Analysis of Overspeed Problem of Doubly-Fed Induction Generator under the Power Grid Fault Condition

In recent years, with the rapid development of wind power industry and the continuous expansion of wind power installed capacity, China's wind power scale has been in the forefront of the world. Doubly-fed Induction Generator (DFIG), which includes power electronic equipment such as voltage source converter, is the main wind turbine at present. The control strategy and operation characteristics are quite different from traditional generators. A severe drop in grid voltage can cause overcurrent to the rotor, at which point the protective device acts to prevent the generator from being damaged, but the torque balance is destroyed. The failure of DFIG to restore torque balance will result in DFIG taking measures to prevent overspeed and cutting off the connection to the grid. In this paper, the DFIG grid-connected model is established, the operation characteristics of DFIG are simulated under the condition of three-phase symmetrical short circuit fault, and the action process and principle of overspeed instability of DFIG are studied.