Analysis and Estimation Method for the Impact of Different Renewable Energy Ratios on Transient Overvoltage under DC Faults

[Objective] To address the ambiguous trends in transient overvoltage caused by unclear definitions of renewable energy ratios， this paper investigates how fluctuations in renewable generation and random unit commitment lead to varying impacts under different ratio scenarios. An analysis and estimation method for transient overvoltage under DC faults at different renewable energy ratios is proposed. [Methods] First， a mathematical model linking transient voltage to power imbalance and short-circuit capacity is established， followed by a sensitivity analysis of key influencing factors. Second， based on renewable energy development planning， the impact of renewable integration on system short-circuit capacity is evaluated. Considering the output characteristics of renewable sources， four distinct definitions of “renewable energy ratio”are introduced， and the resulting trends in transient overvoltage with increasing ratio are systematically analyzed. Finally， using capacity-based ratio as a case， a fast estimation method for transient overvoltage is developed by incorporating active power imbalance， clarifying the influence of system transmission power. [Results] Following a DC fault， the peak transient overvoltage at the sending end varies significantly depending on the specific type of renewable energy ratio. Moreover， the peak overvoltage increases gradually with higher system transmission power， which validates the theoretical analysis. [Conclusions] The proposed analysis and estimation method provides a solid theoretical foundation for understanding transient overvoltage behavior under varying renewable energy ratios， offering valuable guidance for power system planning， higher renewable integration， and operational dispatch.