Abstract：When the grid voltage is unbalanced, the current and voltage fluctuate greatly, and the unified power quality controller (UPQC) based on modular multilevel converter (MMC) is difficult to adjust power quality with simple PI control. Aiming at the unbalanced operating state of MMC-UPQC in the power grid voltage, this paper proposes a differential flat control (DFBC) method based on positive and negative sequence separation, which can comprehensively manage the power quality problems of voltage and current. Firstly, according to the topology of MMC-UPQC, the mathematical model under unbalanced power grid is established by analyzing the internal characteristics of MMC-UPQC, and the flatness and stability of MMC-UPQC are verified. Then, the detection quantity is separated without phase-locked loop through a method of positive and negative sequence separation. Based on the differential flat control theory, a differential flat controller that combines feedforward reference trajectory and error feedback compensation is built and applied to a multi-level, high-voltage power quality compensation system,which can solve the grid power quality problem under the unbalanced grid voltage. Finally, the experiment verifies the effectiveness and superiority of the MMC-UPQC system based on the proposed differential flat controller in solving the problems of voltage rising, sagging and injected harmonic.
江畅, 程启明, 马信乔, 赵淼圳. 不平衡电网电压下基于模块化多电平变流器的统一电能质量调节器的微分平坦控制[J]. 电工技术学报, 2021, 36(16): 3410-3421.
Jiang Chang, Cheng Qiming, Ma Xinqiao, Zhao Miaozhen. Differential Flat Control for Unified Power Quality Controller Based on Modular Multilevel Converter under Unbalanced Grid Voltage. Transactions of China Electrotechnical Society, 2021, 36(16): 3410-3421.
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2021, Vol. 36 
