The Control Strategies of Modular Multilevel Converter-High Voltage Direct Current Transmission under Unbalanced Grid Voltage Conditions
Zhang Jianpo1, Li Naixin2, Tian Xincheng2
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding 071001 China; 2. State Grid Tangshan Power Corporation Tangshan 063000 China
Abstract:Under unbalanced grid conditions, the power characteristics of high voltage direct current transmission based on modular multilevel converter (MMC-HVDC) are analyzed. In order to control the positive and negative sequence currents uniformly, a composite controller combing proportional integer with quasi resonant current controller is introduced as the synchronous rotational reference frame. Thus, the current sequences extraction can be avoided. The control strategies for eliminating the negative sequence current and active power ripples are studied, and the voltage dependent current order limiter (VDCOL) is also designed according to the voltage drop and imbalance indicator. Features of leg circulating current are analyzed, and accordingly the circulating current suppressor is designed to reduce the additional power loss. At last, the simulation model is built in PSCAD/EMTDC. The effectiveness and feasibility of these proposed control strategies are verified.
张建坡, 李耐心, 田新成. 电网电压不平衡条件下模块化多电平换流器高压直流输电控制策略[J]. 电工技术学报, 2016, 31(22): 205-212.
Zhang Jianpo, Li Naixin, Tian Xincheng. The Control Strategies of Modular Multilevel Converter-High Voltage Direct Current Transmission under Unbalanced Grid Voltage Conditions. Transactions of China Electrotechnical Society, 2016, 31(22): 205-212.
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