A new hardware strategy is proposed to increase the reliability of the Switch-Ladder multilevel inverter against short-circuit (S.C.) faults in the H-Bridge and main switches Blocks. The strategy includes passive and active bypassing. Passive bypassing approach hires fuses in series-connection with the ladder`s steps. Instead, in the active method, relays are replaced the fuses and receive commands from a controller that monitors the short-circuit failures continuously. When a switch fails in short circuit behaviour, the ladder contains the failed switch is converted to open-circuit (O.C.). Owning to the ability of Switch-Ladder multi-level inverter to tolerate open-circuit faults due to its configuration and switching strategy, reliability is increased against short-circuit failures through inverting the short-circuit to open-circuit. At last the experimental result validates the claims.

The feasibility of a staircase-output, diode clamping multilevel inverter based on multiwinding transformer is investigated through experimental results including: output voltage and current waveforms under resistive and inductive loads and the THD. The 2.5 kW, 7-level prototype of the constructed configuration proves the ability to act as an inverter under resistive and inductive loads and generates outputs with 2.1–11.5% of THD and 92.5% of peak efficiency. At last, a table of comparison with the closest topology is brought.

This paper provides experimental results for a 2.5-kW 47-level prototype of the switch-ladder multilevel inverter including the following: input and output voltage and current waveforms under resistive and inductive loads, efficiency, total harmonic distortion, voltage stresses across the switches, behavior of the system under fault condition, and no-load power dissipation. The most important advantage of this inverter is that only four switches conduct in each interval in low frequency. This matter, beside the elimination of switching losses, has made this inverter an efficient choice with 97% peak efficiency. The ability to continue working with open-circuit modules is another advantage of the inverter. Furthermore, some important factors behind the unreliability and inefficiency of inverters have been improved, including the following: low duty cycle of conducting switches, staircase voltage stresses across switches with low-voltage steppes, line switching frequency results in low temperature of switches, possibility of removing low-pass filters, and independence to capacitors. The inverter is proposed to be an advantageous choice in low-voltage stand-alone photovoltaic applications.

In this paper, a new configuration for diode-clamped multilevel inverter based on multiwinding transformer is proposed, described and simulated. The most important difference between this proposed DC-AC-AC structure and basic structure is that in the proposed structure, back-to-back connected outputs of a multi-winding transformer are superseded the capacitors in basic structure. Simulation a 7 levels of proposed configuration shows 10% THD.

Due to high initial cost of photovoltaic generators, it is necessary to use high efficient converters to convert DC output of Photovoltaic systems to AC. This is done by efficient inverters. Between various inverter structures, staircase output inverters have a special place. Most of these inverters use structures that are constituted of series-connected switches. This limits efficiency and reliability. In this paper, an efficient and reliable staircase output inverter structure based on two ladders of switches is discussed. The major advantages of this structure are higher reliability and efficiency. This structure has low on-state power dissipation which means more performance especially when working with low voltage low power photovoltaic systems. The other advantage of this inverter is reliability when switches fail in form of open circuit. By choosing a special switching strategy, this inverter has ability to continue working with some failed open circuit switches. Increasing the number of levels increases the reliability of this inverter. Moreover, low switching frequency, let to use Photovoltaic output isolator as driver for switches, which means more capability for compactness in Integrated Power Modules (IPM). In this paper, first the structure of this inverter is discussed then the on-state power dissipation is calculated in form of using Mosfets and other p-n junction switches, then simulation result is brought.