Low frequency HVac transmission to increase power transfer capacity

The need for a large scale upgrade in the bulk power transmission capacity of the electric grid is critical for integrating large amounts of renewable generation and various smart grid technologies. System requirements to maintain adequate security margins and steady state power transfer limits over long distances lead to flow levels which are well below the thermal capacity of existing lines. This paper outlines the limitations of current approaches for increasing the power transfer capacity in a transmission corridor and explains an alternative approach for increasing the power throughput of high voltage three phase ac transmission lines by decreasing their frequency. Modular Multilevel Converters (MMCs) are proposed as an attractive alternative for realizing high power ac-ac frequency conversion. Their generalized topology of bridge of bridge (BoB) is described, and simulation results of a 60Hz ac to 20Hz ac three phase BoB converter are shown.