A sinusoidal charging strategy for battery energy storage systems use in light electric vehicles

This work develops a novel sinusoidal charging strategy for use in light electric vehicles (LEVs). To generate a sinusoidal charging current, the switching frequency of the series-resonant converter is less than half of the resonant frequency. Thus, the series-resonant converter is operated in discontinuous current mode (DCM) to achieve the zero-current-switching (ZCS) condition. As a result, high energy conversion is ensured. Novel sinusoidal charging topologies with a simple structure, low cost, easy control, and high efficiency are presented for the battery energy storage systems (BESSs) of LEVs. The operating principles and design procedure of the novel sinusoidal charger circuits will be analyzed in detail. The optimal properties of the resonant components are derived from the novel sinusoidal charger circuit configuration. Simulation and experimental results are obtained for a laboratory prototype and demonstrate the feasibility of the proposed strategy. Finally, prototypes of the novel sinusoidal charger circuit that is designed for LEVs with a 48V-12Ah lead-acid BESS are constructed and tested to confirm the theoretical predictions. The maximum charging efficiency of the charging period is 95.95%. Experimental results reveal the satisfactory performance of the novel high-frequency sine-wave charging strategy, which is particular appropriate for BESSs in LEVs.