Improved Temperature Monitoring and Protection Method of Three-Level NPC Application Based on Half-Bridge IGBT Modules

The overheating stress of power devices is the main cause of converter system failures, so real-time temperature acquisition, as well as timely over-temperature protection, under various operating conditions are key to achieving a more reliable energy conversion. In this paper, an improved three-dimensional (3-D) coupled thermal model for insulated gate bipolar transistors (IGBTs) and related heatsink is constructed by considering the thermal coupling effects at both the device- and the module level. Furthermore, the coupled thermal impedance parameters are thereby extracted based on the finite-element method (FEM), so that the dynamic loss and transient temperature distribution under actual working conditions can be obtained based on this electro-thermal coupling model. Meanwhile, to avoid the overheating damage of power devices due to untimely action of the negative temperature coefficient (NTC) thermistor over-temperature protection, this article aims at the idle IGBT device in the three-level neutral-point clamped (NPC) application using IGBT half-bridge modules, combined with the emitter terminal temperature, and finally realizes the multiple over-temperature protection settings. The improved temperature monitoring methods proposed in this paper are realized by the drive and control circuits and verified through simulation and experimental results.