Research And Design Of Series High Power LLC Resonant Converter

High efficiency and high power density DC/DC converter is the focus of power electronics research.To achieve high power density,the converter must be high frequency,but high frequency will lead to an increase of switching loss and decrease of efficiency.In order to overcome the switching loss,soft-switching circuit is the only way to solve the problem.LLC resonant converter has the advantages of low voltage stress,soft switching and high efficiency.It is widely used in DC charging power supply,aerospace and communication broadcast power supply,etc.In this paper,the research and design of high-power LLC resonant converter is carried out based on the charging power supply applied in DC charging pile.In this paper,the working principle and gain characteristics of full-bridge LLC resonant converter are analyzed based on the simulation waveform.Based on the First Harmonic Approximation method(FHA),the traditional gain formula is further simplified.A simple and clear method for designing the optimal resonant parameters is presented.According to the designed resonant parameters,the resonant transformer,resonant inductance and resonant capacitance are designed.With the help of the mathematical analysis software maple,the all-round theoretical verification has been carried out.Secondly,the controller of series LLC converter is analyzed and designed in detail.The controller design includes staggered control,voltage sharing and current sharing control,fuzzy adaptive PID control and constant pressure and constant current closed loop control.Then based on the previous analysis,the hardware circuit and software algorithm are designed.The hardware circuit includes control circuit and power circuit.The control circuit takes TMS320F2808 as the control core,and the extended circuit includes DC bus voltage and current detection circuit.Reset circuit,overvoltage and overcurrent detection circuit,core voltage fault protection circuit,communication circuit,etc.The power circuit includes resonant circuit,auxiliary power supply circuit and PWM drive circuit.The software algorithm includes the initialization of the program,the control flow and the method from S domain to discretization of the control algorithm.Finally,an experimental prototype of 15 kW is made,and the theoretical analysis and control strategy are verified by experiment waveform,the results show that the resonance parameters designed in this paper meet the design requirements and have high efficiency.