-frequency transformer. The downscaled system has been exclusively tested so as to confirm the overall compensating performance of the hybrid filter and the filtering performance of a switching-ripple filter for mitigating switching-ripple voltages produced by the active filter. Experimental results verify that the hybrid filter achieves harmonic compensation of the source current in all the operating regions from no-load to the rated-load conditions, and that the switching-ripple filter reduces the switching-ripple voltages as expected.

Comparative analysis of gyrotron backward-wave oscillators operating at different cyclotron harmonics

International Nuclear Information System (INIS)

Yeh, Y.S.; Chang, T.H.; Wu, T.S.

2004-01-01

A comparative analysis between the fundamental and second cyclotron harmonics of gyrotron backward-wave oscillators (gyro-BWOs) is presented. The simulation results reveal that nonlinear field contraction is a common feature for both harmonic interactions. Besides, the electron transit angle, used to characterize the axial modes of the fundamental harmonic TE 11 mode at the start-oscillation conditions, is found to be applicable even for the second harmonic TE 21 mode. Each axial mode of either the fundamental harmonic TE 11 or the second harmonic TE 21 modes is maintained at a constant value of the electron transit angle while changing the operating parameters, such as magnetic field and beam voltage. Extensive numerical calculations are conducted for the start-oscillation currents and tuning properties. Moreover, single-mode operating regimes are suggested where the second harmonic TE 21 gyro-BWO could generate a considerable output power, comparing with the fundamental harmonic TE 11 gyro-BWO

Selective Compensation of Voltage Harmonics in a Grid-Connected Microgrid

DEFF Research Database (Denmark)

Savaghebi, M.; Guerrero, Josep M.; Jalilian, A.

2011-01-01

In this paper, a method for selective voltage harmonic compensation in a grid-connected microgrid is presented. Harmonic compensation is done through proper control of distributed generators (DGs) interface converters. In order to achieve proper sharing of compensation effort among the DGs, a power...... named “Harmonic Distortion Power (HDP)” is defined. In the proposed method, active and reactive power control loops are considered to control the powers injected by the DGs. Also, a virtual impedance loop and voltage and current proportional-resonant controllers are included. Simulation results show...

Image Formation in Second-Harmonic Near-Field Microscopy

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Lozovski, Valeri Z.; Pedersen, Kjeld

1999-01-01

contributions in the effective current, i.e., the currents generated by the self-consistent fields at the fundamental and second-harmonic frequencies. The self-consistent problem for both frequencies is solved exactly by use of the diagram technique adapted from quantum electrodynamics. Preliminary numerical...

Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

Science.gov (United States)

Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

2016-06-01

We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

Experimental determination of harmonic conditions amplification in a distribution network by capacitor bank switching

DEFF Research Database (Denmark)

Baloi, Alexandru; Kocewiak, Lukasz Hubert; Bak, Claus Leth

2012-01-01

The paper presents a study comprising laboratory measurements for the evaluation of the harmonic amplification due to capacitor bank switching. The mathematical model of the amplification factors of the current flowing on the circuit elements is presented. Theoretical aspects, regarding the total...... harmonic distortion (THD) of the capacitor current computed using the amplification factor, are originally presented. Nonlinear loads as six pulse rectifier and National Instruments measurement sensors together with LabView software were used on the laboratory set-up. The main instrument of the method...... is the harmonic impedance, “seen” in the bus of the capacitor bank switching. MatLab Simulink is used for the determination of the harmonic impedance....

Current-use pesticides in stream water and suspended particles following runoff: exposure, effects, and mitigation requirements.

Science.gov (United States)

Bereswill, Renja; Streloke, Martin; Schulz, Ralf

2013-06-01

The European Union's directive for sustainable use of pesticides requires implementing risk mitigation measures at streams threatened by pesticide entries. The need for mitigation measures was investigated at 10 stream sites within an intensively used arable region in central Germany by characterizing pesticide exposure following edge-of-field runoff and effects on the aquatic macroinvertebrates. Moreover, the influence of riparian buffer strip width (as a mitigation measure) at the sampling sites was considered. Generally, invertebrate fauna was dominated by pesticide-tolerant species, suggesting a high pesticide exposure at almost all sites. This result is also reflected by the elevated levels of suspended particle contamination in terms of toxic units (logTUMax  > -2), corresponding to one-hundredth of the median lethal concentration (LC50) to Daphnia magna. At two sites that received high aqueous-phase entries of the pyrethroid lambda-cyhalothrin (logTUMax  > -0.6), the abundance and number of sensitive species in terms of the species at risk index decreased during the pesticide application period. In contrast, no acute significant negative effects on macroinvertebrates were observed at sites characterised by low water-phase toxicity (logTUMax  < -3.5). An influence of riparian buffer strip width on pesticide exposure was not observed, supposedly because of the presence of erosion rills and ephemeral ditches. In conclusion, results show that mitigation measures (such as the improvement of currently present riparian buffer strips) are needed in the study area. Copyright © 2013 SETAC.

Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

Energy Technology Data Exchange (ETDEWEB)

Kant, Niti [Department of Physics, Lovely Professional University, Phagwara, Punjab 144 402 (India); Nandan Gupta, Devki [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, Hyyong [Advanced Photonics Research Institute (APRI) and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

2012-01-15

In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

International Nuclear Information System (INIS)

Kant, Niti; Nandan Gupta, Devki; Suk, Hyyong

2012-01-01

In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

Improving the performance of the power supply of the MGC-20 cyclotron harmonic coils

International Nuclear Information System (INIS)

Hagras, A.A.M

2008-01-01

Correction of lower harmonics of the MGC-20 cyclotron magnetic field is of great importance for its operation. Actually, stability of the acceleration process, attainment of the final energy of the accelerated beam and efficiency of the beam extraction system depend on the lower harmonics control. Error in the magnetic field lower harmonics can reduce the efficiency of the beam extraction resulting in complete disappearance of the extracted beam of the cyclotron. For control of the cyclotron MGC-20 magnetic field lower harmonics, the so called inner and outer harmonic coils are provided.These harmonic coils must be fed by a very high accuracy current source power supply. This power supply must be equipped with a high resolution measurement and control scheme to achieve the imposed requirements of adjustment of the first harmonic magnetic field.Harmonic coils are supplied with conventional SCR controlled converters with analog control strategy. Frequent interruption of operation and difficulties in the adjustment of harmonic coil current lead to economical and research - time losses.This research project aims to replace this conventional system with a more effective, accurate and less complicated digital control system based on Motorola DSP56F807 and high switching frequency power circuit. Actually all the bulky modules including the analog integrator, the signal monitoring and protection, the pulse phase modulator and the comparator are all replaced by a single module circuit.

Automatic adjustment of bias current for direct current superconducting quantum interference device

International Nuclear Information System (INIS)

Makie-Fukuda, K.; Hotta, M.; Okajima, K.; Kado, H.

1993-01-01

A new method of adjusting the bias current of dc superconducting quantum interference device (SQUID) is described. It is shown that the signal-to-noise ratio of a SQUID magnetometer connected in a flux-locked loop configuration is proportional to the second harmonic of the output signal from the SQUID. A circuit configuration that can automatically optimize a SQUID's bias current by measuring this second harmonic and adjusting the bias current accordingly is proposed

Numerical artifacts in the Generalized Porous Medium Equation: Why harmonic averaging itself is not to blame

Science.gov (United States)

Maddix, Danielle C.; Sampaio, Luiz; Gerritsen, Margot

2018-05-01

The degenerate parabolic Generalized Porous Medium Equation (GPME) poses numerical challenges due to self-sharpening and its sharp corner solutions. For these problems, we show results for two subclasses of the GPME with differentiable k (p) with respect to p, namely the Porous Medium Equation (PME) and the superslow diffusion equation. Spurious temporal oscillations, and nonphysical locking and lagging have been reported in the literature. These issues have been attributed to harmonic averaging of the coefficient k (p) for small p, and arithmetic averaging has been suggested as an alternative. We show that harmonic averaging is not solely responsible and that an improved discretization can mitigate these issues. Here, we investigate the causes of these numerical artifacts using modified equation analysis. The modified equation framework can be used for any type of discretization. We show results for the second order finite volume method. The observed problems with harmonic averaging can be traced to two leading error terms in its modified equation. This is also illustrated numerically through a Modified Harmonic Method (MHM) that can locally modify the critical terms to remove the aforementioned numerical artifacts.

Investigation of Reactive Power Control Effects on Flicker and Harmonics Emission of a DFIG Wind Turbine

Directory of Open Access Journals (Sweden)

Amir Nagizadeh Ghoogdareh

2013-01-01

Full Text Available One of the most important power quality aspects in wind farms is voltage fluctuation or flicker which should be investigated due to the nature of wind speed variations. These variations result in power and voltage fluctuations at the load bus. Moreover, the wind generation systems may be assumed as a harmonics source because of their power electronic converters. There are numerous factors that affect flicker and harmonic emission of grid-connected wind turbines during continuous operation, such as wind characteristics (e.g. mean wind speed, turbulence intensity, type of generator and grid conditions (e.g. short circuit capacity, grid impedance angle. In this paper, an IEC based flickermeter is first modeled and then a variable speed wind turbine has been simulated by Matlab/Simulink software. The flicker and harmonics emissions of wind turbines equipped with DFIG during continuous operation and using output reactive control are investigated. The simulation results show that control of wind turbine output reactive power is an effective means for flicker mitigation during continuous operation. However, there should be a compromise between flicker reduction and harmonics level increase to enhance the whole power quality of wind turbine.

Harmonic Inverse FEL Interaction at 800nm

CERN Document Server

Sears, C M S; Siemann, R; Spencer, J E

2005-01-01

The inverse Free Electron Laser (IFEL) interaction has recently been proposed and demonstrated as a premodulator for High Gain Harmonic Generation (HGHG) experiments. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. The harmonic IFEL can add flexibility to HGHG FEL design.

Efficient second- and third-harmonic radiation generation from relativistic laser-plasma interactions

Energy Technology Data Exchange (ETDEWEB)

Singh, Mamta; Gupta, D. N., E-mail: dngupta@physics.du.ac.in [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, H. [Department of Physics and Photon Science, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

2015-06-15

We propose an idea to enhance the efficiency of second- and third-harmonic generation by considering the amplitude-modulation of the fundamental laser pulse. A short-pulse laser of finite spot size is modeled as amplitude modulated in time. Amplitude-modulation of fundamental laser contributes in quiver velocity of the plasma electrons and produces the strong plasma-density perturbations, thereby increase in current density at second- and third-harmonic frequency. In a result, the conversion efficiency of harmonic generation increases significantly. Power conversion efficiency of harmonic generation process is the increasing function of the amplitude-modulation parameter of the fundamental laser beam. Harmonic power generated by an amplitude modulated laser is many folds higher than the power obtained in an ordinary case.

Efficient second- and third-harmonic radiation generation from relativistic laser-plasma interactions

International Nuclear Information System (INIS)

Singh, Mamta; Gupta, D. N.; Suk, H.

2015-01-01

We propose an idea to enhance the efficiency of second- and third-harmonic generation by considering the amplitude-modulation of the fundamental laser pulse. A short-pulse laser of finite spot size is modeled as amplitude modulated in time. Amplitude-modulation of fundamental laser contributes in quiver velocity of the plasma electrons and produces the strong plasma-density perturbations, thereby increase in current density at second- and third-harmonic frequency. In a result, the conversion efficiency of harmonic generation increases significantly. Power conversion efficiency of harmonic generation process is the increasing function of the amplitude-modulation parameter of the fundamental laser beam. Harmonic power generated by an amplitude modulated laser is many folds higher than the power obtained in an ordinary case

Atto second high harmonic sources

International Nuclear Information System (INIS)

Nam, Chang Hee

2008-01-01

High harmonic generation is a powerful method to produce attosecond pulses. The high harmonics, emitted from atoms driven by intense femtosecond laser pulses, can from an attosecond pulse train with equally spaced harmonic spectrum or an isolated single attosecond pulse with broad continuum spectrum. Using high power femtosecond laser technology developed at CXRC, we have investigated the spectral and temporal characteristics of high harmonics obtained from gaseous atoms. The spectral structure of harmonics could be manipulated by controlling laser chirp, and continuous tuning of harmonic wavelengths was achieved. For rigorous temporal characterization of attosecond harmonic pulses a cross correlation technique was applied to the photoionization process by harmonic and IR femtosecond pulses and achieved the complete temporal reconstruction of attosecond pulse trains, revealing the detailed temporal structure of the attosecond chirp by material dispersion. The duration of attosecond high harmonic pulses is usually much longer than that of transform limited pulses due to the inherent chirp originating from the harmonic generation process. The attosecond chirp compensation in the harmonic generation medium itself was demonstrated, thereby realizing the generation of near transform limited attosecond pulses. The interference of attosecond electron wave packets, generated from an atom by attosecond harmonic pulses, will be also presented

Current level detector

International Nuclear Information System (INIS)

Kerns, C.R.

1977-01-01

A device is provided for detecting the current level of a dc signal. It includes an even harmonic modulator to which a reference ac signal is applied. The unknown dc signal acts on the reference ac signal so that the output of the modulator includes an even harmonic whose amplitude is proportional to the unknown dc current. The device may be used to provide overcurrent protection for proportional wire chambers

Probabilistic Harmonic Calculation in Distribution Networks with Electric Vehicle Charging Stations

Directory of Open Access Journals (Sweden)

Jianxue Wang

2014-01-01

Full Text Available Integrating EV charging station into power grid will bring impacts on power system, among which the most significant one is the harmonic pollution on distribution networks. Due to the uncertainty of the EV charging process, the harmonic currents brought by EV charging stations have a random nature. This paper proposed a mathematical simulation method for studying the working status of charging stations, which considers influencing factors including random leaving factor, electricity price, and waiting time. Based on the proposed simulation method, the probability distribution of the harmonic currents of EV charging stations is obtained and used in the calculation of the probability harmonic power flow. Then the impacts of EVs and EV charging stations on distribution networks can be analyzed. In the case study, the proposed simulation and analysis method is implemented on the IEEE-34 distribution network. The influences of EV arrival rates, the penetration rate, and the accessing location of EV charging station are also investigated. Results show that this research has good potential in guiding the planning and construction of charging station.

Harmonic Analyzing of the Double PWM Converter in DFIG Based on Mathematical Model

Directory of Open Access Journals (Sweden)

Jing Liu

2017-12-01

Full Text Available Harmonic pollution of double fed induction generators (DFIGs has become a vital concern for its undesirable effects on power quality issues of wind generation systems and grid-connected system, and the double pulse width modulation (PWMconverter is one of the main harmonic sources in DFIGs. Thus the harmonic analysis of the converter in DFIGs is a necessary step to evaluate their harmonic pollution of DFIGs. This paper proposes a detailed harmonic modeling method to discuss the main harmonic components in a converter. In general the harmonic modeling could be divided into the low-order harmonic part (up to 30th order and the high-order harmonic part (greater than order 30 parts in general. The low-order harmonics are produced by the circuit topology and control algorithm, and the harmonic component will be different if the control strategy changes. The high-order harmonics are produced by the modulation of the switching function to the dc variable. In this paper, the low-order harmonic modeling is established according to the directions of power flow under the vector control (VC, and the high-order harmonic modeling is established by the switching function of space vector PWM and dc currents. Meanwhile, the simulations of harmonic a components in a converter are accomplished in a real time digital simulation system. The results indicate that the proposed modeling could effectively show the harmonics distribution of the converter in DFIGs.

Analysis of tidal currents in the North Sea from shipboard acoustic Doppler current profiler data

Science.gov (United States)

Vindenes, Håvard; Orvik, Kjell Arild; Søiland, Henrik; Wehde, Henning

2018-06-01

North Sea tidal currents are determined by applying harmonic analysis to ship-borne acoustic Doppler current profiler data recorded from 1999 to 2016, covering large areas of the northern North Sea. Direct current measurement data sets of this magnitude are rare in the otherwise well investigated North Sea, and thus it is a valuable asset in studying and expanding our understanding of its tidal currents and circulation in general. The harmonic analysis is applied to a least squares fit of the current observations at a set of knot points. Results from the harmonic analysis compare favorably to tidal parameters estimated from observations from moored instruments. The analysis shows that the tides are characterized by strong semi-diurnal component, with amplitudes of the principal Lunar constituent ranging from 1.6 cm/s in the Skagerrak to 67 cm/s in the Fair Isle Channel. Diurnal tides are found to be approximately one fifth the strength of the predominant semi-diurnal constituent. Output from a regional barotropic tide model compares well to tidal current determined from the harmonic analysis of the Acoustic Doppler Current Profiler data.

MREIT experiments with 200 µA injected currents: a feasibility study using two reconstruction algorithms, SMM and harmonic B(Z).

Science.gov (United States)

Arpinar, V E; Hamamura, M J; Degirmenci, E; Muftuler, L T

2012-07-07

Magnetic resonance electrical impedance tomography (MREIT) is a technique that produces images of conductivity in tissues and phantoms. In this technique, electrical currents are applied to an object and the resulting magnetic flux density is measured using magnetic resonance imaging (MRI) and the conductivity distribution is reconstructed using these MRI data. Currently, the technique is used in research environments, primarily studying phantoms and animals. In order to translate MREIT to clinical applications, strict safety standards need to be established, especially for safe current limits. However, there are currently no standards for safe current limits specific to MREIT. Until such standards are established, human MREIT applications need to conform to existing electrical safety standards in medical instrumentation, such as IEC601. This protocol limits patient auxiliary currents to 100 µA for low frequencies. However, published MREIT studies have utilized currents 10-400 times larger than this limit, bringing into question whether the clinical applications of MREIT are attainable under current standards. In this study, we investigated the feasibility of MREIT to accurately reconstruct the relative conductivity of a simple agarose phantom using 200 µA total injected current and tested the performance of two MREIT reconstruction algorithms. These reconstruction algorithms used are the iterative sensitivity matrix method (SMM) by Ider and Birgul (1998 Elektrik 6 215-25) with Tikhonov regularization and the harmonic B(Z) proposed by Oh et al (2003 Magn. Reason. Med. 50 875-8). The reconstruction techniques were tested at both 200 µA and 5 mA injected currents to investigate their noise sensitivity at low and high current conditions. It should be noted that 200 µA total injected current into a cylindrical phantom generates only 14.7 µA current in imaging slice. Similarly, 5 mA total injected current results in 367 µA in imaging slice. Total

Secondary Control for Compensation of Voltage Harmonics and Unbalance in Microgrids

DEFF Research Database (Denmark)

Savaghebi, Mehdi; Vasquez, Juan Carlos; Jalilian, Alireza

2012-01-01

of these controllers includes a selective virtual impedance loop which is considered to improve sharing of fundamental and harmonic components of load current among the DG units. The sharing improvement is provided at the expense of increasing voltage unbalance and harmonic distortion. Thus, the secondary control...... level is applied to manage the compensation of SLB voltage unbalance and harmonics by sending proper control signals to the primary level. DGs compensation efforts are controlled locally at the primary level. The system design procedure for selecting proper control parameters is discussed. Simulation...

High-harmonic spectroscopy of oriented OCS molecules: emission of even and odd harmonics.

Science.gov (United States)

Kraus, P M; Rupenyan, A; Wörner, H J

2012-12-07

We study the emission of even and odd high-harmonic orders from oriented OCS molecules. We use an intense, nonresonant femtosecond laser pulse superimposed with its phase-controlled second harmonic field to impulsively align and orient a dense sample of molecules from which we subsequently generate high-order harmonics. The even harmonics appear around the full revivals of the rotational dynamics. We demonstrate perfect coherent control over their intensity through the subcycle delay of the two-color fields. The odd harmonics are insensitive to the degree of orientation, but modulate with the degree of axis alignment, in agreement with calculated photorecombination dipole moments. We further compare the shape of the even and odd harmonic spectra with our calculations and determine the degree of orientation.

Harmonic content in the variable-frequency ac power line of TFTR

International Nuclear Information System (INIS)

Zabar, Z.; Bronner, G.; McMurray, S.; Karady, G.

1979-12-01

Studies were made of the harmonic content of the current and voltage at the generator bus of the Tokamak Fusion Test Reactor. Out of numerous load scenarios, one case was considered in detail. The harmonics were found acceptable for the generator; however, control problems and substantial telecommunications interference may result, requiring appropriate control measures and shielded telecommunication lines

Harmonic supergraphs

International Nuclear Information System (INIS)

Galperin, A.; Ivanov, E.; Ogievetsky, V.; Sokatchev, E.

1985-01-01

This paper completes a descrption of the quantization procedure in the harmonic superspace approach. The Feynman rules for N=2 matter and Yang-Mills theories are derived and the various examples of harmonic supergraph calculations are given. Calculations appear to be not more difficult than those in the N=1 case. The integration over harmonic variables does not lead to any troubles, a non-locality in these disappears on-shell. The important property is that the quantum corrections are always writen as integrals over the full harmonic superspace even though the initial action is an integral over the analytic subspace. As a by-product our results imply a very simple proof of finiteness of a wide class of the N=4, d=2 non-linear Σ-models. The most general self-couplings of hypermultiplets including those with broken SU(2) are considered.The duality relations among the N=2 linear multiplet and both kinds of hypermultiplet are established

Harmonic voltage excess problem test and analysis in UHV and EHV grid particular operation mode

Science.gov (United States)

Lv, Zhenhua; Shi, Mingming; Fei, Juntao

2018-02-01

The test and analysis of the power quality of some 1000kV UHV transmission lines and 500kV EHV transmission lines is carried out. It is found that there is harmonic voltage excess problems when the power supply of the UHV and EHV voltage line is single-ended or single-loop, the problem basically disappeared after the operation mode change, different operating conditions, the harmonic current has not been greatly affected, indicating that the harmonic voltage changes mainly caused by the system harmonic impedance. With the analysis of MATLAB Simulink system model, it can be seen that there are specific harmonic voltage excess in the system under the specific operating mode, which results in serious distortion of the specific harmonic voltage. Since such phenomena are found in 500kV and 1000kV systems, it is suggested that the test evaluation work should be done under the typical mode of operation in 500kV, 1000kV Planning and construction process to prevent the occurrence of serious distortion and the regional harmonic current monitoring and suppression work should be done.

Analysis of neutral current in three-phase systems with harmonic pollution; Analisis de la corriente de neutro en sistemas trifasicos con polucion armonica

Energy Technology Data Exchange (ETDEWEB)

Suarez, J.A.; Mauro, G.F. di; Dimenna, C.; Anaut, D.; Aguero, C. [Universidad Nacional Mar del Plata (Argentina). Fac. de Ingenieria. Grupo LAT], e-mail: lat@mdp.edu.ar

2009-07-01

This paper analyzes potential variables that affect the neutral current when connected receivers presents nonlinear characteristics. Were simulated scenarios in the Alternative Transients Program combining the type and number of units loads, fed on sinusoidal voltages, symmetrical, balanced, asymmetrical and unbalanced. Also has been studied the effect of voltage harmonics. As a result of simulations with asymmetric and unbalanced sources was found variations in the neutral current up to 5%. Analysis of diversity effects and attenuation reported significant variances: 10% and 20% respectively. The results achieved show that asymmetries and imbalances in power have a slight impact on the neutral current, while the more prominent were the diversity and attenuation effects.

Harmonic analysis of electrified railway based on improved HHT

Science.gov (United States)

Wang, Feng

2018-04-01

In this paper, the causes and harms of the current electric locomotive electrical system harmonics are firstly studied and analyzed. Based on the characteristics of the harmonics in the electrical system, the Hilbert-Huang transform method is introduced. Based on the in-depth analysis of the empirical mode decomposition method and the Hilbert transform method, the reasons and solutions to the endpoint effect and modal aliasing problem in the HHT method are explored. For the endpoint effect of HHT, this paper uses point-symmetric extension method to extend the collected data; In allusion to the modal aliasing problem, this paper uses the high frequency harmonic assistant method to preprocess the signal and gives the empirical formula of high frequency auxiliary harmonic. Finally, combining the suppression of HHT endpoint effect and modal aliasing problem, an improved HHT method is proposed and simulated by matlab. The simulation results show that the improved HHT is effective for the electric locomotive power supply system.

Constant DC-Capacitor Voltage-Control-Based Harmonics Compensation Strategy of Smart Charger for Electric Vehicles in Single-Phase Three-Wire Distribution Feeders

Directory of Open Access Journals (Sweden)

Fuka Ikeda

2017-06-01

Full Text Available This paper discusses harmonic current compensation of the constant DC-capacitor voltage-control (CDCVC-based strategy of smart chargers for electric vehicles (EVs in single-phase three-wire distribution feeders (SPTWDFs under nonlinear load conditions. The basic principle of the CDCVC-based harmonics compensation strategy under nonlinear load conditions is discussed in detail. The instantaneous power flowing into the three-leg pulse-width modulated (PWM rectifier, which performs as a smart charger, shows that the CDCVC-based strategy achieves balanced and sinusoidal source currents with a unity power factor. The CDCVC-based harmonics compensation strategy does not require any calculation blocks of fundamental reactive, unbalanced active, and harmonic currents. Thus, the authors propose a simplified algorithm to compensate for reactive, unbalanced active, and harmonic currents. A digital computer simulation is implemented to confirm the validity and high practicability of the CDCVC-based harmonics compensation strategy using PSIM software. Simulation results demonstrate that balanced and sinusoidal source currents with a unity power factor in SPTWDFs are obtained on the secondary side of the pole-mounted distribution transformer (PMDT during both the battery-charging and discharging operations in EVs, compensating for the reactive, unbalanced active, and harmonic currents.

Degenerate Fermi gas in a combined harmonic-lattice potential

International Nuclear Information System (INIS)

Blakie, P. B.; Bezett, A.; Buonsante, P.

2007-01-01

In this paper we derive an analytic approximation to the density of states for atoms in a combined optical lattice and harmonic trap potential as used in current experiments with quantum degenerate gases. We compare this analytic density of states to numerical solutions and demonstrate its validity regime. Our work explicitly considers the role of higher bands and when they are important in quantitative analysis of this system. Applying our density of states to a degenerate Fermi gas, we consider how adiabatic loading from a harmonic trap into the combined harmonic-lattice potential affects the degeneracy temperature. Our results suggest that occupation of excited bands during loading should lead to more favorable conditions for realizing degenerate Fermi gases in optical lattices

A novel harmonic control approach of distributed generation converters in a weak microgrid

DEFF Research Database (Denmark)

Ding, Guangqian; Gao, Feng; Tang, Yi

2014-01-01

as well as the long distance communication between the PCC and the converter are fully eliminated. In order to avoid overcompensation, a harmonic current limitation algorithm is implemented in the control loop. bBy properly dispatching the harmonic compensation capability, multiple DG unites can...

Electroencephalography in ellipsoidal geometry with fourth-order harmonics.

Science.gov (United States)

Alcocer-Sosa, M; Gutierrez, D

2016-08-01

We present a solution to the electroencephalographs (EEG) forward problem of computing the scalp electric potentials for the case when the head's geometry is modeled using a four-shell ellipsoidal geometry and the brain sources with an equivalent current dipole (ECD). The proposed solution includes terms up to the fourth-order ellipsoidal harmonics and we compare this new approximation against those that only considered up to second- and third-order harmonics. Our comparisons use as reference a solution in which a tessellated volume approximates the head and the forward problem is solved through the boundary element method (BEM). We also assess the solution to the inverse problem of estimating the magnitude of an ECD through different harmonic approximations. Our results show that the fourth-order solution provides a better estimate of the ECD in comparison to lesser order ones.

Modified Synchronous Reference Frame Based Shunt Active Power Filter with Fuzzy Logic Control Pulse Width Modulation Inverter

Directory of Open Access Journals (Sweden)

Suleiman Musa

2017-05-01

Full Text Available Harmonic distortion in power networks has greatly reduced power quality and this affects system stability. In order to mitigate this power quality issue, the shunt active power filter (SAPF has been widely applied and it is proven to be the best solution to current harmonics. This paper evaluates the performance of the modified synchronous reference frame extraction (MSRF algorithm with fuzzy logic controller (FLC based current control pulse width modulation (PWM inverter of three-phase three-wire SAPF to mitigate current harmonics. The proposed FLC is designed with a reduced amount of membership functions (MFs and rules, and thus significantly reduces the computational time and memory size. Modeling and simulations of SAPF are carried out using MATLAB/Simulink R2012a with the power system toolbox under steady-state condition, and this is followed with hardware implementation using a TMS320F28335 digital signal processor (DSP, Specrum Digital Inc., Stafford, TX, USA. The results obtained demonstrate a good and satisfactory response to mitigate the harmonics in the system. The total harmonic distortion (THD for the system has been reduced from 25.60% to 0.92% and 1.41% in the simulation study with and without FLC, respectively. Similarly for the experimental study, the SAPF can compensate for the three-phase load current by reducing THD to 5.07% and 7.4% with and without FLC, respectively.

Harmonic Lattice Dynamics of Germanium

Energy Technology Data Exchange (ETDEWEB)

Nelin, G

1974-07-01

The phonon dispersion relations of the DELTA-, LAMBDA-, and SIGMA-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field.

Harmonic Lattice Dynamics of Germanium

International Nuclear Information System (INIS)

Nelin, G.

1974-01-01

The phonon dispersion relations of the Δ-, Λ-, and Σ-directions of germanium at 80 K are analysed in terms of current harmonic lattice dynamical models. On the basis of this experience, a new model is proposed which gives a unified account of the strong points of the previous models. The principal elements of the presented theory are quasiparticle bond charges combined with a valence force field

Harmonic operation of high gain harmonic generation free electron laser

International Nuclear Information System (INIS)

Deng Haixiao; Chinese Academy of Sciences, Beijing; Dai Zhimin

2008-01-01

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL. Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy. (authors)

Impedance Based Analysis and Design of Harmonic Resonant Controller for a Wide Range of Grid Impedance

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

2014-01-01

This paper investigates the effect of grid impedance variation on harmonic resonant current controllers for gridconnected voltage source converters by means of impedance-based analysis. It reveals that the negative harmonic resistances tend to be derived from harmonic resonant controllers...... in the closed-loop output admittance of converter. Such negative resistances may interact with the grid impedance resulting in steady state error or unstable harmonic compensation. To deal with this problem, a design guideline for harmonic resonant controllers under a wide range of grid impedance is proposed...

Experimental measurements of competition between fundamental and second harmonic emission in a quasi-optical gyrotron

International Nuclear Information System (INIS)

Alberti, S.; Pedrozzi, M.; Tran, M.Q.; Hogge, J.P.; Tran, T.M.; Muggli, P.; Joedicke, B.; Mathews, H.G.

1990-04-01

A quasi-optical gyrotron (QOG) designed for operation at the fundamental (Ω ce ≅100 GHz) exhibits simultaneous emission at Ω ce and 2Ω ce (second harmonic). For a beam current of 4 A, 20% of the total RF power is emitted at the second harmonic. The experimental measurements show that the excitation of the second harmonic is only possible when the fundamental is present. The frequency of the second harmonic is locked by the frequency of the fundamental. Experimental evidence shows that when the second harmonic is not excited, total efficiency is enhanced. (author) 6 refs., 5 figs., 1 tab

Polarization control of high order harmonics in the EUV photon energy range.

Science.gov (United States)

Vodungbo, Boris; Barszczak Sardinha, Anna; Gautier, Julien; Lambert, Guillaume; Valentin, Constance; Lozano, Magali; Iaquaniello, Grégory; Delmotte, Franck; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

2011-02-28

We report the generation of circularly polarized high order harmonics in the extreme ultraviolet range (18-27 nm) from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. To circularly polarize the initially linearly polarized harmonics we have implemented a four-reflector phase-shifter. Fully circularly polarized radiation has been obtained with an efficiency of a few percents, thus being significantly more efficient than currently demonstrated direct generation of elliptically polarized harmonics. This demonstration opens up new experimental capabilities based on high order harmonics, for example, in biology and materials science. The inherent femtosecond time resolution of high order harmonic generating table top laser sources renders these an ideal tool for the investigation of ultrafast magnetization dynamics now that the magnetic circular dichroism at the absorption M-edges of transition metals can be exploited.

General Lp-harmonic Blaschke bodies

Indian Academy of Sciences (India)

Lutwak introduced the harmonic Blaschke combination and the harmonic Blaschke body of a star body. Further, Feng and Wang introduced the concept of the -harmonic Blaschke body of a star body. In this paper, we define the notion of general -harmonic Blaschke bodies and establish some of its properties.

Space debris mitigation - engineering strategies

Science.gov (United States)

Taylor, E.; Hammond, M.

The problem of space debris pollution is acknowledged to be of growing concern by space agencies, leading to recent activities in the field of space debris mitigation. A review of the current (and near-future) mitigation guidelines, handbooks, standards and licensing procedures has identified a number of areas where further work is required. In order for space debris mitigation to be implemented in spacecraft manufacture and operation, the authors suggest that debris-related criteria need to become design parameters (following the same process as applied to reliability and radiation). To meet these parameters, spacecraft manufacturers and operators will need processes (supported by design tools and databases and implementation standards). A particular aspect of debris mitigation, as compared with conventional requirements (e.g. radiation and reliability) is the current and near-future national and international regulatory framework and associated liability aspects. A framework for these implementation standards is presented, in addition to results of in-house research and development on design tools and databases (including collision avoidance in GTO and SSTO and evaluation of failure criteria on composite and aluminium structures).

QED effects induced harmonics generation in extreme intense laser foil interaction

Science.gov (United States)

Yu, J. Y.; Yuan, T.; Liu, W. Y.; Chen, M.; Luo, W.; Weng, S. M.; Sheng, Z. M.

2018-04-01

A new mechanism of harmonics generation (HG) induced by quantum electrodynamics (QED) effects in extreme intense laser foil interaction is found and investigated by particle-in-cell (PIC) simulations. When two laser pulses with identical intensities of 1.6× {10}24 {{W}} {{{cm}}}-2 are counter-incident on a thin foil target, harmonics emission is observed in their reflected electromagnetic waves. Such harmonics radiation is excited due to transversely oscillating electric currents coming from the vibration of QED effect generated {e}-{e}+ pairs. The effects of laser intensity and polarization were studied. By distinguishing the cascade depth of generated photons and pairs, the influence of QED cascades on HG was analyzed. Although the current HG is not an efficient way for radiation source applications, it may provide a unique way to detect the QED processes in the near future ultra-relativistic laser solid interactions.

Performance of unified power quality conditioner (UPQC) based on fuzzy controller for attenuating of voltage and current harmonics

Science.gov (United States)

Milood Almelian, Mohamad; Mohd, Izzeldin I.; Asghaiyer Omran, Mohamed; Ullah Sheikh, Usman

2018-04-01

Power quality-related issues such as current and voltage distortions can adversely affect home and industrial appliances. Although several conventional techniques such as the use of passive and active filters have been developed to increase power quality standards, these methods have challenges and are inadequate due to the increasing number of applications. The Unified Power Quality Conditioner (UPQC) is a modern strategy towards correcting the imperfections of voltage and load current supply. A UPQC is a combination of both series and shunt active power filters in a back-to-back manner with a common DC link capacitor. The control of the voltage of the DC link capacitor is important in achieving a desired UPQC performance. In this paper, the UPQC with a Fuzzy logic controller (FLC) was used to precisely eliminate the imperfections of voltage and current harmonics. The results of the simulation studies using MATLAB/Simulink and Simpower system programming for R-L load associated through an uncontrolled bridge rectifier was used to assess the execution process. The UPQC with FLC was simulated for a system with distorted load current and a system with distorted source voltage and load current. The outcome of the comparison of %THD in the load current and source voltage before and after using UPQC for the two cases was presented.

Higher harmonics generation in relativistic electron beam with virtual cathode

Energy Technology Data Exchange (ETDEWEB)

Kurkin, S. A., E-mail: KurkinSA@gmail.com; Badarin, A. A.; Koronovskii, A. A.; Hramov, A. E. [Saratov State Technical University, Politechnicheskaja 77, Saratov 410028, Russia and Saratov State University, Astrakhanskaja 83, Saratov 410012 (Russian Federation)

2014-09-15

The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources.

High-order harmonic generation: A coherent ultrashort emission in the XUV range

International Nuclear Information System (INIS)

Salieres, Pascal; Hergott, Jean-Francois; Le Deroff, Laurent; Merdji, Hamed; Carre, Bertrand; Auguste, Thierry; Monot, Pascal; D'Oliveira, Pascal; Joyeux, Denis; Phalippou, Daniel

2000-01-01

We review the recent progress in theoretical and experimental understanding of harmonic generation by intense laser pulses. We present investigations on the spatial and temporal coherence properties of the harmonic emission, showing that they can be controlled. Finally, we give some examples of current applications of this XUV source, in particular in the diagnostic of dense plasmas

12 CFR 702.108 - Risk mitigation credit.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Risk mitigation credit. 702.108 Section 702.108... CORRECTIVE ACTION Net Worth Classification § 702.108 Risk mitigation credit. (a) Who may apply. A credit union may apply for a risk mitigation credit if on any of the current or three preceding effective dates...

The harmonization of banking legislation in the EU

Directory of Open Access Journals (Sweden)

Shkëlqesa Çitaku

2016-03-01

Full Text Available This paper attempts to assess the current legislation of banking in the European Union. The process of unification in Europe is also followed by efforts to harmonize and unify the laws of the member states. In the field of banking industry the precondition for harmonization of laws is the integration of internal market with the free movement of capital. The regulation and supervision of banks in EU still remains fragmented. European member states still have diverse regulations concerning the role of the state. The European Commission has the important function of proposing EU legislation on financial services including banks and ensuring that EU law is properly applied throughout the EU. Banks are considered as a key industry enabling all the economic activities via depositing, crediting and arranging of payments. A number of secondary legislation has been adopted by the EU institutions to harmonize the national banking law of Member States. The principles and objectives set by the European Commission Treaty depend on four EU freedoms with the aim of effective and open market including banks. Therefore it was a continuous process of harmonization of national banking regulation via secondary law since the 70’s.

General Lp-harmonic Blaschke bodies

Indian Academy of Sciences (India)

Abstract. Lutwak introduced the harmonic Blaschke combination and the harmonic. Blaschke body of a star body. Further, Feng and Wang introduced the concept of the L p- harmonic Blaschke body of a star body. In this paper, we define the notion of general. L p-harmonic Blaschke bodies and establish some of its ...

Short Review: Mitigation of Current Environmental Concerns from Methanol Synthesis

Directory of Open Access Journals (Sweden)

Andrew Young

2013-06-01

Full Text Available Methanol has become a widely used and globally distributed product. Methanol is very important due to the current depletion of fossil fuels. Industrially, methanol produced from the catalytic reaction of synthetic gas composed of hydrogen, carbon monoxide, and carbon dioxide. Methanol production has brought great attention due to carbon dioxide as the main source of greenhouse gas emissions. Combined of reducing CO2 emissions and supplying an alternative fuel source has created the idea of a carbon neutral cycle called “the methanol economy”. The best catalyst for the methanol economy would show a high CO2 conversion and high selectivity for methanol production. This paper investigates research focused on catalyst development for efficient methanol synthesis from hydrogenation of carbon dioxide through added various supports and additives such as silica, zirconium, and palladium. Catalysts that displayed the highest activity included a zirconia and silicon-titanium oxide promoted Cu/Zn/Al2O3 catalyst. Alternative method of catalyst preparation, include the oxalate-gel, solid-state reaction, co-precipitation and combustion method also investigated.  © 2013 BCREC UNDIP. All rights reservedReceived: 10th October 2012; Revised: 7th February 2012; Accepted: 10th February 2013[How to Cite: Young, A., Lesmana, D., Dai, D.J., Wu, H.S. (2013. Short Review: Mitigation of Current En-vironmental Concerns from Methanol Synthesis. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1: 1-13. (doi:10.9767/bcrec.8.1.4055.1-13][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4055.1-13] | View in  |

Algal Supply System Design - Harmonized Version

Energy Technology Data Exchange (ETDEWEB)

Jared Abodeely; Daniel Stevens; Allison Ray; Debor

2013-03-01

The objective of this design report is to provide an assessment of current technologies used for production, dewatering, and converting microalgae cultivated in open-pond systems to biofuel. The original draft design was created in 2011 and has subsequently been brought into agreement with the DOE harmonized model. The design report extends beyond this harmonized model to discuss some of the challenges with assessing algal production systems, including the ability to (1) quickly assess alternative algal production system designs, (2) assess spatial and temporal variability, and (3) perform large-scale assessments considering multiple scenarios for thousands of potential sites. The Algae Logistics Model (ALM) was developed to address each of these limitations of current modeling efforts to enable assessment of the economic feasibility of algal production systems across the United States. The (ALM) enables (1) dynamic assessments using spatiotemporal conditions, (2) exploration of algal production system design configurations, (3) investigation of algal production system operating assumptions, and (4) trade-off assessments with technology decisions and operating assumptions. The report discusses results from the ALM, which is used to assess the baseline design determined by harmonization efforts between U.S. DOE national laboratories. Productivity and resource assessment data is provided by coupling the ALM with the Biomass Assessment Tool developed at PNNL. This high-fidelity data is dynamically passed to the ALM and used to help better understand the impacts of spatial and temporal constraints on algal production systems by providing a cost for producing extracted algal lipids annually for each potential site.

Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

Directory of Open Access Journals (Sweden)

N. J. Milardovich

2014-10-01

Full Text Available A numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially-available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severely harmonic emission limits should be defined for LED lamps.

Second-harmonic generation in second-harmonic fiber Bragg gratings.

Science.gov (United States)

Steel, M J; de Sterke, C M

1996-06-20

We consider the production of second-harmonic light in gratings resonant with the generated field, through a Green's function approach. We recover some standard results and obtain new limits for the uniform grating case. With the extension to nonuniform gratings, we find the Green's function for the second harmonic in a grating with an arbitrary phase shift at some point. We then obtain closed form approximate expressions for the generated light for phase shifts close to π/2 and at the center of the grating. Finally, comparing the uniform and phase-shifted gratings with homogeneous materials, we discuss the enhancement in generated light and the bandwidth over which it occurs, and the consequences for second-harmonic generation in optical fiber Bragg gratings.

Harmonic Interaction Analysis in Grid Connected Converter using Harmonic State Space (HSS) Modeling

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

2015-01-01

-model, are introduced to analyze these problems. However, it is found that Linear Time Invariant (LTI) base model analysis makes it difficult to analyze these phenomenon because of time varying system operation trajectories, varying output impedance seen by grid connected systems and neglected switching component......An increasing number of power electronics based Distributed Generation (DG) systems and loads generate coupled harmonic as well as non-characteristic harmonic with each other. Several methods like impedance based analysis, which is derived from conventional small signal- and average...... during the modeling process. This paper investigates grid connected converter by means of Harmonic State Space (HSS) small signal model, which is modeled from Linear Time varying Periodically (LTP) system. Further, a grid connected converter harmonic matrix is investigated to analyze the harmonic...

Wiggler magnetic field assisted third harmonic generation in expanding clusters

Science.gov (United States)

Vij, Shivani

2018-04-01

A simple theoretical model is constructed to study the wiggler magnetic field assisted third harmonic generation of intense short pulse laser in a cluster in its expanding phase. The ponderomotive force of laser causes density perturbations in cluster electron density which couples with wiggler magnetic field to produce a nonlinear current that generates transverse third harmonic. An intense short pulse laser propagating through a gas embedded with atomic clusters, converts it into hot plasma balls via tunnel ionization. Initially, the electron plasma frequency inside the clusters ω pe > \\sqrt{3}{ω }1 (with ω 1 being the frequency of the laser). As the cluster expands under Coulomb force and hydrodynamic pressure, ω pe decreases to \\sqrt{3}{ω }1. At this time, there is resonant enhancement in the efficiency of the third harmonic generation. The efficiency of third harmonic generation is enhanced due to cluster plasmon resonance and by phase matching due to wiggler magnetic field. The effect of cluster size on the expansion rate is studied to observe that the clusters of different radii would expand differently. The impact of laser intensity and wiggler magnetic field on the efficiency of third harmonic generation is also explored.

Digital model for harmonic interactions in AC/DC/AC systems

Energy Technology Data Exchange (ETDEWEB)

Guarini, A P; Rangel, R D; Pilotto, L A.S.; Pinto, R J; Passos, Junior, R [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)

1994-12-31

The main purpose of this paper is to present a model for calculation of HVdc converter harmonics taking into account the influence of the harmonic interactions between the ac systems in dc link transmissions. The ideas and methodologies used in the model development take into account the dc current ripple and ac voltage distortion in the ac systems. The theory of switching functions is applied to contemplate for the frequency conversions between the ac and dc sides, in an iterative process. It is possible then to obtain, even in balanced situations, non-characteristic harmonics that are produced by frequencies originated in the other terminal, which can be significant in a strongly coupled system, such as back-to-back configuration. (author) 9 refs., 3 figs.

Input Harmonic Analysis on the Slim DC-Link Drive Using Harmonic State Space Model

DEFF Research Database (Denmark)

Yang, Feng; Kwon, Jun Bum; Wang, Xiongfei

2017-01-01

The harmonic performance of the slim dc-link adjustable speed drives has shown good performance in some studies but poor in some others. The contradiction indicates that a feasible theoretical analysis is still lacking to characterize the harmonic distortion for the slim dc-link drive. Considerin...... results of the slim dc-link drive, loaded up to 2.0 kW, are presented to validate the theoretical analysis....... variation according to the switching instant, the harmonics at the steady-state condition, as well as the coupling between the multiple harmonic impedances. By using this model, the impaction on the harmonics performance by the film capacitor and the grid inductance is derived. Simulation and experimental...

Harmonic-suppressed quadrature-input frequency divider for OFDM systems

International Nuclear Information System (INIS)

Fu Haipeng; Ren Junyan; Li Wei; Li Ning

2011-01-01

A fully balanced harmonic-suppressed quadrature-input frequency divider is proposed. The frequency divider improves the quadrature phase accuracy at the output by using both input I/Q signals. Compared with conventional dividers, the circuit achieves an output I/Q phase sequence that is independent of the input I/Q phase sequence. Moreover, the third harmonic is effectively suppressed by employing a double degeneration technique. The design is fabricated in TSMC 0.13-μm CMOS and operated at 1.2 V. While locked at 8.5 GHz, the proposed divider measures a maximum third harmonic rejection of 45 dB and a phase noise of −124 dBc/Hz at a 10 MHz offset. The circuit achieves a locking range of 15% while consuming a total current of 4.5 mA. (semiconductor integrated circuits)

Data harmonization and model performance

Science.gov (United States)

The Joint Committee on Urban Storm Drainage of the International Association for Hydraulic Research (IAHR) and International Association on Water Pollution Research and Control (IAWPRC) was formed in 1982. The current committee members are (no more than two from a country): B. C. Yen, Chairman (USA); P. Harremoes, Vice Chairman (Denmark); R. K. Price, Secretary (UK); P. J. Colyer (UK), M. Desbordes (France), W. C. Huber (USA), K. Krauth (FRG), A. Sjoberg (Sweden), and T. Sueishi (Japan).The IAHR/IAWPRC Joint Committee is forming a Task Group on Data Harmonization and Model Performance. One objective is to promote international urban drainage data harmonization for easy data and information exchange. Another objective is to publicize available models and data internationally. Comments and suggestions concerning the formation and charge of the Task Group are welcome and should be sent to: B. C. Yen, Dept. of Civil Engineering, Univ. of Illinois, 208 N. Romine St., Urbana, IL 61801.

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

DEFF Research Database (Denmark)

Yang, Yongheng; Davari, Pooya; Blaabjerg, Frede

2016-01-01

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

Harmonic ratcheting for fast acceleration

Science.gov (United States)

Cook, N.; Brennan, J. M.; Peggs, S.

2014-04-01

A major challenge in the design of rf cavities for the acceleration of medium-energy charged ions is the need to rapidly sweep the radio frequency over a large range. From low-power medical synchrotrons to high-power accelerator driven subcritical reactor systems, and from fixed focus alternating gradient accelerators to rapid cycling synchrotrons, there is a strong need for more efficient, and faster, acceleration of protons and light ions in the semirelativistic range of hundreds of MeV/u. A conventional way to achieve a large, rapid frequency sweep (perhaps over a range of a factor of 6) is to use custom-designed ferrite-loaded cavities. Ferrite rings enable the precise tuning of the resonant frequency of a cavity, through the control of the incremental permeability that is possible by introducing a pseudoconstant azimuthal magnetic field. However, rapid changes over large permeability ranges incur anomalous behavior such as the "Q-loss" and "f-dot" loss phenomena that limit performance while requiring high bias currents. Notwithstanding the incomplete understanding of these phenomena, they can be ameliorated by introducing a "harmonic ratcheting" acceleration scheme in which two or more rf cavities take turns accelerating the beam—one turns on when the other turns off, at different harmonics—so that the radio frequency can be constrained to remain in a smaller range. Harmonic ratcheting also has straightforward performance advantages, depending on the particular parameter set at hand. In some typical cases it is possible to halve the length of the cavities, or to double the effective gap voltage, or to double the repetition rate. This paper discusses and quantifies the advantages of harmonic ratcheting in general. Simulation results for the particular case of a rapid cycling medical synchrotron ratcheting from harmonic number 9 to 2 show that stability and performance criteria are met even when realistic engineering details are taken into consideration.

Preliminary study of synthetic aperture tissue harmonic imaging on in-vivo data

DEFF Research Database (Denmark)

Rasmussen, Joachim Hee; Hemmsen, Martin Christian; Sloth Madsen, Signe

2013-01-01

. Results from the image quality study show, that in the current configuration on the UltraView system, where no transmit apodization was applied, SASB-THI and DRF-THI produced equally good images. It is expected that given the use of transmit apodization, SASB-THI could be further improved.......A method for synthetic aperture tissue harmonic imaging is investigated. It combines synthetic aperture sequential beamforming (SASB) with tissue harmonic imaging (THI) to produce an increased and more uniform spatial resolution and improved side lobe reduction compared to conventional B......-mode imaging. Synthetic aperture sequential beamforming tissue harmonic imaging (SASB-THI) was implemented on a commercially available BK 2202 Pro Focus UltraView ultrasound system and compared to dynamic receive focused tissue harmonic imaging (DRF-THI) in clinical scans. The scan sequence...

Comparison study among conventional, tissue harmonic and pulse inversion harmonic images to evaluate pleural effusion and ascites

International Nuclear Information System (INIS)

Chung, Hwan Hoon; Kim, Yun Hwan; Kang, Chang Ho; Park, Bum Jin; Chung, Kyoo Byung; Suh, Won Hyuck

2000-01-01

To determine the most useful sonographic technique to evaluate pleural effusion and ascites by comparing conventional, tissue harmonic and pulse inversion harmonic images. 12 patients having pleural effusion and 14 patients having ascites were included in this study. 18 patients were male and 8 patients were female. Average age was 54.8 yrs (25-77). We compared images which had been taken at the same section with 3 above mentioned sonographic techniques. Evaluation was done by 3 radiologists in consensus and grades were given to 3 techniques from 1 to 3. Evaluating points were 1) normal structures that border the fluid such as liver, peritoneal lining, pleura, 2) septation in fluid, 3) debris floating in fluid, and 4) artifacts. Pulse inversion harmonic image was the best in image quality for normal structures, followed by tissue harmonic and conventional image (p<0.05). Pulse inversion harmonic image was better than conventional image to evaluate septation in fluid (p<0.05), but there were no statistically significant difference between pulse inversion and tissue harmonic images, and tissue harmonic and conventional images. Tissue harmonic image was better than pulse inversion harmonic and conventional images to evaluate debris floating in fluid (p<0.05) but there was no statistically significant difference between these two latter techniques. Artifacts were most prominent on conventional image followed by tissue harmonic and pulse inversion harmonic image (p<0.05). Pulse inversion harmonic image was the best sonographic technique to evaluate pleural effusion or ascites, However, Tissue harmonic image was the best for evaluation of debris.

Comparison study among conventional, tissue harmonic and pulse inversion harmonic images to evaluate pleural effusion and ascites

Energy Technology Data Exchange (ETDEWEB)

Chung, Hwan Hoon; Kim, Yun Hwan; Kang, Chang Ho; Park, Bum Jin; Chung, Kyoo Byung; Suh, Won Hyuck [Korea University College of Medicine, Seoul (Korea, Republic of)

2000-12-15

To determine the most useful sonographic technique to evaluate pleural effusion and ascites by comparing conventional, tissue harmonic and pulse inversion harmonic images. 12 patients having pleural effusion and 14 patients having ascites were included in this study. 18 patients were male and 8 patients were female. Average age was 54.8 yrs (25-77). We compared images which had been taken at the same section with 3 above mentioned sonographic techniques. Evaluation was done by 3 radiologists in consensus and grades were given to 3 techniques from 1 to 3. Evaluating points were 1) normal structures that border the fluid such as liver, peritoneal lining, pleura, 2) septation in fluid, 3) debris floating in fluid, and 4) artifacts. Pulse inversion harmonic image was the best in image quality for normal structures, followed by tissue harmonic and conventional image (p<0.05). Pulse inversion harmonic image was better than conventional image to evaluate septation in fluid (p<0.05), but there were no statistically significant difference between pulse inversion and tissue harmonic images, and tissue harmonic and conventional images. Tissue harmonic image was better than pulse inversion harmonic and conventional images to evaluate debris floating in fluid (p<0.05) but there was no statistically significant difference between these two latter techniques. Artifacts were most prominent on conventional image followed by tissue harmonic and pulse inversion harmonic image (p<0.05). Pulse inversion harmonic image was the best sonographic technique to evaluate pleural effusion or ascites, However, Tissue harmonic image was the best for evaluation of debris.

[The health food product Noni--does marketing harmonize with the current status of research?].

Science.gov (United States)

Johansen, Rolf

2008-03-13

Norwegian cancer patients frequently use Noni. The objective of this study was to find out whether the way noni is marketed in Norway and the health claims made about the product harmonize with current scientific knowledge of its benefits/adverse effects. An overview of medical research on noni was obtained from three databases. Web sites for private persons and for companies that sell noni in Norway were examined. Books, pamphlets etc. from a company specializing in selling information material about noni, were also examined. 48 scientific articles were included in the study, but none of these were clinical studies of humans. Several pharmacological effects of noni have been shown in vitro and in animal models (e.g., increased survival for animals with cancer). Information material describes noni as a health-promoting product that patients with most diseases will benefit from. Noni is to a great extent sold by multi-level marketing, but is also commonly sold by health food stores. There is no scientific basis for claiming that patients will benefit from using noni for any diseases. The way this product is sold has several worrying aspects.

Physics of tissue harmonic imaging by ultrasound

Science.gov (United States)

Jing, Yuan

Tissue Harmonic Imaging (THI) is an imaging modality that is currently deployed on diagnostic ultrasound scanners. In THI the amplitude of the ultrasonic pulse that is used to probe the tissue is large enough that the pulse undergoes nonlinear distortion as it propagates into the tissue. One result of the distortion is that as the pulse propagates energy is shifted from the fundamental frequency of the source pulse into its higher harmonics. These harmonics will scatter off objects in the tissue and images formed from the scattered higher harmonics are considered to have superior quality to the images formed from the fundamental frequency. Processes that have been suggested as possibly responsible for the improved imaging in THI include: (1) reduced sensitivity to reverberation, (2) reduced sensitivity to aberration, and (3) reduction in side lobes. By using a combination of controlled experiments and numerical simulations, these three reasons have been investigated. A single element transducer and a clinical ultrasound scanner with a phased array transducer were used to image a commercial tissue-mimicking phantom with calibrated targets. The higher image quality achieved with THI was quantified in terms of spatial resolution and "clutter" signals. A three-dimensional model of the forward propagation of nonlinear sound beams in media with arbitrary spatial properties (a generalized KZK equation) was developed. A time-domain code for solving the KZK equation was validated with measurements of the acoustic field generated by the single element transducer and the phased array transducer. The code was used to investigate the impact of aberration using tissue-like media with three-dimensional variations in all acoustic properties. The three-dimensional maps of tissue properties were derived from the datasets available through the Visible Female project. The experiments and simulations demonstrated that second harmonic imaging (1) suffers less clutter associated with

Current Harmonics Cancellation in Three-Phase Four-Wire Systems by Using a Four-Branch Star Filtering Topology

DEFF Research Database (Denmark)

Rodriguez, Pedro; Candela, J. I.; Luna, A.

2009-01-01

This paper presents a new solution for filtering current harmonics in three-phase four-wire networks. The original four-branch star (FBS) filter topology presented in this paper is characterized by a particular layout of single-phase inductances and capacitors, without using any transformer......, a specific implementation of a three-phase four-wire hybrid power filter is presented as an illustrative application of the filtering topology. An extensive evaluation using simulation and experimental results from a DSP-based laboratory prototype is conducted in order to verify and validate the good...... only passive components are employed, or as a hybrid filter, when its behavior is improved by integrating a power converter into the filter structure. The paper analyzes the proposed topology, and derives fundamental concepts about the control of the resulting hybrid power filter. From this analysis...

Effect of self-focusing on resonant third harmonic generation of laser in a rippled density plasma

International Nuclear Information System (INIS)

Kaur, Sukhdeep; Sharma, A. K.; Yadav, Sushila

2010-01-01

Resonant third harmonic generation by a Gaussian laser beam in a rippled density plasma is studied. The laser ponderomotive force induces second harmonic longitudinal velocity on electrons that couples with the static density ripple to produce a density perturbation at 2ω,2k+q, where ω and k are the frequency and wave number of the laser and q is the ripple wave number of the laser. This density perturbation beats with electron oscillatory velocity at ω,k-vector to produce a nonlinear current driving the third harmonic generation. In the regime of quadratic nonlinearity, the self-focusing of the laser enhances the third harmonic power. However, at higher intensity, plasma density is significantly reduced on the axis, detuning the third harmonic resonance and weakening the harmonic yield. Self-focusing causes enhancement in the efficiency of harmonic generation.

A control strategy based on UTT and I CosΘ theory of three-phase ...

African Journals Online (AJOL)

The performance of the implemented control algorithm is evaluated in terms of power-factor correction; load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell and voltage dips in a three-phase four-wire distribution system for different combination of linear and ...

Harmonic Patterns in Forex Trading

OpenAIRE

Nemček, Sebastian

2013-01-01

This diploma thesis is committed to examination of validity of Harmonic Patterns in Forex trading. Scott Carney described existing and introduced new Harmonic Patterns in 1999 in his book Harmonic Trader. These patterns use the Fibonacci principle to analyze price action and to provide both bullish and bearish trading signals. The goal of this thesis is to find out whether harmonic trading strategy on selected pairs is profitable in FX market, which patterns are the most profitable and what i...

An Enhanced Power Sharing Scheme for Voltage unbalance and harmonics compensation in an islanded AC microgrid

DEFF Research Database (Denmark)

Han, Yang; Shen, Pan; Zhao, Xin

2016-01-01

In this paper, an enhanced hierarchical control structure with multiple current loop damping schemes for voltage unbalance and harmonics compensation in ac islanded microgrid is proposed to address unequal power sharing problems. The distributed generation (DG) is properly controlled to autonomou......In this paper, an enhanced hierarchical control structure with multiple current loop damping schemes for voltage unbalance and harmonics compensation in ac islanded microgrid is proposed to address unequal power sharing problems. The distributed generation (DG) is properly controlled...... to autonomously compensate voltage unbalance and harmonics while sharing the compensation effort for the real power, reactive power, unbalance and harmonic powers. The proposed control system of the microgrid mainly consists of the positive sequence real and reactive power droop controllers, voltage and current......) technique is adopted to send the compensation command of the secondary control and auxiliary control from the microgrid control center (MGCC) to the local controllers of DG unit. Finally, the hardware-in-the-loop (HIL) results using dSPACE 1006 platform are presented to demonstrate the effectiveness...

Calculation of induced rotor current in induction motors using a slotted semi-analytical harmonic model

NARCIS (Netherlands)

Sprangers, R.L.J.; Gysen, B.L.J.; Paulides, J.J.H.; Waarma, J.; Lomonova, E.A.

2014-01-01

Recently, strong improvements have been made in the applicability of harmonic modeling techniques for electrical machines with slotted structures. Various implementations for permanent magnet motors and actuators have been investigated and applied in design and optimization tools. For the slotted

Sub-harmonic bunching with the AGOR cyclotron

NARCIS (Netherlands)

Brandenburg, S; Roobol, LP; Stokroos, M; Marti, F

2001-01-01

A quasi-single gap buncher with saw-tooth voltage has been designed and is currently being built at the KVI. It operates at a sub-harmonic of the RF frequency and has a duty cycle of 80% at 15 MHz. We report on the design of the new buncher, and on results of tests with our sinusoidal buncher to

Analytic and algorithmic aspects of generalized harmonic sums and polylogarithms

International Nuclear Information System (INIS)

Ablinger, Jakob; Schneider, Carsten

2013-01-01

In recent three-loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short S-sums) arise. They are characterized by rational (or real) numerator weights also different from ±1. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincare iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the S-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation w.r.t. the external summation index and different multi-argument relations, for the compactification of S-sum expressions. Finally, we calculate algebraic relations for infinite S-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package HarmonicSums.

Analytic and algorithmic aspects of generalized harmonic sums and polylogarithms

Energy Technology Data Exchange (ETDEWEB)

Ablinger, Jakob; Schneider, Carsten [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation; Bluemlein, Johannes [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

2013-01-15

In recent three-loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short S-sums) arise. They are characterized by rational (or real) numerator weights also different from {+-}1. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincare iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the S-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation w.r.t. the external summation index and different multi-argument relations, for the compactification of S-sum expressions. Finally, we calculate algebraic relations for infinite S-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package HarmonicSums.

Analytic and algorithmic aspects of generalized harmonic sums and polylogarithms

Energy Technology Data Exchange (ETDEWEB)

Ablinger, Jakob; Schneider, Carsten [Research Institute for Symbolic Computation (RISC), Johannes Kepler University, Altenbergerstraße 69, A-4040, Linz (Austria); Blümlein, Johannes [Deutsches Elektronen–Synchrotron, DESY, Platanenallee 6, D-15738 Zeuthen (Germany)

2013-08-15

In recent three-loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short S-sums) arise. They are characterized by rational (or real) numerator weights also different from ±1. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincaré iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the S-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation with respect to the external summation index and different multi-argument relations, for the compactification of S-sum expressions. Finally, we calculate algebraic relations for infinite S-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package HarmonicSums.

Tuvan throat singing and harmonics

Science.gov (United States)

Ruiz, Michael J.; Wilken, David

2018-05-01

Tuvan throat singing, also called overtone singing, provides for an exotic demonstration of the physics of harmonics as well as introducing an Asian musical aesthetic. A low fundamental is sung and the singer skillfully alters the resonances of the vocal system to enhance an overtone (harmonic above the fundamental). The result is that the listener hears two pitches simultaneously. Harmonics such as H8, H9, H10, and H12 form part of a pentatonic scale and are commonly selected for melody tones by Tuvan singers. A real-time spectrogram is provided in a video (Ruiz M J 2018 Video: Tuvan Throat Singing and Harmonics http://mjtruiz.com/ped/tuva/) so that Tuvan harmonics can be visualized as they are heard.

Quantum efficiency harmonic analysis of exciton annihilation in organic light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Price, J. S.; Giebink, N. C., E-mail: ncg2@psu.edu [Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2015-06-29

Various exciton annihilation processes are known to impact the efficiency roll-off of organic light emitting diodes (OLEDs); however, isolating and quantifying their contribution in the presence of other factors such as changing charge balance continue to be a challenge for routine device characterization. Here, we analyze OLED electroluminescence resulting from a sinusoidal dither superimposed on the device bias and show that nonlinearity between recombination current and light output arising from annihilation mixes the quantum efficiency measured at different dither harmonics in a manner that depends uniquely on the type and magnitude of the annihilation process. We derive a series of analytical relations involving the DC and first harmonic external quantum efficiency that enable annihilation rates to be quantified through linear regression independent of changing charge balance and evaluate them for prototypical fluorescent and phosphorescent OLEDs based on the emitters 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran and platinum octaethylporphyrin, respectively. We go on to show that, in most cases, it is sufficient to calculate the needed quantum efficiency harmonics directly from derivatives of the DC light versus current curve, thus enabling this analysis to be conducted solely from standard light-current-voltage measurement data.

Mitigating amphibian chytridiomycosis in nature

Science.gov (United States)

Garner, Trenton W. J.; Schmidt, Benedikt R.; Martel, An; Pasmans, Frank; Muths, Erin L.; Cunningham, Andrew A.; Weldon, Che; Fisher, Matthew C.; Bosch, Jaime

2016-01-01

Amphibians across the planet face the threat of population decline and extirpation caused by the disease chytridiomycosis. Despite consensus that the fungal pathogens responsible for the disease are conservation issues, strategies to mitigate their impacts in the natural world are, at best, nascent. Reducing risk associated with the movement of amphibians, non-amphibian vectors and other sources of infection remains the first line of defence and a primary objective when mitigating the threat of disease in wildlife. Amphibian-associated chytridiomycete fungi and chytridiomycosis are already widespread, though, and we therefore focus on discussing options for mitigating the threats once disease emergence has occurred in wild amphibian populations. All strategies have shortcomings that need to be overcome before implementation, including stronger efforts towards understanding and addressing ethical and legal considerations. Even if these issues can be dealt with, all currently available approaches, or those under discussion, are unlikely to yield the desired conservation outcome of disease mitigation. The decision process for establishing mitigation strategies requires integrated thinking that assesses disease mitigation options critically and embeds them within more comprehensive strategies for the conservation of amphibian populations, communities and ecosystems.

Design-Oriented Analysis of Resonance Damping and Harmonic Compensation for LCL-Filtered Voltage Source Converters

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang

2014-01-01

This paper addresses the interaction between harmonic resonant controllers and active damping of LCL resonance in voltage source converters. A virtual series R-C damper in parallel with the filter capacitor is proposed with the capacitor current feedback loop. The phase lag resulting from...... crossover frequency defined by the proportional gain of current controller. This is of particular interest for high-performance active harmonic filtering applications and low-pulse-ratio converters. Case studies in experiments validate the theoretical analysis....

Tissue Harmonic Synthetic Aperture Imaging

DEFF Research Database (Denmark)

Rasmussen, Joachim

The main purpose of this PhD project is to develop an ultrasonic method for tissue harmonic synthetic aperture imaging. The motivation is to advance the field of synthetic aperture imaging in ultrasound, which has shown great potentials in the clinic. Suggestions for synthetic aperture tissue...... system complexity compared to conventional synthetic aperture techniques. In this project, SASB is sought combined with a pulse inversion technique for 2nd harmonic tissue harmonic imaging. The advantages in tissue harmonic imaging (THI) are expected to further improve the image quality of SASB...

Superstrings and harmonic superspace

International Nuclear Information System (INIS)

Kallosh, R.E.; AN SSSR, Moscow. Fizicheskij Inst.)

1987-01-01

The paper on superstrings and harmonic superspace is a contribution to the book dedicated to E.S. Fradkin on his sixtieth birthday. The purpose of the paper is to propose a description of N = 2,3 superspace which could be used for the investigation of the effective d = 10 harmonic superspace corresponding to the heterotic superstring. A description is given of the structure of semi-simple Lie algebras in the Cartan-Weyl basis, as well as the general properties of the even, compact part of harmonic superspace. The main properties of the four-dimensional N = 2 SYM theory are discussed, along with the N = 3, d = 4 super Yang-Mills theory. Finally the relation between the harmonic superspace and the heterotic E 8 x E 8 superstring is examined. (U.K.)

On the conformal equivalence of harmonic maps and exponentially harmonic maps

International Nuclear Information System (INIS)

Hong Minchun.

1991-06-01

Suppose that (M,g) and (N,h) are compact smooth Riemannian manifolds without boundaries. For m = dim M ≥3, and Φ: (M,g) → (N,h) is exponentially harmonic, there exists a smooth metric g-tilde conformally equivalent to g such that Φ: (M,g-tilde) → (N,h) is harmonic. (author). 7 refs

Waveguide harmonic damper for klystron amplifier

International Nuclear Information System (INIS)

Kang, Y.

1998-01-01

A waveguide harmonic damper was designed for removing the harmonic frequency power from the klystron amplifiers of the APS linac. Straight coaxial probe antennas are used in a rectangular waveguide to form a damper. A linear array of the probe antennas is used on a narrow wall of the rectangular waveguide for damping klystron harmonics while decoupling the fundamental frequency in dominent TE 01 mode. The klystron harmonics can exist in the waveguide as waveguide higher-order modes above cutoff. Computer simulations are made to investigate the waveguide harmonic damping characteristics of the damper

Experimental Research on Vibrations of Double Harmonic Gear Transmission

Directory of Open Access Journals (Sweden)

Sava Ianici

2017-11-01

Full Text Available Gears transmission can be important sources of vibration in the mechanical system structures and can have a significant share in the overall vibration level. The current trend of significant increase in powers and speeds transmitted by modern mechanical systems, along with the size reduction, may cause a worsening of the behaviour of transmissions with gears in terms of vibration, especially when the optimization criteria were not respected in the design, execution and installation phase. This paper presents a study of vibrations that occur in a double harmonic gear transmission (DHGT, based on experimental research. The experimental researches revealed that in a double harmonic gear transmission the vibrations are initiated and develop in the multipara harmonics engagement of the teeth and in the kinematic couplings materialized between the wave generator and the flexible toothed wheel. These vibrations are later transmitted by means of the shafts and bearings to the transmission housing, respectively, through the walls of it, propagating in the air.

Losses in electric motors caused by harmonics; Harmoniske overtoners betydning for tabene i elmotorer

Energy Technology Data Exchange (ETDEWEB)

Johansson, M. [Dansk Energi Analyse A/S, Glostrup (Denmark); Kehr, J.M. [ABB A/S, Skovlunde (Denmark); Hoejte Hansen, H. [Balslev A/S, Glostrup (Denmark)

2012-03-15

the motor. The results of the lab measurements correspond very well to the losses calculated. On this basis it is concluded that harmonic currents and voltages cause energy losses in induction motors directly supplied, but that the energy losses are fairly low at the levels of distortion, a THDU of up to 6 to 8 %, which occur in Danish industry. Motors, which are supplied through a frequency converter, are not influenced by the harmonics in the supply mains. The analysis of the motor losses shows that the losses from the load torque, caused by the 5., 11., 17. etc harmonics, are considerably lower than the (very small) current heat losses in the motor, which have been caused by the same harmonics. The analysis also shows that the current displacement in the motors reduces the currents and the losses from the higher harmonics. Considering losses consequently the lower harmonics and especially 5. and 7. harmonics are most important. (LN)

Beam test of a grid-less multi-harmonic buncher

International Nuclear Information System (INIS)

Ostroumov, P.N.; Aseev, V.N.; Barcikowski, A.; Clifft, B.; Pardo, R.; Sharamentov, S.I.; Sengupta, M.

2008-01-01

The Argonne Tandem Linear Accelerator System (ATLAS) is the first superconducting heavy-ion linac in the world. Currently ATLAS is being upgraded with the Californium Rare Ion Breeder Upgrade (CARIBU). The latter is a funded project to expand the range of shortlived, neutron-rich rare isotope beams available for nuclear physics research at ATLAS. To avoid beam losses associated with the existing gridded multi-harmonic buncher (MHB), we have developed and built a grid-less four-harmonic buncher with fundamental frequency of 12.125 MHz. In this paper, we report the results of the MHB commissioning and ATLAS beam performance with the new buncher.

Photovoltaic-STATCOM with Low Voltage Ride through Strategy and Power Quality Enhancement in a Grid Integrated Wind-PV System

Directory of Open Access Journals (Sweden)

Lakshman Naik Popavath

2018-04-01

Full Text Available The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind, resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the islanding of renewables caused by severe voltage variations (voltage sag and swell. Current harmonics and voltage sag strongly affect the performance of renewable-based power systems. Various conventional methods (passive filters, capacitor bank, and UPS are not able to mitigate harmonics and voltage sag completely. Based on several studies, custom power devices can mitigate harmonics completely and slightly mitigate voltage sags with reactive power supplies. To ensure the generating units remain grid-connected during voltage sags and to improve system operation during abnormal conditions, efficient and reliable utilization of PV solar farm inverter as STATCOMs is needed. This paper elaborates the dynamic performance of a VSC-based PV-STATCOM for power quality enhancement in a grid integrated system and low voltage ride through (LVRT capability. LVRT requirements suggest that the injection of real and reactive power supports grid voltage during abnormal grid conditions. The proposed strategy was demonstrated with MATLAB simulations.

Disruption mitigation studies in DIII-D

International Nuclear Information System (INIS)

Taylor, P.L.; Kellman, A.G.; Evans, T.E.

1999-01-01

Data on the discharge behavior, thermal loads, halo currents, and runaway electrons have been obtained in disruptions on the DIII-D tokamak. These experiments have also evaluated techniques to mitigate the disruptions while minimizing runaway electron production. Experiments injecting cryogenic impurity killer pellets of neon and argon and massive amounts of helium gas have successfully reduced these disruption effects. The halo current generation, scaling, and mitigation are understood and are in good agreement with predictions of a semianalytic model. Results from killer pellet injection have been used to benchmark theoretical models of the pellet ablation and energy loss. Runaway electrons are often generated by the pellets and new runaway generation mechanisms, modifications of the standard Dreicer process, have been found to explain the runaways. Experiments with the massive helium gas puff have also effectively mitigated disruptions without the formation of runaway electrons that can occur with killer pellets

KINETIC-J: A computational kernel for solving the linearized Vlasov equation applied to calculations of the kinetic, configuration space plasma current for time harmonic wave electric fields

Science.gov (United States)

Green, David L.; Berry, Lee A.; Simpson, Adam B.; Younkin, Timothy R.

2018-04-01

We present the KINETIC-J code, a computational kernel for evaluating the linearized Vlasov equation with application to calculating the kinetic plasma response (current) to an applied time harmonic wave electric field. This code addresses the need for a configuration space evaluation of the plasma current to enable kinetic full-wave solvers for waves in hot plasmas to move beyond the limitations of the traditional Fourier spectral methods. We benchmark the kernel via comparison with the standard k →-space forms of the hot plasma conductivity tensor.

Harmonic supergraphs. Green functions

International Nuclear Information System (INIS)

Galperin, A.; Ivanov, E.; Gievetsky, V.; Sokatchev, E.

1985-01-01

The quantization procedure in the harmonic superspace approach is worked out. Harmonic distributions are introduced and are used to construct the analytic superspace delta-functions and the Green functions for the hypermultiplet and the N=2 Yang-Mills superfields. The gauge fixing is described and the relevant Faddeev-Popov ghosts are defined. The corresponding BRST transformations are found. The harmonic superspace quantization of the N=2 gauge theory turns out to be rather simple and has many parallels with that for the standard (N=0) Yang-Mills theory. In particular, no ghosts-forghosts are needed

A pretandem harmonic buncher

International Nuclear Information System (INIS)

Lin, Qui-xun; Van Wechel, T.D.

1987-01-01

A single gap harmonic buncher has been constructed as a pretandem buncher. Over 85% of a proton dc beam has been bunched into pulses. The width (fwhm) of the pulses is 0.7 ns. The buncher is based on that built at Argonne. Changes were made to the buncher's configuration so that the buncher could be tuned to the desired four harmonic frequencies. A method of calibrating and setting the relative phases and amplitudes of the four harmonic frequencies has been used to obtain an optimum sawtooth-like bunching waveform

Harmonic Interaction Analysis in Grid-connected Converter using Harmonic State Space (HSS) Modeling

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede

2017-01-01

research about the harmonic interaction. However, it is found that the Linear Time Invariant (LTI) based model analysis makes it difficult to analyze these phenomena because of the time-varying properties of the power electronic based systems. This paper investigates grid-connected converter by using......An increasing number of power electronic based Distributed Generation (DG) systems and loads generate not only characteristic harmonics but also unexpected harmonics. Several methods like impedance based analysis, which are derived from the conventional average model, are introduced to perform...

Harmonic strengths of PEP dipoles and some related effects and lessons

International Nuclear Information System (INIS)

Spencer, J.E.

1981-09-01

The harmonic content of magnets such as the standard PEP bend is (among other things) a function of excitation current, the way the current is set and even the magnetization history. For instance, harmonic strengths generally vary not only with the magnitude of the current but the direction and rate at which the current is approached and set. The field distribution resulting from different procedures can vary markedly depending on both the mechanical and magnetic design and the degree to which eddy current effects are emphasized. Variations among magnets of the same design result from variations in the iron as well as overall magnet fabrication procedures. Because the field distribution may also depend in the previous history of a magnet, all PEP dipoles were subjected to what are called ''magnetization'' and ''standardization'' cycles before measurement---the latter depending on the former and intended to set the initial conditions of the magnet to a reproducible standard. The primary goal of the magnetic measurements was then to determine the dipole strength as a function of current for each magnet based on a practical setting algorithm. The main constraints on the algorithm were reproducibility of the integrated field, speed, power and reduction of higher harmonics. Quadrupole and sextupole strengths were also measured on about one-half of the magnets at one current. This note presents the data and discusses it from the the viewpoint of subsequent measurements with stored beams. The most important conclusion is that inability to fully distribute laminations according to heat number and/or strike number results in ''magnetic personalities'' among the magnets which are quite difficult to deal with afterwards although one can distribute ''non-standard'' magnets to minimize orbit distributions. 26 refs., 8 figs., 3 tabs

Co-creation of climate change mitigation policies

DEFF Research Database (Denmark)

Hoff, Jens Villiam

The focus of this paper is on the places where citizens and public authorities meet – possible involving other stakeholders as well – to discuss, formulate and implement climate change mitigation policies at the local level. Through looking at a number of concrete cases stemming from the CIDEA re...... mitigation policies should be aimed at finding ways to support citizen initiated initiatives to a greater extent than is currently the case. Keywords: climate change mitigation, co-creation, behaviour, communities, citizen driven innovation....

Controllability in tunable chains of coupled harmonic oscillators

DEFF Research Database (Denmark)

Buchmann, Lukas Filip; Mølmer, Klaus; Petrosyan, David

2018-01-01

any desired Gaussian state requires at most 3 N ( N −1)/2 operations. We illustrate this capability by engineering squeezed pseudo-phonon states—highly nonlocal, strongly correlated states that may result from various nonlinear processes. Tunable chains of coupled harmonic oscillators can......We prove that temporal control of the strengths of springs connecting N harmonic oscillators in a chain provides complete access to all Gaussian states of N −1 collective modes. The proof relies on the construction of a suitable basis of cradle modes for the system. An iterative algorithm to reach...... be implemented by a number of current state-of-the-art experimental platforms, including cold atoms in lattice potentials, arrays of mechanical micro-oscillators, and coupled optical waveguides....

Controllability in tunable chains of coupled harmonic oscillators

Science.gov (United States)

Buchmann, L. F.; Mølmer, K.; Petrosyan, D.

2018-04-01

We prove that temporal control of the strengths of springs connecting N harmonic oscillators in a chain provides complete access to all Gaussian states of N -1 collective modes. The proof relies on the construction of a suitable basis of cradle modes for the system. An iterative algorithm to reach any desired Gaussian state requires at most 3 N (N -1 )/2 operations. We illustrate this capability by engineering squeezed pseudo-phonon states—highly nonlocal, strongly correlated states that may result from various nonlinear processes. Tunable chains of coupled harmonic oscillators can be implemented by a number of current state-of-the-art experimental platforms, including cold atoms in lattice potentials, arrays of mechanical micro-oscillators, and coupled optical waveguides.

Controllability in tunable chains of coupled harmonic oscillators

DEFF Research Database (Denmark)

Buchmann, Lukas Filip; Mølmer, Klaus; Petrosyan, David

2018-01-01

We prove that temporal control of the strengths of springs connecting N harmonic oscillators in a chain provides complete access to all Gaussian states of N −1 collective modes. The proof relies on the construction of a suitable basis of cradle modes for the system. An iterative algorithm to reach...... any desired Gaussian state requires at most 3 N ( N −1)/2 operations. We illustrate this capability by engineering squeezed pseudo-phonon states—highly nonlocal, strongly correlated states that may result from various nonlinear processes. Tunable chains of coupled harmonic oscillators can...... be implemented by a number of current state-of-the-art experimental platforms, including cold atoms in lattice potentials, arrays of mechanical micro-oscillators, and coupled optical waveguides....

HARMONICS ANALYSIS OF SYSTEM USING SHUNT ACTIVE POWER FILTER BY MATLAB SIMULATION

OpenAIRE

VAISHALI PARDHI; Dr.A K KORI

2017-01-01

The widely use of nonlinear loads, such as diode and thyristor, rectifiers, computers, consumer electronics, uninterruptible power supplies and adjustable speed drives results in the distorted current waveforms in the electrical distribution systems. Harmonics is a major problem in power systems that have become serious recently owing to the wide use of power electronics-related equipment. The input power factor of most of these equipments is poor. There is a great need to reduce these harmon...

State-space-based harmonic stability analysis for paralleled grid-connected inverters

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Chen, Zhe

2016-01-01

This paper addresses a state-space-based harmonic stability analysis of paralleled grid-connected inverters system. A small signal model of individual inverter is developed, where LCL filter, the equivalent delay of control system, and current controller are modeled. Then, the overall small signal...... model of paralleled grid-connected inverters is built. Finally, the state space-based stability analysis approach is developed to explain the harmonic resonance phenomenon. The eigenvalue traces associated with time delay and coupled grid impedance are obtained, which accounts for how the unstable...... inverter produces the harmonic resonance and leads to the instability of whole paralleled system. The proposed approach reveals the contributions of the grid impedance as well as the coupled effect on other grid-connected inverters under different grid conditions. Simulation and experimental results...

Multidimensional high harmonic spectroscopy

International Nuclear Information System (INIS)

Bruner, Barry D; Soifer, Hadas; Shafir, Dror; Dudovich, Nirit; Serbinenko, Valeria; Smirnova, Olga

2015-01-01

High harmonic generation (HHG) has opened up a new frontier in ultrafast science where attosecond time resolution and Angstrom spatial resolution are accessible in a single measurement. However, reconstructing the dynamics under study is limited by the multiple degrees of freedom involved in strong field interactions. In this paper we describe a new class of measurement schemes for resolving attosecond dynamics, integrating perturbative nonlinear optics with strong-field physics. These approaches serve as a basis for multidimensional high harmonic spectroscopy. Specifically, we show that multidimensional high harmonic spectroscopy can measure tunnel ionization dynamics with high precision, and resolves the interference between multiple ionization channels. In addition, we show how multidimensional HHG can function as a type of lock-in amplifier measurement. Similar to multi-dimensional approaches in nonlinear optical spectroscopy that have resolved correlated femtosecond dynamics, multi-dimensional high harmonic spectroscopy reveals the underlying complex dynamics behind attosecond scale phenomena. (paper)

Rethinking Rectification: AC-DC Power Supply in Package

DEFF Research Database (Denmark)

Pejtersen, Jens; Knott, Arnold; Jørgensen, Ivan Harald Holger

efficiency, while drawing high input peak current with a high harmonic content. Mitigating these non-idealities requires higher order EMI filters and a subsequent power factor correction stage. Advanced active rectifier topologies can mitigate all three non-idealities simultaneously while balancing power...

A seven harmonic actively compensated Langmuir probe for the GEC Cell

Science.gov (United States)

Goodyear, A.; Nolle, L.; Hopgood, A. A.; Picton, P. D.; Braithwaite, N.

2001-10-01

The uncertainty of Langmuir probe measurements in capacitively coupled discharges depends to a great extent on how well harmonic components in the plasma potential are accounted for. The extent to which individual harmonics distort a probe characteristic has been determined across power and pressure parameter-space in the GEC cell. Langmuir probe current-voltage measurements are distorted by RF components across the probe sheath. A seven harmonic waveform was applied to the probe tip to actively match that generated by the plasma. In some circumstances harmonics above the 3rd contributed RF components of the order of the electron temperature in magnitude. Measurement of the EEDF was found to be particularly sensitive to these components. Optimization of the applied waveform (seven amplitudes and seven phases) was achieved using artificially intelligent control. This is advantageous given the large number of (possibly interacting) parameters and permits tracking of changes in plasma conditions. An algorithm utilizing simulated annealing determines the optimum waveform in a far shorter time than a skilled human operator can.

Audibility of harmonics in 'periodic white noise'

NARCIS (Netherlands)

Duifhuis, H.; Tomesen, H.H.

1970-01-01

In a previous article (Duifhuis, 1970) results' concerning the audibility of harmonics in a periodic pulse have been presented. Each of the lower harmonics could be perceived separately, whereas the high harmonics were heard together as one complex signal. High harmonics, however, appeared to be

Suppression of the Second Harmonic Subgroup Injected by an AC EAF: Design Considerations and Performance Estimation of a Shunt APF

Directory of Open Access Journals (Sweden)

Emre Durna

2018-04-01

Full Text Available This paper proposes a design methodology for an active power filter (APF system to suppress the second harmonic subgroup injected by an AC electric arc furnace (EAF to the utility grid. The APF system is composed of identical parallel units connected to the utility grid via a specially-designed coupling transformer. Each APF converter is a three-phase three-wire two-level voltage source converter (VSC. The number of parallel APF units, coupling transformer MVA rating, and turns ratio are optimized in the view of the ratings of commercially-available high voltage (HV IGBTs. In this research work, line current waveforms sampled at 25.6-kS/s on the medium voltage (MV side of a 65-MVA EAF transformer are then used to extract the second harmonic subgroup, 95-, 100-, and 105-Hz current components, by multiple synchronous reference frame (MSRF analysis, which was previously proposed to decompose EAF current interharmonics and harmonics in real-time. By summing up this digital data of the second harmonic subgroup, the reference current signal for the APF system is produced in real-time. A detailed model of the APF system is then run on EMTDC/PSCAD to follow the produced reference current signal according to hysteresis band control philosophy. The simulation results show that the proposed APF system can successfully suppress the second harmonic subgroup of an AC EAF.

Probabilistic Harmonic Modeling of Wind Power Plants

DEFF Research Database (Denmark)

Guest, Emerson; Jensen, Kim H.; Rasmussen, Tonny Wederberg

2017-01-01

A probabilistic sequence domain (SD) harmonic model of a grid-connected voltage-source converter is used to estimate harmonic emissions in a wind power plant (WPP) comprised of Type-IV wind turbines. The SD representation naturally partitioned converter generated voltage harmonics into those...... with deterministic phase and those with probabilistic phase. A case study performed on a string of ten 3MW, Type-IV wind turbines implemented in PSCAD was used to verify the probabilistic SD harmonic model. The probabilistic SD harmonic model can be employed in the planning phase of WPP projects to assess harmonic...

Low-order-mode harmonic multiplying gyrotron traveling-wave amplifier in W band

International Nuclear Information System (INIS)

Yeh, Y. S.; Chen, C. H.; Yang, S. J.; Lai, C. H.; Lin, T. Y.; Lo, Y. C.; Hong, J. W.; Hung, C. L.; Chang, T. H.

2012-01-01

Harmonic multiplying gyrotron traveling-wave amplifiers (gyro-TWAs) allow for magnetic field reduction and frequency multiplication. To avoid absolute instabilities, this work proposes a W-band harmonic multiplying gyro-TWA operating at low-order modes. By amplifying a fundamental harmonic TE 11 drive wave, the second harmonic component of the beam current initiates a TE 21 wave to be amplified. Absolute instabilities in the gyro-TWA are suppressed by shortening the interaction circuit and increasing wall losses. Simulation results reveal that compared with Ka-band gyro-TWTs, the lower wall losses effectively suppress absolute instabilities in the W-band gyro-TWA. However, a global reflective oscillation occurs as the wall losses decrease. Increasing the length or resistivity of the lossy section can reduce the feedback of the oscillation to stabilize the amplifier. The W-band harmonic multiplying gyro-TWA is predicted to yield a peak output power of 111 kW at 98 GHz with an efficiency of 25%, a saturated gain of 26 dB, and a bandwidth of 1.6 GHz for a 60 kV, 7.5 A electron beam with an axial velocity spread of 8%.

On bunch lengthening using the fourth harmonic cavity in the NSLS VUV ring

International Nuclear Information System (INIS)

Wachtel, J.M.

1988-02-01

It has been suggested that the phase of the beam excited voltage in the harmonic cavity can be controlled by detuning its resonant frequency from the beam current harmonic. Unfortunately the detuning needed to flatten the acceleration waveform also corresponds to the region of Robinson instability for the harmonic cavity. Therefore, lengthening the bunch may be followed by large amplitude synchrotron oscillation of the bunch center of mass. Bunch lengthening is discussed in this note from several points of view. There follows a simple review of single electron oscillations in a quartic potential. Then equations are developed for the coupled oscillations of a cavity and a rigid bunch as a fully nonlinear, time dependent initial value problem. Next, a computer program that solves these equations for one, two or more cavities, with and without externally driven fields, is described and some simulations of the harmonic cavity interaction are shown. Finally, the fully nonlinear equations are linearized to derive a dispersion relation for the case of beam excitation in the harmonic cavity. 6 refs., 5 figs

Standards related to harmonic disturbances and its evolution; La normalisation relative aux perturbations harmoniques et son evolution

Energy Technology Data Exchange (ETDEWEB)

Deflandre, T. [Electricite de France (EDF), 92 - Clamart (France). Direction des Etudes et Recherches

1996-09-01

The objective of this document is to provide an overview of the various normative documents and regulations that may be useful in the field of harmonics as references to a network user, fitter, manufacturer or operator. Several documents that are presently developed at Electricite de France are also presented, together with the connecting regulation that is included in the Emeraude contract. The following points are discussed: hierarchy of normative documents, harmonic emission standards and more especially the NF EN 610003-2 standards ``Limits for the emission of harmonic currents for equipment having an inrush current inferior or equal to 16 A per phase``; document status, immunity standards, compatibility and environment standards, documents under study and the Emeraude contract

Complex harmonic modal analysis of rotor systems

International Nuclear Information System (INIS)

Han, Dong Ju

2015-01-01

Complex harmonic analysis for rotor systems has been proposed from the strict complex modal analysis based upon Floquet theory. In this process the harmonic balance method is adopted, effectively associated with conventional eigenvalue analysis. Also, the harmonic coefficients equivalent to dFRFs in harmonic mode has been derived in practice. The modes are classified from identifying the modal characteristics, and the adaptation of harmonic balance method has been proven by comparing the results of the stability analyses from Floque theory and the eigen analysis. The modal features of each critical speed are depicted in quantitatively and qualitatively by showing that the strengths of each component of the harmonic coefficients are estimated from the order of magnitude analysis according to their harmonic patterns. This effectiveness has been verified by comparing with the numerical solutions

Stray voltage mitigation

Energy Technology Data Exchange (ETDEWEB)

Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

2008-04-09

This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

Effect of pulse slippage on resonant second harmonic generation of a short pulse laser in a plasma

International Nuclear Information System (INIS)

Nitikant; Sharma, A K

2004-01-01

The process of second harmonic generation of an intense short pulse laser in a plasma is resonantly enhanced by the application of a magnetic wiggler. The wiggler of suitable wave number k-vector 0 provides necessary momentum to second harmonic photons to make harmonic generation a resonant process. The laser imparts an oscillatory velocity to electrons and exerts a longitudinal ponderomotive force on them at (2ω 1 ,2k-vector 1 ), where ω 1 and k-vector 1 are the frequency and the wave number of the laser, respectively. As the electrons acquire oscillatory velocity at the second harmonic, the wiggler magnetic field beats with it to produce a transverse second harmonic current at (2ω 1 ,2k-vector 1 +k-vector 0 ), driving the second harmonic electromagnetic radiation. However, the group velocity of the second harmonic wave is greater than that of the fundamental wave, hence, the generated pulse slips out of the main laser pulse and its amplitude saturates

Harmonic uniflow engine

Science.gov (United States)

Bennett, Charles L.

2016-03-22

A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.

Analysis of Harmonic Coupling and Stability in Back-to-Back Converter Systems for Wind Turbines using Harmonic State Space (HSS)

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

2015-01-01

Understanding about harmonic propagation in wind turbine converter is fundamental to research the influence of these on a large network harmonic distortion. Therefore, the analysis of wind turbine converter harmonic spectrum as well as the influence of converter operating point into the network i...... connected into the large wind farm model to analyze the overall steady-state harmonic as well as harmonic stability. All theoretical modeling and analysis is verified by means of simulation and experimental results.......Understanding about harmonic propagation in wind turbine converter is fundamental to research the influence of these on a large network harmonic distortion. Therefore, the analysis of wind turbine converter harmonic spectrum as well as the influence of converter operating point into the network...... is urgently important issues in harmonic studies on wind farm. However, the conventional modeling procedure and simplified model for controller design are not enough to analyze such complicated systems. Besides, they have many limitations in terms of including a non-linear component, different operating...

Harmonic Calculation Toolbox in Industry Application for Adjustable Speed Drive

DEFF Research Database (Denmark)

Asiminoaei, Lucian; Blaabjerg, Frede; Hansen, Steffan

2004-01-01

Previous to electrical installation of large power non-linear loads, a comprehensive design-study is often required in order to determine if the overall installation complies with international regulations in respect to harmonics. Current THD voltage distortion and power factor are just few...

High-frequency harmonic imaging of the eye

Science.gov (United States)

Silverman, Ronald H.; Coleman, D. Jackson; Ketterling, Jeffrey A.; Lizzi, Frederic L.

2005-04-01

Purpose: Harmonic imaging has become a well-established technique for ultrasonic imaging at fundamental frequencies of 10 MHz or less. Ophthalmology has benefited from the use of fundamentals of 20 MHz to 50 MHz. Our aim was to explore the ability to generate harmonics for this frequency range, and to generate harmonic images of the eye. Methods: The presence of harmonics was determined in both water and bovine vitreous propagation media by pulse/echo and hydrophone at a series of increasing excitation pulse intensities and frequencies. Hydrophone measurements were made at the focal point and in the near- and far-fields of 20 MHz and 40 MHz transducers. Harmonic images of the anterior segment of the rabbit eye were obtained by a combination of analog filtering and digital post-processing. Results: Harmonics were generated nearly identically in both water and vitreous. Hydrophone measurements showed the maximum second harmonic to be -5 dB relative to the 35 MHz fundamental at the focus, while in pulse/echo the maximum harmonic amplitude was -15dB relative to the fundamental. Harmonics were absent in the near-field, but present in the far-field. Harmonic images of the eye showed improved resolution. Conclusion: Harmonics can be readily generated at very high frequencies, and at power levels compliant with FDA guidelines for ophthalmology. This technique may yield further improvements to the already impressive resolutions obtainable in this frequency range. Improved imaging of the macular region, in particular, may provide significant improvements in diagnosis of retinal disease.

Disruption mitigation experiment with massive gas injection of HT-7

International Nuclear Information System (INIS)

Zhuang Huidong; Zhang Xiaodong

2013-01-01

Massive gas injection (MGI) is a promising method on disruption mitigation. The working principle of the fast valve for disruption mitigation was introduced. The disruption mitigation experiments by MGI on HT-7 were described. The experiment shows that the impurities radiation is improved by injecting appropriate amount of gas, and the current quench rate is slow down, so the electromagnetic load on the device is mitigated. The experiments show that the fast valve can completely satisfy the requirement of disruption mitigation on HT-7. (authors)

Capacity Calculation of Shunt Active Power Filters for Electric Vehicle Charging Stations Based on Harmonic Parameter Estimation and Analytical Modeling

Directory of Open Access Journals (Sweden)

Niancheng Zhou

2014-08-01

Full Text Available The influence of electric vehicle charging stations on power grid harmonics is becoming increasingly significant as their presence continues to grow. This paper studies the operational principles of the charging current in the continuous and discontinuous modes for a three-phase uncontrolled rectification charger with a passive power factor correction link, which is affected by the charging power. A parameter estimation method is proposed for the equivalent circuit of the charger by using the measured characteristic AC (Alternating Current voltage and current data combined with the charging circuit constraints in the conduction process, and this method is verified using an experimental platform. The sensitivity of the current harmonics to the changes in the parameters is analyzed. An analytical harmonic model of the charging station is created by separating the chargers into groups by type. Then, the harmonic current amplification caused by the shunt active power filter is researched, and the analytical formula for the overload factor is derived to further correct the capacity of the shunt active power filter. Finally, this method is validated through a field test of a charging station.

Computer model for harmonic ultrasound imaging.

Science.gov (United States)

Li, Y; Zagzebski, J A

2000-01-01

Harmonic ultrasound imaging has received great attention from ultrasound scanner manufacturers and researchers. In this paper, we present a computer model that can generate realistic harmonic images. In this model, the incident ultrasound is modeled after the "KZK" equation, and the echo signal is modeled using linear propagation theory because the echo signal is much weaker than the incident pulse. Both time domain and frequency domain numerical solutions to the "KZK" equation were studied. Realistic harmonic images of spherical lesion phantoms were generated for scans by a circular transducer. This model can be a very useful tool for studying the harmonic buildup and dissipation processes in a nonlinear medium, and it can be used to investigate a wide variety of topics related to B-mode harmonic imaging.

Harmonics in power systems of ships with electrical propulsion drives. Comparison between different converters

Energy Technology Data Exchange (ETDEWEB)

Lehtonen, M [VTT Energy, Espoo (Finland). Energy Systems

1996-11-01

In this report the effects of harmonics in marine power systems is discussed and a comparison is given between the most typical converter types, including pulse width modulated drives, load commutated inverters and cycloconverters. The effect of harmonic distortion on the power system equipment and loads is first briefly discussed. Special attention is given to the circumstances in the low voltage distribution system, where general load equipment is connected. In addition to the total harmonic distortion the effect of voltage deviation to the supply quality is also considered. The origin of harmonics in the load currents of the three converter types is then considered. The differences between the converters are outlined, and the most typical spectra are presented. The possible means for reducing the harmonic distortion are also studied. The solutions considered are the increasing of the short circuit level, the use of harmonic filters and the increasing of the pulse number. In the case of cycloconverters, the optimization of the phase shift between the parallel operating bridges is also presented. Finally the effects of different converter types on the voltage quality are compared using calculations made for a typical marine power system. (author)

High-order harmonics generation from overdense plasmas

International Nuclear Information System (INIS)

Quere, F.; Thaury, C.; Monot, P.; Martin, Ph.; Geindre, J.P.; Audebert, P.; Marjoribanks, R.

2006-01-01

Complete test of publication follows. When an intense laser beam reflects on an overdense plasma generated on a solid target, high-order harmonics of the incident laser frequency are observed in the reflected beam. This process provides a way to produce XUV femtosecond and attosecond pulses in the μJ range from ultrafast ultraintense lasers. Studying the mechanisms responsible for this harmonic emission is also of strong fundamental interest: just as HHG in gases has been instrumental in providing a comprehensive understanding of basic intense laser-atom interactions, HHG from solid-density plasmas is likely to become a unique tool to investigate many key features of laser-plasma interactions at high intensities. We will present both experimental and theoretical evidence that two mechanisms contribute to this harmonic emission: - Coherent Wake Emission: in this process, harmonics are emitted by plasma oscillations in te overdense plasma, triggered in the wake of jets of Brunel electrons generated by the laser field. - The relativistic oscillating mirror: in this process, the intense laser field drives a relativistic oscillation of the plasma surface, which in turn gives rise to a periodic phase modulation of the reflected beam, and hence to the generation of harmonics of the incident frequency. Left graph: experimental harmonic spectrum from a polypropylene target, obtained with 60 fs laser pulses at 10 19 W/cm 2 , with a very high temporal contrast (10 10 ). The plasma frequency of this target corresponds to harmonics 15-16, thus excluding the CWE mechanism for the generation of harmonics of higher orders. Images on the right: harmonic spectra from orders 13 et 18, for different distances z between the target and the best focus. At the highest intensity (z=0), harmonics emitted by the ROM mechanism are observed above the 15th order. These harmonics have a much smaller spectral width then those due to CWE (below the 15th order). These ROM harmonics vanish as soon

Harmonic response of coupled and uncoupled granular YBCO

International Nuclear Information System (INIS)

Torralba, Maria Veronica S; Sarmago, Roland V

2004-01-01

The harmonic responses of granular YBCO were obtained via mutual inductance measurements. Two samples, one with and another without intergranular coupling, were investigated in terms of the harmonic components of magnetization at various field amplitudes and frequencies. By comparing the behaviour of the features in the harmonics to that of the peaks in the fundamental response, we explicitly identified which features in the harmonics originate from intragranular harmonic generation and which arise due to a contribution of intergranular coupling. Harmonic responses were obtained despite the absence of vortices and even harmonics were detected in a purely AC magnetic field

Study on A Control Method of PAPF for Resonance Damping and Harmonics Compensation in Power System

DEFF Research Database (Denmark)

Zhou, Fang; Wu, Longhui; Chen, Zhe

2009-01-01

In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound with traditi......In power system, capacitors are widely used to compensate reactive power, which generally cause resonance problems in harmonic distorted network. In this paper, A method of using a parallel active power filter (PAPF) to damp the resonances is proposed. The proposed method is compound...... with traditional method, it shows that whether the capacitor current is included in the detecting current of PAPF or not. Also the PAPF with proposed method has strong ability in harmonic compensation. Finally, the experiment results are presented to verify the analysis....

Electromagnetic cyclotron harmonic waves

International Nuclear Information System (INIS)

Ohnuma, T.; Watanabe, T.; Hamamatsu, K.

1981-09-01

Electromagnetic electron cyclotron harmonic waves just below the electron cyclotron harmonics are investigated numerically and experimentally. Backward waves which are observed to propagate nearly perpendicular to the magnetic field just below the electron cyclotron frequency in a high density magnetoplasma are confirmed to be in accord with the theoretical electromagnetic cyclotron waves. (author)

Second harmonic generation in a bounded magnetoplasma

International Nuclear Information System (INIS)

Thomas, D.G.

1975-01-01

An experimental study of second harmonic generation in a magnetized plasma contained in a cylindrical cavity resonator shows how the harmonic power varies with fundamental power, background gas pressure, and magnetization. Two cavities were designed. For each the TM010 resonance was in the S-band and the TM011 resonance in the C-band. Both frequencies were harmonically related when the d.c. discharge sustaining the plasma was adjusted to give plasma frequencies of approximately 0.7 GHz and 1.53 GHz. The experimental results show the harmonic power approximately proportional to the square of the fundamental power from 5 to 100 mw, and a decreasing function of pressure from 10 to 150 millitorr. Experiments at constant plasma frequency and varying magnetic field from 0 to 3000 Gauss show a sharp drop in harmonic power to undetectable levels when the electron cyclotron frequency approximates either the fundamental or second harmonic frequencies. These effects are attributed, respectively, to the coupling of fundamental power to other modes and to cavity detuning away from the harmonic. With the plasma frequency adjusted to maintain simultaneous resonance of fundamental and harmonic, a harmonic signal maximum occurred when the upper hybrid frequency approximated the harmonic frequency. Several anomalies, apparently related to the magnetization, background gas, and electron density distribution were observed. Otherwise, the results are qualitatively consistent with the first order theory for a cold, collisional plasma

Investigation And Mitigation Techniques Of Power Quality Problems In Nuclear Installations

International Nuclear Information System (INIS)

Ayad, N.; Elsherbiny, E.; Eleissawi, H.; Zaher, M.; AbdelSalam, G.

2013-01-01

The electrical power systems are exposed to different types of power quality disturbances problems. Investigation and monitoring of power quality is necessary to maintain accurate operation of sensitive equipment especially for nuclear installations. The present research discusses investigation and monitoring of power quality problems for the electrical sources of nuclear installations. Field power quality data is collected by power analyzer and analyzed with reference to power quality standards. There were several disturbances exceeded the thresholds, they were voltage harmonics and voltage flicker. Mitigation techniques were suggested to install a passive filter at low voltage side and all sensitive and critical loads should be isolated and fed through uninterruptible power supply (UPS)

Contribution of the magnetic resonance to the third harmonic generation from a fishnet metamaterial

Science.gov (United States)

Reinhold, J.; Shcherbakov, M. R.; Chipouline, A.; Panov, V. I.; Helgert, C.; Paul, T.; Rockstuhl, C.; Lederer, F.; Kley, E.-B.; Tünnermann, A.; Fedyanin, A. A.; Pertsch, T.

2012-09-01

We investigate experimentally and theoretically the third harmonic generated by a double-layer fishnet metamaterial. To unambiguously disclose most notably the influence of the magnetic resonance, the generated third harmonic was measured as a function of the angle of incidence. It is shown experimentally and numerically that when the magnetic resonance is excited by a pump beam, the angular dependence of the third harmonic signal has a local maximum at an incidence angle of θ≃20∘. This maximum is shown to be a fingerprint of the antisymmetric distribution of currents in the gold layers. An analytical model based on the nonlinear dynamics of the electrons inside the gold shows excellent agreement with experimental and numerical results. This clearly indicates the difference in the third harmonic angular pattern at electric and magnetic resonances of the metamaterial.

Interharmonic mitigation of adjustable speed drives using an active DC-link capacitor

DEFF Research Database (Denmark)

Soltani, Hamid; Loh, Poh Chiang; Blaabjerg, Frede

2015-01-01

Current and voltage source Adjustable - Speed Drives (ASDs) exert distortion currents in the grid which may lead to some interharmonic components other than the characteristic harmonic components. The frequencies of the line current interharmonics, generated by these ASDs, depend on the motor...

Intense harmonic generation from various ablation media

International Nuclear Information System (INIS)

Ozaki, T.; Elouga, L.; Suzuki, M.; Kuroda, H.; Ganeev, R.A.

2006-01-01

Complete test of publication follows. High-order harmonic generation (HHG) is a unique source of coherent extreme ultraviolet (XUV) radiation, which can produce soft x-rays within the spectral 'water-window' (between 2.3 and 4.4 nm), and ultimately short pulses with attosecond duration. However, the intensity of present-day harmonics is still low, and serious applications will need an increase of the conversion efficiency. Instead of using gas media, one can also use ablation material, produced on solid targets using a low-intensity prepulse, as the nonlinear medium to generate high-order harmonics. Recently, we have successfully demonstrated the generation of up to the 63 rd harmonic (λ = 12.6 nm) of a Ti:sapphire laser radiation using boron ablation, and a strong enhancement in the intensity of the 13 th harmonic from indium ablation. These harmonics were generated with a modest laser (10 mJ, 150 fs) and with the pre-pulse to main pulse energy ratio constant. In this paper, we perform systematic investigations of ablation harmonics, using the 200 mJ, 30 fs Ti:sapphire beam line of the Canadian Advanced Laser Light Source (ALLS) facility. ALLS allows studying ablation harmonics over wider experimental parameters, and with independent control over the pre-pulse and main pulse energies. The 10 Hz, 200 mJ Ti:sapphire beam line of ALLS is divided into two beams. Each beam has its own energy control system, which allows independent control over the energy of each beam. One of the beams is used as a pre-pulse for creating ablation, which is focused onto the solid target without pulse compression, with pulse duration of 200 ps. The second beam is used as the main pulse for harmonic generation. The main pulse is delayed in time relative to the pre-pulse by propagating through an optical delay line, and then sent through a pulse compressor. The compressed pulse duration have typical pulse duration of 30 fs FWHM, which is then focused onto the ablation medium using MgF 2

Harmonic balance approach to the periodic solutions of the (an)harmonic relativistic oscillator

International Nuclear Information System (INIS)

Belendez, Augusto; Pascual, Carolina

2007-01-01

The first-order harmonic balance method via the first Fourier coefficient is used to construct two approximate frequency-amplitude relations for the relativistic oscillator for which the nonlinearity (anharmonicity) is a relativistic effect due to the time line dilation along the world line. Making a change of variable, a new nonlinear differential equation is obtained and two procedures are used to approximately solve this differential equation. In the first the differential equation is rewritten in a form that does not contain a square-root expression, while in the second the differential equation is solved directly. The approximate frequency obtained using the second procedure is more accurate than the frequency obtained with the first due to the fact that, in the second procedure, application of the harmonic balance method produces an infinite set of harmonics, while in the first procedure only two harmonics are produced. Both approximate frequencies are valid for the complete range of oscillation amplitudes, and excellent agreement of the approximate frequencies with the exact one are demonstrated and discussed. The discrepancy between the first-order approximate frequency obtained by means of the second procedure and the exact frequency never exceeds 1.6%. We also obtained the approximate frequency by applying the second-order harmonic balance method and in this case the relative error is as low 0.31% for all the range of values of amplitude of oscillation A

Harmonically excited orbital variations

International Nuclear Information System (INIS)

Morgan, T.

1985-01-01

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs

Expansion into lattice harmonics in cubic symmetries

Science.gov (United States)

Kontrym-Sznajd, G.

2018-05-01

On the example of a few sets of sampling directions in the Brillouin zone, this work shows how important the choice of the cubic harmonics is on the quality of approximation of some quantities by a series of such harmonics. These studies led to the following questions: (1) In the case that for a given l there are several independent harmonics, can one use in the expansion only one harmonic with a given l?; (2) How should harmonics be ordered: according to l or, after writing them in terms of (x4 + y4 + z4)n (x2y2z2)m, according to their degree q = n + m? To enable practical applications of such harmonics, they are constructed in terms of the associated Legendre polynomials up to l = 26. It is shown that electron momentum densities, reconstructed from experimental data for ErGa3 and InGa3, are described much better by harmonics ordered with q.

Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

Science.gov (United States)

Holliday, Ezekiel S. (Inventor)

2014-01-01

Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

Explaining the harmonic sequence paradox.

Science.gov (United States)

Schmidt, Ulrich; Zimper, Alexander

2012-05-01

According to the harmonic sequence paradox, an expected utility decision maker's willingness to pay for a gamble whose expected payoffs evolve according to the harmonic series is finite if and only if his marginal utility of additional income becomes zero for rather low payoff levels. Since the assumption of zero marginal utility is implausible for finite payoff levels, expected utility theory - as well as its standard generalizations such as cumulative prospect theory - are apparently unable to explain a finite willingness to pay. This paper presents first an experimental study of the harmonic sequence paradox. Additionally, it demonstrates that the theoretical argument of the harmonic sequence paradox only applies to time-patient decision makers, whereas the paradox is easily avoided if time-impatience is introduced. ©2011 The British Psychological Society.

Harmonic d-tensors

Energy Technology Data Exchange (ETDEWEB)

Hohmann, Manuel [Physikalisches Institut, Universitaet Tartu (Estonia)

2016-07-01

Tensor harmonics are a useful mathematical tool for finding solutions to differential equations which transform under a particular representation of the rotation group SO(3). In order to make use of this tool also in the setting of Finsler geometry, where the objects of relevance are d-tensors instead of tensors, we construct a set of d-tensor harmonics for both SO(3) and SO(4) symmetries and show how these can be used for calculations in Finsler geometry and gravity.

A Framework to Analyze the Stochastic Harmonics and Resonance of Wind Energy Grid Interconnection

Directory of Open Access Journals (Sweden)

Youngho Cho

2016-08-01

Full Text Available This paper addresses a modeling and analysis methodology for investigating the stochastic harmonics and resonance concerns of wind power plants (WPPs. Wideband harmonics from modern wind turbines (WTs are observed to be stochastic, associated with real power production, and they may adversely interact with the grid impedance and cause unexpected harmonic resonance, if not comprehensively addressed in the planning and commissioning of the WPPs. These issues should become more critical as wind penetration levels increase. We thus propose a planning study framework comprising the following functional steps: First, the best fitted probability density functions (PDFs of the harmonic components of interest in the frequency domain are determined. In operations planning, maximum likelihood estimations (MLEs followed by a chi-square test are used once field measurements or manufacturers’ data are available. Second, harmonic currents from the WPP are represented by randomly-generating harmonic components based on their PDFs (frequency spectrum and then synthesized for time domain simulations via inverse Fourier transform. Finally, we conduct a comprehensive assessment by including the impacts of feeder configurations, harmonic filters and the variability of parameters. We demonstrate the efficacy of the proposed study approach for a 100-MW offshore WPP consisting of 20 units of 5-MW full converter turbines, a realistic benchmark system adapted from a WPP under development in Korea and discuss lessons learned through this research.

HARMONIZATION OF TAX POLICIES: REVIEWING MACEDONIA AND CROATIA

Directory of Open Access Journals (Sweden)

Sasho Kozuharov

2015-12-01

Full Text Available The tax harmonization is a complex issue in the process of European integration. The tax harmonization is a process of convergence of the tax system based on mutual set of rules and, in general, it means existence of identical or similar tax rates for the tax payers in European Union, i.e. Euro zone. In case there are identical tax rates, then we are talking about a, so called, total explicit tax harmonization, whereas, if there are similar tax rates, we are talking about partial explicit tax harmonization, which refers to determination of the highest and the lowest tax rates. Thus, countries can determine the tax rates of certain taxes. The total harmonization, besides tax rates harmonization, means structural harmonization or harmonization of the tax structure. The harmonization of direct taxes mainly relies on the following main objectives: avoiding tax evasion and elimination of double taxation. The harmonization of regulations and directives in the field of indirect taxes is necessary in terms of establishing a single market, or removal of barriers to the free movement of goods, people, services and capital.

Enteric methane mitigation technologies for ruminant livestock: a synthesis of current research and future directions.

Science.gov (United States)

Patra, Amlan Kumar

2012-04-01

Enteric methane (CH(4)) emission in ruminants, which is produced via fermentation of feeds in the rumen and lower digestive tract by methanogenic archaea, represents a loss of 2% to 12% of gross energy of feeds and contributes to global greenhouse effects. Globally, about 80 million tonnes of CH(4) is produced annually from enteric fermentation mainly from ruminants. Therefore, CH(4) mitigation strategies in ruminants have focused to obtain economic as well as environmental benefits. Some mitigation options such as chemical inhibitors, defaunation, and ionophores inhibit methanogenesis directly or indirectly in the rumen, but they have not confirmed consistent effects for practical use. A variety of nutritional amendments such as increasing the amount of grains, inclusion of some leguminous forages containing condensed tannins and ionophore compounds in diets, supplementation of low-quality roughages with protein and readily fermentable carbohydrates, and addition of fats show promise for CH(4) mitigation. These nutritional amendments also increase the efficiency of feed utilization and, therefore, are most likely to be adopted by farmers. Several new potential technologies such as use of plant secondary metabolites, probiotics and propionate enhancers, stimulation of acetogens, immunization, CH(4) oxidation by methylotrophs, and genetic selection of low CH(4)-producing animals have emerged to decrease CH(4) production, but these require extensive research before they can be recommended to livestock producers. The use of bacteriocins, bacteriophages, and development of recombinant vaccines targeting archaeal-specific genes and cell surface proteins may be areas worthy of investigation for CH(4) mitigation as well. A combination of different CH(4) mitigation strategies should be adopted in farm levels to substantially decrease methane emission from ruminants. Evidently, comprehensive research is needed to explore proven and reliable CH(4) mitigation technologies

Harmonic mappings into manifolds with boundary

International Nuclear Information System (INIS)

Chen Yunmei; Musina, R.

1989-08-01

In this paper we deal with harmonic maps from a compact Riemannian manifold into a manifold with boundary. In this case, a weak harmonic map is by definition a solution to a differential inclusion. In the first part of the paper we investigate the general properties of weak harmonic maps, which can be seen as solutions to a system of elliptic differential equations. In the second part we concentrate our attention on the heat flow method for harmonic maps. The result we achieve in this context extends a result by Chen and Struwe. (author). 21 refs

Harmonic engine

Science.gov (United States)

Bennett, Charles L [Livermore, CA

2009-10-20

A high efficiency harmonic engine based on a resonantly reciprocating piston expander that extracts work from heat and pressurizes working fluid in a reciprocating piston compressor. The engine preferably includes harmonic oscillator valves capable of oscillating at a resonant frequency for controlling the flow of working fluid into and out of the expander, and also preferably includes a shunt line connecting an expansion chamber of the expander to a buffer chamber of the expander for minimizing pressure variations in the fluidic circuit of the engine. The engine is especially designed to operate with very high temperature input to the expander and very low temperature input to the compressor, to produce very high thermal conversion efficiency.

Coherent harmonics generated by a super-short electron pulse

International Nuclear Information System (INIS)

Ding Wu

1996-01-01

A novel mechanism generating superradiance harmonics is found. In this superradiance harmonics, the temporal width of harmonics is extremely short, the ratio of high harmonic fundamental wave is much higher than the known superradiance harmonics

Harmonic lasing in X-ray FELs

Energy Technology Data Exchange (ETDEWEB)

Schneidmiller, E.A.; Yurkov, M.V.

2012-05-15

Harmonic lasing in a free electron laser with a planar undulator (under the condition that the fundamental frequency is suppressed) might be a cheap and efficient way of extension of wavelength ranges of existing and planned X-ray FEL facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental frequency. In this paper we perform a parametrization of the solution of the eigenvalue equation for lasing at odd harmonics, and present an explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental harmonic. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of X-ray beam at saturation. Considering 3rd harmonic lasing as a practical example, we come to the conclusion that it is much more robust than usually thought, and can be widely used in the existing or planned X-ray FEL facilities. In particular, LCLS after a minor modification can lase to saturation at the 3rd harmonic up to the photon energy of 25-30 keV providing multi-gigawatt power level and narrow bandwidth. As for the European XFEL, harmonic lasing would allow to extend operating range (ultimately up to 100 keV), to reduce FEL bandwidth and to increase brilliance, to enable two-color operation for pump-probe experiments, and to provide more flexible operation at different electron energies. Similar improvements can be realized in other X-ray FEL facilities with gap-tunable undulators like FLASH II, SACLA, LCLS II, etc. Harmonic lasing can be an attractive option for compact X-ray FELs (driven by electron beams with a relatively low energy), allowing the use of the standard undulator technology instead of small-gap in-vacuum devices. Finally, in this paper we discover that in a part of the

Symmetries in physics and harmonics

International Nuclear Information System (INIS)

Kolk, D.

2006-01-01

In this book the symmetries of elementary particles are described in relation to the rules of harmonics in music. The selection rules are described in connections with harmonic intervals. Also symmetry breaking is considered in this framework. (HSI)

Power Quality Problems Due to Transformer Inrush Current

OpenAIRE

Tokić, A.; Uglešić, I.

2017-01-01

Transformer energization can produce a large nonsinuoidal inrush current which contains both odd and higher order harmonic components that can put transformer winding under mechanical stress. Additionally, they can cause irregular tripping of harmonic protection relays. Furthermore, in relatively weak power systems, such as is the Bosnian system, the superposition of harmonic components with system resonance frequencies may produce temporary overvoltages (TOV). Transformer wind...

Electromagnetic field standards in Central and Eastern European countries: current state and stipulations for international harmonization.

Science.gov (United States)

Gajsek, P; Pakhomov, A G; Klauenberg, B J

2002-04-01

Electromagnetic field standards in the West are based on well-established acute biological effects that could be considered as signaling a potentially adverse health effect. The specific absorption rate, which is proportional to the tissue heating (thermal effects), represents the basic restriction of exposure to Radio-Frequency (RF) fields. On the other hand, Eastern European standards are designed to protect from potential non-thermal effects that might be caused by chronic exposure to very low intensities, where a so-called "power load" (a product of field intensity and duration of exposure) represents the basic limitation. Thus, electromagnetic field standards in Eastern European countries differ considerably from those which are proposed by the International Commission of Non-ionizing Radiation Protection and the Standards Coordinating Committee 28 of the Institute of Electrical and Electronics Engineers, Inc. In the present paper, the strategies for development of exposure limit values in electromagnetic fields standards currently in force in Eastern and Central European countries are discussed. Some differences as well as similarities of the national health and safety standards and the main obstacles to harmonization of these standards with those being established by Western national and international organizations and agencies are presented.

Analysis of Harmonics Suppression by Active Damping Control on Multi Slim DC-link Drives

DEFF Research Database (Denmark)

Yang, Feng; Máthé, Lászlo; Lu, Kaiyuan

2016-01-01

Compared with conventional dc-link drive, slim dc-link drive is expected to achieve lower cost and longer life time. However, harmonics distortion problem may occur in such drive systems. This paper proposes to use an active damping control method to suppress the harmonic distortion...... with the benefit of low cost and also low loss. A new analysis method, based on the frequency domain impedance model, is presented to explore the mechanism of harmonics suppression. Also, a general method is presented to build the impedance model of a PMSM drive system using Field Oriented Control (FOC) method....... Some design issues, including power levels, current control bandwidth and harmonic interaction, are discussed when the drive system is fed by a weak grid. Case studies on a two-drive system composed by two slim dc-link drive units are provided to verify the proposed analysis method....

Harmonic Injection-Based Power Fluctuation Control of Three-Phase PV Systems under Unbalanced Grid Voltage Conditions

Directory of Open Access Journals (Sweden)

Nian-Cheng Zhou

2015-02-01

Full Text Available Unbalanced voltage will inevitably cause power and DC voltage fluctuations in a three-phase PV system. The deterioration of power quality will do great harm to the PV panels and the loads, so it is necessary to suppress the power fluctuations. This paper further explores the coefficients control strategy of PV converters under unbalanced voltage conditions, aiming to suppress power fluctuations by controlling the injection of some specific orders of current harmonics into the grid. In order to achieve this, the current reference of the PV inverter has been changed by bringing in two control coefficients, and the expression of each order of the current harmonics has been deduced. Based on the standards of PV systems, the regions from which the coefficients can be selected are determined. Then, by tuning these coefficients in the feasible regions, the output parameters (power fluctuation, current THD and odd harmonics can be controlled precisely. The model of this method is built and simulated in PSCAD/EMTDC, and as a result, it is shown that the power fluctuations can be restricted according to different power quality requirements.

Harmonic generation effect in high-Tc films

International Nuclear Information System (INIS)

Khare, Neeraj; Shrivastava, S.K.; Padmanabhan, V.P.N.; Khare, Sangeeta; Gupta, A.K.

1997-01-01

Harmonic generation in thick BPSCCO and thin YBCO films are reported. The application of an ac field (H ac > H c1 ) of frequency f causes the generation of odd harmonics of frequency (2n+1)f. The application of dc field in addition to the ac field causes the appearance of even harmonics also in the BPSCCO film. However, the appearance of even harmonics is not observed in YBCO film with high J c ∼ 1.6x10 6 A/cm 2 and appearance of second harmonic with small magnitude is observed in YBCO film with low J c ∼ 2x10 3 A/cm 2 . The variation of amplitudes of these harmonics are studied as a function of magnitude of ac and dc field and the results are explained in the framework of critical state model. A high-T c film magnetometer based on the measurement of the amplitude of second harmonic has been developed whose field sensitivity is ∼ 1.5x10 -8 T. (author)

High-harmonic generation in a dense medium

International Nuclear Information System (INIS)

Strelkov, V.V.; Platonenko, V.T.; Becker, A.

2005-01-01

The high-harmonic generation in a plasma or gas under conditions when the single-atom response is affected by neighboring ions or atoms of the medium is studied theoretically. We solve numerically the three-dimensional Schroedinger equation for a single-electron atom in the combined fields of the neighboring particles and the laser, and average the results over different random positions of the particles using the Monte Carlo method. Harmonic spectra are calculated for different medium densities and laser intensities. We observe a change of the harmonic properties due to a random variation of the harmonic phase induced by the field of the medium, when the medium density exceeds a certain transition density. The transition density is found to depend on the harmonic order, but it is almost independent of the fundamental intensity. It also differs for the two (shorter and longer) quantum paths. The latter effect leads for ionic densities in the transition regime to a narrowing of the harmonic lines and a shortening of the attosecond pulses generated using a group of harmonics

Modeling of Synergy Between 4th and 6th Harmonic Absorptions of Fast Waves on Injected Beams in DIII-D Tokamak

International Nuclear Information System (INIS)

Choi, M.; Pinsker, R. I.; Chan, V. S.; Muscatello, C. M.; Jaeger, E. F.

2011-01-01

In recent moderate to high harmonic fast wave heating and current drive experiments in DIII-D, a synergy effect was observed when the 6 th harmonic 90 MHz fast wave power is applied to the plasma preheated by neutral beams and the 4 th harmonic 60 MHz fast wave. In this paper, we investigate how the synergy can occur using ORBIT-RF coupled with AORSA. Preliminary simulations suggest that damping of 4 th harmonic FW on beam ions accelerates them above the injection energy, which may allow significant damping of 6 th harmonic FW on beam ion tails to produce synergy.

Design and implementation of predictive filtering system for current reference generation of active power filter

Energy Technology Data Exchange (ETDEWEB)

Kilic, Tomislav; Milun, Stanko; Petrovic, Goran [FESB University of Split, Faculty of Electrical Engineering, Machine Engineering and Naval Architecture, R. Boskovica bb, 21000, Split (Croatia)

2007-02-15

The shunt active power filters are used to attenuate the harmonic currents in power systems by injecting equal but opposite compensating currents. Successful control of the active filters requires an accurate current reference. In this paper the current reference determination based on predictive filtering structure is presented. Current reference was obtained by taking the difference of load current and its fundamental harmonic. For fundamental harmonic determination with no time delay a combination of digital predictive filter and low pass filter is used. The proposed method was implemented on a laboratory prototype of a three-phase active power filter. The algorithm for current reference determination was adapted and implemented on DSP controller. Simulation and experimental results show that the active power filter with implemented predictive filtering structure gives satisfactory performance in power system harmonic attenuation. (author)

Harmonic sums and polylogarithms generated by cyclotomic polynomials

Energy Technology Data Exchange (ETDEWEB)

Ablinger, Jakob; Schneider, Carsten [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation; Bluemlein, Johannes [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

2011-05-15

The computation of Feynman integrals in massive higher order perturbative calculations in renormalizable Quantum Field Theories requires extensions of multiply nested harmonic sums, which can be generated as real representations by Mellin transforms of Poincare-iterated integrals including denominators of higher cyclotomic polynomials. We derive the cyclotomic harmonic polylogarithms and harmonic sums and study their algebraic and structural relations. The analytic continuation of cyclotomic harmonic sums to complex values of N is performed using analytic representations. We also consider special values of the cyclotomic harmonic polylogarithms at argument x=1, resp., for the cyclotomic harmonic sums at N{yields}{infinity}, which are related to colored multiple zeta values, deriving various of their relations, based on the stuffle and shuffle algebras and three multiple argument relations. We also consider infinite generalized nested harmonic sums at roots of unity which are related to the infinite cyclotomic harmonic sums. Basis representations are derived for weight w=1,2 sums up to cyclotomy l=20. (orig.)

Conceptual model of a logical system processor of selection to electrical filters for correction of harmonics in low voltage lines

Science.gov (United States)

Lastre, Arlys; Torriente, Ives; Méndez, Erik F.; Cordovés, Alexis

2017-06-01

In the present investigation, the authors propose a conceptual model for the analysis and the decision making of the corrective models to use in the mitigation of the harmonic distortion. The authors considered the setting of conventional models, and such adaptive models like the filters incorporation to networks neuronal artificial (RNA's) for the mitigating effect. In addition to the present work is a showing of the experimental model that learns by means of a flowchart denoting the need to use artificial intelligence skills for the exposition of the proposed model. The other aspect considered and analyzed are the adaptability and usage of the same, considering a local reference of the laws and lineaments of energy quality that demands the Department of Electricity and Energy Renewable (MEER) of Equator.

Second harmonic ion cylotron resonance heating by the fast magnetosonic wave on the PLT tokamak

International Nuclear Information System (INIS)

Thompson, H.R. Jr.

1984-01-01

Second harmonic ion cyclotron resonance heating by the fast magnetosonic wave, and the propagation of the fast wave from the fundamental of the ion cyclotron frequency to its second harmonic was investigated in a hydrogen plasma on the PLT tokamak. The theory of fast magnetosonic wave propagation was extended to include the effects of density gradients, plasma current, and impurity ion species. The damping of the fast wave at the second harmonic is calculated, where the theory has been extended to include the full radial dependence of the fast wave fields. Power deposition profiles and eigenmode Q's are calculated using this theory. The effects of the interaction between the ion Bernstein wave and the fast magnetosonic wave are calculated, and enhanced fast wave damping is predicted. The antenna loading is calculated including the effects of overlap of the fast wave eigenmodes. During the second harmonic heating experiments, the antenna loading was characterized as a function of the plasma parameters, and efficient coupling of the RF power to the plasma at high density was observed. At very low densities, fast wave eigenmodes were identified on PLT, and their Q's are measured. Eigenmodes with different toroidal directions of propagation were observed to exhibit large splitting in density due to the plasma current. Efficient bulk heating, with centrally peaked profiles, is observed at the second harmonic, and a tail, which decreases monotonically with energy, is observed on the ion distribution

Harmonic Stability Analysis of Offshore Wind Farm with Component Connection Method

DEFF Research Database (Denmark)

Hou, Peng; Ebrahimzadeh, Esmaeil; Wang, Xiongfei

2017-01-01

In this paper, an eigenvalue-based harmonic stability analysis method for offshore wind farm is proposed. Considering the internal cable connection layout, a component connection method (CCM) is adopted to divide the system into individual blocks as current controller of converters, LCL filters...

Mitigation potential of horizontal ground coupled heat pumps for current and future climatic conditions: UK environmental modelling and monitoring studies

Science.gov (United States)

García González, Raquel; Verhoef, Anne; Vidale, Pier Luigi; Gan, Guohui; Wu, Yupeng; Hughes, Andrew; Mansour, Majdi; Blyth, Eleanor; Finch, Jon; Main, Bruce

2010-05-01

model predictions of soil moisture content and soil temperature with measurements at different GCHP locations over the UK. The combined effect of environment dynamics and horizontal GCHP technical properties on long-term GCHP performance will be assessed using a detailed land surface model (JULES: Joint UK Land Environment Simulator, Meteorological Office, UK) with additional equations embedded describing the interaction between GCHP heat exchangers and the surrounding soil. However, a number of key soil physical processes are currently not incorporated in JULES, such as groundwater flow, which, especially in lowland areas, can have an important effect on the heat flow between soil and HE. Furthermore, the interaction between HE and soil may also cause soil vapour and moisture fluxes. These will affect soil thermal conductivity and hence heat flow between the HE and the surrounding soil, which will in turn influence system performance. The project will address these issues. We propose to drive an improved version of JULES (with equations to simulate GCHP exchange embedded), with long-term gridded (1 km) atmospheric, soil and vegetation data (reflecting current and future environmental conditions) to reliably assess the mitigation potential of GCHPs over the entire domain of the UK, where uptake of GCHPs has been low traditionally. In this way we can identify areas that are most suitable for the installation of GCHPs. Only then recommendations can be made to local and regional governments, for example, on how to improve the mitigation potential in less suitable areas by adjusting GCHP configurations or design.

Exact solution of the time-dependent harmonic plus an inverse harmonic potential with a time-dependent electromagnetic field

International Nuclear Information System (INIS)

Yuece, Cem

2003-01-01

In this paper, the problem of the charged harmonic plus an inverse harmonic oscillator with time-dependent mass and frequency in a time-dependent electromagnetic field is investigated. It is reduced to the problem of the inverse harmonic oscillator with time-independent parameters and the exact wave function is obtained

Young children's harmonic perception.

Science.gov (United States)

Costa-Giomi, Eugenia

2003-11-01

Harmony and tonality are two of the most difficult elements for young children to perceive and manipulate and are seldom taught in the schools until the end of early childhood. Children's gradual harmonic and tonal development has been attributed to their cumulative exposure to Western tonal music and their increasing experiential knowledge of its rules and principles. Two questions that are relevant to this problem are: (1) Can focused and systematic teaching accelerate the learning of the harmonic/tonal principles that seem to occur in an implicit way throughout childhood? (2) Are there cognitive constraints that make it difficult for young children to perceive and/or manipulate certain harmonic and tonal principles? A series of studies specifically addressed the first question and suggested some possible answers to the second one. Results showed that harmonic instruction has limited effects on children's perception of harmony and indicated that the drastic improvement in the perception of implied harmony noted approximately at age 9 is due to development rather than instruction. I propose that young children's difficulty in perceiving implied harmony stems from their attention behaviors. Older children have less memory constraints and more strategies to direct their attention to the relevant cues of the stimulus. Younger children focus their attention on the melody, if present in the stimulus, and specifically on its concrete elements such as rhythm, pitch, and contour rather than its abstract elements such as harmony and key. The inference of the abstract harmonic organization of a melody required in the perception of implied harmony is thus an elusive task for the young child.

Classical and multilinear harmonic analysis

CERN Document Server

Muscalu, Camil

2013-01-01

This two-volume text in harmonic analysis introduces a wealth of analytical results and techniques. It is largely self-contained and useful to graduates and researchers in pure and applied analysis. Numerous exercises and problems make the text suitable for self-study and the classroom alike. The first volume starts with classical one-dimensional topics: Fourier series; harmonic functions; Hilbert transform. Then the higher-dimensional Calderón-Zygmund and Littlewood-Paley theories are developed. Probabilistic methods and their applications are discussed, as are applications of harmonic analysis to partial differential equations. The volume concludes with an introduction to the Weyl calculus. The second volume goes beyond the classical to the highly contemporary and focuses on multilinear aspects of harmonic analysis: the bilinear Hilbert transform; Coifman-Meyer theory; Carleson's resolution of the Lusin conjecture; Calderón's commutators and the Cauchy integral on Lipschitz curves. The material in this vo...

Higher order harmonics of reactor neutron equation

International Nuclear Information System (INIS)

Li Fu; Hu Yongming; Luo Zhengpei

1996-01-01

The flux mapping method using the higher order harmonics of the neutron equation is proposed. Based on the bi-orthogonality of the higher order harmonics, the process and formulas for higher order harmonics calculation are derived via the source iteration method with source correction. For the first time, not only any order harmonics for up-to-3-dimensional geometry are achieved, but also the preliminary verification to the capability for flux mapping have been carried out

A hybrid active filter for damping of harmonic resonance in industrial power systems

OpenAIRE

Fujita, Hideaki; Yamasaki, Takahiro; Akagi, Hirofumi

1998-01-01

This paper proposes a hybrid active filter for damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th tuned passive filter. The active filter is characterized by detecting the 5th harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by t...

Bounce-harmonic Landau Damping of Plasma Waves

Science.gov (United States)

Anderegg, Francois

2015-11-01

We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v vph / 5 . The measurements are conducted in trapped pure ion plasmas contained in Penning-Malmberg trap, with wave-coherent LIF diagnostics of particle velocities. Our focus is on bounce harmonics damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

Harmonic Instability Assessment Using State-Space Modeling and Participation Analysis in Inverter-Fed Power Systems

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

2017-01-01

parameters on the harmonic instability of the power system. Moreover, the harmonic-frequency oscillation modes are identified, where participation analysis is presented to evaluate the contributions of different states to these modes and to further reveal how the system gives rise to harmonic instability......This paper presents a harmonic instability analysis method using state-space modeling and participation analysis in the inverter-fed ac power systems. A full-order state-space model for the droop-controlled Distributed Generation (DG) inverter is built first, including the time delay of the digital...... control system, inner current and voltage control loops, and outer droop-based power control loop. Based on the DG inverter model, an overall state-space model of a two-inverter-fed system is established. The eigenvalue-based stability analysis is then presented to assess the influence of controller...

Staging Evaluation and Response Criteria Harmonization (SEARCH) for Childhood, Adolescent and Young Adult Hodgkin Lymphoma (CAYAHL): Methodology statement.

Science.gov (United States)

Flerlage, Jamie E; Kelly, Kara M; Beishuizen, Auke; Cho, Steve; De Alarcon, Pedro A; Dieckmann, Ute; Drachtman, Richard A; Hoppe, Bradford S; Howard, Scott C; Kaste, Sue C; Kluge, Regine; Kurch, Lars; Landman-Parker, Judith; Lewis, Jocelyn; Link, Michael P; McCarten, Kathleen; Punnett, Angela; Stoevesandt, Dietrich; Voss, Stephan D; Wallace, William Hamish; Mauz-Körholz, Christine; Metzger, Monika L

2017-07-01

International harmonization of staging evaluation and response criteria is needed for childhood, adolescence, and young adulthood Hodgkin lymphoma. Two Hodgkin lymphoma protocols from cooperative trials in Europe and North America were compared for areas in need of harmonization, and an evidence-based approach is currently underway to harmonize staging and response evaluations with a goal to enhance comparisons, expedite identification of effective therapies, and aid in the approval process for new agents by regulatory agencies. © 2017 Wiley Periodicals, Inc.

Discretized representations of harmonic variables by bilateral Jacobi operators

Directory of Open Access Journals (Sweden)

Andreas Ruffing

2000-01-01

Full Text Available Starting from a discrete Heisenberg algebra we solve several representation problems for a discretized quantum oscillator in a weighted sequence space. The Schrödinger operator for a discrete harmonic oscillator is derived. The representation problem for a q-oscillator algebra is studied in detail. The main result of the article is the fact that the energy representation for the discretized momentum operator can be interpreted as follows: It allows to calculate quantum properties of a large number of non-interacting harmonic oscillators at the same time. The results can be directly related to current research on squeezed laser states in quantum optics. They reveal and confirm the observation that discrete versions of continuum Schrodinger operators allow more structural freedom than their continuum analogs do.

Biological processes for mitigation of greenhouse gases

Energy Technology Data Exchange (ETDEWEB)

Benemann, John R. [California Univ., Dept. of Plant and Microbial Biology, Berkeley, CA (United States)

1999-07-01

Biological processes driven by photosynthesis cycle through the atmosphere well over an order of magnitude more CO{sub 2} than is currently emitted from the combustion of fossils fuels. Already human activities control and appropriate almost half the primary photosynthetic productivity of the planet. Better management of natural and man-made ecosystems affords many opportunities for mitigation of greenhouse gases, through sink enhancements, source reduction and substitution of fossil fuels with biofuels. Biofuels can be recovered from most organic wastes, from agricultural and forestry residues, and from biomass produced solely for energy use. However, the currently low costs of fossil fuels limits the market for biofuels. Accounting for the greenhouse mitigation value of biofuels would significantly increase their contribution to world fuel suppliers, estimated to be currently equivalent to about 15% of fossil fuel usage. Another limiting factor in expanding the use of biofuels is the relatively low solar energy conversion efficiencies of photosynthesis. Currently well below 1% of solar energy is converted into biomass energy even by intensive agricultural or forestry systems, with peak conversion efficiencies about 2 to 3% for sugar cane or microalgae cultures. One approach to increase photosynthetic efficiencies, being developed at the University of California Berkeley, is to reduce the amount of light-gathering chlorophyll in microalgae and higher plants. This would reduce mutual shading and also increase photosynthetic efficiencies under full sunlight intensities. Estimates of the potential of photosynthetic greenhouse mitigation processes vary widely. However, even conservative estimates for biofuels substituting for fossil fuels project the potential to reduce a large fraction of current increases in atmospheric CO{sub 2} levels. Biofuels production will require integration with existing agronomic, forestry and animal husbandry systems, and improved

Determination of Total Harmonic Distortion (THD) on a 33kv ...

African Journals Online (AJOL)

Modern day AC power systems are proliferated by the introduction of several kinds of nonlinear loads which generate harmonics in a power system and this has a cumulative negative effect on power quality. Examples of nonlinear loads are power electronic devices, which cause distortion of voltage and current waveforms ...

Understanding fifth-harmonic generation in CLBO

Science.gov (United States)

Patankar, S.; Yang, S. T.; Moody, J. D.; Bayramian, A. J.; Swadling, G. F.; Barker, D.; Datte, P.; Mennerat, G.; Norton, M.; Carr, C. W.; Begishev, I. A.; Bromage, J.; Ross, J. S.

2018-02-01

We report on results of fifth harmonic generation in Cesium Lithium Borate (CLBO) using a three-crystal cascaded frequency conversion scheme designed to study the energy balance of the final sum frequency generation stage. The experimental setup independently combines the first and fourth harmonic of a Nd:Glass laser in a 5mm thick CLBO crystal. Energy balance between the incoming and output energy is close to unity when the CLBO is out of phase matching and approximately 80% when the crystal is in phase matching. A detailed analysis of the residual fundamental and fourth harmonic energy indicates 5th harmonic light is being generated but only 26% is unaccounted for. We attribute the missing light to linear transmission loss in the CLBO oven. The ratio of the output to input energy is unity when the missing 5th harmonic is incorporated into the calculations. Two-dimensional plane wave mixing simulations show agreement with the results at lower intensities.

Third Harmonic Imaging using a Pulse Inversion

DEFF Research Database (Denmark)

Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt

2011-01-01

The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...

Validation Techniques of network harmonic models based on switching of a series linear component and measuring resultant harmonic increments

DEFF Research Database (Denmark)

Wiechowski, Wojciech Tomasz; Lykkegaard, Jan; Bak, Claus Leth

2007-01-01

In this paper two methods of validation of transmission network harmonic models are introduced. The methods were developed as a result of the work presented in [1]. The first method allows calculating the transfer harmonic impedance between two nodes of a network. Switching a linear, series network......, as for example a transmission line. Both methods require that harmonic measurements performed at two ends of the disconnected element are precisely synchronized....... are used for calculation of the transfer harmonic impedance between the nodes. The determined transfer harmonic impedance can be used to validate a computer model of the network. The second method is an extension of the fist one. It allows switching a series element that contains a shunt branch...

Mitigation gambles: uncertainty, urgency and the last gamble possible

Science.gov (United States)

Shue, Henry

2018-05-01

A rejection by current generations of more ambitious mitigation of carbon emissions inflicts on future generations inherently objectionable risks about which they have no choice. Any gains through savings from less ambitious mitigation, which are relatively minor, would accrue to current generations, and all losses, which are relatively major, would fall on future generations. This mitigation gamble is especially unjustifiable because it imposes a risk of unlimited losses until carbon emissions cease. Ultimate physical collapses remain possible. Much more ominous is prior social collapse from political struggles over conflicting responses to threatened physical collapse. The two most plausible objections to the thesis that less ambitious mitigation is unjustifiable rely, respectively, on the claim that negative emissions will allow a later recovery from a temporary overshoot in emissions and on the claim that ambitious mitigation is incompatible with poverty alleviation that depends on inexpensive fossil fuels. Neither objection stands up. Reliance on negative emissions later instead of ambitious mitigation now permits the passing of tipping points for irreversible change meanwhile, and non-carbon energy is rapidly becoming price competitive in developing countries like India that are committed to poverty alleviation. This article is part of the themed issue `The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

Mitigation gambles: uncertainty, urgency and the last gamble possible.

Science.gov (United States)

Shue, Henry

2018-05-13

A rejection by current generations of more ambitious mitigation of carbon emissions inflicts on future generations inherently objectionable risks about which they have no choice. Any gains through savings from less ambitious mitigation, which are relatively minor, would accrue to current generations, and all losses, which are relatively major, would fall on future generations. This mitigation gamble is especially unjustifiable because it imposes a risk of unlimited losses until carbon emissions cease. Ultimate physical collapses remain possible. Much more ominous is prior social collapse from political struggles over conflicting responses to threatened physical collapse. The two most plausible objections to the thesis that less ambitious mitigation is unjustifiable rely, respectively, on the claim that negative emissions will allow a later recovery from a temporary overshoot in emissions and on the claim that ambitious mitigation is incompatible with poverty alleviation that depends on inexpensive fossil fuels. Neither objection stands up. Reliance on negative emissions later instead of ambitious mitigation now permits the passing of tipping points for irreversible change meanwhile, and non-carbon energy is rapidly becoming price competitive in developing countries like India that are committed to poverty alleviation.This article is part of the themed issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'. © 2018 The Author(s).

Benefits from the BESSY FEL Higher Harmonic Radiation

CERN Document Server

Goldammer, K

2005-01-01

In the FEL process, bunching and coherent radiation is produced at the fundamental frequency as well as its higher harmonics. BESSY proposes a linac-based cascaded High-Gain Harmonic-Generation (HGHG) free electron laser (FEL) multi-user facility. The BESSY soft X-ray FEL will be seeded by three lasers spanning the spectral range of 230nm to 460nm. Two to four HGHG stages downconvert the seed wavelength to the desired radiation range of 1.24nm to 51nm using higher harmonic bunching. As a surplus, higher harmonic radiation is intrinsically produced in each FEL stage. Radiation on a higher harmonic of the FEL frequency is of high interest because it yields the possibility to reduce the number of FEL stages. This paper details extensive studies of the higher harmonic content of the BESSY FEL radiation. Important aspects of FEL interaction on higher harmonics as resulting from theory and from numerical simulations are discussed. For the case of the BESSY FEL, methods for improving the harmonic content are present...

Superconducting self-correcting harmonic coils for pulsed superconducting dipole or multipole magnets

International Nuclear Information System (INIS)

Dael, A.; Kircher, F.; Perot, J.

1975-01-01

Due to the zero resistance of a superconducting wire, an induced current in a closed superconducting circuit is continuously exactly opposed to its cause. This phenomenon was applied to the correction of the field harmonics of a pulsed magnet by putting short-circuited superconducting coils of particular symmetry in the useful aperture of the magnet. After a review of the main characteristics of such devices, the construction of two correcting coils (quadrupole and sextupole) is described. Experimental results of magnetic efficiency and time behavior are given; they are quite encouraging, since the field harmonics were reduced by one or two orders of magnitude

The electrochemistry of IGSCC mitigation

International Nuclear Information System (INIS)

Macdonald, D.D.

2002-01-01

A brief review is presented of the electrochemical mitigation of intergranular stress corrosion cracking (IGSCC) in watercooled reactor heat transport circuit structural materials. Electrochemical control and mitigation is possible because of the existence of a critical potential for intergranular stress corrosion cracking and due to the feasibility of modifying the environment to displace the corrosion potential to a value that is more negative than the critical value. However, even in cases where the corrosion potential cannot be displaced sufficiently in the negative direction to become more negative than the critical potential, considerable advantage is accrued, because of the roughly exponential dependence of the crack growth rate on potential. The most important parameters in affecting electrochemical control over the corrosion potential and crack growth rate are the kinetic parameters (exchange current densities and Tafel constants) for the redox reactions involving the principal radiolysis products of water (O 2 , H 2 H 2 O 2 ), external solution composition (concentrations of O 2 , H 2 O 2 , and H 2 ), flow velocity, and the conductivity of the bulk environment. The kinetic parameters for the redox reactions essentially determine the charge transfer impedance of the steel surface, which is shown to be one of the key parameters in affecting the magnitude of the coupling current and hence the crack growth rate. The exchange current densities, in particular, are amenable to control by catalysis or inhibition, with the result that surface modification techniques are highly effective in controlling and mitigating intergranular stress corrosion cracking in reactor coolant circuit materials. (orig.)

International Cooperation in Nuclear E&T: On the Way to Nuclear Training Harmonization

International Nuclear Information System (INIS)

Filipev, I.; Karmanov, F.; Artisyuk, V.; Karezin, V.; Sushkov, P.

2016-01-01

Full text: Global use of nuclear power is likely to continue to grow in the coming decades. Some countries have chosen to invite multiple vendors for NPP technology supply. The worldwide expansion of nuclear power use and the multi-vendor paradigm inevitably lead to the need of harmonized approaches towards safety and the initial step here is harmonization of education and training (E&T) efforts between recipient and vendor countries and between vendors as well. Establishing international and regional E&T networks is the vital mechanism of the harmonization. The present paper gives an example of collaboration between Russia and the EU through achievements of ENEN-RU projects aimed at harmonization of E&T efforts in nuclear field. One of the goals of this activity is to introduce double-degree programmes in nuclear engineering in Russian and EU universities. To support this initiative ROSATOM-CICE&T is currently developing multimedia-based fundamental educational courses in Russian and English languages. The courses will be also used as the backbone for new nuclear engineering programmes in the universities of newcomer states. To provide a harmonized development of operating personnel career trajectories in these countries an applied bachelor programme for operating personnel has been developed. (author

Hermitian harmonic maps into convex balls

International Nuclear Information System (INIS)

Li Zhenyang; Xi Zhang

2004-07-01

In this paper, we consider Hermitian harmonic maps from Hermitian manifolds into convex balls. We prove that there exist no non-trivial Hermitian harmonic maps from closed Hermitian manifolds into convex balls, and we use the heat flow method to solve the Dirichlet problem for Hermitian harmonic maps when the domain is compact Hermitian manifold with non-empty boundary. The case where the domain manifold is complete(noncompact) is also studied. (author)

A study of parametric instability in a harmonic gyrotron: Designs of third harmonic gyrotrons at 94 GHz and 210 GHz

International Nuclear Information System (INIS)

Saraph, G.P.; Antonsen, T.M. Jr.; Nusinovich, G.S.; Levush, B.

1995-01-01

Mode competition can present a major hurdle in achieving stable, efficient operation of a gyrotron at the cyclotron harmonics. A type of mode interaction in which three modes at different cyclotron harmonics are parametrically coupled together is analyzed here. This coupling can lead to parametric excitation or suppression of a mode; cyclic mode hopping; or the coexistence of three modes. Simulation results are presented for the parametric instability involving modes at the fundamental, second harmonic, and third harmonic of the cyclotron frequency. It is shown that the parametric excitation can lead to stable, efficient operation of a high-power gyrotron at the third harmonic. Based on this phenomenon, two practical designs are presented here for the third harmonic operation at 94 and 210 GHz. copyright 1995 American Institute of Physics

Harmonic disturbance location by applying Bayesian inference

NARCIS (Netherlands)

Ye, G.; Xiang, Y.; Cuk, V.; Cobben, J.F.G.

2016-01-01

Harmonic pollution is one of the most important power quality issues in electric power systems. Correct location of the main harmonic disturbance source is a key step to solve the problem. This paper presents a method to detect the location of harmonic disturbance source in low voltage network

Introduction to classical and quantum harmonic oscillators

CERN Document Server

Bloch, Sylvan C

2013-01-01

From conch shells to lasers . harmonic oscillators, the timeless scientific phenomenon As intriguing to Galileo as they are to scientists today, harmonic oscillators have provided a simple and compelling paradigm for understanding the complexities that underlie some of nature's and mankind's most fascinating creations. From early string and wind instruments fashioned from bows and seashells to the intense precision of lasers, harmonic oscillators have existed in various forms, as objects of beauty and scientific use. And harmonic oscillation has endured as one of science's most fascinating con

Dual aperture dipole magnet with second harmonic component

Science.gov (United States)

Praeg, Walter F.

1985-01-01

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Second-harmonic generation in shear wave beams with different polarizations

Science.gov (United States)

Spratt, Kyle S.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

2015-10-01

A coupled pair of nonlinear parabolic equations was derived by Zabolotskaya [1] that model the transverse components of the particle motion in a collimated shear wave beam propagating in an isotropic elastic solid. Like the KZK equation, the parabolic equation for shear wave beams accounts consistently for the leading order effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to that present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The work by Wochner et al. [2] considered shear wave beams with translational polarizations (linear, circular and elliptical), wherein second-order nonlinear effects vanish and the leading order nonlinear effect is third-harmonic generation by the cubic nonlinearity. The purpose of the current work is to investigate the quadratic nonlinear term present in the parabolic equation for shear wave beams by considering second-harmonic generation in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. In order for second-order nonlinear effects to be present, a broader class of source polarizations must be considered that includes not only the familiar translational polarizations, but also polarizations accounting for stretching, shearing and rotation of the source plane. It is found that the polarization of the second harmonic generated by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-harmonic generation from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic.

Second-harmonic generation in shear wave beams with different polarizations

Energy Technology Data Exchange (ETDEWEB)

Spratt, Kyle S., E-mail: sprattkyle@gmail.com; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F. [Applied Research Laboratories, The University of Texas at Austin, P. O. Box 8029, Austin, Texas 78713–8029, US (United States)

2015-10-28

A coupled pair of nonlinear parabolic equations was derived by Zabolotskaya [1] that model the transverse components of the particle motion in a collimated shear wave beam propagating in an isotropic elastic solid. Like the KZK equation, the parabolic equation for shear wave beams accounts consistently for the leading order effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to that present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The work by Wochner et al. [2] considered shear wave beams with translational polarizations (linear, circular and elliptical), wherein second-order nonlinear effects vanish and the leading order nonlinear effect is third-harmonic generation by the cubic nonlinearity. The purpose of the current work is to investigate the quadratic nonlinear term present in the parabolic equation for shear wave beams by considering second-harmonic generation in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. In order for second-order nonlinear effects to be present, a broader class of source polarizations must be considered that includes not only the familiar translational polarizations, but also polarizations accounting for stretching, shearing and rotation of the source plane. It is found that the polarization of the second harmonic generated by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-harmonic generation from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic.

Second-harmonic generation in shear wave beams with different polarizations

International Nuclear Information System (INIS)

Spratt, Kyle S.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

2015-01-01

A coupled pair of nonlinear parabolic equations was derived by Zabolotskaya [1] that model the transverse components of the particle motion in a collimated shear wave beam propagating in an isotropic elastic solid. Like the KZK equation, the parabolic equation for shear wave beams accounts consistently for the leading order effects of diffraction, viscosity and nonlinearity. The nonlinearity includes a cubic nonlinear term that is equivalent to that present in plane shear waves, as well as a quadratic nonlinear term that is unique to diffracting beams. The work by Wochner et al. [2] considered shear wave beams with translational polarizations (linear, circular and elliptical), wherein second-order nonlinear effects vanish and the leading order nonlinear effect is third-harmonic generation by the cubic nonlinearity. The purpose of the current work is to investigate the quadratic nonlinear term present in the parabolic equation for shear wave beams by considering second-harmonic generation in Gaussian beams as a second-order nonlinear effect using standard perturbation theory. In order for second-order nonlinear effects to be present, a broader class of source polarizations must be considered that includes not only the familiar translational polarizations, but also polarizations accounting for stretching, shearing and rotation of the source plane. It is found that the polarization of the second harmonic generated by the quadratic nonlinearity is not necessarily the same as the polarization of the source-frequency beam, and we are able to derive a general analytic solution for second-harmonic generation from a Gaussian source condition that gives explicitly the relationship between the polarization of the source-frequency beam and the polarization of the second harmonic

Renormalization group decimation technique for disordered binary harmonic chains

International Nuclear Information System (INIS)

Wiecko, C.; Roman, E.

1983-10-01

The density of states of disordered binary harmonic chains is calculated using the Renormalization Group Decimation technique on the displacements of the masses from their equilibrium positions. The results are compared with numerical simulation data and with those obtained with the current method of Goncalves da Silva and Koiller. The advantage of our procedure over other methods is discussed. (author)

Fast harmonic field mapper

International Nuclear Information System (INIS)

Au, R.; Fowler, M.; Hanawa, H.; Riedel, J.; Qua, Z.G.

1984-01-01

In early 1983 it was decided to mount coils on arms separated by 120 degrees and buck them out so that the third harmonic dphi/dt component would be cancelled and thus the first and second field harmonics could be very accurately measured. The original intention was to do as others had done, namely, use fast ADC's to read the voltages, and computer process the result to get the Fourier components. However, because of the 100 to 1 dynamic range of the fast ADC's and the likelihood that noise would be a problem, the authors decided to do things differently. Using a fast Fourier transform analyzer was considered, but this instrument is very expensive, so they decided to use a completely electronic analog approach: The authors decided to use active bandpass filters to render the harmonic components

Stability and nonlinear dynamics of gyrotrons at cyclotron harmonics

International Nuclear Information System (INIS)

Saraph, G.P.; Nusinovich, G.S.; Antonsen, T.M. Jr.; Levush, B.

1992-01-01

Gyrotrons operating at higher harmonics of the cyclotron frequency can overcome the frequency limitations caused by achievable strength of the magnetic field. However, the excitation of modes at the fundamental frequency exhibit a major problem for stable operation of harmonic gyrotron at high power with high efficiency. Therefore the issues of stability of gyrotron operation at the cyclotron harmonics and nonlinear dynamics of mode interaction are of great importance. The results of the authors stability analysis and multimode simulation are presented here. A detailed nonlinear theory of steady state single mode operation at cyclotron harmonics has been presented previously, taking into account beam-wave coupling and nonlinear gain function at cyclotron harmonics. A set of equations describing low gain regime interaction of modes resonant at different cyclotron harmonics was studied before. The multifrequency time-dependent nonlinear analysis presented here is based on previous gyrotron studies and beam-wave interaction at cyclotron harmonics. The authors have determined the parameter space for stable single mode operation at the second harmonic. The nonlinear dynamics of mode evolution and mode interaction for a harmonic gyrotron is presented. A new nonlinear effect in which the parasite at the fundamental harmonic helps excite the operating mode at the second harmonic has been demonstrated

MISSIONS: The Mobile-Based Disaster Mitigation System in Indonesia

Science.gov (United States)

Passarella, Rossi; Putri Raflesia, Sarifah; Lestarini, Dinda; Rifai, Ahmad; Veny, Harumi

2018-04-01

Disaster mitigation is essential to minimize the effects of disasters. Indonesia is one of the disaster prone areas in Asia and the government explores the usage of Information technology (IT) to aid its mitigation efforts. Currently, there are Indonesian websites which hold information regarding the weather monitoring, climate conditions, and geophysics. But, there is no clear indicator of mitigation efforts or things to do during an emergency. Therefore, this research proposed MISSIONS, a disaster mitigation model using geo-fencing technique to detect the location of the users through their mobile devices. MISSIONS uses mobile-based disaster mitigation system as a way to disseminate critical information to victims during emergency when they are in disaster zones using virtual fences. It aims to help the government to reduce the effects of disaster and aid in the mitigation efforts. The implementation result shows that MISSIONS have a high accuracy in detecting user whereabouts.

Space and time harmonics related problems and their mitigation for ...

Indian Academy of Sciences (India)

system the transient mechanical loading due to persistent torque fluctuations reduce life of gear-box ... Since both rotor and stator side current fundamental frequencies ... eters are known and do not vary with temperature, aging and operating ...

High order harmonic generation in rare gases

Energy Technology Data Exchange (ETDEWEB)

Budil, Kimberly Susan [Univ. of California, Davis, CA (United States)

1994-05-01

The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~10¹³-10¹⁴ W/cm²) is focused into a dense (~10¹⁷ particles/cm³) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.

Harmonic Instability Analysis of Single-Phase Grid Connected Converter using Harmonic State Space (HSS) modeling method

DEFF Research Database (Denmark)

Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth

2015-01-01

The increasing number of renewable energy sources at the distribution grid is becoming a major issue for utility companies, since the grid connected converters are operating at different operating points due to the probabilistic characteristics of renewable energy. Besides, typically, the harmonics...... proposes a new model of a single phase grid connected renewable energy source using the Harmonic State Space modeling approach, which is able to identify such problems and the model can be extended to be applied in the multiple connected converter analysis. The modeling results show the different harmonic...... and impedance from other renewable energy sources are not taken carefully into account in the installation and design. However, this may bring an unknown harmonic instability into the multiple power sourced system and also make the analysis difficult due to the complexity of the grid network. This paper...

Linking high harmonics from gases and solids.

Science.gov (United States)

Vampa, G; Hammond, T J; Thiré, N; Schmidt, B E; Légaré, F; McDonald, C R; Brabec, T; Corkum, P B

2015-06-25

When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed.

Superconformal geometry from the Grassmann and harmonic analyticities II: The N=4SU(2) conformal case

International Nuclear Information System (INIS)

Saidi, E.H.; Zakkari, M.

1990-05-01

N=4SU(2) conformal invariance is studied in harmonic superspace. It is shown that the N=4SU(2) conformal structure is equivalent to the harmonic analyticity. The solutions of the superconformal constraints are worked out in detail and the conformal properties of all objects of interests are given. A realization of the N=4 current in terms of the free (F.S.) hypermultiplet is obtained. (author). 10 refs

Double Harmonic Transmission (D.H.T.

Directory of Open Access Journals (Sweden)

Sava Ianici

2006-10-01

Full Text Available The paper presents the construction and functioning of a new type of harmonic drive named double harmonic transmission (D.H.T.. In the second part of this paper is presented the dynamic analysis of the double harmonic transmission, which is based on the results of the experimental researches on the D.H.T. This study of the stress status and the forces distribution is necessary for to determine the durability on the portant elements of the D.H.T.

Pseudo harmonic morphisms on Riemannian polyhedra

International Nuclear Information System (INIS)

Aprodu, M.A.; Bouziane, T.

2004-10-01

The aim of this paper is to extend the notion of pseudo harmonic morphism (introduced by Loubeau) to the case when the source manifold is an admissible Riemannian polyhedron. We define these maps to be harmonic in the sense of Eells-Fuglede and pseudo-horizontally weakly conformal in our sense. We characterize them by means of germs of harmonic functions on the source polyhedron, in the sense of Korevaar-Schoen, and germs of holomorphic functions on the Kaehler target manifold. (author)

Coherent harmonic production using a two-section undulator FEL

Energy Technology Data Exchange (ETDEWEB)

Jaroszynski, D.A. [Commissariat a l`Energie, Bruyeres-le-Chatel (France); Prazeres, R.; Glotin, F. [Centre Universitaire Paris-Sud (France)] [and others

1995-12-31

We present measurements and a theoretical analysis of a new method of generating harmonic radiation in a free-electron laser oscillator with a two section undulator in a single optical cavity. To produce coherent harmonic radiation the undulator is arranged so that the downstream undulator section resonance frequency matches a harmonic of the upstream undulator. Both the fundamental and the harmonic optical fields evolve in the same optical cavity and are coupled out with different extraction fractions using a hole in one of the cavity mirrors. We present measurements that show that the optical power at the second and third harmonic can be enhanced by more than an order of magnitude in this fundamental/harmonic configuration. We compare the production of harmonic radiation of a two sectioned fundamental/harmonic undulator with that produced from a FEL operating at its highest efficiency with a step-tapered undulator, where the bunching at the end of the first section is very large. We examine, the dependence of the harmonic power on the intracavity power by adjusting the optical cavity desynchronism, {delta}L. We also examine the evolution of the fundamental and harmonic powers as a function of cavity roundtrip number to evaluate the importance of the small signal gain at the harmonic. We compare our measurements with predictions of a multi-electron numerical model that follows the evolution of fundamental and harmonic power to saturation. This fundamental/harmonic mode, of operation of the FEL may have useful applications in the production of coherent X-ray and VUV radiation, a spectral range where high reflectivity optical cavity mirrors are difficult or impossible to manufacture.

Second-harmonic imaging of semiconductor quantum dots

DEFF Research Database (Denmark)

Østergaard, John Erland; Bozhevolnyi, Sergey I.; Pedersen, Kjeld

2000-01-01

Resonant second-harmonic generation is observed at room temperature in reflection from self-assembled InAlGaAs quantum dots grown on a GaAs (001) substrate. The detected second-harmonic signal peaks at a pump wavelength of similar to 885 nm corresponding to the quantum-dot photoluminescence maximum....... In addition, the second-harmonic spectrum exhibits another smaller but well-pronounced peak at 765 nm not found in the linear experiments. We attribute this peak to the generation of second-harmonic radiation in the AlGaAs spacer layer enhanced by the local symmetry at the quantum-dot interface. We further...

Harmonic Series Meets Fibonacci Sequence

Science.gov (United States)

Chen, Hongwei; Kennedy, Chris

2012-01-01

The terms of a conditionally convergent series may be rearranged to converge to any prescribed real value. What if the harmonic series is grouped into Fibonacci length blocks? Or the harmonic series is arranged in alternating Fibonacci length blocks? Or rearranged and alternated into separate blocks of even and odd terms of Fibonacci length?

Tuvan Throat Singing and Harmonics

Science.gov (United States)

Ruiz, Michael J.; Wilken, David

2018-01-01

Tuvan throat singing, also called overtone singing, provides for an exotic demonstration of the physics of harmonics as well as introducing an Asian musical aesthetic. A low fundamental is sung and the singer skillfully alters the resonances of the vocal system to enhance an overtone (harmonic above the fundamental). The result is that the…

Shunt hybrid active power filter for harmonic mitigation: A practical ...

Indian Academy of Sciences (India)

shunt HAPF, APF is connected in series with PPF and the whole system is connected in parallel to the load. ... LC filter, it will force a fundamental reactive current to flow into it. ..... Since SHAPF is operating as a boost rectifier, d.c. voltage.

A Harmonized Process Model for Digital Forensic Investigation Readiness

OpenAIRE

Valjarevic , Aleksandar; Venter , Hein

2013-01-01

Part 2: FORENSIC MODELS; International audience; Digital forensic readiness enables an organization to prepare itself to perform digital forensic investigations in an efficient and effective manner. The benefits include enhancing the admissibility of digital evidence, better utilization of resources and greater incident awareness. However, a harmonized process model for digital forensic readiness does not currently exist and, thus, there is a lack of effective and standardized implementations...

Output Current Ripple Reduction Algorithms for Home Energy Storage Systems

Directory of Open Access Journals (Sweden)

Jin-Hyuk Park

2013-10-01

Full Text Available This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI controller for an energy storage system (ESS. In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model.

New Evidence That Nonlinear Source-Filter Coupling Affects Harmonic Intensity and fo Stability During Instances of Harmonics Crossing Formants.

Science.gov (United States)

Maxfield, Lynn; Palaparthi, Anil; Titze, Ingo

2017-03-01

The traditional source-filter theory of voice production describes a linear relationship between the source (glottal flow pulse) and the filter (vocal tract). Such a linear relationship does not allow for nor explain how changes in the filter may impact the stability and regularity of the source. The objective of this experiment was to examine what effect unpredictable changes to vocal tract dimensions could have on fo stability and individual harmonic intensities in situations in which low frequency harmonics cross formants in a fundamental frequency glide. To determine these effects, eight human subjects (five male, three female) were recorded producing fo glides while their vocal tracts were artificially lengthened by a section of vinyl tubing inserted into the mouth. It was hypothesized that if the source and filter operated as a purely linear system, harmonic intensities would increase and decrease at nearly the same rates as they passed through a formant bandwidth, resulting in a relatively symmetric peak on an intensity-time contour. Additionally, fo stability should not be predictably perturbed by formant/harmonic crossings in a linear system. Acoustic analysis of these recordings, however, revealed that harmonic intensity peaks were asymmetric in 76% of cases, and that 85% of fo instabilities aligned with a crossing of one of the first four harmonics with the first three formants. These results provide further evidence that nonlinear dynamics in the source-filter relationship can impact fo stability as well as harmonic intensities as harmonics cross through formant bandwidths. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Theoretical description of high-order harmonic generation in solids

International Nuclear Information System (INIS)

Kemper, A F; Moritz, B; Devereaux, T P; Freericks, J K

2013-01-01

We consider several aspects of high-order harmonic generation in solids: the effects of elastic and inelastic scattering, varying pulse characteristics and inclusion of material-specific parameters through a realistic band structure. We reproduce many observed characteristics of high harmonic generation experiments in solids including the formation of only odd harmonics in inversion-symmetric materials, and the nonlinear formation of high harmonics with increasing field. We find that the harmonic spectra are fairly robust against elastic and inelastic scattering. Furthermore, we find that the pulse characteristics can play an important role in determining the harmonic spectra. (paper)

Direct-phase-variable model of a synchronous reluctance motor including all slot and winding harmonics

International Nuclear Information System (INIS)

Obe, Emeka S.; Binder, A.

2011-01-01

A detailed model in direct-phase variables of a synchronous reluctance motor operating at mains voltage and frequency is presented. The model includes the stator and rotor slot openings, the actual winding layout and the reluctance rotor geometry. Hence, all mmf and permeance harmonics are taken into account. It is seen that non-negligible harmonics introduced by slots are present in the inductances computed by the winding function procedure. These harmonics are usually ignored in d-q models. The machine performance is simulated in the stator reference frame to depict the difference between this new direct-phase model including all harmonics and the conventional rotor reference frame d-q model. Saturation is included by using a polynomial fitting the variation of d-axis inductance with stator current obtained by finite-element software FEMAG DC (registered) . The detailed phase-variable model can yield torque pulsations comparable to those obtained from finite elements while the d-q model cannot.

Voltage harmonic elimination with RLC based interface smoothing filter

International Nuclear Information System (INIS)

Chandrasekaran, K; Ramachandaramurthy, V K

2015-01-01

A method is proposed for designing a Dynamic Voltage Restorer (DVR) with RLC interface smoothing filter. The RLC filter connected between the IGBT based Voltage Source Inverter (VSI) is attempted to eliminate voltage harmonics in the busbar voltage and switching harmonics from VSI by producing a PWM controlled harmonic voltage. In this method, the DVR or series active filter produces PWM voltage that cancels the existing harmonic voltage due to any harmonic voltage source. The proposed method is valid for any distorted busbar voltage. The operating VSI handles no active power but only harmonic power. The DVR is able to suppress the lower order switching harmonics generated by the IGBT based VSI. Good dynamic and transient results obtained. The Total Harmonic Distortion (THD) is minimized to zero at the sensitive load end. Digital simulations are carried out using PSCAD/EMTDC to validate the performance of RLC filter. Simulated results are presented. (paper)

Three-dimensional harmonic control of a nuclear reactor

International Nuclear Information System (INIS)

Potapenko, P.T.

1989-01-01

Algorithms for neutron flux control based on harmonic three-dimensional core are considered. The essence of the considered approach includes determination of harmonics amplitudes by signals self-powered detectors placed in reactor channels and reconstruction of neutron field distribution over the reactor core volume using the data obtained. Neutron field harmonic control is shown to be reduced to independent measurement and calculation of height harmonics in channels using techniques developed for channel power control

A multi-harmonic generalized energy balance method for studying autonomous oscillations of nonlinear conservative systems

Science.gov (United States)

Balaji, Nidish Narayanaa; Krishna, I. R. Praveen; Padmanabhan, C.

2018-05-01

The Harmonic Balance Method (HBM) is a frequency-domain based approximation approach used for obtaining the steady state periodic behavior of forced dynamical systems. Intrinsically these systems are non-autonomous and the method offers many computational advantages over time-domain methods when the fundamental period of oscillation is known (generally fixed as the forcing period itself or a corresponding sub-harmonic if such behavior is expected). In the current study, a modified approach, based on He's Energy Balance Method (EBM), is applied to obtain the periodic solutions of conservative systems. It is shown that by this approach, periodic solutions of conservative systems on iso-energy manifolds in the phase space can be obtained very efficiently. The energy level provides the additional constraint on the HBM formulation, which enables the determination of the period of the solutions. The method is applied to the linear harmonic oscillator, a couple of nonlinear oscillators, the elastic pendulum and the Henon-Heiles system. The approach is used to trace the bifurcations of the periodic solutions of the last two, being 2 degree-of-freedom systems demonstrating very rich dynamical behavior. In the process, the advantages offered by the current formulation of the energy balance is brought out. A harmonic perturbation approach is used to evaluate the stability of the solutions for the bifurcation diagram.

Blast Mitigation Using Water - A Status Report

National Research Council Canada - National Science Library

Kailasanath, K

2002-01-01

..., and aggressive research and development', this report reviews the current knowledge base on blast mitigation using water and identifies the key issues that need to be resolved in order to develop...

Seeding High Gain Harmonic Generation with Laser Harmonics produced in Gases

CERN Document Server

Lambert, Guillaume; Couprie, Marie Emmanuelle; Garzella, David; Doria, Andrea; Giannessi, Luca; Hara, Toru; Kitamura, Hideo; Shintake, Tsumoru

2004-01-01

Free electron Lasers employing High Gain Harmonic generation (HGHG) schemes are very promising coherent ligth sources for the soft X-ray regime. They offer both transverse and longitudinal coherence, while Self Amplified Spontaneous Emission schemes have a longitudinal coherence limited. We propose here to seed HGHG with high harmonics produced by a Ti:Sa femtosecond laser focused on a gas jet, tuneable in the 100-10 nm spectral region. Specifities concerning the implementation of this particular laser source as a seed for HGHG are investigated. Semi analytical , numerical 1D and 3D calculations are given, for the cases of the SCSS, SPARC and ARC-EN-CIEL projects.

Recent progress of below-threshold harmonic generation

International Nuclear Information System (INIS)

Xiong, Wei-Hao; Peng, Liang-You; Gong, Qihuang

2017-01-01

The harmonics generated from the interaction of a strong laser field with atoms and molecules in the gas phase can be applied as coherent light sources and detecting techniques for structures and dynamics in matter. In the last three decades, the most prevailing experimental and theoretical studies have been focused on the high-order harmonic generation due to its applications in attosecond science. However, low-order harmonics near the ionization threshold of the target have been less explored, partially because the spectrum in this region is more complicated from both the theoretical and experimental point of view. After several pioneering investigations in the mid 1990s, near threshold harmonics (NTHs) begun to draw a great attention again because of the development of high repetition rate cavity enhanced harmonics about 10 years ago. Very recently, NTHs have attracted a lot of experimental and theoretical studies due to their potential applications as light sources and complicated mechanisms. In this topical review, we will summarize the progress of NTHs, including the early and recent experimental measurements in atoms and molecules, as well as the relevant theoretical explorations of these harmonics. (topical review)

Harmonic generation with a dual frequency pulse.

Science.gov (United States)

Keravnou, Christina P; Averkiou, Michalakis A

2014-05-01

Nonlinear imaging was implemented in commercial ultrasound systems over the last 15 years offering major advantages in many clinical applications. In this work, pulsing schemes coupled with a dual frequency pulse are presented. The pulsing schemes considered were pulse inversion, power modulation, and power modulated pulse inversion. The pulse contains a fundamental frequency f and a specified amount of its second harmonic 2f. The advantages and limitations of this method were evaluated with both acoustic measurements of harmonic generation and theoretical simulations based on the KZK equation. The use of two frequencies in a pulse results in the generation of the sum and difference frequency components in addition to the other harmonic components. While with single frequency pulses, only power modulation and power modulated pulse inversion contained odd harmonic components, with the dual frequency pulse, pulse inversion now also contains odd harmonic components.

A DC to 3-phase series-resonant converter with low harmonic distortion

NARCIS (Netherlands)

Huisman, H.; Haan, de S.W.H.

1985-01-01

A type of dc to 3-phase series-resonant converter (s.r.converter) or potentially submegawatt industrial applications is presented. The converter provides variable-frequency sine-wave currents, with low harmonic distortion at the output terminals, and with the frequency ranging from -200 through dc

Harmonic and geometric analysis

CERN Document Server

Citti, Giovanna; Pérez, Carlos; Sarti, Alessandro; Zhong, Xiao

2015-01-01

This book presents an expanded version of four series of lectures delivered by the authors at the CRM. Harmonic analysis, understood in a broad sense, has a very wide interplay with partial differential equations and in particular with the theory of quasiconformal mappings and its applications. Some areas in which real analysis has been extremely influential are PDE's and geometric analysis. Their foundations and subsequent developments made extensive use of the Calderón–Zygmund theory, especially the Lp inequalities for Calderón–Zygmund operators (Beurling transform and Riesz transform, among others) and the theory of Muckenhoupt weights.  The first chapter is an application of harmonic analysis and the Heisenberg group to understanding human vision, while the second and third chapters cover some of the main topics on linear and multilinear harmonic analysis. The last serves as a comprehensive introduction to a deep result from De Giorgi, Moser and Nash on the regularity of elliptic partial differen...

Harmonization versus Mutual Recognition

DEFF Research Database (Denmark)

Jørgensen, Jan Guldager; Schröder, Philipp

The present paper examines trade liberalization driven by the coordination of product standards. For oligopolistic firms situated in separate markets that are initially sheltered by national standards, mutual recognition of standards implies entry and reduced profits at home paired with the oppor......The present paper examines trade liberalization driven by the coordination of product standards. For oligopolistic firms situated in separate markets that are initially sheltered by national standards, mutual recognition of standards implies entry and reduced profits at home paired...... countries and three firms, where firms first lobby for the policy coordination regime (harmonization versus mutual recognition), and subsequently, in case of harmonization, the global standard is auctioned among the firms. We discuss welfare effects and conclude with policy implications. In particular......, harmonized standards may fail to harvest the full pro-competitive effects from trade liberalization compared to mutual recognition; moreover, the issue is most pronounced in markets featuring price competition....

Contribution in the area of harmonics in electric power systems; Contribuicoes na area de harmonicos em sistemas eletricos de potencia

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Aloisio de

1989-07-01

A general approach of the state of art of the harmonic generation, its sources, its limits, its measurement methods and its effects on the electric system components is presented. This thesis shows that this is an open field to research, modelling and solutions. It also helps towards the investigation of the effects caused by harmonics on the conventional KWh energy meters and on potential and current transformers. It presents the basis for the development and construction of prototypes to be utilized in the generation and measurement of harmonics. Finally a practical approach has been given to calculate the equivalent harmonic impedance as seen by a giving consumer. (author)

Extended blackout mitigation strategy for PWR

International Nuclear Information System (INIS)

Prošek, Andrej; Volkanovski, Andrija

2015-01-01

Highlights: • Equipment for mitigation of the extended blackout is investigated. • Analysis is done with deterministic safety analysis methods. • Strategy to prevent core heatup and not overfill steam generator is proposed. • Six types of reactor coolant system loss scenarios are investigated. • Pump flowrates and available start time to feed steam generators is determined. - Abstract: The accident at the Fukushima Daiichi nuclear power plant demonstrated the vulnerability of the plants on the loss of electrical power and loss of the ultimate heat sink events. A set of measures are proposed and currently implemented in response of the accident at the Fukushima Daiichi nuclear power plant. Those measures include diverse and flexible mitigation strategies that increase the defence-in-depth for beyond-design-basis scenarios. Mitigation strategies are based on the utilization of the portable equipment to provide power and water to the nuclear power plants in order to maintain or restore key safety functions. The verification of the proposed measures with the plant specific safety analyses is endorsed in the mitigation strategies. This paper investigates utilization of the turbine driven auxiliary feedwater pump (TD-AFW) or portable water injection pump for the mitigation of the event of loss of all alternate current sources and batteries (extended station blackout). Methodology for assessment of the required pump injection flow rate with the application of the standard deterministic safety analysis code is developed and presented. The required injection rate to the steam generators is calculated from the cumulative water mass injected by the turbine driven auxiliary feedwater pump in the analysed scenarios, when desired normal level is maintained automatically. The developed methodology allows assessment of the required injections rates of pump, TD-AFW or portable, for different plant configurations and number of flow rate changes. The methodology is applied

Extended blackout mitigation strategy for PWR

Energy Technology Data Exchange (ETDEWEB)

Prošek, Andrej, E-mail: andrej.prosek@ijs.si; Volkanovski, Andrija, E-mail: andrija.volkanovski@ijs.si

2015-12-15

Highlights: • Equipment for mitigation of the extended blackout is investigated. • Analysis is done with deterministic safety analysis methods. • Strategy to prevent core heatup and not overfill steam generator is proposed. • Six types of reactor coolant system loss scenarios are investigated. • Pump flowrates and available start time to feed steam generators is determined. - Abstract: The accident at the Fukushima Daiichi nuclear power plant demonstrated the vulnerability of the plants on the loss of electrical power and loss of the ultimate heat sink events. A set of measures are proposed and currently implemented in response of the accident at the Fukushima Daiichi nuclear power plant. Those measures include diverse and flexible mitigation strategies that increase the defence-in-depth for beyond-design-basis scenarios. Mitigation strategies are based on the utilization of the portable equipment to provide power and water to the nuclear power plants in order to maintain or restore key safety functions. The verification of the proposed measures with the plant specific safety analyses is endorsed in the mitigation strategies. This paper investigates utilization of the turbine driven auxiliary feedwater pump (TD-AFW) or portable water injection pump for the mitigation of the event of loss of all alternate current sources and batteries (extended station blackout). Methodology for assessment of the required pump injection flow rate with the application of the standard deterministic safety analysis code is developed and presented. The required injection rate to the steam generators is calculated from the cumulative water mass injected by the turbine driven auxiliary feedwater pump in the analysed scenarios, when desired normal level is maintained automatically. The developed methodology allows assessment of the required injections rates of pump, TD-AFW or portable, for different plant configurations and number of flow rate changes. The methodology is applied

Beam dynamics in CIME for third harmonic

International Nuclear Information System (INIS)

Chautard, F.; Bourgarel, M.P.

2000-01-01

This report presents the results from simulations for beam dynamics in CIME third harmonics. Details are given regarding the procedures to reach the adaptation at the inflector exit. The aim of these simulation is to determine, for any given ion, the beam correlations at the inflector exit as well as the current values in the isochronous coils for all the field levels. Although not all the steps of the simulation are thoroughly displayed, the report gathers all the the elements necessary for CIME control. Information useful for controlling the Very Low Energy line, the main field and the isochronous coils are also presented. The report has the following content: I. Introduction. II. The field maps and the used codes. A. The maps of CIME magnetic fields; B. The 3D map of CIME electric potentials; C. The maps of 3D electric potentials in the CIME central region; D. Code LIONS and sorting codes. III. Central region. A. An outlook. B.Central rays; IV. Determination of beam correlations. A. Analytical calculation of adaptation conditions; B. Calculation of adaptation conditions based on particle distributions; C. Creating the beam matrices. D. Calculation method for inverse return correlations. V. Results of simulations. VI. Interpolation of isochronous coils at the referential frequency. VII. The interpolation code PARAM. VIII. Conclusions. The paper is supplemented by 4 appendices. The harmonics 2, 4 and 5 are currently under way and the results will be reported in a future paper

The rate of plasma heating by harmonic ion cyclotron waves in tokamaks

International Nuclear Information System (INIS)

Moslehi-Fard, M.; Sobhanian, S.; Solati-Kia, F.

2002-01-01

In tokamaks, the toroidal magnetic field, B φ , is due to the current in coils around plasma, and the poloidal magnetic field B p results from the plasma itself. Usually B φ p , and the combination of these two fields forms a nested set of toroidal magnetic surfaces. The equilibrium Grad-Shafranov equation is investigated and it is shown that the particle products of fusion with different pitch angles on these surfaces have different orbital shapes. In the JET tokamak, the α particles with pitch angle θ smaller than 54.8 deg are passing, those with θ between 54.8 deg and 65.1 deg have trapping-passing orbits but for θ greater than 65.1 deg the orbit has a banana form. Other tokamaks such as Alcator and ITER are also considered. The passing, trapping-passing and banana orbits in these tokamaks are traced. The results obtained from this calculation are analyzed. The wave damping has been investigated produced from interaction with particles, particularly α particles, and the rate of heating for l = 1 to 8 harmonics is plotted. The results of calculation show that heating at the fourth harmonic reaches a maximum. For higher harmonics, the heating does not change much from the fourth harmonic. (author)

Challenges in Implementing Emission Mitigation Technologies in Indonesia Agricultural Sector: Criticizing the Available Mitigation Technologies

Directory of Open Access Journals (Sweden)

Malahayati Marissa

2018-03-01

Full Text Available Reduction of Green House Gas (GHG emissions in the agricultural sector is the main target for reducing non-CO2 emissions. In Indonesia, the agricultural sector is the third largest GHG emitter, far behind that from Land Use Change and Forestry (LUCF and the energy sector. However, the agricultural sector is the biggest contributor of non-CO2 emissions and is also the most vulnerable sector to climate change. The Indonesian government is committed to reduce total emission inform current levels by 29% by 2030 under Nationally Determined Contribution (NDC. This will require reductions in emissions from all sectors including agriculture. Several mitigation technologies have been recommended by UNFCCC for implementation such as replacing urea with ammonium sulfate fertilizer; replacing nitrogen fertilizer with multicontent fertilizer; water irrigation management; replacing roughage with concentrate as livestock feed; and building biogas digesters. From our Computer General Equilibrium (CGE simulation, if the focus of mitigation technology implementation in agriculture is to reduce non-CO2 emissions gases such as CH4 and N2O, then a comprehensive approach is needed. If the government implements the technology partially, we predict there will be a trade-off between CH4 and N2O emission. However, our simulation shows the loss to GDP caused by a new emission mitigation policy is very high even though Indonesia has invested for mitigation technology in agriculture. This is because we consider the additional investment needed will be costly and some technologies may not be suitable for implementation in Indonesia. In this research, we review current literature and examine each technology and its cost and compatibility with Indonesian situations in order to make policy recommendations for implementation by the Indonesia government.

A current detection based on an extension of the Prony's method

Energy Technology Data Exchange (ETDEWEB)

Deng, C.; Xia, X.; Gong, F. [Changsha Univ. of Science and Technology, Changsha (China). College of Electrical Engineering

2009-07-01

The Prony method for spectrum estimation was combined with an adaptive frequency tracking and current frequency demultiplication method as a harmonic detection system. An injective active power filter was used for effective harmonic wave management. The automated system includes a digital signal processor and a high-speed interfacing device. An algorithm was developed to consider the slow voltage changes in the power grid as well as potential mutations in current harmonics. Widrow-Hoff's LMS algorithm was used to develop rolling steps for the filter. The method was used to detect harmonic waves with a sampling frequency of 400 Hz. Results of the study showed that the detection method can be used in real time to detect fundamental and first harmonics in electric power grids. 10 refs., 2 tabs., 1 fig.

Two examples of escaping harmonic maps

International Nuclear Information System (INIS)

Pereira do Valle, A.; Verjovsky, A.

1988-12-01

This paper is part of a study on the existence of special harmonic maps on complete non-compact Riemannian manifolds. We generalize the notion of escaping geodesic and prove some results on the existence of escaping harmonic maps. 11 refs, 6 figs

Financial Impact of Cancer Drug Wastage and Potential Cost Savings From Mitigation Strategies.

Science.gov (United States)

Leung, Caitlyn Y W; Cheung, Matthew C; Charbonneau, Lauren F; Prica, Anca; Ng, Pamela; Chan, Kelvin K W

2017-07-01

Cancer drug wastage occurs when a parenteral drug within a fixed vial is not administered fully to a patient. This study investigated the extent of drug wastage, the financial impact on the hospital budget, and the cost savings associated with current mitigation strategies. We conducted a cross-sectional study in three University of Toronto-affiliated hospitals of various sizes. We recorded the actual amount of drug wasted over a 2-week period while using current mitigation strategies. Single-dose vial cancer drugs with the highest wastage potentials were identified (14 drugs). To calculate the hypothetical drug wastage with no mitigation strategies, we determined how many vials of drugs would be needed to fill a single prescription. The total drug costs over the 2 weeks ranged from $50,257 to $716,983 in the three institutions. With existing mitigation strategies, the actual drug wastage over the 2 weeks ranged from $928 to $5,472, which was approximately 1% to 2% of the total drug costs. In the hypothetical model with no mitigation strategies implemented, the projected drug cost wastage would have been $11,232 to $149,131, which accounted for 16% to 18% of the total drug costs. As a result, the potential annual savings while using current mitigation strategies range from 15% to 17%. The financial impact of drug wastage is substantial. Mitigation strategies lead to substantial cost savings, with the opportunity to reinvest those savings. More research is needed to determine the appropriate methods to minimize risk to patients while using the cost-saving mitigation strategies.

Demonstration and Validation of a Waste-to-Energy Conversion System for Fixed DoD Installations

Science.gov (United States)

2013-09-01

equipment replacement costs. Mixed Result. Single point failures were observed, but were determined to be feedstock specific. Mitigation strategies have...40 kWe net electric output. Power quality Variations in voltage, frequency, flicker , harmonics, power factor and direct current injection...replacement costs. Mixed Result. Single point failures were observed, but were determined to be feedstock specific. Mitigation strategies have

Three phase active power filter with selective harmonics elimination

Directory of Open Access Journals (Sweden)

Sozański Krzysztof

2016-03-01

Full Text Available This paper describes a three phase shunt active power filter with selective harmonics elimination. The control algorithm is based on a digital filter bank. The moving Discrete Fourier Transformation is used as an analysis filter bank. The correctness of the algorithm has been verified by simulation and experimental research. The paper includes exemplary results of current waveforms and their spectra from a three phase active power filter.

PROTECTION OF HOUSEHOLD APPLIANCES INDUCTION MOTORS AGAINST OVERCURRENT TAKING INTO ACCOUNT NONLINEAR DISTORTION OF PHASE CURRENT

Directory of Open Access Journals (Sweden)

A.G. Sereda

2015-06-01

Full Text Available Purpose. Theoretical justification and engineering of induction motors heat protection method from overload currents taking into account nonlinear distortion of the phase current and implementation as a microprocessor device functioning algorithm. Methodology. To solve the problem used the theory of the representing complex harmonic oscillations analog signals expansion into the oscillation spectrum forming elementary harmonic components in order to compare their properties by applying the theory of discrete signals and systems, as well as methods of spectral analysis and discrete signals filtering. The harmonic analysis versatility is that any periodic signal may be synthesized from harmonic oscillation of certain amplitude, frequency and initial phase. A mathematical model for determining the phase current harmonic content of power supply networks with isolated neutral and non-linear loads types and, as a consequence, the distortion of sinusoidal phase current change is developed by multiplying the analog current in time dependency on the grate delta-function with different sampling intervals, in which the use of simple and widely used in relay protection units, in particular electronic overcurrent relays, mathematical operations of integration squares instantaneous current allows the most in harmony with the mathematical tools to build other network protection types. Findings. The necessity to increase the sensitivity of the induction motors heat protection from overload currents taking into account nonlinear distortion of the phase currents is proved. By nonlinear distortion harmonic analysis of the phase currents the motor protection reliability increasing provided by taking into account the higher harmonic components of the phase currents, which causes to additional losses and heating of the stator winding. It uses the simplest and widely used in protective relaying mathematical apparatus determining of most significant higher harmonics

Harmonic calculation software for industrial applications with ASDs

DEFF Research Database (Denmark)

Blaabjerg, Frede; Asiminoaei, Lucian; Hansen, Steffan

2007-01-01

This article describes the evaluation of new harmonic calculation software. By using a combination of a prestored database and new interpolation techniques the software can provide the harmonic data on real applications of a very fast speed. The harmonic results obtained with this software have a...

Audibility of high harmonics in a periodic pulse

NARCIS (Netherlands)

Duifhuis, H.

1970-01-01

A periodic pulse consisting of sufficiently narrow pulses has a frequency spectrum which contains all harmonics with equal amplitude. Owing to the limited resolving power of the hearing organ, only the low harmonics can be perceived separately. The high harmonics are heard together as one complex

Mitigation of commutation failures in LCC–HVDC systems based on superconducting fault current limiters

Energy Technology Data Exchange (ETDEWEB)

Lee, Jong-Geon; Khan, Umer Amir; Lee, Ho-Yun; Lim, Sung-Woo; Lee, Bang-Wook, E-mail: bangwook@hanyang.ac.kr

2016-11-15

Commutation failure in line commutated converter based HVDC systems cause severe damages on the entire power grid system. For LCC–HVDC, thyristor valves are turned on by a firing signal but turn off control is governed by the external applied AC voltage from surrounding network. When the fault occurs in AC system, turn-off control of thyristor valves is unavailable due to the voltage collapse of point of common coupling (PCC), which causes the commutation failure in LCC–HVDC link. Due to the commutation failure, the power transfer interruption, dc voltage drop and severe voltage fluctuation in the AC system could be occurred. In a severe situation, it might cause the protection system to block the valves. In this paper, as a solution to prevent the voltage collapse on PCC and to limit the fault current, the application study of resistive superconducting fault current limiter (SFCL) on LCC–HVDC grid system was performed with mathematical and simulation analyses. The simulation model was designed by Matlab/Simulink considering Haenam-Jeju HVDC power grid in Korea which includes conventional AC system and onshore wind farm and resistive SFCL model. From the result, it was observed that the application of SFCL on LCC–HVDC system is an effective solution to mitigate the commutation failure. And then the process to determine optimum quench resistance of SFCL which enables the recovery of commutation failure was deeply investigated.

Mitigation of commutation failures in LCC–HVDC systems based on superconducting fault current limiters

International Nuclear Information System (INIS)

Lee, Jong-Geon; Khan, Umer Amir; Lee, Ho-Yun; Lim, Sung-Woo; Lee, Bang-Wook

2016-01-01

Commutation failure in line commutated converter based HVDC systems cause severe damages on the entire power grid system. For LCC–HVDC, thyristor valves are turned on by a firing signal but turn off control is governed by the external applied AC voltage from surrounding network. When the fault occurs in AC system, turn-off control of thyristor valves is unavailable due to the voltage collapse of point of common coupling (PCC), which causes the commutation failure in LCC–HVDC link. Due to the commutation failure, the power transfer interruption, dc voltage drop and severe voltage fluctuation in the AC system could be occurred. In a severe situation, it might cause the protection system to block the valves. In this paper, as a solution to prevent the voltage collapse on PCC and to limit the fault current, the application study of resistive superconducting fault current limiter (SFCL) on LCC–HVDC grid system was performed with mathematical and simulation analyses. The simulation model was designed by Matlab/Simulink considering Haenam-Jeju HVDC power grid in Korea which includes conventional AC system and onshore wind farm and resistive SFCL model. From the result, it was observed that the application of SFCL on LCC–HVDC system is an effective solution to mitigate the commutation failure. And then the process to determine optimum quench resistance of SFCL which enables the recovery of commutation failure was deeply investigated.

Mitigation of commutation failures in LCC-HVDC systems based on superconducting fault current limiters

Science.gov (United States)

Lee, Jong-Geon; Khan, Umer Amir; Lee, Ho-Yun; Lim, Sung-Woo; Lee, Bang-Wook

2016-11-01

Commutation failure in line commutated converter based HVDC systems cause severe damages on the entire power grid system. For LCC-HVDC, thyristor valves are turned on by a firing signal but turn off control is governed by the external applied AC voltage from surrounding network. When the fault occurs in AC system, turn-off control of thyristor valves is unavailable due to the voltage collapse of point of common coupling (PCC), which causes the commutation failure in LCC-HVDC link. Due to the commutation failure, the power transfer interruption, dc voltage drop and severe voltage fluctuation in the AC system could be occurred. In a severe situation, it might cause the protection system to block the valves. In this paper, as a solution to prevent the voltage collapse on PCC and to limit the fault current, the application study of resistive superconducting fault current limiter (SFCL) on LCC-HVDC grid system was performed with mathematical and simulation analyses. The simulation model was designed by Matlab/Simulink considering Haenam-Jeju HVDC power grid in Korea which includes conventional AC system and onshore wind farm and resistive SFCL model. From the result, it was observed that the application of SFCL on LCC-HVDC system is an effective solution to mitigate the commutation failure. And then the process to determine optimum quench resistance of SFCL which enables the recovery of commutation failure was deeply investigated.

Enhancement of harmonic generation using a two section undulator

International Nuclear Information System (INIS)

Prazeres, R.; Glotin, F.; Jaroszynski, D.A.; Ortega, J.M.; Rippon, C.

1999-01-01

Enhancement of the 2nd and 3rd harmonic of the wavelength of a Free-Electron Laser (FEL) has been measured when a single electron beam is crossing a two-section undulator. To produce the harmonic radiation enhancement, the undulator is arranged so that the resonance wavelength of the 2nd undulator (downstream) matches a harmonic of the 1st undulator (upstream). Both the fundamental and the harmonic optical fields evolve in the same optical cavity and are coupled out with different extraction efficiency, through a hole in one of the cavity mirrors. We present measurements that show that the optical power at the 2nd and 3rd harmonic can be enhanced, by about one order of magnitude, in two configurations: when the resonance wavelength of the 2nd undulator matches the harmonic of 1st one (harmonic configuration), or when the gap of the 2nd undulator is slightly larger than first one (step-tapered configuration). We examine the dependence of the harmonic power on the gap of the 2nd undulator. This fundamental/harmonic mode of operation of the FEL may have useful applications in the production of coherent X-ray and VUV radiation, a spectral range where high reflectivity optical cavity mirrors are difficult or impossible to manufacture

Effects of harmonic roving on pitch discrimination

DEFF Research Database (Denmark)

Santurette, Sébastien; de Kérangal, Mathilde le Gal; Joshi, Suyash Narendra

2015-01-01

Performance in pitch discrimination tasks is limited by variability intrinsic to listeners which may arise from peripheral auditory coding limitations or more central noise sources. The present study aimed at quantifying such “internal noise” by estimating the amount of harmonic roving required...... to impair pitch discrimination performance. Fundamental-frequency difference limens (F0DLs) were obtained in normal-hearing listeners with and without musical training for complex tones filtered between 1.5 and 3.5 kHz with F0s of 300 Hz (resolved harmonics) and 75 Hz (unresolved harmonics). The harmonicity...... that could be used to quantify the internal noise and provide strong constraints for physiologically inspired models of pitch perception....