Study Of Charging Balancing System Of Batery Based On FPGA&NIOSⅡ

Battery system is the power source of hybrid electric vehicles (HEV) and electric vehicles (EV). Their performance is directly dependent on the characteristics of battery system. In practical applications, the unbalance of power battery is enhanced with the increased charge-discharge cycle number, resulting in the damage of single element and the earlier failure of battery system. Therefore the balancing technique of battery system is crucial for both the performance and life improvement of power battery and the development and industrialization of HEV and EV.Firstly, this dissertation proposed the task and goal of the charging balancing system of battery. Then, it analyzed the difficulty of battery balancing technique. Based on the existing design methods, according to the task and goal of charging balancing system, a layered balancing design of distributed DC/DC circuit was proposed. Finally, the design was theoretically analyzed and verified by experiments.This dissertation describes the research into charge-discharge characteristic and charging technique of NIMH battery, according to which a battery balancing system based on buck-boost circuit and FPGA/NIOSâ…¡was designed. The main circuit of the system adopted a layered balancing structure to lower the voltage stress and loss of switch components. The control circuit was based upon FPGA/NIOS II embed system and able to control multiple switch components and increase the balancing speed. The control strategy was to lookup table in order to increase the balancing speed. Based on the voltage difference (the difference between the single element voltage and the mean voltage) maximum, various frequency tables were chosen to generate switch component driving signal so that the balancing circuit was able to produce enough balancing current in the whole balancing process.It was verified by the experimental results that the suggested power battery balancing system by this dissertation greatly improved the balancing characteristics of the NIMH battery. Compared with other balancing systems, this system has faster balancing speed. The system is highly efficient, compact, reliable, and appropriate to practical engineering applications. The battery balancing system can be easily extended in further into highly integrated battery management system (BMS), which has more functions including high voltage protection, temperature control, SOC calculation, etc. It also brings up an innovative design method for BMS.