Open-Circuit Fault-Tolerant Method for Half-Bridge Switches of Three-Level Quasi-Switched Boost T-Type Inverter to Improve Voltage Gain

Abstract

The three-level quasi-switched boost T-type inverter (3L-qSBT2I) can feature buck-boost operating and shoot-through (ST) immunity with high voltage gain and low component voltage rating. In order to improve the reliability of 3L-qSBT2I, this paper proposes an open-circuit fault-tolerant (OC-FT) method to solve OC faults of semiconductor devices. Under this approach, OC faults of half-bridge switches of the T2I branch are addressed. To solve these faults, one extra normally-closed (NC) relay is integrated with the 3L-qSBT2I, which connects neutral points of DC-link voltage and inverter side. In normal condition, this relay is closed and the inverter operates like a conventional 3L-qSBT2I. In post-fault operation, this relay is opened and the inverter operates like a two-level inverter. A new two-level space vector modulation (SVM) scheme is introduced to control this inverter. Unlike any traditional OC-FT methods, in this proposed method, almost large voltage vectors are still used, in post-fault operating. Therefore, the voltage gain of the proposed method is increased compared to others. Comparison study and experimental results are presented to validate the proposed topology and FT method.

Keywords

• T-type inverter
• quasi-switched boost
• fault-tolerant
• three-level inverter
• open-circuit fault