Active power fluctuations and control in hydraulic disturbance of variable speed pumped storage plants

Abstract

Variable-speed pumped-storage unit (VSPSU) is state-of-the-art technology and has appeared as a new orientation of the world pumped-storage industry in recent years, but the dynamic performance of VSPSU under hydraulic disturbance has yet to be developed. The hydraulic disturbance means that normally operating pumped-storage units are inevitably affected by sudden operation changes of other units in the same waterway system. It is an important working condition in transient simulations of pumped-storage plants. In this study, a nonlinear model of a VSPSP containing multiple units is established based in MATLAB/Simulink, integrating hydraulic, mechanical, and electrical subsystems. The model is validated through comparison with on-site experiments. The fast power control strategy is adopted, enabling the unit to follow the power command rapidly and stably. The simulations show that VSPSU outperforms fixed-speed pumped-storage unit (FSPSU) in mitigating active power fluctuations under hydraulic disturbance. But VSPSU still faces active power fluctuations. This phenomenon is induced by the effect of the speed pulling-back control, which is used to keep the unit speed within the allowable speed variation range. Factors that influence the active power fluctuations are analyzed, and a useful countermeasure is proposed to solve active power fluctuations. The findings in this paper could provide understanding and guidance for the practical operation of VSPSUs.