Improvement of switched structure semi-active battery/supercapacitor hybrid energy storage system for electric vehicles

Abstract

Among new configurations of battery/supercapacitor (SC) hybrid energy storage systems (HESSs) for electric vehicles (EVs), several can be united under the common name of ‘switched structure’. Their features are the ability to switch their structure during operation to direct power of a DC-bus from the battery or from the SC bank, as well as the use of a low-power DC–DC converter that connects both ESSs. Here, such a switched structure between battery/SC HESS was improved, which made it possible to obtain new operating modes. They expand the operating range of the SC bank, while the DC-bus voltage range remains relatively small. As a result, the installed capacity of the SC bank can be reduced by 50% without decreasing the available energy of the SC bank. An algorithm for the energy management system was developed according to the rule-based strategy that allows to choose one from the eight operating modes. The simulation of investigated EV operation with the proposed HESS was carried out during the transport cycle on a model developed through the energetic macroscopic representation approach. The simulation results are confirmed by experiments on a scaled-down experimental setup.