Research On Bidirectional DC/DC Converter For Auxiliary Power System Of Electric Vehicle

In recent years, the problem of oil shortage and environmental pollution has become more and more serious, which has become a major concern of the domestic and foreign.Since 2003, most gas station in various regions of our country is short of oil in an emergency. At the same time, the central and eastern part of China in recent months often appear haze weather, the environmental problem is getting worse. Pure electric vehicles is using electric energy instead of fossil energy and other fossil fuels, especially the advantages of high efficiency and zero emissions has been widely concerned by all over the world. However, the battery itself and its charging and discharging technology in electric vehicle has always been the key problem of the rapid development in electric vehicles. Using the auxiliary power system of electric vehicles can effectively compensate for the lack of battery, and the auxiliary power system mainly including the super capacitor, bi-directional DC/DC converter and its control circuit. Through bi-directional DC/DC converter can not only released the energy stored in super capacitor when the electric vehicle is starting and acceleration, but also recovered feedback energy when the electric vehicle is deceleration and braking, and also realized the two-way flow of energy. Based on above, this dissertation designed a two phase interleaved bi-directional half bridge DC/DC converter based on the controlled soft-switching technology.First, in the four typical non-isolated bi-directional DC/DC converter, chose two-way half bridge DC/DC converter with the minimum voltage and current stress as the basic structural unit in this dissertation. Then, in order to reduce the single power device to withstand the amount of current, improve the power levels, this dissertation adopts multiple topology, puts two half bridge DC/DC converter interleaved, and constitutes two phase interleaved bi-directional half bridge DC/DC converter.Secondly, the two phase interleaved bi-directional half bridge DC/DC converter adopts soft-switching technology. The dissertation uses controlled soft-switchingtechnology which has convenient control and lower cost, by adding an appropriate amount of inductance and capacitance element, but not the semiconductor device in the main circuit to achieve the soft-switching.In the control mode, this dissertation chose a voltage and current double closed loop control mode, and the output value of the voltage outer loop is given as the set point value of each current inner loop, so that the effect of parallel current sharing is achieved.According to the design requirements in dissertation, each element parameters in converter are calculated. In the Matlab/Simulink platform, the main circuit model and the control circuit model of the two interleaved bi-directional half bridge DC/DC converter are built, and the simulation analysis is carried out on the boost and buck operation mode.The simulation results show that the element parameters in converter is correct, and the control strategy is feasible.Finally, this dissertation set up a two phase interleaved bi-directional half bridge DC/DC converter rated power of 180 W which uses TMS320F2812 DSP as control chip,and do the Boost and Buck experiment separately. According to the experimental results,it is shown that the design of converter meets the basic requirements, and also proves that the design scheme in this dissertation is feasible.