Development of a Direct Medium Voltage Single Stage LLC Resonant Solar PV Inverter

In this study, a direct medium voltage (MV) grid connected solar PV inverter topology is proposed based on LLC resonant converter and high frequency transformer (HFT). Rectified sinusoidal AC output voltage is formed at the converter stage and a line frequency unfolder inverter is utilized to connect to the MV grid. Line frequency MV Unfolder avoids high-speed switching at MV stage and reduces switching losses are minimized. A combination of phase shift and switching frequency modulation is employed to follow the reference current at the output of the grid. A 150kW rated inverter is analyzed with mathematical calculations. A MV HFT is designed, simulated, developed, and verified through experimental results. The topology is simulated with MV grid connection in MATLAB/Simulink and a prototype is built for 4.16kV single phase output. Experimental results for ZVS conditions at MV have been carried out.