Real-time coolant temperature monitoring in power electronics using linear parameter-varying models for variable coolant flow situations

In power converters of (hybrid) electric vehicles, the power losses within the semiconductors (diodes and IGBTs) lead to strong self-heating. Therefore, methods for online monitoring of the relevant temperatures are a very important topic regarding thermal self-protection. In order to reduce the number of sensors (and costs) it can be advantageous to use fewer sensors than the number of relevant temperatures and to use a model-based method to reconstruct/estimate the non-measureable temperatures. However, the accuracy of such models in water cooled systems is affected if the coolant flow rate deviates from nominal (constant) flow rate. This paper presents a method to estimate the junction temperatures of the semiconductors and the coolant inlet and outlet temperature of a 3 phase voltage inverter for automotive usage. It proposes a linear parameter-varying model to cope with variable coolant flow situations. Eventually, the method is verified by measurements.