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A new DC/AC inverter with ability of supplying two AC loads, independently, based on flying-capacitor topology is proposed. Flying capacitor enables the converter to have three-level output voltages which results in high-quality output waveforms. Comparing to conventional flying capacitor inverter (FCI) for supplying two loads, the new inverter has lower numbers of semiconductor switches and flying capacitors, up to 25 and 50%, respectively. Comparing to recent works, proposed inverter provides better trade-off between number of components and independent control of loads. Three-phase topology of the proposed inverter consists of three parallel single-phase modules. The inverter can operate in both constant and variable output frequencies. A switched model along with an effective control strategy based on Karnauph Map is also derived for the proposed inverter. High performance of the inverter is verified with both simulation and experimental results. The proposed inverter can mostly be used in applications, such as motor drive, UPS systems, hybrid electric vehicles, and photovoltaic (PV) systems.

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A new inverter topology for single-phase photovoltaic (PV) systems is proposed in this study. The proposed inverter offers a four-level voltage in its output terminals. This feature results in easier filtering in comparison with other conventional two-level or three-level inverters. In addition, the proposed four-level inverter (PFLI) has a transformer-less topology, which decreases the size, weight, and cost of the entire system and increases the overall efficiency of the system. Although the inverter is transformer-less, it produces a negligible leakage ground current (LGC), which makes this inverter suitable for PV grid-connected applications. The performance of the proposed inverter is compared with that of a four-level neutral point clamped inverter (FLNPCI). Theoretical analysis and computer simulations verify that the PFLI topology is superior to FLNPCI in terms of efficiency and suitability for use in PV transformer-less systems.

Because of the characteristics of high efficiency and low cost, the transformer-less photovoltaic (PV) grid-connected inverters have been popularized in the application of solar electric generation system in residential market. However, in these inverters the ground leakage current through the stray capacitors between the PV array and the ground is harmful and causes losses and electromagnetic interference. This paper presents a new four-level single-phase inverter for grid-connected photovoltaic systems with a low leakage current. The proposed inverter can operate in non-unity power factors. For minimizing the leakage current, a switching control strategy is presented. The simulation results verify the superiority of the proposed inverter structure.

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Modular multilevel converters (MMCs) are used in medium and high power applications due to various advantages, such as modularity, scalability, high efficiency, and low THD. In this paper, an improved model predictive control (IMPC) is used to control the converter output current and the circulating current. Using a discrete mathematical model of MMC and the neighboring index values with respect to their previously applied values, the calculation burden can be reduced rapidly even the number of sub-modules (SMs) increases. By applying this method, the control system complexity and the number of switching states are reduced. In addition, a Kalman filter (KF) is applied to estimate the capacitor voltage of the SMs, by using two arm voltage sensors in each leg of MMC. The combination of IMPC and KF reduces the computational burden and the number of voltage sensors. The efficiency and superiority of the proposed method are verified by simulation results of 5-and 11-level three-phase MMC and practical implementation of a laboratory single-phase converter with four SMs in each arm.