Hydraulic-mechanical-electrical coupled model framework of variable-speed pumped storage system: Measurement verification and accuracy analysis

With the large-scale operation of wind and solar energy, the demand for energy storage in power grids has increased sharply. As a reliable means of long-term energy storage, the variable-speed pumped-storage power station (VSPSU) is a new development direction for pumped storage that has attracted increasing attention owing to its advantages of more rapid and flexible action. However, accurately predicting the transient process of a VSPSU is a key challenge in its design and operation. The inconsistent time step required for the fine simulation of the hydraulic-machine subsystem (millisecond level) and the electrical subsystem (microsecond level) is the main challenge that hinders the coordination of system simulation efficiency and accuracy and restricts further development of the entire coupling system simulation. Simultaneously, a coupling refinement model verified by multi-condition measurements has not been reported. This paper proposes a VSPSU hydraulic-mechanicalelectrical coupling model framework that has been verified experimentally. The innovation of the model framework lies in the realization of the fine solution of the hydraulic and electrical systems through the coupling strategy of the variable simulation step size rather than using model simplification. Based on a real micro-VSPSU system, we conducted experiments under various operating conditions and compared the measurements with the numerical simulation results. The results showed that in the generation mode, the maximum simulation error of the proposed coupling model framework on the hydraulic-mechanical side was 2.29 %, and the maximum simulation error on the electrical side was 9.59 %. Finally, we quantified the contribution of key parameters in the model framework to the dynamic response process and clarified the influence of physical parameters on the transient process in the VSPSU. Compared with conventional models, the advantage of the proposed coupling framework is that it can realize the coupling of a hydraulic-mechanical-electrical system without simplification, which has been verified by measuring multiple working conditions. This framework provides a reliable tool for the parameter design and operation optimization of VSPSU.