Design of a hybrid energy storage system using adaptive digital filtering for electric vehicle applications

The integration of lithium-ion batteries and ultracapacitors within a hybrid energy storage system (HESS) plays an instrumental role in enhancing electric vehicles’ (EVs) performance and prolonging battery lifespan. The bidirectional DC-DC converter manages the power flow between the ultracapacitors (UCs) and the common DC bus, thereby reducing the battery's peak current and extending its lifespan. This work proposed a novel and cost-effective method to mitigate unpredictable current stress by integrating the battery pack with a HESS. In this proposed configuration, UCs are utilized to absorb rapid transients and peak current demands, thereby smoothing the battery current profile. Therefore, the battery pack supplies the baseline load, while the UCs handle high-frequency current components, effectively reducing resistive heating and extending the operational lifetime of the battery. To confirm the proposed HESS's feasibility and improved performance, its performance is evaluated using MATLAB/Simulink. Subsequently, the simulation results are verified by hardware experiments conducted under the conditions of the Worldwide Harmonized Light Vehicle Test Cycle (WLTC). The simulation and hardware experimental results collectively substantiate the superior performance of the proposed HESS equipped with the Adaptive Digital-Filter-Based Energy Management Strategy (ADFB-EMS), which outperforms the standard fixed-cut-off frequency.