Research On An Improved Three-Phase Two-transistor Power Factor Correction Circuit

AC/DC converter is the most widely used converter in the power system. In order to reduce the harmonic pollution of power supply and improve the power factor, people are using more and more power factor correction technology. At present, the single-phase PFC is already developed, but the three-phase PFC is still in the stage of library works. In recent years, discontinuous current mode control implementation for three-phase AC-DC converters with active power filtering and power factor correction schemes has attracted special interest in industrial and telecommunication energy systems. This control strategy has practical advantages since it has a simple and cost-effective configuration. However, for emergency engine-driven generators, most three-phase PFC converters with discontinuous current mode control have not been effectively adopted in practice because the conventional PFC circuit configuration has some disadvantages for engine-driven generators connected to three-phase AC mains. In this paper, the comparison between the improved boost type dual-transistor PFC circuit and the conventional one is presented. First we analyze the working principal of the conventional PFC circuit, give out its 9 working modes. And we analyze the inherent reason of high current harmonic, find out that the duty cycle of the transistors ties in with the PFC effect. And in order to overcome the disadvantage of the conventional circuit, we present an improved PFC circuit and its working principal as well. In chapter 4, the famous software toolkit PSPICE is used to validating the rationality and correctness of the improved circuit. Then an experimental installation is given. The main devices and parameters, and all parts of the control circuit are designed. Finally, the experimental waveforms and results are given. In conclusion, the correctness and feasibility of this improved three-phase boost type dual-transistor power factor correction converter are proved by the theoretical analyses, simulation research and experimental validation. Compared with the conventional circuit, the PFC effect is much better but the cost is not that much.