Conceptual study and operational overview on Variable Frequency Transformer used for grid interconnections

Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to electrical substations located near demand centers. Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in long-distance transmission. Since 2004, an alternative technology has been in commercial operation in North America, which has proven to be a reliable and stable vehicle to move power between two points. The two points in question need not be synchronous. This technology is the Variable Frequency Transformer, or VFT. Variable frequency transformers provide transmission solutions for a smarter grid, enabling transmission system operators to control power flows between power grids with high reliability, speed and efficiency, while offering flexibility It is a controllable, bi-directional transmission device that can transfer power between asynchronous networks. Variable Frequency Transformers can convert this power to and from grids without converting the power into DC thus eliminating the harmonic distortions. Another advantage with VFT is that we can have infinite phase shifts between the two powers where as in conventional devices we could have only few predefined phase shifts. This paper introduces the VFT and provides a brief explanation of the technology and its benefits.