Fault-tolerant control strategy of the cascaded five-level inverter based on divided voltage modulation algorithm

When a fault happens to the five-level inverter, the unbalanced voltage may lead to the motor drive system collapse. A fault-tolerant control strategy based on the divided voltage modulation algorithm is proposed in this paper to keep the voltage balance and ensure the stable operation of the motor drive system under the fault condition. This modulation algorithm divides the reference voltage into two parts to achieve the independent control of each H-bridge. When an IGBT open fault (OPF) occurs in one H-bridge, it won't affect the control of other H-bridges to remove the faulty H-bridge from the inverter. This method can reduce switching loss and control the IGBT OPF fault. A design example is presented for an induction motor drive system, and simulation results validate the proposed solution.