Research on Low Voltage Ride-Through Control Strategy of Doubly Fed Induction Generator

In the power system with high proportion of wind power generation equipment, when a fault occurs in the power grid due to the large capacity of wind turbines, direct removal may cause grid collapse, requiring wind turbines to continue to be remained interconnected with the power grid for a specified duration when the voltage drops, to provide a certain amount of reactive current to the grid. Upon the successful formulation of the equivalent model of the doubly fed induction generator (DFIG), the main control methods of DFIG are briefly discussed in this paper. The transient characteristics of DFIG during three-phase fault in power grid are studied in depth. The influence of voltage drop on the DC bus voltage of rotor-side converter and the current flowing through the rotor is analyzed. A control strategy is proposed to improve LVRT capability of DFIG by using DC unloading circuit and rotor dynamic virtual resistance. This study can not only improve the transient characteristics of DFIG, but also improve the stability of power grid operation with high proportion of new energy generators.