An adaptive control strategy of crowbar for the low voltage ride-through capability enhancement of DFIG

Doubly-fed induction generator (DFIG) is sensitive to the disturbance of grid voltage, and its low voltage ride-through (LVRT) technology is still a hotspot issue. Rotor side crowbar is widely used to realize LVRT. However, traditional fixed crowbar can’t strike a balance between the limitation of rotor over current and DC-bus over voltage, and the crowbar is usually activated repeatedly due to the inappropriate deactivation strategy. Based on the analysis of rotor current considering crowbar operations, an improved LVRT method that dynamically adjusting crowbar resistance and adaptively deactivating the crowbar circuit is proposed. The corresponding adaptive control strategy and the resistance setting method are given. With the proposed scheme, both the rotor current and DC-bus voltage can be controlled within the restriction. Besides, the crowbar can be deactivated in the least time under the precondition of avoiding being reactivated, which will effectively reduce the absorbed reactive power from the system and benefit the service life of switching devices. The effectiveness of proposed LVRT scheme is verified by MATLAB/Simulink simulation.