Research On Battery Energy Storge Bidirectional DC/DC Converter

Bidirectional DC/DC converter enables the energy storge system to adapt to wide voltage range operation of the battery and can achieve charge and discharge management, which has an important position in energy storge system, certain theoretical research significance and good prospect of engineering application. In this paper, the three-phase interleaved bi-directional DC/DC converter is used as the object, and the main circuit topology, working mode, working performance, charge and discharge control strategy and power allocation are reasearched.Traditional Buck/Boost converters have some disadvantages, such as high current ripple coefficient, small capacity, large filter element and so on. In order to overcome this defect, this paper introduces three-phase interleaved bidieectional DC/DC converter to energy storage system, and reasrarches operating mode in discharging and charging direction, designs main circuit parameters and operating performance of this converter. Simulation model is built. Through the theoretical and simulation results, the superiority of the three-phase interleaved bi-directional DC/DC converter in the battery energy storage system compared with the traditional Buck/Boost converter is verified.Small signal model of three-phase bidirectional interleaved DC/DC converter is established. Based on which the transfer function of the system is derivated and coupling relationship of the current of three-phase arm inductor is analyzed, proving that three phase currents are coupled, but their coupling relationship is weak and it is not necessary to add the decoupling link in the control scheme. The control strategy of converter in charging and discharging mode is reasearched. The converter can control the battery to discharge while tracking load power on the basis of stabilizing the DC bus voltage when it works in Boost mode, and control the battery’s constant current and constant voltage two-stage charging when it works in Buck mode.The power distribution control strategy when various modules comprised of batteries and DC/DC converters are paralleled in a high power level is reasearched. Based on the state of charge of each energy storage module, traditional discharge capacity proportional allocation method has the disadvantage that the rate of power distribution is slow. In order to overcome this defect, the discharing power distribution control strategy based on power of the state of charge is proposed, which can significantly accelerate the rate of power distribution by changing the current correction parameter. Meanwhile, combined with the battery’s two-stage charging needs, the charging power distribution control strategy based on power of the state of charge is proposed. In order to prenevt the charing power of each energy storge module exceeding the rated limit on the premise that the sum of each module’s charing power remains static, the power correction algorithm is proposed. Finally, the simulation model is built in Matlab/Simulink, steady state in charge and discharge process and transient state that some energy storage modules drop out or put into energy storage system in charge and discharge process or some energy storage modules enter into constant voltage charging stage in charge process are simulated, and the validity and feasibility of the proposed control strategy are verified.