Dynamic Voltage Restorer (DVR) Improve Operation of DFIG Wind Turbine Under Unbalance Grid Voltage Sags

In view of the doubly-fed wind power generator (DFIG) under grid voltage unbalance, double frequency disturbance component will cause a series of electrical and mechanical problems. A novel DFIG-DVR system is proposed to ride-through unbalance grid voltage conditions, the series coupled DVR of which always maintain the constant of stator voltage, isolating primary causes of problems for grid voltage unbalanced fault. In the process of fault operation, DFIG can still achieve the target for rotor side converter to accomplish decoupled power control and grid side converter to maintain constant on dc voltage. DFIG-DVR system model was established by MATLAB/Simulink. Comparison and analysis are conducted about whether DVR is switched under the condition of unbalanced grid voltage. The simulation results show that the proposed control scheme can realize low voltage ride-through(LVRT) operation of DFIG under the conditions of unbalanced grid voltage.