Control Method for Cascaded H-Bridge Multilevel Inverter Failures

To increase the fault tolerance for cascaded H-bridge inverter, this paper presents a novel switch-based control method for operating the inverter when one or more switches are damaged. To control the inverter under faulty mode, only the faulty switches are disposed, the control signals for other switches in the faulty cell are modified according to the fault type. The influence of various faults on space vectors is analysed and the maximum achievable output voltage of the inverter with faulty switches is calculated. Compared with existing cell-based control methods, this method generates higher voltage space vector magnitudes and reduces the influence of switch problems on motor operation in most faulty modes, while keeping producing a balanced line to line voltage, the reliability of the system is then enhanced. The simulated results agree with the theoretical analysis