Variable frequency transformer for asynchronous power transfer

The core technology of the VFT is a rotary transformer with three-phase windings on both rotor and stator. A motor and drive system are used to adjust the rotational position of the rotor relative to the stator, thereby controlling the magnitude and direction of the power flowing through the VFT [1]. The world’s first VFT was recently installed and commissioned in HydroQuebec’s Langlois substation, where it will be used to exchange up to 100 MW of power between the asynchronous power grids of Quebec (Canada) and New York (USA) [2]. General VFT concept and core