I. Introduction
It is a consensus around the world that developing renewable energy could well contribute to relieve energy crisis ,as well as deduce environmental pollution [1]-[2]. And benefitting from policy and financial support, wind energy has developed rapidly and achieved remarkable results[3]-[4]. However, large-scale wind energy integration increases the risk of SSO, which influences the security and stability of power grid[2], [5]-[10]. In recent years, SSO events have occurred in several wind farms in Texas of USA, offshore wind farm (WF) in UK, as well as in Hebei, Xinjiang and other regions of China[5]-[10], bringing huge economic losses and security risks to the power system. To solve this problem, a lot of good works have been carried out to inhibit SSO, and achieve certain results[5]-[8], [11]-[18].