PURPOSE: To protect a power converter in a harmonic reactive power compensator which compensates the harmonic current and reactive power of a load from an overload quickly without degrading the performance regardless of a load state.

CONSTITUTION: A converter capacity is operated by a converter power operator 7 from a system voltage which is the output of a voltage detector 4 which detects the voltage of a power system 1 and a power converter output current which is the output of a current detector 6 which detects the output current of the power converter. If the capacity exceeds a rated capacity, the gain of a detected load current value which is the output of a current detector 5 which detects the load current is varied by a variable gain circuit 8 to avoid the saturation of a signal and, further, a compensation current command Ic* which is the output of a compensation current operator 10 which operates the compensation current command Ic* is limited to a value corresponding to the rated capacity to protect the power converter 3 from an overload.