Research And Design Of Bidirectional LLC Resonant Converter For Electric Vehicle Charger

With the rapid development of electric vehicle technology,the bidirectional charging module which can realize the function of power bidirectional flow has been widely used in new energy and other fields.In this dissertation,bidirectional LLC resonant converter,which is composed of Type-4 and Type-11 resonators,is studied and designed for DC/DC part of bidirectional charging module.Based on the analysis of the working state of bidirectional LLC resonant converter,the steady state model is established.The influence of the resonant parameters on the DC gain characteristics and the input impedance characteristics of the resonator is analyzed.And the conditions of MOSFET failure and ZVS soft-switching are analyzed.Meanwhile,this dissertation uses the extended function description analysis method to establish the small signal model system of the converter.The influence of the switching frequency and load variation on the stability and dynamic response characteristics of the model system is analyzed,and the theoretical basis of the compensator parameter design is provided.And according to the technical index of the electric vehicle,the converter main power circuit is designed and the loss analysis is carried out,which provides the reference for the further optimization of the circuit parameters.According to the principle of PFM,a hardware control circuit is designed and a soft-start capacitor is added in the circuit to avoid the failure mode of the MOSFET when the converter starts.Meanwhile a simulation model of bidirectional LLC resonant converter is built in Saber simulation software,and the resonant parameters and control parameters are simulated and validated.The voltage and curent waveforms and the efficiency of the converter in the bidirectional operation mode are tested,and the rationality and validity of the parameter design are verified.