A New Cascaded Solar Photovoltaic Converter with Main and Extension Power Unit for Medium Voltage Grid-Tied Applications

A new multilevel converter configuration is introduced in this paper to feed the large-scale solar power in a three-phase grid. It is connected to the grid of 11 kV for a 1 MW medium power application. It utilizes twelve switches with symmetric progression to have nine levels in phase voltage and seventeen levels in line voltage. It has two units i.e. main power unit (MPU) and extension power units (EPU), which handle the solar power in a modular manner. Various states and operating modes are detailed to showcase the perfect operation of each level. This configuration is extendable to feed more power in a modular manner. Firstly, the converter operation is discussed, and later the converter is connected to the grid with a threephase closed-loop controller. The modeling and simulation are presented to test the system in an intermittent solar environment. A switching strategy with selective harmonics elimination (SHE) is employed to feed the power at fundamental frequency switching. This new solar converter feeds power in steady-state and dynamic conditions. The large-scale power is extendable with the extension of power units or a cascaded converter arrangement. Finally, a new solar converter is tested in Simulink to showcase the superiority of converter dynamics and control at the megawatt level for efficient grid-tied operation.