For possible cascading trip-off events caused by dynamic voltage problem of large-scale wind farms

the evolution mechanism and special spatiotemporal characteristic of cascading trip-off of wind farms is analyzed first and verified by simulation. Then the reactive power sources in wind farms involving doubly-fed induction generator (DFIG) and their regulation characteristics are analyzed. The voltage and reactive power emergency control strategy is put forward using static var compensator (SVC) and DFIG. The control principle proposed consists in using DFIG and SVC to jointly output capacitive reactive power during the fault based on the decoupled control of DFIG

at the same time to limit active power output of DFIG

so as to increase the voltage of DFIG. Fault cleared

DFIG provides some reactive power according to its terminal voltage to offset the lagging effect of SVC. Simulation results show that the emergency control strategy proposed is able to successfully suppress large-scale cascading trip-off of wind farm cluster. This work is supported by the Major Program of National Natural Science Foundation of China (No. 51190103) and State Grid Corporation of China (No. SGNX0000FZJS1400729).