Study On Multiple Soft-switching Bidirectional DC/DC Converter For Electric Vehicle

With energy depletion, the oil crisis is coming, research of electric vehicles in the world is in full swing. As cars in the real driving process frequent acceleration, deceleration, starting, braking and changes in energy storage battery voltage, it's necessary to provide a stable DC source to the motor to avoid the influences. Consideration for improving energy efficiency and battery utilization, the energy need to be fed back into the battery automatically when cars suddenly brake producing a higher counter-electromotive force.Bi-directional DC/DC converter plays an important role between the storage battery and the motor, its development is particularly urgent.After researching a variety of bi-directional DC/DC converters home and abroad, this paper investigated a topology based on the basic half-bridge module which has simple structure and good performance. Three-phase interleaved topology is formed for the characteristics of vehicle high-power.The concept and the five basic features of controlled soft-switching technique are generalized and sorted out. Then three-phase interleaved bi-directional DC/DC converter is designed to use the controlled soft-switching technique, just by controlling the switch turn-off signal to achieve soft-switching without any additional semiconductor devices. With the characteristic of it's forword half-bridge, the inductance current of the converter is designed to work in positive and negative alternate mode to make the inductor current exchange energy with the up and down capacitors of swiches in the appropriate deadtime, then the purpose of soft-switching effect is achieved. The inductance will be greatly reduced in this way. The mode associated voltage and current ripples voltage and current ripples can be alleviated by multiphase interleaved operation. This paper adopts a voltage and current double close-loop control strategy to balances the inductor currents among cell modules using a same reference current from the common voltage closed-loop.The proposed circuit is simulated with Matlab/Simulink software, and the simulation results under different circumstances illustrate that the performance of the topology proposed converter is correct and effective in the Boost mode and the Buck mode.Finally, the hardware circuit of three-phase interleaved bi-directional DC/DC converter rated at 40W which took SG3525 as its center control chip was constructed. The feasibility of the program is verified through analysising and observation of switching waveforms and output waveforms.