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Sui L.-D.,Shanghai JiaoTong University | Zheng Y.-H.,Shanghai JiaoTong University | Wang X.,Shanghai JiaoTong University | Li L.-X.,Shanghai JiaoTong University | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

In order to lower the switching losses and reduce the harmonic content of the cascade SVG, the method of PAM+PWM is introduced. Four H bridges constitute the PAM unit, every H bridge works under the fundamental frequency, so the switching losses are low. One H bridge constitutes the PWM unit, the PWM unit can compensate the harmonic content of the output step waveform of the PAM unit, it can greatly reduce the voltage and current distortion factor and improve the power quality. The pulse cycle transposition is used on the DC side, it can effectively solve the problem of the DC capacitors voltage unbalance of the PAM unit. The PWM unit outputs the reactive current by the current direct control method, it can improve control accuracy and response speed of the device. The model of SVG with chain inverter is built in Matlab/Simulink, the result proves the validity of the method. Source


Zhou C.,Shanghai JiaoTong University | Zheng Y.,Shanghai JiaoTong University | Wang X.,Shanghai JiaoTong University | Li L.,Shanghai JiaoTong University | And 2 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2014

An analysis model is established aiming at the inaccuracy of split-capacitor-type three-phase-four-wire DSTATCOM used in the reactive power compensation for unbalanced load and its control strategy based on dual-loop controller is proposed aiming at the poor periodic signal tracking of the traditional PI controller. It combines the PI controller, which has quick response to instruction, with the repetitive controller, which has high accuracy of periodic signal control, and applies the dual-loop controller in the inner current loop of DSTATCOM to track the current. The design of the controller is analyzed in detail and verified by simulation and experiment. Results indicate that, the split-capacitor-type three-phase-four-wire DSTATCOM controlled by the proposed strategy has better compensation effect than by the traditional PI control method, guarantees the response speed, improves the accuracy of current tracking, achieves the reactive power compensation for the unbalanced load, reduces output current and THD, and improves the quality of grid-connection current. Source


Li G.,Northeast Dianli University | Tan L.,Northeast Dianli University | Wang Z.,Northeast Dianli University | Chen H.,Songyuan Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2016

Because the upper and under bridge arm voltage of each phases are inconformity with each other based on MMC-HVDC, resulting in the internal circulation of converter. Circulation will cause each phase converter arm current distortion, so it is important to suppress the circulation. The usual method for inhibition circulation inhibits the internal circulation of converter under the normal operation condition. Firstly, it analyzes the method of inhibiting circulation under normal circumstances. Then, it focuses on the effects of unbalanced current under fault condition on the internal circulation and DC current through the AC system single-phase ground fault analysis and designs the additional controller to improve the traditional inhibition circulation strategy under fault conditions. Finally, it verifies the feasibility of theoretical analysis and improvement measures through the PSCAD/EMTDC simulation experiments. © 2016, Power System Protection and Control Press. All right reserved. Source


Li K.,Shanghai JiaoTong University | Zheng Y.H.,Shanghai JiaoTong University | Wang X.,Shanghai JiaoTong University | Li L.X.,Shanghai JiaoTong University | And 2 more authors.
Applied Mechanics and Materials | Year: 2014

To realize the STATCOM based on Modular Multilevel Converter (MMC), a simplified double-closed loop structure, simplifying from the control method of High Voltage Direct Current (HVDC) based on MMC, is presented. ConsideringMMC's DC side using capacitors, a part-controlling method based on energy balancing is proposed, to solve the voltage balancing problem. With the part-controlling fixing thechanging capacitors'voltage and the simplified double-closed loop control method, voltage fluctuation could be reduced, and the load's reactive power could be compensated. The correctness and the effectiveness of the MMC-STATCOM controllingscheme is verified by Matlab/Simulink. © (2014) Trans Tech Publications, Switzerland. Source


Zhang Y.L.,Shanghai JiaoTong University | Zheng Y.H.,Shanghai JiaoTong University | Li L.X.,Shanghai JiaoTong University | Wang X.,Shanghai JiaoTong University | And 2 more authors.
Applied Mechanics and Materials | Year: 2014

With GIS being widely used, partial discharge detecting and defect pattern recognition become more and more meaningful and important. To realize defects identification of partial discharge map in GIS, a novel method based on Radical Basis Function (RBF) neural network is proposed. Firstly, a model is constructed to simulate the discharge pattern map by the use of random function randint. Secondly, based on the model above, a lot of data which meet the condition can be collected to provide for pattern recognition. Then, a RBF network is introduced to identify the pattern recognition. It can be trained by using the data above. Finally, through changing training error, high correct rate can be got. These indicate that the method is effective. © (2014) Trans Tech Publications, Switzerland. Source

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