Third harmonic input current cancellation strategy for single-phase power factor correction with non-electrolytic capacitors

Electrolytic capacitors are widely applied because of low volume and cost, however their lifetime is quite limited typically less than 10000h. An improved control strategy for PFC converters with small storage capacitance suitable for medium and high power is proposed on the basis of conventional ACM PFC, which effectively eliminates third harmonic input current due to the low energy-storage capacitance. Compared to other methods to eliminate electrolytic capacitors, the proposed method has the advantage of nearly unity power factor, suitable for medium and large power application. A simulation analysis is made and a 325W digitally controlled prototype with a 50µF polyester film capacitor verifies the approach. The proposed method does not require additional components and it is easily implemented in practical situations.