Electric systems for Pumped Storage PlantsTechnology Evaluation

Abstract

The report describes shortly the state-of-the-art within electrical systems for pumped storage plants. Three main different systems are presented and evaluated: Constant speed, adjustable speed with doubly-fed induction machine and adjustable speed with a full rated frequency converter. Pumped storage hydropower systems have been used for more than hundred years with a global installed capacity of 130 GW. However, there are continuous development and improvement going on with respect to design, rating, application areas and control. One of the most important advances during the last decades has been the development of adjustable speed systems to allow for a certain extent of controllable power in pumping mode. Pumped storage technology is commercially available for ratings up to 500 MW in unit size for constant speed and 400 MW for adjustable speed (with doubly-fed machines). In the following work it is important to specify the requirements and needs to pumped storage plants in Norway. For a test unit, an adjustable speed installation based on a doubly-fed induction machine is recommended in a first stage. In the next stage, the same frequency converter can be modified to be used as a full rated converter connected to a synchronous machine as unit number two. The constant speed system with a synchronous machine directly connected to the grid does not need a test unit for experimental verification to the same extent that is needed for the alternative adjustable speed systems.

Electric systems for Pumped Storage PlantsTechnology Evaluation