| Under the pressure of increasing depletion of oil resources and environment pollution, pure electric vehicle(PEV) has became one of the most prosperous new energy vehicles because of its advantages of high efficiency and zero emission. In the urban cycles of frequent acceleration and braking, PEV can make the most of regenerative braking ability of motors to improve operational efficiency and reuse the braking energy, so as to prolong the driving range of PEV. The single battery energy storage system can hardly meet the high power density requirements when the vehicle is at motor-start, accelerating and regenerative braking because of its disadvantage of low power density, which can shorten the service life of the battery. Therefore, an auxiliary energy storage system with high power density is needed to complement the lack of energy supply of single battery energy storage system. As a new energy storage device with high power density, short charging and discharging time and long cycle life, ultra-capacitor(UC) can form the hybrid energy storage system(HESS)with battery, which can integrate the advantages of battery and UC and improve the performance of energy storage system in PEV significantly. This paper focuses on regenerative braking system and the control strategy of energy management of HESS in PEV.Firstly, on the basis of the study of operating characteristic between battery and UC, construction and parameters of HESS were decided. In the case of permanent magnet dc motor, theory of the regenerative braking process was analyzed. Based on ECE braking rules and the maximum regenerative braking force of motor, segmented distribution of front and rear wheel braking force was proposed in order to improve the efficiency of braking energy recovery. In addition, control methods of battery and UC charging loop in regenerative braking process were studied to ensure the safety and rapidity of braking energy recovery. Simulation models were built in MATLAB,and the effectiveness of distribution strategy of braking force and control method of charging process is verified.Secondly, the redevelopment of ADVISOR was studied, including modification of driving cycles and every module of HESS. In the view of rapid descent of UC voltage in the cycles of frequent acceleration and braking, a new fuzzy logic control strategy based on velocity modification was proposed based on analysis of power requirement to manage energy of HESS. Simulation models were built in ADVISOR,and simulation results indicate that the new fuzzy logic control strategy based on velocity modification can optimize charging and discharging current of battery better and prolong the service life of battery.Finally, the energy management experiment system of small power HESS was developed, and software and hardware circuit were designed in detail. The experiment study of energy management system was carried out. The experiment results prove the feasibility of selected HESS structure under pulse load and the superiority of the proposed strategy of energy management. |
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