The Research Of3-phase PFC System Based On Optimal Control Of Grid Current

In recent years, with the continuous development and the wide range ofapplications of power electronics, control methods of various power electronic devicesbecame more efficient and more energy-saving. However, due to the extensive use ofthose devices or equipments, they produce a large number of harmonics which impedethe development of power electronics technology seriously in power system, which hasbeen more and more attracted by the people about harmonics suppression issues. PowerFactor Correction technology is a effective method to manage harmonics in powersystem. More reliable, more stable, more in line with the actual situation systemcontrolled strategies are more and more concerned, and they are becoming hot issues inthe field of power electronics gradually.In order to suppress the harmonics pollution from grid effectively, in this paper anew repetitive controller has been proposed to suppress the harmonics pollution andimprove the power quality of grid current in3-phase PFC system. Consider repetitivecontrol algorithm is greatly affected by grid frequency, so a new self-adaptive algorithmis proposed to adjust the parameter of repetitive controller on line according to thechanges of grid frequency, the self-adaptive controller can identify the changes of gridfrequency automatically、 improve the stability of system and efficiency of energytransmission. Related discussion and research works are developed in this paper inresponse to those problems above.Firstly, built mathematical models of system according to the structure andworking principle of3-phase PFC system, and designed the control loop according tothe mathematical models of3-phase PFC system.Secondly, proposed a new control strategy called repetitive controller in parallelwith PI controller according to the problem of traditional PI controller hard to suppressthe harmonics pollution which was produced by grid. Analyzed the working principle ofrepetitive controller, and verified the effectiveness of this controller by mathematicalderivation and simulation.Thirdly, analyzed the necessity of self-adapting repetitive controller, compared thetwo controlled results when grid frequency was stable and unstable in the condition ofadding the repetitive controller, and verified the proposed controller by simulation andexperiment that it can improve the current waveform quality after the repetitive controller was self-adapted.Fourthly, built a simulation model of3-phase PFC system and developed aprototype which capacity was10KVA and tested, a detailed analysis of the simulationand experimental results, verified the stability and efficiency of working system underthe two conditions of grid harmonics polluting and frequency shifting.