With the nonlinear load increasing of rectifiers and frequency converters in the power system, the concussion and imbalance caused by nonlinear loads results in voltage wave and current wave distortion. Sometimes it will have bad influence on the power quality. APF(Active Power Filter) is widely used in harmonic pollution restraint. It is important to detect the current signals and control compensation signals in APF. So the control of compensation signals is focused on in the paper. Though hysteresis loop,...