A Three-phase Nine-level Fault Tolerant Asymmetrical Inverter

The reliability in inverters has gained a vast importance for their enhanced economic operation of the system. This paper proposes a three-phase reliable nine-level inverter with fault ride through capability. The proposed inverter synthesizes nine levels in the output with two asymmetrical voltage sources configured at a ratio of 1:3 under healthy operation. The inverter is analyzed for open circuit faults in switches. A reliability analysis is carried out for proposed inverter and compared with classical Cascaded-H Bridge. Combined control logic is implemented to control the inverter in accordance with the operating conditions. The circuit is operated with sinusoidal pulse width modulation under healthy condition, and it is made to operate with switching frequency optimal-based pulse width modulation (SFO-PWM) under fault cases, as it enhances fundamental DC value. The proposed inverter is simulated in MATLAB/SIMULINK, and the results are validated by an experimental setup.