Shengqing Li, Yao Ming, Yuwen Zhang, and Wenfeng Wu
Doubly-fed induction generator, low-voltage ride through, voltage drop, crowbar circuit, automation level
Doubly-fed induction generator (DFIG) often adopts a crowbar protective circuit to realize low-voltage ride through (LVRT) under low-voltage fault of the grid. Crowbar resistance will affect the LVRT effect of the unit significantly. Time domain expression of transient current of the wind turbine generator system under the voltage drop fault and the calculation formula of fault current at the rotor side were deduced through space vector analysis and Laplace transformation based on the transient mathematical model of the DFIG system under voltage drop. A crowbar resistance adjustment method conforming to engineering practices was proposed, which overcame the overcurrent at the rotor side and overvoltage of the DC bus after the crowbar protective circuit is applied. The case study and the simulation test demonstrated that the proposed method inhibits the transient fault current component effectively and can increase the automation level of the DFIG system.
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