A New Cascaded Medium Voltage Converter for Direct Integration of Large-Scale Solar Plant

This paper proposes a new converter configuration for the direct integration of large-scale solar photovoltaic plant (LSPV) with a medium voltage (MV) grid (Typically 11 kV). This modular multilevel converter topology uses four cells in each phase to have seventeen levels in pole voltage. Each module has two PV sources with six switches to generate
$(\mathbf{0}, +\mathbf{V}_{\mathbf{pv}}, +\mathbf{2}\mathbf{V}_{\mathbf{pv}},+\mathbf{3}\mathbf{V}_{\mathbf{pv}}, +4\mathbf{V}_{\mathbf{pv}})$
. The converter controls the solar power flow in closed loop and feeds it to the grid with improved power quality (perfectly meeting the IEEE grid code 519). The PV end control, decoupling end control and switching end control are detailed. Moreover, the converter modules for each phase are switched at fundamental frequency using a round function based nearest level switching scheme (NLSS). The converter is tested with a change in solar profile. The results are presented with a professional MATLAB tool showing that large-scale power is transferred to MV grid perfectly with new configuration.