Fault-Tolerant Operation of Three-Phase Cascaded H-Bridge Converters Using an Auxiliary Module

摘要

This paper presents a new fault-tolerant solution for cascaded H-bridge (CHB) converters, which generates equal output voltages in both prefault and single fault conditions. To generate a balanced three-phase voltage with the highest amplitude regardless of the fault location and its type, an auxiliary module is employed in series with the CHB converter. The auxiliary module is a two-level voltage-source inverter with a capacitive dc link. The module is brought to the circuit after fault detection and its capacitor is charged by a novel algorithm to the reference value. Then, using the space vector modulation, the inverter's reference space vector is synthesized and the voltage of auxiliary module is kept constant. The validation of the proposed method is confirmed by simulations and experiments on a three-phase five-level CHB converter.