A Real-Time Adaptive IGBT Thermal Model Based on an Effective Heat Propagation Path Concept

Abstract

The information of junction temperature is crucial for the operational management of insulated-gate bipolar transistor (IGBT) modules. In practice, the junction temperature is typically estimated by using an electrothermal model. IGBT modules are subject to various aging processes during operation, some of which, e.g., substrate solder crack, change the thermal impedance of the IGBT module. However, few works in the literature have included the aging effect on the online thermal behavior modeling of IGBT modules. This article proposes an effective heat propagation path (EHPP)-based real-time adaptive thermal model for IGBT modules, where the EHPP is proposed to quantify the impact of substrate solder cracks on the heat propagation inside the IGBT modules. A straightforward relationship between substrate solder crack and the degree of nonuniformity of case temperature distribution is established. This relationship is then used to approximate the EHPP of the IGBT module in different substrate solder health conditions in real time using the measured nonuniformity of case temperature distribution. Based on the change of the EHPP, the parameters of a thermal equivalent circuit (TEC) model, e.g., an improved Cauer-type TEC, are adjusted online and in real time to track the thermal behavior changes of the IGBT modules caused by substrate solder cracks, leading to a real-time substrate-solder-aging-adaptive thermal model. The proposed real-time adaptive thermal model is validated by simulation studies and experimental tests for a commercial IGBT module.