Power management control strategy of battery-supercapacitor hybrid energy storage system used in electric vehicles

Energy storage and power management are two critical factors to the performance of various electric vehicles (EV), including pure, hybrid, and plug-in hybrid EVs. This chapter focuses on the state-of-the-art technologies of hybrid energy storage systems (HESS) for EVs, mainly in power management strategy. It analyzes low-level hybrid topologies of hybrid system. The chapter discusses high-level supervisory control between battery and supercapacitor. It describes the advantages and disadvantages of four commonly used hybrid structures for EVs. Effective management of power flow via optimal use of supercapacitor bank and battery pack and via an efficient power flow controller are the key to achieving high performance. The chapter investigates some power management strategies from both time domain control and frequency domain control to improve system efficiency, battery life cycle, and robustness of the hybrid system. A power management strategy based on wavelet transform algorithm has proved effective in dealing with the transient phenomena in load power demand.