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Zhang Y.,CAS Institute of Electrical Engineering | Zhang Y.,Chinese Academy of Sciences | Hu S.,CAS Institute of Electrical Engineering | Dong Z.,Beijing Corona Technology Co. | Zhao B.,CAS Institute of Electrical Engineering
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

Compared with permanent magnet synchronous generator, electrical excited synchronous generator has the advantage of adjustable excitation. This paper presents an excitation control scheme which can regulate the stator voltage under variable speed operation situation. The RMS stator voltage and the rotate speed of the generator are obtained through a software phase-locked loop, and a PI regulator is used to control the stator voltage tracking the speed-votage curve. As the DC voltage is controlled constant in the converter topology, a set of excitation controller based on the chopper circuit is designed. It can meet the demand for automatic de-excitation without extra equipment. The proposed control algorithm and structure was simulated in the Matlab software platform and tested with the 1.5 MW synchronous generator. The simulation and experimental results show that the excitation control scheme is simple and reliable, with high rapid response capability and good effect of steady state control. Source


Huang W.,CAS Institute of Electrical Engineering | Huang W.,University of Chinese Academy of Sciences | Huang W.,Chinese Academy of Sciences | Fu X.,Beijing Corona Technology Co. | And 5 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

As a common solid-state switch, the thyristor bidirectional switch can be used in parallel with the back-to-back converter occasions, such as AC-HVDC hybrid transmission and wind turbine low-voltage-ride-through. A new forced turn-off strategy has been proposed, in order to shut down the thyristor immediately. The strategy makes use of DC bus by assigning switch status for IGBT of the converter, according to the direction of current flows through thyristors. Based on the model of second-order oscillation circuit, mathematical relationship of turn-off time and circuit parameters has been derived, while declination of DC voltage during the turn-off process has also been analyzed. Experiment results proved that the strategy can dramatically shorten the turn-off process of thyristor bidirectional switches, to guarantee fast response of the parallel converters. Source


Huang W.-H.,CAS Institute of Electrical Engineering | Huang W.-H.,University of Chinese Academy of Sciences | Huang W.-H.,Chinese Academy of Sciences | Hu S.-J.,CAS Institute of Electrical Engineering | And 5 more authors.
Dianji yu Kongzhi Xuebao/Electric Machines and Control | Year: 2014

This paper discusses the application of dynamic voltage restorers (DVRs) for low voltage ride through (LVRT) of wind turbine generators. In order to enhance the dynamic performance of DVRs, a multiloop plus feedforward control strategy based on resonant regulator is proposed. The grid voltage feedward can limit the overshot of the compensation voltage. The resonant regulator was applied in the voltage loop, in order to achieve zero steady error, and omit the coordinate transformation and the phase-locked loop. In the meanwhile, the discussion for reactive power compensation capability of DVR under normal and faulty condition was also carried out. By categorizing and comparing different compensation strategies, the limitation of reactive power compensation capability for DVR was pointed out. The simulation results in Matlab/SIMULINK shows that the proposed strategy stabilizes the stator voltage quickly and effectively, limits the stator current overshoot, and realizes the LVRT smoothly. Finally, experiment was carried out on a 110kW motor platform. Source


Huang W.,CAS Institute of Electrical Engineering | Huang W.,University of Chinese Academy of Sciences | Huang W.,Chinese Academy of Sciences | Hu S.,CAS Institute of Electrical Engineering | And 5 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

The generating mechanism of circulating currents in parallel three-phase boost rectifiers is analyzed. A model of the circulating current in α-β-0 stationary coordinate system is established. Base on this, the circulating current is classified into three components: common-mode circulating current, differential-mode circulating current and high frequency circulating current. The affecting factors of three components are also revealed. With these understanding, controllers based on proportional and resonant regulators are designed separately for common-mode and differential-mode circulating current. Since rotating transformation and phase detection are eliminated in α-β-0 coordinate system, a simple structure and small computational cost are achieved. Experiments are carried out on a 600 kVA mutual-driving test-bed. The results prove the validity of the analysis and the proposed control strategy. © 2014 State Grid Electric Power Research Institute Press. Source


Huang W.,CAS Institute of Electrical Engineering | Huang W.,University of Chinese Academy of Sciences | Huang W.,Chinese Academy of Sciences | Hu S.,CAS Institute of Electrical Engineering | And 4 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2014

The neutral point clamping (NPC) three-level converters have broad application prospects with megawatt wind turbines. The power losses of the switching devices must be considered in such high-power applications. Practical loss-calculating formulas are derived based on the analysis of the conduction and switching principles of the converters. The difference between the motor-side power converter (MPC) and the grid-side power converter (GPC) in power losses distribution is identified. Combined with the characteristics of wind power, the influence of power fluctuation on efficiency is also analyzed. It is concluded that the efficiency has positive correlation with the converted power. Simulation results of a co-simulation platform using MATLAB/Simulink and GH Bladed show the validity of the analysis. ©2014 State Grid Electric Power Research Institute Press Source

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