Research On Bi-directional DC/DC Converter For Small Electric Vehicles

Automotive industry has been developed continuously for hundreds of years, itreflects the glorious history of the development of science and technology civilization,promotes global economic growth rapidly and provides convenient transportationsimultaneously, but energy crisis and environmental pollution problems which arecaused by it become seriously outstanding, Traditional internal combustion enginetechnology and current social problems become a contradiction, development of newenergy vehicles receives more attention. Many auto makers at home and abroad andscientific research units spend a lot of manpower and material resources on coreproblems related to electric vehicles, vehicles need to implement the condition thatenergy flow run between electric power energy storage and load in two directions,bi-directional DC/DC converter is the key component of realizing two-way flow ofenergy, the study also becomes more popular recently, mainly concentrates in newcircuit topology and control strategy, and how to improve the efficiency of theconverter, in order to realize energy saving target.This paper states the current research in bi-directional DC/DC convertertopology, analyses the isomorphic topology and suited applications of bi-directionalDC/DC series resonance converter (SRC), and determine the topological circuit in thispaper. Then analyzes the working principle of the bi-directional full bridge SRC andestablishes equivalent circuit for different loads using a new method according to itswork mode, gets soft switching conditions, does the modeling of main circuit usingextended description function method simply and accurately, The effectiveness of thismethod is verified by comparing amplitude frequency response of transfer functionfrom theoretical analysis by MATLAB simulation and amplitude frequency responseof the main circuit by PSIM AC sweep. It optimizes parameters of full bridge SRCwith two types of load before simulation，two directions power flow of the controlprocess and the generating mechanism of phase shift waveform are introduced indetail, then the power of forward and reverse flow simulation and the voltageregulation simulation for the system are carried out. Full bridge series resonance isstudied in the generating mechanism of system circulation, and how to suppressinternal system circulation, improve the system efficiency.