Prototype Design and Controller Implementation for a Battery-Ultracapacitor Hybrid Electric Vehicle Energy Storage System

This paper presents the modeling, design, and novel control strategy development for a hybrid switched-capacitor bidirectional dc/dc converter, applicable for a hybrid electric vehicle energy storage system. The proposed control strategy is based on the power profile of the traction motor and the gradient of battery current. Features of voltage step-down, voltage step-up, and bidirectional power flow are integrated into a single circuit, and are verified on an experimental prototype. The developed control strategy enables simpler dynamics, compared to a standard buck converter with input filter, good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both buck and boost modes of operation.