Active Fault-Tolerant Control for Three-Level T-Type Converter With Unbalanced Neutral-Point Voltage Modulation

Le résumé fourni par la source

The rectifier and inverter in the T-type back-to-back converter are interconnected via a capacitance with a DC-link midpoint. Faults in the inverter switches of the converter will result in current distortion, load power loss, and DC voltage unbalance, which subsequently impact rectifier operation and grid power quality. Whereas many studies have focused on achieving complete inner switch fault tolerance in three-level inverters, outer switch faults have typically required additional redundant hardware elements or modifications to control references to reduce output voltage amplitude. This paper proposes an active fault-tolerant control (FTC) method for three-level T-type converters with unbalanced neutral-point (NP) voltage modulation to tolerate outer switch faults. The rectifier actively induces the unbalanced NP voltage by injecting zero-sequence components and providing sufficient DC voltage support for the inverter's voltage synthesis. The inverter's separated phase FTC uses healthy legs to achieve the faulty phase voltage synthesis and injects zero-sequence components to fully exploit the DC voltage. This active FTC method avoids the use of faulty switches, maintaining normal converter operation. Hardware-in-the-loop (HIL) testing results demonstrate that the output AC current harmonics are less than 5% and the DC voltage ripples are less than 4%, verifying that the FTC achieves higher performance under various load conditions.

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