Inter-Turn Short-Circuit Fault-Ride-Through for DFIG Wind Turbines

Inter-Turn Short-Circuit (ITSC) of the stator winding is one of the most common faults in asynchronous generators. A significant feature of ITSC is the increase of the current in the faulty phase. Improper treatment may lead to unnecessary power loss or further deterioration. Therefore, this paper proposes a fault ride-through strategy under the stator ITSC fault for Doubly-Fed Induction Generator (DFIG) wind turbines. When the closed-loop state observer detects the fault and the current is higher than the rated current, the faulty wind turbine switches to down-regulation mode for protecting the faulty generator. The rotational speed reference is kept at the maximum value. Then the difference between the current and the rated current with the proportion-integration operation is superimposed to the original generator torque reference. Simulation results show that the faulty phase current can be decreased to the rated value, effectively. Although the power output is reduced as well, the impact of the fault does not develop to a failure. So the faulty wind turbine can continue to operate before the maintenance. The proposed strategy can avoid the unnecessary power loss caused by shut-down, improve the operational capacity of wind turbines and reduce the maintenance costs under the ITSC fault.