A milestone in the Alps

2013-10-01 - ABB has commissioned the world's largest frequency converter at a pump storage plant for one of the leading hydroelectric power companies in Switzerland.

By ABB Communications

As more and more intermittent wind and solar power generation is added to the electricity grid, energy storage solutions are gaining in importance.

Pumped storage power plants, such as those found in the Swiss Alps, are ideal partners for the expanding use of solar and wind. They behave like huge batteries, ensuring the necessary balance between production and consumption. When power is plentiful, water is pumped from a lower altitude lake to replenish a higher altitude lake, where it remains stored. When power is needed, water is released, instantly turning turbines as the water falls to rapidly generate electricity.

The higher altitude lake
Until now, at the Grimsel 2 facility, the only way to adjust power consumption during the pump operation to the surplus power available was to regulate the number of pumps employed. The balancing power was then generated using valuable stored water from other lakes.

Today, however, an ABB PCS 8000 power converter has been fitted to one of the four, 80 megawatt synchronous generator/motor sets, so that the pumping operation can be optimized to use water more efficiently as a resource for electricity production. The powerful 100 megavolt amperes (MVA) converter, including its dedicated transformers, is around 10 meters long and 7 meters wide. It is housed on two floors behind an imposing machine hall.

By upgrading one of the generator/motor sets from fixed speed to variable speed, the synchronous machine can now operate between 600 and 765 rpm in pump mode. By means of more than 1000 power semiconductor elements, the frequency can be varied - and hence the speed of rotation – and in so doing the power absorbed by the pump can be controlled. In the case of Grimsel 2 by between 60 and 91 MW. This means that no further valuable stored water from other lakes is required to balance the power.

"Our Varspeed is a pioneering project and the world's largest frequency converter ever installed in a hydroelectric power plant," explains Dr. Gianni Biasiutti, CEO of KWO (Kraftwerke Oberhasli AG) a leading hydropower company in Switzerland that provides on average about 2,350 gigawatt-hours (GWh) of electricity per year, the equivalent annual consumption of around 1.2 million people. This approach has awakened the scientific community and will influence the way future pumped storage facilities could be designed.”

Watch the video to learn more about the project

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