High frequency link multi-winding power electronic transformer using modular multilevel converter for renewable energy integration

Grid integration of multiple renewable energy sources using a power electronic transformer (PET) topology is presented in this paper. A modular multilevel converter (MMC) is proposed as the power converter on the high voltage grid side to generate high frequency sinusoidal voltages. A single multi-winding high frequency transformer (HFT) interfaces different wind generators/photovoltaic arrays using many H-bridge converters and PWM inverters. The leakage inductance of the transformer acts as the smoothening filter for the current through the HFT. With sinusoidal voltages and smooth currents through the transformer, there is significant reduction in transformer losses and also natural commutation of leakage energy is obtained. The operating principle, modulation and control of the proposed PET is validated by simulations in MATLAB/Simulink.