电网不对称故障下电压源换流器系统的暂态同步稳定性分析OA

The stability of voltage source converters(VSC)system based on the phase-locked loop(PLL)is very prominent during asymmetric grid faults.This article establishes a transient synchronous stability model based on the dual-sequence PLL of VSC system during low voltage ride through(LVRT)by referring to the equivalent rotor swing equation of synchronous generator(SG).Based on the model,the synchronization characteristics of the VSC system under asymmetric grid faults are described,and the interaction mechanisms,as well as the transient instability phenomena of positive and negative sequence PLL during asymmetric faults are explained.Moreover,by using the equal area criterion(EAC),the influence of sequence control switching action,detection delay,and interaction of positive and negative sequence PLL on the transient synchronous stability of VSC system are analyzed,respectively.In addition,a transient stability assessment criterion based on the critical fault clearance angle and time is proposed.Finally,the analysis results are validated through simulation.