Research On Shunt PFC Technology Based On Direct Current Control Scheme

Power factor correction technology is an effective method of restraining harmonic currents and increasing power factor, which has been widely studied and applied.Refer to shunt active power filter topology, the concept of parallel PFC is proposed in this paper. The load compensation current is acquired by the inverter, which is parallel accessed between the power supply and output load. The direct current control method requires neither detecting load current nor extracting harmonics and reactive current or the fundamental active current through a complex algorithm.A single full-bridge inverter structure is simple and easy to control relatively. Based on single-bridge, shunt PFC is studied in this paper. The design method of main circuit and control circuit parameters is introduced. Then a prototype of the shunt PFC system is realized. Simulation and experiments show that the compensated power factor is close to 1, harmonic content is greatly reduced.In order to increase the bandwidth of the inverter and realize high-order harmonic current compensation, multiple shunt inverters with CPS-SPWM technique are discussed. That will increase the equivalent switching frequency to achieve the system requirements. Simulation and experiments show that the shunt PFC system is of good compensation and PFC performance, DC side voltage is easy to implement. With CPS-SPWM technique, the device can be at a lower switching frequency to achieve a high equivalent switching frequency.For the purpose of using medium-power switching devices in high voltage situations, cascaded inverter is studied. The DC side voltage of each inverter must be balanced. Simulation study based on the control of DC capacitor balanced analysis.