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Thermal Coupling Analysis in a Multichip Paralleled IGBT Module for a DFIG Wind Turbine Power Converter

Thermal coupling between adjacent insulated gate bipolar transistor (IGBT) or diode chips is the result of nonuniform temperature distribution in a multichip IGBT module. This affects the junction temperatures and hence the total power loss predicted for the module. The study first investigates the impact of thermal coupling effect on the junction temperatures through a finite element method, and then develops a thermal coupling impedance model to represent such effects. The effect is shown to reduce with the distance exponentially. The model result agrees well with the test. The validated model is then used to predict the junction temperature swings during operational power cycling in a doubly fed induction generator wind turbine, showing the difference between the rotor and grid side converters. The model presented and the results obtained may be important for reliability evaluation and condition monitoring in the wind turbine power converters as well as in other multichip-paralleled power electronic systems.