Electrothermal-Based Junction Temperature Estimation Model for Converter of Switched Reluctance Motor Drive System

Abstract

In this paper, an electrothermal-based junction temperature estimation model is proposed for an asymmetric half-bridge converter of a switched reluctance motor drive system. In the current chopping control mode, there exists a particularly uneven temperature distribution on converters due to not only the thermal coupling effects and dissipating boundary conditions, but also the different device losses in the same phase bridge. For the purpose of precise estimation for junction temperature, first, the power loss of converter is accurately calculated by the interpolation method with the help of Simulink and LTspice. Second, the thermal coupling effects and dissipating boundary conditions are analyzed in the three-dimensional finite-element method (FEM) model. According to the step power response extraction, a coupling impedance matrix is used to describe the nonnegligible thermal coupling effects between devices, and the complete heatsink can be decoupled into multiple subdivisions that represent the different heat dissipating boundary conditions. Then, with coupling impedances and subheatsink impedances in series, a compact RC network model can be built for junction temperature estimation. Consequently, analytical investigation in conjunction with FEM simulation and experiment measurements demonstrate the validity of the proposed model.