Sequence Impedance Modeling and Stability Analysis of Load Converter with Virtual Inertia Control Connected to Weak Grid
Liu Yifeng1, Zhou Xiaoping1, Hong Lerong1, Xia Haitao1, Tian Hao2
1. National Electric Power Conversion and Control Engineering Technology Research Center Hunan University Changsha 410082 China; 2. State Grid Qianjiang Electric Power Company Qianjiang 433100 China
Abstract:Both load virtual synchronous machine (LVSM) and load converter based on DC-link capacitor virtual inertia control (DLCVIC-LC) can enhance the power system inertia. However, inevitably, there are some interaction problems like harmonic resonance in weak grids. In this paper, considering the DC-link voltage dynamics and frequency-coupling effects, the general sequence impedance formulas for three-phase load converters were derived. Then, the precise sequence impedance models were built for impedance characteristics comparison analysis of LVSM and DLCVIC-LC. The analysis shows that the positive-sequence impedance of LVSM is generally inductive, which is basically consistent with the grid impedance characteristics and hardly causes harmonic resonance. In contrast, the positive-sequence impedance of LCVIC is negative-resistive-capacitive (i.e., phase angle is between -180° and -90°) in the middle-frequency band, which is likely to cause harmonic oscillation in weak grids. Furthermore, based on the derived model and Nyquist stability criterion, the effects of grid impedance and other control parameters on the stability of the two load converters connected to the grid were analyzed. Finally, experiments were performed to validate the analysis.
刘一锋, 周小平, 洪乐荣, 夏海涛, 田皓. 虚拟惯性控制的负荷变换器接入弱电网的序阻抗建模与稳定性分析[J]. 电工技术学报, 2021, 36(4): 843-856.
Liu Yifeng, Zhou Xiaoping, Hong Lerong, Xia Haitao, Tian Hao. Sequence Impedance Modeling and Stability Analysis of Load Converter with Virtual Inertia Control Connected to Weak Grid. Transactions of China Electrotechnical Society, 2021, 36(4): 843-856.
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