Rapid calculation of static voltage stability under branch outage based on Z-index in wind farms

Based on local voltage stability index L, this paper proposes a quick method to calculate the voltage stability index under branch outage. Using the power flow equations and status information of pre-contingency case, the middle state is established between original network and N-1 network through substitution theorem and the sensitivity of voltage stability index, to deduce the algorithm of post-contingency static stability index about pre-contingency injected power under different branch outage. The results in IEEE14-bus system including wind power generation show its feasible and effective.