Two-Level Coordinated Power Control Strategy for Multiple Variable Speed Pumped Storage Units Participating in Primary Frequency Regulation

This paper proposes a novel two-level coordinated control strategy for multiple double-fed variable speed pumped storage (VSPS) units participating in primary frequency regulation. First, auxiliary variables are introduced to clearly address the coupling relationship between the electromagnetic and the mechanical subsystem of the VSPS, establishing an accurate system frequency response (SFR) model containing VSPS. Based on this model, the analytical expression of the SFR is derived using the Routh reduction method. This expression serves as the basis for the prediction model of the upper-level model predictive control (MPC). To ensure the stable execution of power commands optimized in the upper level, the rotor speeds of VSPS units should be consistent. The reason is that inconsistent rotor speeds of VSPS units exacerbate turbulence in the water, consequently increasing energy losses. To address this issue, a consistency control strategy is proposed to drive the operating states of all VSPS units to converge and maintain consistency. Through the coordination of the upper- and lower-level control, the computational burden and the dependency on the mode can be effectively alleviated. Finally, hard-ware-in-the-loop test results verify that the proposed control method is more effective in improving SFR while realizing the consistency of VSPS units' operating states.