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Liu P.,Xian Jiaotong University | Wang Y.,Xian Jiaotong University | Lei W.,Xian Jiaotong University | Yao W.,Xuji Flexible Transmission System Corporation
Dianwang Jishu/Power System Technology | Year: 2015

There are such defects as too much states to be predicted, heavy burden of calculated amount and unable to be implemented by existing processors in the model prediction control for modular multilevel converters (MMC). Combining with sub-modules capacitor voltage sorting strategy, an optimized model predictive control (OMPC) strategy is proposed, thus the calculated amount of model predictive control (MPC) algorithm is evidently reduced and it comes true to apply this algorithm in MMC. A simulation and experimental platform for 23-level MMC is constructed and compared with frequently used closed-loop vector control strategy based on cascaded proportion integration (PI) controller, and the comparison results show that the proposed control strategy is of feasibility and superiority. ©, 2015, Power System Technology Press. All right reserved. Source


Liu P.,Xian Jiaotong University | Wang Y.,Xian Jiaotong University | Lei W.,Xian Jiaotong University | Yao W.,Xuji Flexible Transmission System Corporation
Dianwang Jishu/Power System Technology | Year: 2015

Arm reactor is an important part of the modular multilevel converter (MMC) and its parameter designing is critical for stable operation of the converter. Beginning with the analysis of harmonic current, by analyzing the structure and working principle of the converter, the constraint relationship between circulating current amplitude and arm reactance was deduced in detail, and then the system general matrix equation was obtained. Based on the above analysis, this paper proposes an arm reactor parameter designing method which can avoid system resonance, meet the requirements of system power transmission and circulating current. Take Zhoushan flexible HVDC project for example, the simulation results based on Matlab/Simlink verify the proposed design method is feasible. ©, 2015, Power System Technology Press. All right reserved. Source


Yi Y.,University of Shanghai for Science and Technology | Luo H.,University of Shanghai for Science and Technology | Hu S.,Xuji Flexible Transmission System Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2016

In order to reduce line-side current harmonic caused by switching frequency and achieve electrical isolation, a grid-connected inverter with a T filter and an isolation transformer is used. To make up for the shortcomings of independent PI control of current and low response rate of traditional current-SPWM control, the method of current-SPWM control of tracking current momentary value with PI control of current and voltage feed-forward is presented. With the analysis of control principle of grid-connected inverter, control model of the grid-connected inverter is designed, transfer functions of every control link are derived and PI parameters are designed. At last, the Matlab simulation results show that the control strategy is feasible. © 2016, Power System Protection and Control Press. All right reserved. Source


Yi Y.-P.,University of Shanghai for Science and Technology | Liu G.,Xuji Flexible Transmission System Corporation | Hu S.-Q.,Xuji Flexible Transmission System Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

This paper presents that using three-level grid-connected technology to study renewable energy generation high-voltage grid-connected converter, introduces the topological structure of main circuit of three-level grid-connected converter, and studies the parameters selection of main circuit. The design methods of the IGBT, clamped diode and DC bus capacitor in the main circuit are given. The paper uses LCL filter to restrain the harmonics injected into power system, and analyses the principle and filter characteristics and builds the mathematic model of the LCL filter. On these basis, experimental circuit of 20 kW three-level grid-connected converter is designed, and experimental results prove the correctness and practicability of the design method. Source


Liu P.,Xian Jiaotong University | Wang Y.,Xian Jiaotong University | Lei W.,Xian Jiaotong University | Yao W.,Xuji Flexible Transmission System Corporation
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2015

Considering all the harmonic components for the arm current, this paper proposes a new steady-state operation characteristic analysis method for the modular multilevel converter(MMC). Based on the analysis of the coupling relationship among the internal electric variables of MMC, the general matrix equation of the system is derived and the analytical expression of the arm current, submodule capacitor voltage and circulating current is obtained, and then the operation law of these variables is concluded. The calculation process is relatively simpler and the analysis results are more accurate with this method. The simulation and experimental results based on 23-level MMC back-to-back platform are compared to the analytical results, respectively. It verifies that the proposed method is feasible and accurate. ©, 2015, Chinese Machine Press. All right reserved. Source

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