Feasibility of exchanging large blocks of power between unsynchronized grids by purely electromechanical means

Conventional wisdom says that a solid state AC/DC/AC conversion system must be used between tie points of nonsynchronized grid systems or synchronized grid systems for which the phase angle difference is too large. In a previous paper by the author (see IEEE Trans. Power Deliv., vol.14, no.1 1999), a method is described for solving the large phase angle problem in synchronized systems. Necessary design criteria are given. The method allows control of power flow in either direction and uses only variable linear elements. This paper shows that it is practical to design an electromechanical machine to control power flow in either direction at a tie between either synchronized or unsynchronized grids such as the East and West grids of the United States. The technology is simple, state of the art, and even allows direct ties between 50 and 60 Hz systems, a feature perhaps of value in other parts of the world. Work described is both theoretical and experimental