Generator Design Possibilities for Full-Size Converter Operation of Large Pumped Storage Power Plants

This article investigates the additional opportunities and aspects in the design process of large hydro power wound-field salient-pole synchronous machines provided by full-size converter (FSC) operation. As a matter of fact, thus far, power converters for hydro power plants have been mainly selected to meet the demands of conventionally designed machines and retrofit applications. The new optimization possibilities in the motor-generator design given by the FSC operation have not yet found much attention in the literature. This article shows how FSC operated hydro power synchronous machines can be designed to have smaller volumes, lower material cost, and higher efficiencies than their conventional counterparts. A cost evaluation of various generator designs including costs for materials as well as costs for power loss during operation is performed. Furthermore, the power loss evaluation cost factors are varied to show their impact on the choice of the machine parameters for an optimum generator design. For the presented evaluation, the partial load operation of large pumped storage power plants in turbine and pumping modes is analyzed, as is the effect of the free choice of the design frequency, the power factor, as well as the synchronous reactance. Finally, a suggestion for the generator design for FSC operation is presented.