Integrated Reconfigurable Configuration for Battery/Ultracapacitor Hybrid Energy Storage Systems

In conventional parallel hybrid energy storage systems (HESSs), there are usually two cascaded converters active when transferring energy between its energy storage systems (ESSs) that result in the overall efficiency drop. Moreover, the dc-link capacitor has to be oversized to limit the voltage ripple during simultaneous energy exchange between the ESSs and load feeding. The integrated reconfigurable configuration for HESSs proposed in this paper allows direct energy transfer between the ESSs by using only a single converter and bypassing the dc link. This reduces the stress on the dc link, reduces the dc-link capacitor size, and improves the efficiency. The proposed configuration can be reconfigured to operate in different operating modes: “feeding a load” mode, “regenerative” mode, “energy exchange” mode, “energy exchange and feeding a load” mode, “balancing” mode, “charging” mode, and “backup” mode. To control the proposed HESS, a battery peak power limiting method is used to allocate the power components between the ESSs. The operating principle of the proposed configuration and its different modes are explained and experimentally verified.