Research on Switch-based Control Method for Cascaded H-Bridge Inverter Failures

To increase the fault tolerance for cascaded H-bridge multilevel inverter(CHMI),a novel control method is presented for operating the inverter when one or more switch devices are damaged.To control the inverter with faulty switches,only the faulty switch is bypassed,the control signals for other switches in the faulty cell are modified according to the fault type.The power cell with faulty switch can still output a two level voltage.The influence of various faults on space vectors is analyzed and the maximum achievable output voltage of the inverter with faulty switch devices is calculated.Compared with existing control methods,this method generates higher voltage space vector magnitudes and reduces the influence of switch problems on motor operation in most fault modes,while maintaining a balanced line to line voltage,the reliability of the system is then enhanced.The simulated results agree with the theoretical analysis.