To constitute a stable, full-automatic drive system, to materialize system interconnection of a wind power generator, to dispense with complication such as the detection and control of wind speed data, and to provide a necessary protection device by combining the wind power generator, a rectifying circuit, the protection device, and a system interconnection inverter together.

Rotation energy from a wind turbine 1 adopting wind power energy is converted into AC electric power by a synchronous power generator 2, converted into DC by a rectifying circuit 3, and then fed to a power system 5 via an inverter 4. Then, the protecting device 11 utilizes an electromagnetic brake by a short-circuit current of the generator, for example in a three-phase generator, to detect the abrupt rise of the rotation speed by a rotation detecting line 12 and stop the power generation by turning on a short circuiting switch 13 via a relay 16. When the system interconnection inverter 4 is stopped by the internal failure, etc., an inverter abnormality detecting line 14 detects it so as to stop it similarly. In detecting the system voltage detecting line 18, the power generation is stopped by the short circuiting switch 13.