Full-size converter operation of hydro power generators: a state-of-the-art review of motivations, solutions, and design implications

This paper reviews motivations and solutions for variable-speed operation in large hydro power plants with a special emphasis on full-size converter operated synchronous generators. First, the established concepts of conventional pumped storage power plants are briefly described. Then, the implemented applications with use of power converters and synchronous machines in hydro power plants, their power ratings, power converter topologies used, and the experiences obtained during operation are reviewed. Concerning its state-of-the-art position in variable-speed pumped storage power plants, the variable-speed capability offered by doubly-fed induction machines is also briefly described, including the power range that can be achieved in pumping mode as well as the power converter ratings of existing power plants. Following this comprehensive analysis, this paper identifies the requirements of today’s power converters and synchronous machines for utilization in large pumped storage power plants as full-size converter operated synchronous generators. It analyzes the design implications on the electric machines driven by such converters, and investigates the advantages of the additional possibilities given by the full-size converter operation that may outweigh the added cost, system complexity, and power loss.