Modulation Wave Translation Method for Three-level ANPC Inverter With Neutral-Point Voltage Balancing in Fault-Tolerant Control Mode

In industrial applications, the reliability of power converters is increasingly emphasized, thus promoting a surge in the application of fault-tolerant control (FTC) techniques. This paper addresses the neutral-point (NP) voltage unbalancing problem of active-neutral-point-clamped (ANPC) inverter in FTC mode. First, the principle of ANPC inverter in normal working (NW) mode and fault-tolerant mode is analyzed, where the traditional FTC method of connecting the NP of the DC side is adopted. Subsequently, under the FTC mode, a unified expression of the carrier-based pulse width modulation (CBPWM) with the superimposed zero-sequence component is derived to simplify the modulation process. On this basis, by shifting the modulation waves and then adjusting the dwell time of a single small vector, the NP voltage balancing is achieved. Finally, simulations are performed to validate the effectiveness of the FTC strategy and NP voltage balancing strategy.