Experimental evaluation of different semi-active configurations for battery-ultracapacitor hybrid energy storage system (HESS)

This paper presents the implementation of a Hybrid Energy Storage System (HESS) for electric vehicles. Two semi-active configurations are analyzed: semi-active Ultracapacitor (UC) and semi-active Battery. Control of the energy of one of the storage elements is performed by a bidirectional non-isolated DC-DC converter. The control strategy is based on the separation of the dynamic components of the power required by the load. Namely, while the UC provides fast dynamic power components efficiently, the complement is provided by the battery bank. The separation of the required power into two components is performed by a filter with variable bandwith depending on UC voltage, which allows obtaining an efficient HESS. Experimental results verifying the HESS control strategies for both semi-active configurations are presented, using a pulsating load to represent the demands of a traction drive system.