Low Voltage Ride Through for DFIG With Series Coupled Compensation

Flux variation of doubly fed induction generator(DFIG) under grid fault and fault recovery leads to rotor overcurrent or rotor overvoltage, and it hazards to the converter at rotor side. For this reason a new low voltage ride through scheme, in which a series coupled compensation(SCC) is connected in series to generator's input terminal via coupling transformer, is proposed to overcome the affections on wind power system due to faults occurred in power grid. The superiorities of the proposed control strategy are as following: the transient current component in both rotor and stator of DFIG can be weakened, thus the unbalanced heating of both rotor and stator windings can be suppressed and the service life of DFIG can be prolonged; DFIG can still output active and reactive power steadily; the converter at DFIG's rotor side is controllable all along during the whole accident operation, thus it is possible to provide reactive power support to faulty power grid. Under the condition of symmetrical and asymmetrical fault occurred in power grid, a simulation model of wind power generation system with capacity of 1 MW is established by PSCAD/EMTDC, and simulation results show that using the proposed control scheme the ride through capability of DFIG under fault occurred in power grid can be improved.