Research On One-cycle Controlled Three-level PFC Converter

Power factor correction (PFC) technology is being widely used in on-line UPS systems nowadays. The input power factor of the UPS is of importantance, which reflect the utilization efficiency of AC power and the harmonics. Therefore, high power factor is being considered more and more important.In this paper, a one-cycle controlled (OCC) three-level Boost PFC converter used for the front end of the half-bridge inverter UPS systems is discussed. This three-level PFC topology is simple to realize, and has small THD, low switching loss and high efficiency. The one-cycle control technique is a novel pulsed nonlinear control technique, which achieves controlling of the average value of the variables to meet the control goal in one switching cycle, and provides fast dynamic response and good input-perturbation rejection. The key compenents of OCC circuit are an integrator and a comparator. Analog integrator is used for its high speed at present.At first, the basic working principle of the three-level PFC is studied, and the small signal model of the circuit is researched. The feasibility of the system is analyzed after discussing the principle of one-cycle controlled PFC converter. A prototype based on analog IC IR1150S which uses OCC technique is built and the technique of designing the converter is offered. Experimental results show that this system is simple, reliable, and it has low THD, high PF and can realize stable and balanced postive/negative DC bus voltage.With the development of digital technique, more and more control algorithms can be implemented by the digital signal processor (DSP). Principle of digital control to realize OCC is discussed in this paper. At last, a prototype based on TMS320LF2407 is built, and the hardware design and the software design are present, furthermore, the main program flow chart is given. The control technique of half-bridge UPS system based on DSP is also studied.