Investigating High-Voltage Safety Concerns in Electric Vehicles Through Voltage Discharge Optimisation

The rapid adoption of electric vehicles coupled with high-voltage battery packs increases safety concerns, especially during crashes. Such safety concerns can be addressed with voltage discharge strategies to reduce the voltage of the DC-bus capacitor. One discharge strategy involves injecting a negative current into the traction motor to dissipate the DC-bus energy through motor windings. One issue with strategies involving the injection of negative d- and q-axis currents into the motor to reduce the speed of the motor and discharge the capacitor quickly is the observation of a large voltage surge due to the energy recovery from the motor. A discharge strategy found in the literature deals with this with piecewise calculation of d- and q-axis currents based on the motor speed. This study investigates this strategy and provides recommendations for improvement and future work with key insights. Using MATLAB Simulink 2023b, this strategy is analysed and compared with other discharge strategies. In certain circumstances with a high-rotor-inertia motor, the performance of the strategy was not deemed adequate. In essence, the lack of testing of discharge strategies on multiple powertrains is deemed as one potential cause of such problems which needs to be addressed in future research.