DC Bus Capacitor Discharge of Permanent-Magnet Synchronous Machine Drive Systems for Hybrid Electric Vehicles

This paper investigates control methods to quickly and safely discharge the high-voltage dc bus capacitor for the permanent-magnet synchronous machine drive systems of hybrid electric vehicles during emergency situations such as a crash event. The published dc bus capacitor discharge strategies either need impractically heavy and bulky hardware or are only effective for low machine speeds. Applying the existing methods under high speeds will lead to loss of the current control and a system shutdown, followed by the bus voltage recharging again. The proposed new control method applies a modulation index controller together with a bus voltage regulator to quickly discharge the bus voltage and avoid any bus recharge regardless of the electric machine speed. Simulation and experimental results are presented to verify the effectiveness of the proposed control algorithm.