Photovoltaic-Powered High-Performance Common-Ground Switched-Capacitor Inverter With Ultra-Wide Input Voltage Range and Constant RMS Output Voltage and Level Count

This article answers a critical requirement for switched-capacitor multilevel inverters SCMLI used in renewable energy applications: capability to provide the same sinusoidal output waveform regardless of big variations in the voltage provided by the photovoltaics or other green cells. The originality of the proposed inverter comes from its capacity of providing five operation regimes, offering gains from 4 to 12, and keeping constant the number of levels in the output waveform. It allows to efficiently handle an input voltage variation between 30 and 90 V while producing a stable 220 V_rms output. A novel structure is presented, as well as a new control approach allowing a smooth passage from an operation regime to another one for a continuous variation of the input voltage. It is a common-ground (CG) topology and features a permanent nonzero input current, which are other two constraints imposed in renewable energy. The new inverter presents the lowest cost function among the CG-SCMLIs. The prototype was supplied by a string of four solar cells and provided a 220V rms sinusoid at the grid, which was not affected even in the worst case when some solar cells broke down.