Comparative Analysis of Passive and Semi-active Hybrid Energy Storage System Topologies for Electric Vehicle

The hybrid energy storage system (HESS) in electric vehicles (EVs) is introduced to reduce battery stress and improve the capture of regenerative braking power. The most common HESS configuration for EV consists of a high voltage battery pack and supercapacitors. There are various possible HESS topologies for EVs. In this paper, a comparison between two possible HESS topologies are considered, namely the semi-active HESS and the passive HESS. The effectiveness of these configurations is analyzed through simulations conducted on an EV conversion MyVi, installed with 30. 2kWh Li-ion battery. The simulation results based on NEDC clearly demonstrate the advantages of using a HESS over a vehicle with a battery as the sole energy storage system. However, the passive HESS, which lacks control and relies on internal resistance and State of Charges (SoCs) for power flow, only slightly reduces the battery discharge rate, failing to meet one of the main purposes of a HESS. On the other hand, the semi-active HESS, equipped with a bidirectional DC-DC converter and controller, effectively limits the battery discharge rate, optimizes power flow management, and maximizes the utilization of both the battery pack and the supercapacitor (SC) bank. The semi-active HESS achieves a longer travel range of approximately 228.2km compared to 211.5km for the passive HESS. Moreover, the semiactive topology successfully minimizes battery usage by recapturing regenerative braking energy, with a recaptured energy value of -0.06kWh, whereas the passive topology only achieves -0.68kWh. The semi-active HESS also exhibits a lower battery RMS current value of 39.00A compared to 46.46A for the passive HESS. Additionally, the semi-active topology utilizes the SC bank more efficiently, supplying almost double the energy compared to the passive topology (6.35kWh vs. 3.29kWh).