A comprehensive FRT scheme of DFIG based on an improved DC chopper and matching control strategy

Based on the study of the shortcomings of various existing fault ride-through (FRT) measures and targeting the problems of a single operation mode and poor FRT ability for the traditional DC chopper, this paper improves the structure of the traditional DC chopper. The improved DC chopper can switch between different operation modes according to different operating conditions of the doubly fed induction generator (DFIG) during voltage dips. Meanwhile, improved control strategies of rotor-side converters and grid-side converters are proposed to match the different operation modes of DC choppers. In addition, in the case of a deep voltage dip, the series impedance is connected to the stator side to enhance the rotor over both the current-limiting ability and the voltage fast recovery ability. The comprehensive application and coordination of the above measures can effectively limit the rotor overcurrent, suppress the DC bus overvoltage of the DFIG during a voltage dip, and accelerate the rapid recovery of the fault voltage. At the same time, the proposed comprehensive FRT scheme can be applied to different voltage dips. The simulation model of the FRT scheme is built on the MATLAB/Simulink software platform; the correctness and effectiveness of the proposed FRT scheme are verified by simulation.