Analysis of Transient Voltage Influencing Factors in Hydro–Wind–Solar Hybrid Systems

This study investigates the dominant mechanisms governing transient-voltage evolution in hydro–wind–solar hybrid systems to address practical engineering requirements. A quantitative index system is constructed to evaluate the factors affecting system transient voltage, and the impacts of key factors are quantified. Specifically, the voltage drop during system faults is mainly affected by fault location and network structure, whereas post-fault recovery depends more on the collaborative process of dynamic reactive power balance and multi-time-scale control. A multi-level transient voltage quantification method is proposed to identify system influencing factors and weak points. The evaluation system comprises maximum voltage drop depth, voltage recovery time, transient voltage severity index (TVSI), hierarchical aggregation indicators, and system-level SSI indicators. The ability of these indicators to characterize systemic risks and disturbance propagation effects is enhanced by introducing fault-point extreme-value correction. The key mechanisms affecting transient voltage stability of hydro–wind–solar hybrid systems are clarified. Multi-scenario analysis shows that transient voltage risks are mainly concentrated in the 220 kV and 110 kV collection layers and are most sensitive during the recovery stage after fault clearing. Detailed quantitative analyses are conducted on four influencing factors: fault location, wind and solar power output, wind-to-solar ratio, and renewable energy penetration rate.