A Switched Capacitor Modified Fibonacci Cell Used for a DC–AC Circuit Supplied by Solar Energy

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%.