A control strategy of boost PFC to minimize current zero-crossing distortion

Single switch boost-type power factor correction (PFC) is applied to reducing power grid harmonic pollution in the fan motors control system. However, the current zero-crossing distortion will affect the PFC performance. To solve this problem, a new current zero-crossing distortion suppressing method and its concrete implementation are proposed. Digital control is adopted and duty ratio feedforward compensation is introduced to reduce the disturbance of input voltage and output voltage on the inductor current, forcing the input current to follow the input voltage changes; the input impedance is analyzed to show that duty ratio feedforward compensation can inhibit the current phase advance. A current sampling method is proposed to get the average current by sampling twice per PWM period. Simulation and experiment results show that the proposed method can inhibit current phase advance, eliminate input current harmonics, and achieve unity power factor correction, verifying the validity of the proposed method.