Patent ID: 8097971

Claim:
A wind turbine generator system comprising: an AC-excited generator, including a stator to be connected to a grid and a rotor coupled to a turbine for rotating the rotor, configured to supply a power to the grid; a converter unit including: an AC exciting converter, including a first DC part, configured to perform power conversion to AC-excite the rotor; and a grid side converter, connected to the stator and to be connected to the grid, including a second DC part connected to the first DC part, configured to perform power conversion to control a DC voltage; a short-circuiting circuit, including an AC input connected a point between the rotor and the AC exciting converter, a switching device, and a resistor which is disconnected and connected by the switching device, configured to short-circuit; and a controller, supplied with a backup power upon decrease in grid voltage, configured to control the AC-exciting converter and the grid side converter, the controller including a first detector for detecting a grid voltage and a second detector for detecting the DC voltage, the controller operating the short-circuiting circuit when decrease in the grid voltage and increase in the DC voltage are detected.