Research On Dynamic Behaviors Of T-type NPC IGBT Module

T-type NPC (neutral point clamped) inverter, featuring in high efficiency and low THD, gradually prevails in market. IGBT (insulated gate bipolar transistor), the main switch in an inverter, plays a key role. This thesis focuses on the impact mechanism and potential damage between IGBT and the T-type NPC inverter, to build foundation for the system design and further improve the system reliability and safety.14 current commuting modes are theoretically analyzed in this artical from the aspect of output current and voltage. In each mode, IGBT performs corresponding dynamic behaviors, specifically in the change of collector-emmitter voltage. Such dynamic behaviors may false trigger the Vce desaturation protection circuit, leading to unexpected system shutdown. The thesis has validated the analysis by building a 15kW T-type NPC inverter, and also put forward a logic algorithm to provide guidance on hardware drive circuit or DSP design depending on the results.To satisfy the demanding of high power output of T-type NPC inverter, this article does research on the paralleling behaviors of T-type IGBT modules for the first time, and brings up the idea of the energy loss mismatch to measure the paralleling identity. The theoretical and experimental results show that the paralleling identity can be achieved by certain temperature deviance when IGBT is turned on. For the turn-off behaviors, the energy loss mismatch rises with temperature deviance, so it is with overvoltage risk and di/dt risk. The article also reveals that there is additional current path in the paralleling T-type IGBT modules, which can causes extra loss. Compared to the two level inverter, the T-type NPC inverter has better performance when paralleling used.The thesis concentrates on the dynamic behaviors of T-tpye IGBT for the first time. The foundings not only provide guidance on the DSP or circuit design of the T-type NPC inverter, to help avoid unexpected false triggering, but also give light on the sink and structure design of T-type NPC inverter.