An Isolated Three Port Bidirectional DC/DC Converter

Comparing to the traditional internal combustion engine vehicle,electric vehicle and plug-in hybrid vehicle have higher conversion efficiency,less pollutant emission and less noise pollution.In today's environment pollution and energy crisis,it is urgent to develop new energy vehicles.At the same time,the renewable energy system is being connected to the power system.With the development of V2G technology,electric vehicles participate in grid regulation as a distributed power source.The bi-directional charging system of electric vehicles with V2G supports the battery energy to be injected back into the grid.Electric vehicles can be used as the buffer of grid energy to achieve full power conversion and better maintain grid stability and reliability.The bi-directional isolated DC/DC converter is an important part of the car charger of electric vehicle.The research on the wide input and wide output bi-directional isolated DC/DC converter is very important.Chapter One begins with the development background and significance of new energy vehicles,describes the classification of new energy vehicles and vehicle system structure.Then it introduces the bi-directional DC/DC converter based on current research status,focusing on the research status of the multi-port bidirectional DC/DC converter.In the Chapter Two,the isolated multi-port bi-directional DC/DC converter is proposed to solve the problems of the existing car charger:such as unable to realize V2G;unable to realize the electrical isolation between the DC bus,the power battery and the low-voltage battery;complex circuit topology and low efficiency,the low-voltage battery can only be charged by the power battery,etc.The converter proposed in this paper can realize the energy transmission between three ports on the premise of reducing the number of components.In addition,the specific control strategy block diagram of G2V mode,which is the most complex of the three operation modes of the converter,is given.An improved method is proposed to solve the problem of power coupling caused by leakage inductance of DC bus.According to the influence of the parameters of each component on the voltage gain curve and other constraints,the L_m,two groups of resonance capacitance and resonance inductance values are designed.At the end of the parameter design stage,the voltage gain of H2L mode is verified.In this paper,the control strategy of the system is also designed,and then a 3.3kw prototype is made according to the theoretical analysis above.The rated working points of G2V,H2L and V2G and the working points in worst conditions are preliminarily verified by experiments.