NOVELTY - The system (20) has a controller (205) connected to a direct current (DC) port of a system side converter (2041) and a DC port of an alternate current (AC) excitation converter (204). An AC excitation type generator (201) is operated to feed generated power to a commercial electric power system (10), and an overcurrent consumptive unit has a rectifier unit for converting AC to DC. Multiple resistors are connected to a DC port of the rectifier unit. A switching unit turns on/off the resistors, and a capacitor (Cd) is connected to the DC port of the rectifier unit.    USE - Wind power generation system for use with a commercial electric power system through a transmission line.    ADVANTAGE - The wind power generation system protects the power converter connected to excitation type generator from over current caused by the system accident or system disturbance to enable the generator to operate without disconnection from the power system. The over current consumptive unit is located distantly from the earth than the converter to reduce earth electrostatic capacity. The breaker protects the generation system during over flow of current by disconnecting the generation system from the electric power system. The upper and lower switching devices of the over current consumptive unit can be prevented from being turned on transiently and simultaneously, thus preventing direct current (DC) short-circuiting. The output current signal infrared (IR) of the converter increases more rapidly, so that the system can be stopped without operating the unit for coping with system faults. The capacitor prevents the switching of the converter from being applied to the DC port of the unit for coping with faults to protect the converter from surging. The current flowing into the rotor can be decreased stepwise, and the current flowing into the converter upon turn-off of the resistor can be reduced by providing the resistors for energy consumption and disconnecting the resistors when turning off. The starting of the converter for charging the DC port of the coping unit with an AC output of the converter can be avoided, thus suppressing rush current caused by charging.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram of a wind power generation system.    Capacitor (Cd)    Commercial electric power system (10)    Wind power generation system (20)    Generator (201)    Propellers (202)    Windmill controller (203)    Alternate current excitation converter (204)    Controller (205)    System side converter (2041)    Generator side converter (2042)