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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.

A new hardware strategy is proposed to increase the reliability of the Switch-Ladder multi-level 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.

Due to several scenarios attached to the fossil fuel resources, the world has experienced a trend popularly towards alternative energy sources especially, renewable and clean in extraction as well as generation. This has raised the demand bar for the often popular solar and wind as the energy sources. As a result, renewable power conversion marketing has also dramatically increased during the past decade. Due to the application of inverters in power generation,the coinciding interest is shared equally and thus has created the basis of research interest on multi-level inverters. To acquire desired form of power, especially when precision, reliability and the economy of the project is considered upon, a multi-level inverter is a beneficial choice. They present ability to control higher amount of voltage and current, low THD, low cost, simple control methods, and compactness. Having exhibited its share of advantages in electronic power conversion, certain previous structures have indicated some limitations which risk hampering its fair deal of positive attributes. Such as the implementation of series connected switches (cascaded),a factor behind the inefficiency, operational heat generation and unreliability. A cascaded structure imposes two important limitations to the system: it limits the efficiency and reliability by increasing the on-state power dissipation in the converter; it directly limits the reliability by increasing the likelihood of failure. The selection of multi-level inverter configurations, on the basis of on-state voltage drop of switches is possible through developing a new mathematical method to calculate the comparative efficiency in staircase diode-clamped, H-bridge and the proposed inverter with pn junction and MOSFET switches. These calculations rely on the onstate voltage drop of p-n junction switches, conducting resistance of MOSFET switches, break down voltage, number of levels, peak output voltage, voltage steps magnitude and the load. The c

In this paper, a new configuration for diode-clamped multilevel inverter based on multi-winding 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.

In renewable power generators, because of high initial cost and duty cycle of systems, efficiency parameter has an important place. For this reason, line frequency controlled multilevel inverters are one of most proper choices for renewable power converters. Among these, diode-clamped multilevel inverter structures are one of most important and best efficient inverters. In this paper, a simple diode-clamped equivalent circuit for exploring the efficiency under resistive loads is proposed, and based on this simple circuit, the on-state power dissipation in improved and original diode-clamped multilevel inverter under resistive loads is analyzed. Then, comparative efficiency equations are extracted for inverters that use metal oxide semiconductor field-effect transistors (MOSFETs) and other p-n junction as switches. These equations enable us to have a better idea of conducting power dissipation in diode-clamped and help us to choose appropriate switches for having a lower on-state power dissipation. Some cases are studied and in the end it is proven that the calculated efficiency under resistive load is a boundary for inductive load with the same impedance in diode-clamped inverter with p-n junction switches. This means that calculating the efficiency under resistive loads enables us to approximately predict efficiency under inductive loads.

A DC-AC-AC multilevel inverter based on a multi-winding transformer is presented. The most important advantage of this inverter is that only four switches conduct during each cycle, which means that it exhibits lower on-state power dissipation. High reliability when switches fail in open-circuit behaviour is another advantage of this inverter structure. Finally, practical results are presented.

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.