Study On Bifurcation Behavior Of Three-level BOOST PFC

The rapid development and wide application of power electronic circuits hasbrought great convenience for the development of society and the life of people. But theuse of power switching device brings serious harmonic pollution to power grid, andeven has bad effects on other equipment on it. The switching power supply often usepwer factor corrector to suppress it, but in practical application there exists irregularnonlinear behavior, which has serious impact on system performance. Therefore,analysis of nonlinear bahavior in power factor corrector in-depth is of great significancefor the optimization of circuit parameters and in improving the system dynamicalperformance.Based on the discussion of various nolinear analysis methods and their merits anddrawbacks, the paper study on the bifurcation behavior of the three-level Boost PFCunder two different control methods-the average current control and one cycle control.Firstly, the paper presents the working principle of three-level Boost PFC underaverage-current-cotrol mode, which is the most widely used in traditional controlmethods. The discrete-map model of three-level Boost PFC is constructed,and theinfluence of changing circuit parameters on the fast-scale bifurcation can be observedthrough simulation. The results show that the circuit is prone to make occurrence ofintermittent bifurcation during the small input voltage range. According to the powerconservation principle, a simlified model is constructed. The slow-scale bifurcationpoint of the system is to be analyzed under different circuit parameters using Floquettheory, the simulation results agree with theretical analysis.The paper introduces one-cycle-control mode into three-level Boost PFC, which isa novel nonlinear control method. On the basis of the analysis of its working principle,the averaged model of the circuit is established based on the power conservationprinciple. The periodic solutions are investigated using the harmonic balance methodand the influence of main circuit parameters on the slow-scale bifurcation of the systemis studied by the Floquet theory. The simulation results show that, compared with theaverage current control, the one cycle control can eliminate the transient and steadyerror in one cycle, with advantages of fast dynamic response and simple circuitrealization. The simulation results are consistent with the theoretical results, and verifiesthe validity of simplified circuit model.On the basis of theoretical analysis and simulation verification, the paper designsthe experiment system of the three-level Boost PFC based on the average-current-control chip UC3854. The experiment further validates the correctness of thetheoretical analysis. Study on the bifurcation existed in the three-level Boost PFC is of great guiding significance for circuit design and laid the foundation for the control ofnonlinear behavior.