Model-based diagnosis and fault tolerant control for multi-level inverters

This paper deals with a model-based approach for diagnosis switch faults in multi-level multi-phase voltage source inverters (VSI). The proposed fault detection and isolation (FDI) method requires only one voltage detector per phase leg to accurately allocate a faulty switch among 2m(n-1) switches in an n-level m-phase VSI. The pole voltage of each phase is monitored and digitized into 2n-1 levels. A fault is detected when an odd level of voltage is observed. After the fault is detected, certain switching modes are applied to the inverter and the resulting voltage levels are observed. By comparing finite numbers of the observed voltage levels to the fault signatures, the location of the faulty switch is accurately determined. The control of the switches is then changed to tolerate the faulty condition. This method is robust to the load variations and suitable for closed loop applications. It is applicable to micro inverters for solar systems with numerous semiconductor switches with minimum number of sensors.