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Power Transmission Without the Power Electronics

GE's variable-frequency transformers transfer power between out-of-sync grids without the problems of semiconductor power electronics

4 min read

14 November 2007--During their low-resolution beginnings, digital music and photography delivered a jarring rendition of sounds and images, full of noticeable discontinuities. Today, you get the same sort of thing from semiconductor-power electronics devices used to manage power flows on high-voltage transmission grids, and those jarring oscillations can damage the high-precision turbines spinning in power plants. This costly problem inspired engineers at General Electric Co.'s Atlanta-based GE Energy division to go back to the future and create a new semiconductor-free-power control device: the variable-frequency transformer, or VFT.

U.S. electricity giant American Electric Power (AEP) started up GE's first commercially produced VFT this summer in Laredo, Texas, to pull in up to 100 megawatts of emergency power from Mexico. Montreal-based Hydro-Québec has been operating a demonstration VFT since 2004 to manage power exchanges with the eastern U.S. grid. By 2010, three more VFTs should be operating in New Jersey to push extra power into chronically undersupplied New York City.

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This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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