Optimized Control Strategy for AC Excitation Power in Large-Scale Variable-Speed Pumped Storage Systems

Aiming at the challenges of multi-mode operation and power decoupling control of large-scale variable-speed pumped storage (VSPS) units, this paper proposes a novel AC excitation power closed-loop strategy based on stator flux-oriented vector control. Unlike the existing studies, the decoupling mechanism of the rotor current $\mathbf{d}-\mathbf{q}$-axis components for active and reactive power is revealed by rigorously deriving the differential mathematical model of the doubly-fed motor under power generation and pumping conditions. In addition, the coupling term feed-forward compensation and dynamic feedforward correction are innovatively introduced to solve the problems of circulating current suppression and current imbalance when multiple inverters are operated in parallel. The inverter speed control system is constructed on the MATLAB/Simulink experimental platform, and the parameters of the SFC module are reasonably designed. During the inverter startup process, the motor speed rises steadily with the power supply frequency and reaches the rated speed successfully, showing good startup stability. The frequency converter reaches the rated frequency after 2 seconds and the motor reaches the set speed. The frequency change is smooth and the motor starts with good response. The change in machine-side voltage is in line with theoretical expectations.