Condition Monitoring of High Voltage Press-Pack IGBT with On-State Collector-Emitter Voltage
Insulated gate bipolar transistor (IGBT) is the critical component in Module multilevel converter (MMC) submodule and is aged under operating condition. As the voltage rating of MMC-HVDC power transmission continues raising, high voltage press-pack IGBT (PPI) will be used widely. Condition monitoring of high voltage PPI is very important to maintain the reliable operation of MMC-HVDC. The purpose of this paper is to use on-state collector-emitter voltage during power cycling experiment as degradation indicator of high voltage PPI. On-state collector-emitter voltage is largely influenced by collector current and junction temperature. The impact of collector current can be ignored in this experiment because the current remains 350A. Junction temperature is very difficult to be directly measured, but gate internal resistance can indirectly reflect the junction temperature. Gate internal resistance can be calculated by peak gate current obtained together with on-state collector-emitter voltage during power cycling experiment. The on-state collector-emitter was measured under different junction temperature when the PPIs are under the same degradation degree. The results show that there is a linear relationship between on-state collector-emitter voltage and junction temperature. The linear relationship is used to strip the influence of junction temperature on on-state collector-emitter voltage obtained during power cycling experiment. After stripping the influence of junction temperature, the results show that the on-state collector-emitter voltages of test PPI samples all increase with the degradation continuing. On-state collector-emitter voltage can be utilized to be degradation indicator of high voltage PPIs.
KeywordsPower cycling High voltage PPI On-state collector-emitter voltage Gate internal resistance Junction temperature