Multiple-input multiple-output medium frequency-link based medium voltage inverter for direct grid connection of photovoltaic arrays

Recent advances in magnetic materials and power semiconductor devices have led to the development of compact and lightweight medium voltage inverter with medium frequency-link, which would be a possible solution to reducing the weight and size of grid-connected photovoltaic (PV) inverter systems. This paper presents the design and analysis of a multiple-input multiple-output medium frequency-link based medium voltage inverters for step-up transformer-less direct grid connection of PV arrays. The multiple-output medium frequency-links generates multiple isolated and balanced dc supplies for all of the H-bridge inverter cells of modular multilevel cascaded (MMC) inverter. To verify the feasibility of the proposed system, a scaled down 1 kV laboratory prototype test platform with 5-level MMC inverter is developed. The design and implementation of the prototyping, test platform, and the experimental results are analyzed and discussed.