Impact of Active Cooling on the Thermal Management of 3-Level NPC Converter for Hybrid Electric Vehicle Application

The application of power electronic converters (PEC) in electric vehicles (EVs) has increased immensely as they provide enhanced controllability and flexibility to these vehicles. Accordingly, the interest in developing innovative and sustainable technologies to ensure safe and reliable operation of PECs has also risen. One of the most difficult challenges experienced during the development of reliable PECs is the design of proper thermal management systems for controlling the junction temperature and reducing the thermal cycling of power semiconductors. The addition of Active Thermal Control (ATC) can mitigate these concerns. Moreover, the performance of the thermal management system can be enhanced further by the integration of active cooling methods. An active cooling system consumes external energy for circulating cooling air or liquid within the PECs. This study investigates the impact of ATC and active liquid cooling on the thermal performance of SiC-based semiconductor devices of a three-level Neutral-Point-Clamped (NPC) inverter that drives the Permanent Magnet Synchronous Machine (PMSM) of an EV. A Cauer-based thermal model, including a heat sink and thermal pad, is developed to explore the combined effect of ATC and active cooling on the thermal performance of the semiconductor switches. The effectiveness of the proposed thermal management system is demonstrated through results obtained from MATLAB/Simulink. Compared to the average junction temperature without any ATC and minimum coolant flow rate, a 1.37% reduction in average temperature was observed when both ATC and maximum coolant flow rates were applied. Moreover, a 23.59% reduction in the largest thermal cycle was observed when both ATC and maximum coolant flow rates were applied.