Improved Continuous Fault Ride Through Control Strategy of DFIG-Based Wind Turbine During Commutation Failure in the LCC-HVDC Transmission System

The commutation failure fault usually occurs in the line-commutated-converter-based high-voltage direct current transmission system. When commutation failure fault occurs, the voltage of sending alternate current (ac) system changes rapidly, and the connected doubly fed induction generator (DFIG)-based wind turbine may be tripped. Thus, the fault ride through (FRT) control strategy of DFIG should be investigated for enhancing the stability of the sending ac system. However, the voltage of the sending ac system during commutation failure is not changed in rectangular in shape, besides, the voltage presents the “first reduce then rise” characteristic, which is not considered in the existing FRT control strategies. In order to realize the continuous FRT of DFIG during commutation failure, the stator flux and electromotive force when the stator voltage changes continuously have been analyzed for the first time in this article. Furthermore, based on the analysis results, an improved continuous FRT control strategy is proposed. The simulation and experiment results validate the effectiveness of the proposed method. The proposed control strategy is not only suitable for the commutation failure condition, but also for the scenario with continuous voltage variation during grid fault, which indicates that the proposed method is general.