Frequency Filtering in Ultracapacitor-Battery Energy Storage System in Electric Vehicles

Abstract

The Energy Storage System (ESS) of an Electric Vehicle (EV) needs to have both high-power density and high-energy density to fulfil the transient power requirement during vehicle accelerating and decelerating and also to have better driving range. Both of these goals can be achieved through the hybridization of energy sources. In this study, a battery and an Ultracapacitor (UC) combination is used to construct a fully-active Hybrid Energy Storage System (HESS). The HESS architecture is built using two bidirectional DC-DC converters, each one for the two energy sources, respectively, and a DC bus. HESS is sized using vehicle dynamic modelling considering the New European Driving Cycle (NEDC). A rule-based power sharing strategy is employed for the HESS. Further, two frequency filtering-based approaches, namely the Low Pass Filtering (LPF) approach and the Wavelet multilevel Haar Transform, have been developed to control the power flow between the energy sources of HESS and reduce overall battery stress during high transient power demand. For the same driving cycle, different power management strategies are compared in terms of battery status (current, SOC, energy) as well as the UC status (current, energy) followed by battery lifetime extension. The main goal of this study is to investigate the performance of an UC-battery HESS for EVs using the MATLAB/Simulink environment. © 2022 IEEE.