HVDC Technology Allows Global AC/DC Conversion

July 31, 2000 by Jeff Shepard

American Electric Power Central Power and Light (AEP, Eagle Pass, TX) and Comision Federal de Electricidad (CFE, Mexico) joined with ABB Power Systems (Switzerland) and Electrical Power Research Institute (EPRI, Palo Alto, CA) to dedicate a first-of-its-kind electrical tie using a new high-voltage direct-current (HVDC) technology. The electric tie links the transmission system of AEP with the Mexican transmission system owned and operated by CFE. The new "asynchronous" technology converts the formerly incompatible ac currents from both countries to dc currents. As a result, operators at AEP's Eagle Pass substation can allow the transfer of power between the two countries without interrupting customers.According to E. Linn Draper Jr., AEP's chairman, president and CEO, the project will serve as an "electrical bridge" between Eagle Pass and Piedras Negras, Mexico.AEP has been working with CFE and EPRI, the utility industry's collaborative science and technology development organization, to develop, test and install the tie. The 36MW dc tie will provide strong voltage support to Piedras Negras and Eagle Pass, Texas, while significantly improving the reliable power delivery service between the two electric grids.ABB Power Systems is the supplier chosen to develop this back-to-back voltage source converter, which is referred to as "HVDC Light." Back-to-back means that ties are contained within the substation, as opposed to previous applications of ties which have employed dc lines, often spanning considerable distances.AEP and CFE will each have the capability of providing emergency service to the other utility without first having to disrupt power on the existing 138kV line between Eagle Pass and Piedras Negras. AEP will operate the tie at Eagle Pass and the tie will be available for use by other utilities through the Electric Reliability Council of Texas Independent System Operator."We know that this project will yield exciting benefits for all of the participants, as well as the customers of both CFE and AEP, and the electric utility industry, as a whole," said Draper.