A wind power generation system by comprising: a double-fed induction generator; a rotor-side converter connected to a secondary winding of the double-fed induction generator; a grid-side converter whose direct-current side is connected to a direct-current side of the rotor-side converter via a direct-current link and whose alternating-current side is connected to a grid; a protection circuit, connected to the secondary winding, for protecting the rotor-side converter; wherein the protection circuit includes: rectifying means, connected to the secondary winding, for rectifying an electric power coming through the secondary winding; power consumption means for consuming the electric power rectified by the rectifying means; switching means, connected to the power consumption means in series, for switching to adjust the electric power flowing into the power consumption means; a capacitor to smooth the electric power flowing into the power consumption means; characterized by further comprising short-circuit means for short-circuiting a voltage rectified by the rectifying means; and a diode being provided so that when the short-circuit means is turned on, a current from the capacitor is prevented from flowing into the short-circuit means; and control means for controlling the protection circuit; and protection circuit voltage detection means for detecting a voltage rectified by the rectifying means, wherein the control means includes a flip-flop and a comparator which turns on the switching means in response to the voltage detected by the protection circuit voltage detection means exceeding a threshold value when the flip-flop has been set, and which turns off the switching means in response to the voltage detected by the protection circuit voltage detection means not exceeding a threshold value, or when the flip-flop has been reset. a double-fed induction generator; a rotor-side converter connected to a secondary winding of the double-fed induction generator; a grid-side converter whose direct-current side is connected to a direct-current side of the rotor-side converter via a direct-current link and whose alternating-current side is connected to a grid; a protection circuit, connected to the secondary winding, for protecting the rotor-side converter; wherein the protection circuit includes: rectifying means, connected to the secondary winding, for rectifying an electric power coming through the secondary winding; power consumption means for consuming the electric power rectified by the rectifying means; switching means, connected to the power consumption means in series, for switching to adjust the electric power flowing into the power consumption means; a capacitor to smooth the electric power flowing into the power consumption means; characterized by further comprising short-circuit means for short-circuiting a voltage rectified by the rectifying means; and a diode being provided so that when the short-circuit means is turned on, a current from the capacitor is prevented from flowing into the short-circuit means; and control means for controlling the protection circuit; and protection circuit voltage detection means for detecting a voltage rectified by the rectifying means, wherein the control means includes a flip-flop and a comparator which turns on the switching means in response to the voltage detected by the protection circuit voltage detection means exceeding a threshold value when the flip-flop has been set, and which turns off the switching means in response to the voltage detected by the protection circuit voltage detection means not exceeding a threshold value, or when the flip-flop has been reset. rectifying means, connected to the secondary winding, for rectifying an electric power coming through the secondary winding; power consumption means for consuming the electric power rectified by the rectifying means; switching means, connected to the power consumption means in series, for switching to adjust the electric power flowing into the power consumption means; a capacitor to smooth the electric power flowing into the power consumption means; characterized by further comprising short-circuit means for short-circuiting a voltage rectified by the rectifying means; and a diode being provided so that when the short-circuit means is turned on, a current from the capacitor is prevented from flowing into the short-circuit means; and control means for controlling the protection circuit; and protection circuit voltage detection means for detecting a voltage rectified by the rectifying means, wherein the control means includes a flip-flop and a comparator which turns on the switching means in response to the voltage detected by the protection circuit voltage detection means exceeding a threshold value when the flip-flop has been set, and which turns off the switching means in response to the voltage detected by the protection circuit voltage detection means not exceeding a threshold value, or when the flip-flop has been reset.