Transient analysis of converter-fed adjustable-speed generator-motor for the pumped storage power plant

A converter‐fed adjustable‐speed generator‐motor for a pumped storage power plant has been developed in order to contribute to the automatic frequency control on an electric power system during pumping operations, as well as to improve the efficiency of turbines during generating operations together with stability. This system consists of a reversible pump turbine, a generator motor, cycloconverter and control units. The rotor of the generator motor, which is coupled directly with the turbine runner, normally is operated at a rotating speed which is equal to the difference between the frequency of the electric power system and that of the rotor current. In the state that a fault has occurred in the primary circuit of the generator motor, the adjustable‐speed generator‐motor fault current differs from that of a conventional synchronous generator motor. This paper describes the fault current analysis results for the condition when a sudden short‐circuit is made on the primary side of the generator motor, and collates the results with the field test and EMTP simulation results.