Impact of wind farms on contingent power system voltage stability

With the global trend towards deregulation in the power system industry, the volume and the complexity of the contingency analysis results in the daily operation and system studies have been increasing. This paper discusses the impact of wind turbine generating units (WTGUs) on power system voltage stability. A probabilistic voltage stability algorithm is developed via power flow analysis where these units are modeled as P-Q bus(es) by detecting the collapse point on the Q-V curves. The developed algorithm also facilitates the computation of both the real and reactive power output of the fixed speed pitch regulated wind turbine at a specific site, wind turbine characteristics, wind speed and terminal voltage. The probabilistic nature of wind is considered by introducing the expected voltage stability margin as an index that combines both of the voltage stability and the wind distribution in one index. The proposed algorithm is implemented and applied on the IEEE 26-bus, voltage stability margin (VSM), and expected voltage stability margin (EVSM) are calculated at each wind speed. The accumulation of the EVSM over a specific period can be considered as the system voltage stability margin which is a single value that can be compared with the voltage stability margin of the all-conventional power system. Finally a contingency analysis for wind power through severe outage cases relevant to conventional power system is investigated.