Research On Active Power Factor Correction Technology Based On DSP

In power electronic devices, switching power supply has the advantage of small size and high efficiency, therefore, the power supply units of electrical equipment are almost switching power supply. However, due to the reduction of input power factor on grid side and the harmonic pollution have become much more serious, the switching power supply has gradually become the main source of harmonics, to solve danger of the problem about harmonics, this paper conducts the study about active power factor correction technology based on DSP.According to the study of domestic and international power factor and active power factor correction, including the basic principles, typical topology, control strategy and the APFC circuit design, this paper designs an APFC system based on DSP. This design chooses Boost topology as the main circuit of the system, and the average current mode control with feed-forward link under continuous current mode as the system control strategy, and the control strategy is achieved through the digital control mode based on DSP. To solve the problem of ripple interference in the control circuit and improve the dynamic performance of system, this design employs the double closed-loop control algorithm with feed-forward link, which is base on the sinusoidal current given by the digital sine. Through the replacement of the reference input inductor current by the digital sine current, the current reference in the current-loop avoid the influence coming from input voltage. Through the calculation of feed-forward voltage average instead of traditional analog feed-forward voltage, the system can effectively avoid the harm brought about by the secondary ripple in the voltage feed-forward link, and the method improves the power factor correction effect. Besides, the introduction of the feed-forward voltage after current loop can reduce the burden of current loop, and improve the voltage dynamic performance. To reduce the loss of switch brought about by the high frequency, improve the circuit efficiency, this paper improves the topology, that is, changing the single-frequency PFC circuit into the double-frequency PFC circuit. In the control circuit, this paper achieves the design of APFC control circuit based on Freescale MC56F8346DSP processor, and according to the double closed-loop control algorithm, this paper makes the design about the current loop, voltage loop and DSP control program. Besides, this paper does the simulation verification on the designed system, and it can be obtained that the design of system has good rationality and efficiency thought the analysis of simulation waveform.