A new switched-capacitor-based multilevel inverter is proposed. It can boost the low and unstable voltage of the solar cells to a large and controllable ac voltage, as required by many standalone consumers or by the electrical grid. It features a high energy processing efficiency as all its switches are submitted to a voltage stress equal to the low input voltage. No output bridge whose transistors would be submitted to the high load voltage is required. A structure with a common ground between the energy cell and the load is created. Thus, the typical leakage current of a solar cell is suppressed. The new circuit is favorably compared with available solutions. The operation of the multilevel inverter is explained for a particular case with 7 levels; the circuit is generalized to a (2n+1) levels one. A 7-levels 484 W power inverter supplied by solar cell is designed and implemented in the laboratory, showing the highest efficiency of 98.43%, and of 96.4% at full-load. A total harmonic distortion (THD) of the output waveform is measured as 23.7%.

A new dc–ac inverter suitable for electrical systems powered by photovoltaics is developed for applications like aircrafts, drones, or satellites. The proposed modular input source-load common ground SCMLI minimizes the number of switches and capacitors which are necessary for getting the desired number of levels in the staircase output waveform. The penalty is an increased voltage stress on a few switches, but this affects the efficiency in a negligible way. The inverter is purposely designed for systems using photovoltaics as the energy source. The common ground eliminates the leakage current of the solar cells which is a cause of energy losses and distortion of the output waveform. The inverter can supply either a standalone load or a micro electric grid. The circuit is proposed for a general number of levels. Then, a particular case is considered: an inverter providing a 9-levels output waveform. It is analyzed, designed and implemented in the laboratory. The measured efficiency of the designed SCMLI at the nominal 500W power is 96.6%.

Equivalence between the switched inductor boost (SIB) converter and the tapped inductor boost (TIB) converter is suggested and the required conditions are derived. Based on the equivalence conditions, it is further shown that dynamic model of the SIB converter is merely a private case of the more general TIB converter. The model is derived using the tapped inductor switcher switched flow graph modeling approach. Simulation and experimental results are also reported.

In this article, a new multioutput switched-capacitor multilevel inverter (SCMLI) and a few trade-off solutions are proposed. It concomitantly features a common input source-load ground, eliminating thus the photovoltaic cell leakage current, a permanent nonzero input current, a high boost factor, equal to that in a similar no common ground inverter, and the smallest number of capacitors and switches per output and per boost factor compared with their count in the available common ground switched-capacitor (SC) inverters. Its basic structure is constituted by two SC subcircuits. The originality of the proposed inverter comes from a novel operation scheme in which one of the two SC subcircuits supplies the positive half-sinusoid of both outputs, whereas the other SC subcircuit supplies the negative half-sinusoid of both outputs. The alternative solutions require a few more switches. Their new switching strategies provide an equal capacitor voltages ripple, thus leading to smaller capacitance values and less capacitor-induced losses. An original design of an input choke allows drastically reducing the input current ripple, as required in alternative energy-powered applications. The new SCMLI was conceived as an inverter powered by a solar cell that supplies standalone residential ac loads of small powers. A laboratory 400 W nine-level prototype is built to verify the theoretical analyses and feasibility of the proposed topology.

Effective sinusoidal voltage regulation is of permanent importance for grid-forming converters. Usually, the following two types of schemes are employed to achieve a high level of performance: 1) single-loop voltage and 2) dual-loop voltage-current control. The performance of both schemes has comprehensively been evaluated in this work, based on the developed discrete-time model of the LC-filtered grid-forming converter. The challenges of insufficient stability margin, constraint bandwidth, and high sensitivity to parameter variation faced by the single-loop control scheme have been addressed, if the high-performance resonant controllers are employed for voltage regulation. Alternatively, the dual-loop control does not experience such issues with the inclusion of inner-current loop which provides active damping for the overall system. The essence of the inner-current loop is identified based on the discrete root locus analysis. Also, to obtain the highest damping and most enhanced stability, the criterion for current loop design has been addressed and a method for optimal tuning of the inner-current loop is developed, where the original plant with the one-sampling delay and the current gain are considered as the equivalent plant for the voltage controller. Experimental results have verified the effectiveness of the developed method for regulation of grid-forming converters.

A Fibonacci-type switched-capacitor (SC) cell is modified in order to be suitable for an innovative, breakthrough switched-capacitor multilevel inverter (SCMLI) fitted for photovoltaics powered systems. Characteristic to such a cell, its capacitor voltages follow a Fibonacci series. Thus, with only a very few capacitors, a very large step-up of the input voltage is realized; and the staircase output waveform of a Modified Fibonacci -based inverter would feature a very large number of levels, being very close to a sinusoid. Such an inverter is necessary if its front-end is a green source of energy which provides only a relative low voltage. A common line-load ground two-output SC-based multilevel inverter is then developed, analyzed and designed. This inverter can feed two loads without interference with each other. The common ground (CG) effectively stops the leakage current of the solar cells. In order to get the same voltage step-up and the same number of levels as in a no-common ground inverter with the same structure, the Modified SC Fibonacci circuit is reinvented, by dividing it into two sub-networks, each one with another function. One of them together with the input source supply the positive half-sinusoids voltages of both outputs, thus assuring a permanent non-zero input current, as required by the front-end environmental-friendly sources of energy. The other SC sub-network supplies the negative half-sinusoids to both loads. The novel CG-SCMLI contains the smallest number of components per output among all the common ground SCMLIs able to provide the same number of levels in the output staircase waveform. The idea was implemented on a 400W 15-levels inverter providing two outputs of 220V rms, of a very small total harmonic distortion of 5.2%.