Research on the reactive power control of wind turbines and dynamic reactive compensation equipment in high-voltage trip-off accident

This paper proposed an explanation on a special phenomenon of voltage change during a large-scale trip-off accident of wind turbine generators (WTGs), which occurred in North China on May 14, 2012. In this accident, the local voltage rose slowly from 209kV to 242kV in 5 seconds after a small-capacity capacitor was switched on. As a result, hundreds of WTGs tripped off due to high voltage. The slow rising process of voltage in this accident is remarkably different from the common feature of voltage change under capacitor switching disturbances. Firstly, the main process of this high voltage trip-off accident is analysed, and the correlation between the change of active power/reactive power and the rise in voltage is discussed. It can be drawn that the voltage rising process was mainly because of the change of reactive power. Secondly, a model of wind-integrated power system is built in DIgSILENT/ PowerFactory. The impact of reactive power control mode of doubly fed induction generators (DFIGs) and static var generators (SVGs) on the voltage change are simulated. The simulation results indicate that both SVGs and DFIGs in constant reactive power control mode can lead to a slow rise in voltage. Furthermore, it is demonstrated that the rise rate of voltage depends on the dynamic response time of WTGs and dynamic reactive compensation equipment. In consideration of the low operation ratio of dynamic reactive compensation equipment at that time, the main reason of this high-voltage trip-off accident is WTGs worked in constant power control mode.