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

Real-time thermal monitoring of power-semiconductor temperatures is an important task to establish thermal protection within a water-cooled power-electronic inverter unit. A model-based method is presented, which estimates the junction temperatures. Via feedback of measured temperature signals, the observer system is also able to estimate the coolant temperature. However, if the module is cooled by variable coolant flow rates, the heat transfer coefficient from heat sink to coolant changes. Consequently, the estimated coolant temperature of the observer system based on a static thermal model becomes inaccurate. This paper proposes a method to adapt the thermal model dependent on the current coolant flow rate using a parameter-varying system design.