A Novel Tri-Mode Bidirectional DC–DC Converter for Enhancing Regenerative Braking Efficiency and Speed Control in Electric Vehicles

A bidirectional dc–dc converter is used to match the voltage levels between a low-voltage battery and a high-voltage traction machine in an electric vehicle. Using a conventional bidirectional converter with a standard voltage range, there is a limitation to the fine variation in the electric vehicle speed. During the regenerative braking process, when the speed decreases below a certain value, the generated voltage is insufficient to charge the battery, hence the regenerated energy cannot be stored. This paper proposes a novel bidirectional converter featuring three distinct operational modes: boost, buck and buck-boost. In the normal driving mode, it operates as a boost converter, providing double gain and accommodating a wide voltage range. During regenerative braking, the proposed converter switches to the buck or buck-boost mode based on the control algorithm. This adaptation is intended to either decrease the generated voltage to charge the battery effectively or to raise the voltage if it is insufficient for charging the battery. This configuration provides voltage stress of half the dc link voltage on the switches. This paper provides a comprehensive analysis of the proposed circuit, a detailed description of the control strategy with pulse generation logic for all switches and a mode transition algorithm. The simulation results of a circuit operating at a 1500 W power level are presented and compared with those of a standard bidirectional converter.