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Low reliability of the inverter is caused by high failure rates of semiconductor components and capacitors as well as high requirements for these components in the design of multilevel inverter topologies. The primary challenges in the reported fault-tolerant topology solutions include high component count, handling single and multiple switch faults, handling open and short switch failures on all fault locations, and achieving natural voltage balancing of the capacitors. This paper proposes a highly resilient fault-tolerant topology to accomplish the above challenges without compromising efficiency during faulty conditions. The acquired experimental results verify the proposed topology’s robustness and efficacy. The proposed topology is evaluated by considering multiple instances of switch failures to encompass various fault locations and types. A comparison with the recently reported fault-tolerant MLI topologies verifies the superiority of the proposed topology.

The objective of reducing the size and cost of the grid-connected photovoltaic system has led to advancements in the field of transformerless grid-connected inverters and gained high popularity in recent years. However, in such systems, the major limitation lies in realizing maximum power from individual modules. In this regard, this paper proposes a modular transformerless grid-connected photovoltaic multilevel inverter that realizes the individual maximum power point (MPP) of each module under different operating scenarios. The presented configuration is simple and modular, providing flexibility to increase the number of inputs with less component count. A single-phase synchronous reference frame PI (SRF-PI) controller has been designed and realized for the proposed system. The systematic procedure for designing the controller has been detailed. The converter and controller allow the system to realize individual MPP of the modules and simultaneously achieve the load demand maintaining the desired grid voltage. This has been verified under different operating scenarios in the MATLAB/Simulink environment. The same has been validated on a 300W laboratory prototype under source and load intermittencies. The proposed configuration has been compared with the similar works reported in the literature and it has been observed that it employs only 18 components. Also, the efficiency of the converter has been observed in the range of 89-95%. Further, the common-mode voltage and the leakage current have been measured to verify their suitability for grid-connected systems as per German VDE 0126-1-1 standards.

Reducing ripples on the capacitor voltage has two benefits: improved output waveform quality and accurate converter size. During the generation of a given output voltage level, the factor “Inherent Redundant Paths (IRPs)” has a considerable impact on the characteristics of multilevel inverter design. The consistent distribution of power loss derives from the Active Neutral Point-Clamed Inverter’s intrinsic redundant route at zero-voltage level generation. Even though it has been claimed that adding intrinsically redundant routes might give fault-tolerance capabilities to MLI topologies, the utilization of these pathways at intermediate voltage levels has not yet been studied. Based on this, the current research provides a unique charging and discharging technique is known as the alternating charging and discharging approach, which reduces capacitor voltage ripple. In addition, the suggested technique permits the inherent voltage balancing of capacitors without the need for supplemental components. The suggested alternative charging and discharging approach is implemented under both healthy and varied switch failure circumstances. In a laboratory prototype, the efficacy of the suggested alternative charging and discharging technique has been empirically tested.

Multilevel inverters are used in a number of high-power applications, including industrial motor drives, flexible power transmission, and, renewable energy systems. Since the MLI design incorporates a large number of devices, the system’s reliability suffers. This has caught the interest of academics all over the world, who are searching for methods to increase the dependability of the MLI design and include fault-tolerant qualities into it, either through software or hardware. Redundancy is a method that has recently gained popularity in solid-state transformer applications where fault tolerance is a highly desired quality. This is because the method provides for greater fault tolerance. The goal of this research is to offer a complete knowledge of the fault tolerance capabilities of MLIs created by the research community over the last few years