Variable Frequency Transformer Design for New Energy Microgrids and Grid Interconnections

The variable frequency transformer (VFT) is investigated in this research for a new type of grid interconnection solution. Taking advantage of the moment of inertia of the rotor, the ability of the power system on coping with the sudden fluctuation can be enhanced. Aiming at a feasible design in this application condition, the design requirement is firstly specified based on the application configuration, and operation principle and kinetic energy analysis of the VFT. The distribution relationship between electromagnetic power and mechanical power, as well as the effects of torque change and grid-side frequency change on power transmission are analyzed to provide reference for the stable transmission and reliable control of VFT power. Then to meet the design specification, the design process is summarized. The design result is verified in a 15-kW design example and test platform.