Design Of Buck-boost Phase-shift Full-bridge DC/DC System For Off-board Charging Pile

With the continuous advancement of science and technology and the rapid development of society,the two global issues of energy crisis and environmental pollution are also increasingly prominent.It has become the consensus of all countries in the world to promote the rapid development of the electric vehicle industry.However,there are still many problems in the development of the electric vehicle industry.For example,charging technology is not yet mature and the charging infrastructure is not yet perfect.These problems hinder the popularization of electric vehicles.Therefore,the development of non-vehicle charging piles is a powerful measure to promote the development of electric vehicles.As an important part of non-vehicle charging piles,the DC/DC system plays a key role in the development of the electric vehicle industry.This thesis takes the non-vehicle charging pole as the research object,and studies the main circuit topology,hardware circuit,software and algorithm of the post-stage DC/DC system.The main research contents are as follows:The overall scheme of non-vehicle charging piles is designed,and the main technical specifications of the subsequent DC/DC system are given.The design scheme of the buck-boost type phase-shifting full-bridge DC/DC converter as the DC-DC charging post-stage power conversion system is proposed.The principle of the typical topology is analyzed.Six switching modes of the half-cycle of the converter are described in detail.Several key technologies of the phase-shifted full-bridge DC/DC converter are discussed.Finally,the main circuit power device is discussed.Conduct selection and analysis.According to the design specifications and functional requirements of the nonvehicle charging pile DC/DC system,the control system and the main hardware circuit are designed to select the control chip required for the charging pile control system.The hardware circuit design mainly includes the sampling circuit and the driving circuit.Communication circuit.At the same time,in order to ensure the safe,efficient and stable operation of the system,hardware overcurrent protection and drive short circuit protection are set on the hardware,and the system software protection program is combined to achieve the double protection effect of hardware and software.The small-signal model of the phase-shifted full-bridge DC/DC converter was established based on the buck converter small-signal model.The basic principles of fuzzy control and fuzzy adaptive PID control were described.The similarities and differences between conventional PID control and fuzzy adaptive PID control were compared and used.Simulink simulates both,and it is found that the fuzzy adaptive PID control has better control effect than the conventional PID control.Then the boost output and buck output of the converter are simulated to verify the feasibility of phaseshifted full-bridge buck-boost output.Finally,including the system software program design.Build a phase-shifted full-bridge DC/DC converter experimental platform,provide the basic equipment required for experimental debugging,capture the waveform of the drive circuit and the main circuit waveform through an oscilloscope,analyze it,and analyze the efficiency of the inverter operating at 70 kW.The test verifies that the system satisfies the design specifications and shows the feasibility of the fuzzy adaptive PID control algorithm.