Power–Speed Hybrid Control Strategy and Dynamic Performance Analysis of Variable Speed Pumped Storage Units in Generating Mode

Variable speed pumped storage units (VSPSUs) offer flexible active-power regulation capability; however, during large power variations, it remains challenging to simultaneously achieve fast power tracking and effective rotor-speed regulation. To address this issue, this paper proposes a power–speed hybrid control strategy for VSPSUs in generating mode. Within a unified control framework, a weighting coefficient λ is introduced to coordinate the allocation of power and speed control objectives between the electromagnetic and hydraulic–mechanical control channels. A sensitivity analysis is further conducted for λ = 0.1–0.9 based on the dynamic performance indices of active power and rotor speed. The results show that, under the operating condition considered, the composite performance index is minimized at λ = 0.5. For an active power step from 0.4 p.u. to 0.8 p.u., compared with power-priority control, the proposed strategy effectively suppresses power oscillations, reducing the active-power overshoot from 29.88% to 0.85% and shortening the ±5% settling time from 2.829 s to 0.230 s. In addition, the proposed strategy maintains good dynamic adaptability when the water inertia time constant Tw varies by ±20%. The proposed method provides a low-complexity control solution for coordinating active-power response and rotor-speed regulation in VSPSUs.