MMC Power Device Loss and Junction Temperature Calculation Considering Junction Temperature Feedback

Abstract

The accurate calculation of loss and junction temperature of modular multilevel converter (MMC) is an important basis for device selection, life prediction and reliability analysis of flexible DC transmission system. Currently, the common method of loss and junction temperature calculation uses the fixed junction temperature method, which has errors with actual situation. An MMC power device loss and junction temperature calculation method considering the feedback of junction temperature is proposed in this paper. Loss distribution of power device is analyzed from the operating mode of the half-bridge sub-module, and then the junction temperature feedback calculation method is introduced in detail on the basis of the fixed junction temperature method. The relative errors of loss and junction temperature calculation in fixed junction temperature method and junction temperature feedback method are analyzed by using the actual converter station MMC system as the calculation example. The distribution characteristics of loss and junction temperature in MMC submodules under different operating conditions are also analyzed. The proposed method can be used as a reference for the loss evaluation of high-voltage and large-capacity flexible DC transmission systems.