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Summary: Multilevel inverters are known as essential converters in renewable sources. First, in this paper, a new submodule is presented, and based on it, a new sub‐multilevel inverter is presented. The proposed sub‐multilevel inverter consists of several unidirectional and bidirectional switches and DC voltage sources. Then, the generalized topology, developed in two modular and cascaded modes, is presented to increase production levels. The proposed submodules are connected in series in the modular topology, increasing production levels. The proposed topology to produce the maximum output levels has the minimum number of IGBTs, drivers, DC voltage sources, etc. Mathematical analyses for conduction and switching losses are provided, and mathematical analyses for the number of devices and voltage across the switches are also presented. In addition to the mathematical analysis of losses, the simulation results are also presented. A general comparison of proposed topology components is presented to demonstrate their advantages. This comparison shows that the proposed topology has the minimum number of power electronic devices. In this paper, nearest level modulation is used to control the proposed topology. The simulation and experimental results of the proposed sub‐multilevel verify the performance of the proposed topology. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFC) have been noticed by researchers due to their high efficiency, low pollution, and high‐power density in distributed generation systems. In this paper, an LCL‐type grid‐tied PEMFC fuel cell power conditioning system is evaluated in a harmonics‐polluted low‐voltage grid. The LCL‐filters can lead to resonance and instability despite their capability to attenuate harmonics. In this research, a transformer has been used to connect the fuel cell inverter to the grid. The grid‐side inductor of LCL‐filter is realized by the leakage inductance of the transformer. In addition, for more effective resonance damping and attenuation of current ripples caused by the grid voltage harmonics, a capacitor voltage comprehensive feedback control has been designed and investigated. The comprehensive feedback control of the capacitor voltage contains proportional, first and second‐order derivative terms. In the proposed control scheme, the capacitor‐current‐feedback is opposed by the capacitor voltage derivative term due to reverse loop gain, which leads to deleting both of these loop gains. As a result, there is no need to utilize a current sensor in this control method. Consequently, the proportional and second‐order derivative terms of the capacitor voltage attenuate the LCL‐filter resonance. A low‐pass filter is also considered in the second‐order derivative loop in the controllable frequency range to ensure system stability. The simulation results of the PEMFC power conditioning system in different conditions confirm the proper attenuation of LCL resonance of grid‐tied inverter, high‐quality current injection to the harmonics polluted grid, the suitable stability, and the appropriate dynamic response for the proposed system. Under the proposed control scheme, the fuel cell power conditioning system demonstrates satisfactory stability. Even when reducing the LCL filter values by 5%–20%, the system maintains its stability effectively. Moreover, the THD of the injected current into the grid, employing the proposed control strategy, has been successfully reduced to an impressive value of 1.97% in a weak and harmonical grid. [ABSTRACT FROM AUTHOR]

Summary: Multilevel inverters have many applications, such as the grid integration of photovoltaic cells, FACTSs devices, electric vehicles, variable speed drives, and smart grids. In this paper, a new bidirectional diode‐based unit is proposed for a symmetric single‐phase modular inverter topology that can achieve high output levels by using a small number of switching and circuit devices. The basic structure can generate nine‐level voltage with only nine IGBTs and two diodes. Another advantage of the proposed topology is the utilization of a half‐bridge module to change the voltage polarity and the low number of its voltage sources. Additionally, the proposed topology can be used as the cascaded structure with different approaches to select the value of voltage sources. The power losses are discussed for the proposed basic module. A comparison has been made with some recently presented topologies to compare the proposed multilevel inverter and demonstrate its superiority. The comparison is performed for the basic module and its generalized structure. In this paper, the pulse width modulation technique is utilized to achieve a voltage waveform with low harmonic content. The proposed basic structure has an efficiency of 58.98% in 5KW power. Finally, the operation of the proposed basic module is simulated, and the laboratory prototype results confirm the accuracy of the simulation results. [ABSTRACT FROM AUTHOR]

In this paper, a novel Cascaded H-Bridge (CHB)-based multilevel inverter for symmetric/asymmetric configurations is presented. The proposed MLI can be utilized in medium-voltage applications such as electrical machine drives as well as grid connection of renewable energy resources. The proposed structure uses fewer count of semiconductor devices at the same voltage level in comparison with classic and advanced structures. Cascaded connection of the proposed basic cells leads to reduce complexity and increase efficiency of the proposed structure. In order to investigate the capability and superiority of the proposed structure, a comprehensive comparison is conducted between this structure and the advanced ones in terms of efficiency, switch and gate driver count, and total blocking voltage (TBV). The fundamental frequency switching method is employed to generate proper switching pulses. The performance of the proposed multilevel inverter is investigated by simulating in MATLAB/Simulink environment. The experimental implementation for proposed 15-level symmetric and 33-level asymmetric structures validates the correctness of simulation results. [ABSTRACT FROM AUTHOR]

This study proposes a multilevel inverter with optimised structure from switching device number point of view. Configuration of the presented multilevel inverter is modular and extendable. Three different methods are introduced to determine the magnitude of DC voltage sources. Characteristics of inverter topology based on suggested methods are given and compared with each other. Also, the proposed multilevel inverter is compared with some similar topologies in terms of controlled switches, driver circuits, DC voltage sources and total blocking voltage to verify its advantages and probable disadvantages where the results show the superiority of the proposed topology in the comparison items. Selective harmonic elimination pulse width modulation technique is applied to achieve output voltage with high quality. Finally, a laboratory prototype of the proposed multilevel inverter is implemented and then, the experimental and simulation results are derived to validate the inverter capability in generating staircase waveforms. [ABSTRACT FROM AUTHOR]

In this paper, the parallel operation of a three‐phase three‐wire inverter and a three‐phase four‐wire inverter in the presence of unbalanced and nonlinear loads is investigated. The proposed control method has two current internal and voltage external control loops. The current internal loop has a proportional‐resonant controller. The voltage external loop has two parts, including voltage controller and load current sharing. In the current sharing part, first, the output of the voltage controller is broken to a harmonic and is shared then between the inverters through the new strategy: (i) supply of harmonic components of load current by four‐leg inverter and sharing fundamental component of load current evenly between the inverters and (ii) supply of zero‐sequence load current by four‐leg inverter and sharing of the rest of components evenly between two inverters. The proposed system is capable of feeding balanced, unbalanced and nonlinear loads and provides the proper sinusoidal voltage at both ends of the loads by exact sharing of power between parallel inverters. The simulation results show the proper functioning of the proposed system. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]