A Flexible Bidirectional Multiport Converter for Battery-Ultracapacitor Hybrid Energy Storage System in Electrified Vehicles

To augment the power management among battery and ultracapacitor (UC) in a hybrid energy storage system (HESS) for electrified vehicles (EVs), a multiport converter having flexibility in power transfer is desirable. With this objective, a bidirectional dual input single output multiport converter is proposed, which can achieve dynamic flexibility of power flow by employing only two high frequency (HF) switches. The converter comprises a pair of dedicated current flow paths to process high and low level of currents. The current flow paths can be flexibly re-allocated with the desired energy storage depending upon the dynamic load power scenarios of an EV. This enables in maneuvering the flow of power between the three ports according to the nature of variations in an EV load profile. Furthermore, the converter ensures single stage power processing in every possible power flow direction while providing independent control over each power flow path. All these features are obtained by utilizing only two HF switches, thereby demonstrating judicious sharing of components with simplified gate driving and control. The performance of the proposed multiport converter corresponding to dynamic EV load profiles is validated through simulation in MATLAB/Simulink and experimentation on a 1 kW laboratory scale hardware prototype.