Maximum Inverter AC Current Prediction Based on Junction Temperature Calculation
Abstract: Semiconductor devices are widely used in the automotive industry, and they are key components of the inverter and the converter in an electric vehicle. Thus, the concern of protecting the inverter and the converter from damaging operation has been raised. The junction temperature is one of the main considerations. It is directly related to the inverter power loss and overheat which can lead to fatigue or even failures. Therefore, to protect the semiconductor device from thermal runaway and apply active thermal control, the junction temperature must be obtained.To derive the junction temperature of an Insulated-Gate Bipolar Transistor (IGBT) and a diode, an instant model is proposed. The instant model updates the junction temperature at the PWM switching frequency (around 2-5 kHz in this thesis). Compared with the traditional algorithm which calculates the average temperature over one fundamental cycle, the instant algorithm can show the instant temperature swing. A high power IGBT module, FF1200R12IE5 Infineon, is selected to verify the algorithm with temperature results from IPOSIM and Power HIL tests. The temperature deviations for different cases are below 6 ◦C and the relative errors are below 10 %.With an accurate estimation of the junction temperature, the current limit is set to avoid that average temperature, maximum temperature and temperature swing exceed their limits. The currentlimits are derived from the curve/ surface fitting method.
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