Study Of A Novel Six-inductance Double-switch PFC Circuit For UPS

Compared with the traditional uncontrolled rectifier circuit, power factor correction circuit has higher input power factor, lower input current harmonic content, which is very important to the input stage features of uninterrupted power supply. The multi-functional single-stage PFC technology combines power factor correction circuit with DC/DC boost circuit, can not only correct the power factor and improve bus voltage in on-line mode of UPS, but also achieve bus booster function in battery mode of UPS. This multi-functional PFC can reduce the cost, simplify the control, and it has become a hot spot in UPS areas. At present, most three-phase UPS adopt six switch multi-functional PFC circuits, which has more switches and more complex control. A six-inductance double-switch PFC circuit, which is suitable for three-phase low cost UPS is proposed in this paper, this circuit has good performance in the aspects of power factor, cost and control in both on-line mode and battery mode.At first, the deficiency of traditional double-switch PFC circuit and double-inductance double-switch PFC circuit are introduced, then the six-inductance double-switch PFC circuit is introduced and its feasibility, principle of PFC, working process, control methods are discussed in detail in this paper.The parameter calculation process and small signal modeling are introduced according to the performance requirements of UPS. Then the small signal model is established, the PI compensation is conducted based on the model and the Bode diagram is plot to verify the stability of the system.MATLAB is used in this paper to simulate the PFC circuit. The improvement of input current is simulated and the LCL filter and its parameters are designed for the current harmonic. The bus voltage waveform of six-inductance double-switch PFC circuit is simulated and several optimization methods are put forward which is aiming reducing the transient and steady state error.At the end of this paper, the experimental prototype is built up and the input current, power factor, working waveforms of bus voltage are measured. The simulation and measured results are basically identical, which proved that the six-inductor double-switch PFC design is feasible.