A high-gain reflex-based bidirectional DC charger with efficient energy recycling for low-voltage battery charging-discharging power control

Abstract

This study proposes a high-gain reflex-charging-based bidirectional DC charger (RC-BDC) to enhance the battery charging efficiency of light electric vehicles (LEV) in a DC-microgrid. The proposed charger topology consists of an unregulated level converter (ULC) and a two-phase interleaved buck-boost charge-pump converter (IBCPC), which together provide low ripple and high voltage conversion ratio. As the high-gain RC-BDC charges, the LEV's battery with reflex charging currents, high battery charging efficiency, and prolonged battery life cycles are achieved. This is possible due to the recovering of negative pulse energy of reflex charging currents to reduce charge dissipations within LEV's batteries. Derivations of the operating principles of the high-gain RC-BDC, analyses of its topology, and the closed-loop control designs were presented. Simulations and experiments were implemented with battery voltage of 48 V and DC-bus voltage of 400 V for a 500 W prototype. The results verify the feasibility of the proposed concept and were compared with the typical constant-current/constant-voltage (CC/CV) charger. The comparison shows that the proposed high gain RC-BDC improves battery charging speed and reduces the battery thermal deterioration effect by about 12.7% and 25%, respectively.