Converters for Pumped Storage Plants
Pumped Hydro Energy Storage Plants have an essential role in electric power grids. They provide spinning reserve and permit the operation of base load power plants at their optimal efficiency by consuming power during low load times to pump up the water to the reservoir at higher altitudes.
Using a wound rotor induction machine for the motor-generator and controlling the slip frequency of the rotor with a power electronics converter makes the necessary speed variation possible. Operation at maximum hydraulic efficiency is enabled in both, turbining and pumping mode, over a larger range of head variation and power/frequency control is possible in the pumping mode as well. Since the power needed in the rotor is only a fraction of the machine rating (roughly proportional to the slip), the rating of the converter and therefore its cost as well as its space demand is minimized. Because of the semiconductor loss optimizing design of the PCS Frequency Converter Platform it is the ideal converter for this kind of application.