T-NPC Soft-Commutated Inverter Based on Reverse Blocking IGBTs with the Novel Concept of a DESAT Control Circuit in the Gate Driver

This article presents the concept of switching and conduction loss reduction in a T-NPC inverter based on IGBT transistors. The method of limiting switching losses involves the connection of an LC circuit designed to cause transistors in vertical branches to shut down under zero voltage conditions. In order to reduce conduction losses, it was proposed to use two reverse blocking transistors connected anti-parallel in the horizontal branch of the inverter. To ensure safe operation of the transistors, a gate driver proposal for controlling the IGBT reverse blocking transistor is presented. The solution is characterized by a changed part of the driver, responsible for short-circuit protection. It eliminates excessive, destructive currents that can potentially flow through the driver circuit under the influence of the power supply voltage of the power circuit connected backwards to the controlled transistor. Examples of applications and benefits of the proposed solution are presented and verified with laboratory tests.