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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. [ABSTRACT FROM AUTHOR]

In this paper, a single phase modified switched-diode topology for both symmetrical and asymmetrical cascaded multilevel inverters is presented. It consists of a Modified Switched-Diode Unit (MSDU) and a Twin Source Two Switch Unit (TSTSU) to produce distinct positive voltage levels according to the operating modes. An additional H-bridge synthesizes a voltage waveform, where the voltage levels of either polarity have less Total Harmonic Distortion (THD). Higher-level inverters can be built by cascading MSDUs. A comparative analysis is done with other topologies. The proposed topology results in reductions in the number of power switches, losses, installation area, voltage stress and converter cost. The Nearest Level Control (NLC) technique is employed to generate the gating signals for the power switches. To verify the performance of the proposed structure, simulation results are carried out by a PSIM under both steady state and dynamic conditions. Experimental results are presented to validate the simulation results. [ABSTRACT FROM AUTHOR]

In this paper, an improved Space Vector Modulation (SVM) based fault tolerant operation on a nine-level Cascaded H-Bridge (CHB) inverter with an additional backup circuit is proposed. Any type of fault in a power converter may result in a power interruption and productivity loss. Three different faults on H-bridge modules in all three phases based on the SVM approach are investigated with diagrams. Any fault in an inverter phase creates an unbalanced output voltage, which can lead to instability in the system. An additional auxiliary unit is connected in series to the three phase cascaded H-bridge circuit. With the help of this and the redundant switching states in SVM, the CHB inverter produces a balanced output with low harmonic distortion. This ensures high DC bus utilization under numerous fault conditions in three phases, which improves the system reliability. Simulation results are presented on three phase nine-level inverter with the automatic fault detection algorithm in the MATLAB/SIMULINK software tool, and experimental results are presented with DSP on five-level inverter to validate the practicality of the proposed SVM fault tolerance strategy on a CHB inverter with an auxiliary circuit. [ABSTRACT FROM AUTHOR]