Design and Implementation of a Distributed Thermal Control System for Power Electronics Components in Hybrid Vehicles

Hybrid electric vehicles and battery electric vehicles (BEV) use power electronics (PE) devices to convert between high voltage DC power of the battery and other formats of power. These PE components requires operation within certain temperature range, otherwise, overheating causes component as well as vehicle performance degradation. Therefore, a thermal management system is required for PE components. This paper focuses on the design and development of such a PE components thermal control system. The proposed control system is a distributed thermal control system in which all the PE components are placed in series within one cooling loop. The advantage of the proposed control system is its reduced system complexity, energy efficiency and flexibility to add future PE components. In addition, electric control unit (ECU) are utilized so that complex control algorithms can be implemented. From theoretical perspective, the proposed control system is proved to have sufficient thermal capacity under extreme hot ambient environment. The proposed control system is implemented and tested in various conditions. Test results show that the maximum coolant temperature reached 73.71°C which further verified that the proposed thermal control system has sufficient thermal capacity. In testing, it is found that residual heat accumulated around PE components after propulsion system becomes inactive and the heat generated during off power mode charging potentially cause coolant after-boil issue. Therefore, adaptive after-run cooling control and off-power mode cooling are designed to cover those conditions when the vehicle propulsion system is inactive.