High Performance Control Of PFC AC/DC Converter For On Board Chargers

The world's governments and automobile companies on the development of new energy vehicles attach great importance due to the low-carbon,emission reduction features owing by new energy vehicles.On-board charger is operated as an interface between the electric vehicle battery system and the power grid.Thus its performance directly affect the charging efficiency of electric vehicles and power grid quality.In a two-stage on-board charger,the front-end PFC AC/DC converter with conventional dual closed-loop PI control,which consists of an external voltage loop and an inner current loop,is used to perform ac/dc conversion and power factor correction.The main drawbacks are poor dynamic performance and insufficient anti-disturbance ability.In addition,aluminum electrolytic capacitor,which is of high failure rate and low-lifetime,is selected as the output capacitor of PFC AC / DC converter.It will affect the reliability of the converter seriously.Therefore,improvement of the dynamic performance and reliability of PFC AC / DC converters has become a hot reseach topic.On the basis of the power control method of PFC AC / DC converter based on differential flat theory,the paper proposes a load-adaptive nonlinear power control method to improve the dynamic performance and eliminate the influence of model uncertainties and unknown disturbance on system performance.For this purpose,the traditional PFC boost converter is used to be main circuit to calculate the parameters of the main circuit and select the part numbers of the active device.Moreover,simulation models of the PFC AC / DC converter with conventional dual closed-loop PI control and nonlinear power control are established respectively with the Matlab/Simulink environment.The improved performance as compared to the conventional control method is verified via simulation.Based on the study of nonlinear power control,this paper focuses on the model-free power control of PFC AC / DC converter for vehicle charger,which aims to enhance the robustness of the converter to model uncertainties,unknown disturbance and measurement noise,morover simplifies the design process of the controller.Therefore,the ultra-local model of the PFC AC / DC converter is established utilising the input and output of the converter.And then the model-free power controller is designed.The feasibility of the proposed control strategy is confirmed through system modeling and simulation.On the basis of the above work,a prototype of the PFC AC / DC converter is designed and manufactured.The experimental test of PFC AC / DC converter system controlled model-free power is implemented based on the dSPACE rapid control prototype platfrm,relevant experimental results validate the feasibility and effectiveness of the control strategy.Finally,the paper focus on the researchof PFC AC / DC converter system integrated with power decoupling circuit including the basic operation principle of the power decoupling circuit,the calculation of the key parameters and the design of the corresponding controller to absorb the alternating current pulsation portion in the output power and the electrolytic capacitor can be directly repalced by film capacitors with small capacitance.Thus the realibility of such PFC AC/DC converters could be improved.The technical advantages of PFC AC / DC converter system integrated with power decoupling circuit are verified by system modeling and simulation.