Real-Time Compact Thermal Models for Health Management of Power Electronics

Implementation of real-time health assessment and thermal management of power electronic devices require real-time electrothermal models that can be used to predict the temperatures of device junctions, interfaces, etc., which cannot ordinarily be measured during service. This paper presents a real-time reduced-order compact thermal model, which is incorporated in a pulsewidth modulation and current controlled full bridge. An accurate representation of the dynamic thermal behavior was obtained experimentally and converted into a simplified multiexponential form then combined with lookup tables that provide estimates of the device losses based on measured values of the phase current. For interfaces away from the surface, such as solder layers, a validated Flotherm model is used to predict the temperatures of the hidden layers. Comparison of the real-time temperature estimates with IR measured values obtained from a high-speed IR camera showed that the reduced-order model was capable in estimating the module's temperatures over a range of modulation conditions. This real-time model is well-suited to the continuous monitoring of the internal behavior of the electrothermal effects within power electronic modules and can thus be used as part of a prognostic tool to provide knowledge through thermal cycling by combining with thermomechanical wear out models for health management of power electronics.