LVRT Capability Enhancement of DFIG With Switch-Type Fault Current Limiter

A low-voltage ride-through (LVRT) strategy for a doubly fed induction generator (DFIG) with a switch-type fault current limiter (STFCL) is presented in this paper. The STFCL is composed of fault-current-limiting inductors, isolation transformers, a diode bridge, a semiconductor switch, a snubber capacitor, and a fault energy absorption bypass. The presented STFCL can insert fault-current-limiting inductors in series with the stator branches on occurrence of a grid fault, which can limit the rotor overcurrent and weaken the rotor back electromagnetic force voltage simultaneously. The safety and controllability of the rotor side converter can thus be guaranteed. The STFCL can also absorb the excessive energy stored in the stator during LVRT with the fault energy absorption bypass so as to prevent the semiconductor devices from overvoltage. The feasibility of the proposed approach is validated by simulation studies on a typical 1.5-MW wind-turbine-driven DFIG system. The validity of the proposed approach is further verified by the experimental results on a 2-kW DFIG prototype.