Thermal network parameter identification of IGBT module based on the cooling curve of junction temperature

The thermal network parameters of IGBT module are wildly used for reliability evaluation, lifetime calculation, health monitoring, and predictive maintenance. Commonly used thermal network parameter identification methods include the finite element method (FEM) and the curve fitting of thermal impedance (Zth) method. The former method calculates directly using the IGBT geometric structure and material properties, but it is difficult to consider the aging procedure of IGBT. The curve fitting method mainly depends on constant loss constraints, which is difficult to guarantee in practical application. In this paper, we propose an IGBT thermal network parameter identification method using the measured junction temperature cooling curve in the procedure of converter shutdown. The relationship between the time constants of junction temperature curve and the thermal network parameters is investigated. We show that the RC parameters can be identified in two different cooling conditions. The obtained RC parameters are in good agreement with the results by JESD51-14 method. The proposed method is simple and easy to implement. In particular, it does not need to consider the dissipation loss of IGBT before shutdown, and is suitable for RC thermal parameter quasi-online measurement.