Anti-interference characteristics of variable speed pumped storage units for load cases of hydraulic disturbances

Abstract

Variable speed pumped storage unit (VSPSU) is an innovative technology, and investigations regarding operating characteristics of VSPSU are significant. However, there are relatively few studies towards hydraulic disturbances of VSPSUs. The hydraulic disturbance means that pumped-storage units, which were originally in steady operation, are inevitably affected by suddenly operating changes of other units in the same waterway system. Normally, it will cause the power output of fixed-speed units to oscillate, and adversely affect the safety of generators and stability of power systems. Hence, investigations of VSPSUs’ characteristics under hydraulic disturbances are necessary. In this paper, VSPSU using doubly fed induction machine (DFIM) is adopted as a study case, and fast power control strategy is used in the controlling of VSPSU. The simulation result shows that VSPSU has good anti-interference performance, and normally operating VSPSU can still maintain stable power output and stator current even under disturbance from other units. However, despite the good anti-interference performance of VSPSU, the mechanical power of VSPSU lags far behind the electromagnetic power, and the hydraulic-mechanical transient processes of VSPSU are similar to that of a fixed-speed unit. The findings in this paper could provide understanding and guidance for practical operation of VSPSUs.