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Hongyang Qing,Chunjiang Zhang,Xiuhui Chai,Hao He,Xiaohuan Wang 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6
When a three-phase four-wire grid-connected energy storage inverter is connected to unbalanced or single-phase loads, a large grid-connected harmonic current is generated due to the existence of a zero-sequence channel. A controller design approach for grid-connected harmonic current suppression is proposed based on proportion–integral–repetitive (PI–repetitive) control for a three-level neutral point clamped (3L-NPC) three-phase four-wire inverter. By designing the variable parameters n (gain coeffi cient of the PI controller) and Qs (gain of the repetitive controller), the eff ect of the PI–repetitive controller gain on current harmonic suppression is analyzed using a three-dimensional amplitude gain curve. A simplifi ed impedance model in the d 0-frame for a three-phase four-wire inverter is proposed. Based on the impedance model in the d0-frame, the system stability is analyzed under diff erent PI–repetitive control gains by the generalized Nyquist criterion. Finally, the optimal controller design is obtained by a gain characteristic and system stability analysis. The controller obtained by this harmonic suppression analysis method can simultaneously ensure the best grid-connected current quality of the three-phase four-wireinverter and the dynamic stability of the system. Simulation and experimental results verify the effectiveness and correctness of the proposed controller design approach for grid-connected harmonic current suppression.