Mitigating HV battery malfunctions in a 48 V P0 mild hybrid system: A novel voltage control strategy

Abstract

When the HV battery of a hybrid electric vehicle encounters severe faults, the 12 V battery can easily become depleted, forcing the vehicle to shut down. To address this issue, this paper proposes a novel voltage control strategy specifically tailored for a 48 V P0 mild hybrid system in a MHEV. The strategy comprises two main components. The first component is a dual closed-loop control strategy with weak magnetic control for the MCU, ensuring a stable voltage output from the BSG in generator mode across a wide speed range. The second component is a hierarchical control-based voltage control strategy for the HCU. In this context, the HCU serves as the central controller, coordinating with the BMS, MCU, DC/DC, and ECU to harmonize the voltage control mode of the hybrid system. The effectiveness of this strategy has been confirmed through bench and vehicle tests. Test results indicate that the strategy enables the hybrid system to maintain acceptable HV bus voltage fluctuations and provides effective hardware protection under various scenarios. The strategy guarantees that the vehicle can continue operating after a severe fault in the 48 V battery, thereby enhancing the robustness of the hybrid electric vehicle system.