Analysis of the Impact of Crowbar and Chopper Protection on Low Voltage Ride Through of DFIG

As the installed capacity of wind power increasing, higher requirements are placed on the low-voltage ride-through capability of wind generator connected to the grid. Based on the analysis of the current grid-connected principle of the wind generator, the operation of the douply-fed asynchronous wind generator under the condition of voltage drop is theoretically analyzed, and a scheme of Crowbar circuit and Chopper circuit is proposed to protect the rotor excitation power supply and the generator itself. The article conducts detailed transient process derivation and simulation verification on various influencing factors such as the option of the Crowbar circuit resistance, the impact of the specific input and output time on the transient process, and the automatic detection and switching of Chopper. The simulation results show that they are consistent with the theory. Simulation is performed in the DFIG model established by Matlab/Simulink to verify its effectiveness. The simulation results show that the combined effect of the two circuits can effectively limit the rotor loop current and DC bus voltage during voltage drops, ensuring the safety of each component of the system; it is also proved that this solution can realize the operation of AC-excited doubly-fed asynchronous wind turbine without disconnecting from the grid during faults, and can play a positive role in stabilizing the grid voltage.