| Abstract |
By replacing the normally DC excited rotor of a synchronous generator with three phase AC-windings, low-frequency currents can be injected, via slip rings, to excite the generator. This allows the rotational speed of the generator to deviate from the synchronous speed. The ability to run at non-synchronous speeds gives a potential to significantly increase the overall efficiency of a hydro power station, especially for pumped-storage plants. In addition, the frequency converter gives the opportunity, by accelerating or decelerating the rotor, to absorb or supply active peak-power from or to the grid. This can give a significant contribution to power system stability in case of fault situa-tions. In addition, the independent reactive power production made possible if a VSI is used in stead of a cycloconverter makes the unit an integrated reactive power compensator. The adjustable speed hydro generator can therefore be used not only to increase power station efficiency, but also as a FACTS component with active as well as reactive power control capabilities. |
