Integrated Energy Management Strategy for Battery Life Extension in Electric Vehicle Hybrid Energy Storage Systems Using an Enhanced Multiport Bidirectional Converter

Abstract

Hybrid energy storage systems (HESSs) combining batteries and ultracapacitors (UCs) can improve the performance and lifespan of electric vehicle (EV) energy storage systems. Their effectiveness depends on the selected multiport converter and energy management strategy (EMS), which play key roles in reducing battery stress and improving longevity. Accordingly, this paper proposes an enhanced multiport converter employing a bidirectional converter for the UC and a unidirectional converter for the battery, enabling bidirectional power transfer among the battery, UC and load through flexible and reconfigurable power-flow paths. An integrated EMS is proposed to provide transient power support during motoring, prioritize UC charging during regenerative braking and initiate C-rate-limited battery charging only after the UC reaches its upper state-of-charge (SoC) limit. The proposed system is evaluated in MATLAB/Simulink using the Urban Dynamometer Driving Schedule (UDDS), while the converter operation is experimentally demonstrated using a laboratory prototype. The simulation results demonstrate a 77.5% reduction in peak battery charging current, 12% reduction in RMS battery charging current and 68.7% reduction in battery charging occurrences compared with the conventional EMS. Furthermore, the proposed EMS increases the regenerative braking energy absorbed by the UC by 36.1%. The comparative battery aging analysis indicates a 58.6% increase in estimated Ah-throughput. These findings demonstrate the effectiveness of the proposed system in enhancing battery longevity and supporting sustainable EV operation.