Enhancing Overload Capability of Electric Truck Inverters via Active Thermal Control

Electric trucks are subject to demanding overload events during operations such as kerbstone climbing, where the inverter operates at low output frequency and high current, leading to significant thermal stress on power semiconductors. To prevent exceeding the junction temperature limits, standard practice often involves limiting torque output or oversizing the power stage, resulting in reduced acceleration performance or increased system cost. This study investigates the use of Active Thermal Control (ATC) to improve inverter operation during such overload conditions, enhancing performance without exceeding thermal limits. Three ATC strategies are evaluated: increase of gate voltage, reduction of switching frequency, and the application of Discontinuous PWM, as well as selected combinations of these strategies. The study quantifies the thermal, lifetime, and waveform quality impact when applying these ATC strategies. Results demonstrate that the junction-to-ambient temperature difference can be reduced by up to 26%, and the number of safe mission repetitions can increase by a factor of five. Alternatively, for a fixed thermal limit, the deliverable output current can be raised by approximately 20%, enhancing acceleration capability without requiring converter oversizing. These findings confirm the potential of individual ATC strategies to enhance inverter robustness and dynamic performance, while showing that their combination enables even greater improvements in demanding electric drive applications.