Fault-tolerant compensation control for T-type three-level inverter with zero-sequence voltage injection

This study proposes a carrier-based PWM strategy with zero-sequence voltage injection for T-type three-level inverter to a tolerant open-circuit fault. The half-bridge and NP bridge open-circuit faults are analysed. The faulty switch can be identified by the average phase current and the deviation of neutral-point (NP) voltage. In the case of half-bridge failure, the fault-tolerant control reduces the distortion of phase current and the amplitude of line-to-line voltage is decreased. In the case of NP failure, the faulty pole voltage becomes two-level instead of three-level and the phase voltage is not reduced. By using the novel zero-sequence voltage injection, the NP voltage is balanced in both half-bridge and NP bridge failures, which do not require additional hardware and complex calculations. The effectiveness of the proposed fault-tolerant PWM strategy and injection of zero-sequence voltage is validated by the simulation and experiment results.