Patterns and Discrimination of Post‐Fault Voltage Instability Induced by LVRT Control Switching in Renewable Energy Stations

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Abstract
The voltage instability induced by low‐voltage ride‐through (LVRT) control switching may occur in renewable energy stations (RESs) after faults, affecting the safe and stable operation of the power system. However, the post‐fault voltage patterns and practical discrimination methods associated with LVRT‐control‐switching‐induced (LCSI) voltage instability remain insufficiently understood, leading to potential operational risks for grid‐connected RESs. This paper investigates the potential post‐fault LCSI voltage patterns and proposes a graphical discrimination method. First, based on the physical model of LVRT control, five potential post‐fault LVRT control switching scenarios of the RES are identified. Second, an analysis method for the LVRT process based on equal voltage curves (EVCs) is proposed. The mechanisms of the LVRT control switching and voltage stability in each scenario are investigated. Two voltage recovery patterns and three voltage instability patterns are identified, including two additional patterns not reported in the previous studies. Then, a graphical method for distinguishing the LCSI voltage patterns is proposed, and the corresponding identification process is provided. Finally, EMT simulations verify the occurrence of the two additional voltage patterns. The computational efficiency, effectiveness, and robustness of the proposed method are further validated using the modified IEEE 39‐bus system and a simplified provincial‐level power system.

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