In this paper, a novel platform for the single phase switched-capacitor multilevel inverters (SCMLIs) is presented. It has several advantages over the classical topologies, such as an appropriate boosting property, higher efficiency, lower number of required dc voltage sources, and other accompanying components with less complexity and lower cost. The basic structure of the proposed converter is capable of making nine-level of the output voltage under different kinds of loading conditions. Hereby, by using the same two capacitors paralleled to a single dc source, a switched-capacitor (SC) cell is made that contributes to boosting the value of the input voltage. In this case, the balanced voltage of the capacitors can be precisely provided on the basis of the series-parallel technique and the redundant switching states. Afterward, to reach the higher number of output voltage levels, two suggested SC cells are connected to each other with a new extended configuration. Therefore, by the use of a reasonable number of required power electronic devices, and also by utilizing only two isolated dc voltage sources, which their magnitudes can be designed based on either symmetric or asymmetric types, a 17- and 49-level of the output voltage are obtained. Based on the proposed extended configuration, a new generalized version of SCMLIs is also derived. To confirm the precise performance of the proposed topologies, apart from the theoretical analysis and a complete comparison, several simulation and experimental results are also given.

Multilevel inverters (MLIs) with switched-capacitor (SC) units have been a widely rehearsed research topic in power electronics since the last decade. Inductorless/transformerless operation with voltage-boosting feature and inherent capacitor self-voltage balancing performance with a reduced electromagnetic interference make the SC-MLI an attractive converter over the other available counterparts for various applications. There have been many developed SC-MLI structures recently put forward, where different basic switching techniques are used to generate multiple (discrete) output voltage levels. In general, the priority of the topological development is motivated by the number of output voltage levels, overall voltage gain, and full dc-link voltage utilization, while reducing the component counts and stress on devices for better efficiency and power density. To facilitate the direction of future research in SC-MLIs, this article presents a comprehensive review, critical analysis, and categorization of the existing topologies. Common fundamental units are generalized and summarized with their merits and demerits. Ultimately, major challenges and research directions are outlined leading to the future technology roadmap for more practical applications.

Recent research on common-ground switched-capacitor transformerless (CGSC-TL) inverters shows some intriguing features, such as integrated voltage boosting ability, possible multilevel output voltage generation, and nullification of the leakage current issue. However, the number of output voltage levels and also the overall voltage boosting ratio of most of the existing CGSC-TL inverters are limited to five and two, respectively. This article presents a generalized circuit configuration of such converters capable of higher voltage gain and output voltage levels generation. A basic five-level (5L) CGSC-TL inverter is first proposed using eight power switches and two self-balanced dc-link capacitors. A generalized extension of the circuit for any output voltage levels and voltage gain is then presented while keeping all the traits of the proposed basic 5L-CGSC-TL inverter. The circuit descriptions, control strategy, design guidelines, comparative study, and the relevant simulation and experimental results for the proposed 5L-CGSC-TL inverters and its seven-level derived topology are presented to validate the effectiveness and feasibility of this proposal.

Photovoltaic (PV) string inverters with transformerless grid-connected architecture is the commonly used solar converters owing to its appliance-friendly and cost-effective benefits. A novel circuit configuration of such converters is presented in this study, which relatively addresses the shortcoming of most of the conventional topologies such as the problem of leakage current, voltage ratio transformations, and power quality. The proposed structure is on the basis of series-parallel switching conversion of the switched-capacitor (SC) cell and is comprised of only six unidirectional power switches with a common-grounded (CG) feature. Through the use of SC cell and CG connection of active and passive used elements, not only is the number of output voltage level enhanced up to five but also a two times voltage boosting feature with a single stage operation as well as elimination of the leakage current is acquired. Herein, to inject a tightly controlled current into the grid, a peak current controller approach has been used which can handle both the active and reactive power supports modes. Theoretical analysis, comparative study, design guidelines and some experimental results are also given to corroborate the feasibility and accurate performance of the proposed topology.

Transformerless grid-connected inverters have been extensively popular in renewable energy-based applications owing to some interesting features like higher efficiency, reasonable cost and acceptable power density. The major concern of such converters is the leakage current problem injected to the grid and also the step-down feature of the output voltage which causes a costly operation for a single stage energy conversion system. A new five-level transformerless inverter topology is presented in this study, which is able to boost the value of the input voltage and can remove the leakage current problem through a common-grounded architecture. Here, providing the five-level of the output voltage with only six power switches is facilitated through the series-parallel switching of a switched-capacitor module. Regarding this switching conversion, the self- voltage balancing of the integrated capacitors over a full cycle of the grid's frequency can be acquired. Additionally, to inject a tightly controlled current to the local grid, a peak current controller-based technique is employed, which can regulate both the active and reactive power support modes. Theoretical analyses besides some experimental results are also given to corroborate the correct performance of the proposed topology.

Voltage source multilevel inverters with reduced leakage current, single-stage voltage step-up feature, compact design, and an efficient performance are a promising technology for high-frequency ac (HFac) microgrids feeding through renewable energy sources. This article proposes a novel single-source common-grounded (CG) step-up nine-level (9L) inverter, which can be applied in HFac microgrid applications. The proposed CG-based boost inverter is comprised of only nine switches (9S) and three self-balanced capacitors. Using the switched-capacitor (SC) technique, a double voltage boosting feature within a single power processing stage is achieved, while the leakage current concern is eliminated due to a CG-based configuration between the input dc source and the null of the grid. With the help of an LC input filter, the input current profile is free from large discontinuous inrush spikes. The working principles of the proposed 9L9S-CGSC inverter are discussed in this article. The modulation and closed-loop control strategy, as well as a comparative study, are presented. Finally, the open and closed-loop grid-tied performances of the proposed topology are evaluated by both simulation and experimental results obtained from a 1.2-kW laboratory-built prototype.