Doubly fed induction generator wind turbines: A novel integrated protection circuit for low-voltage ride-through strategy

This paper proposes an integrated low-voltage ride-through (ILVRT) scheme to improve the transient responses of the doubly fed induction generator (DFIG) based wind turbines. The proposed strategy integrates a series-dynamic-resistor, a dc-link chopper, and a crowbar (CRW) with a coordinated switching control strategy. Generally, when the CRW short-circuits the rotor windings, the rotor-side power converter (RSPC) is blocked and the DFIG becomes a squirrel-cage induction generator. This temporary configuration acquires its magnetization current from the grid, which leads to a more voltage-dip. On the other hand, if the CRW is combined with the series R-L circuit, the RSPC remains connected to the sliprings, and hence, the active/reactive (P-Q) control is partially maintained. Moreover, the terminal voltage depression is reduced compared to when only the CRW scheme is applied. Following a brief discussion of two conventional LVRT strategies, the proposed ILVRT scheme is designed with an improved switching control algorithm which minimizes the CRW activation time. By applying the proposed ILVRT approach, the negative effects of the grid faults and two conventional strategies can be avoided. Finally, the performance comparison between the two conventional LVRT strategies and the proposed ILVRT scheme is conducted with the simulation results using MATLAB/Simulink software.