Features of a drive system for pump-storage plant applications based on the use of double-fed induction machine with a multistage-multilevel frequency converter

The paper presents the modeling and simulation study of a variable speed pump-storage power plant composed of a reversible turbine, a doubly fed induction machine (DFIM), and a multistage-multilevel frequency converter. The DFIM rotor circuit is fed by a 5-level NPC VSI. The inverter DC-link capacitor voltages are kept in balance by means of four multistage PWM rectifiers. The paper considers start-up responses and performance characteristics of the drive system along with its behavior under the stator short-circuit fault conditions. An emphasis is placed upon modifying the PD PWM modulation waveforms in order to level RMS values of currents flowing in PWM rectifiers and related secondary windings of a step-down transformer.