volume | PIER Journals

Abstract

To address output current over-limit issues, power oscillations, and degraded transient stability in virtual synchronous generators (VSGs) under asymmetric faults, this paper proposes a variable-weight virtual-impedance-based current balancing control strategy for quasi-Z-source inverter-based VSG (qZSI-VSG) systems. First, a detailed mathematical model of the qZSI-VSG is established to analyze the influence of key parameters on the system's dynamic behavior. By leveraging the VSG operating characteristics in the dq reference frame, a negative-sequence current reference generation method is subsequently developed to effectively suppress negative-sequence components under various unbalanced grid conditions. In addition, a PI controller is introduced to regulate active and reactive power deviations, enabling online calculation of adaptive weighting factors for real-time adjustment of the virtual impedance. This mechanism improves both current balancing performance and transient response. Experimental results verify that the proposed strategy can significantly reduce negative-sequence currents and power oscillations, thereby enhancing the transient stability of the system during asymmetric faults and demonstrating its feasibility and effectiveness.

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Dr. Yang Zhang

Dr. Dingai Zhong

Dr. Xiuhai Yang

Dr. Wei Zhang

Dr. Ziquan Wei

Dr. Zhun Cheng