Analysis of Power Regulation Characteristics for Pumped Storage Plants Containing a Variable-Speed Unit with a Full-Size Converter and a Fixed-Speed Unit Considering Hydraulic Disturbances Under Turbine Mode

The rapid and frequent power regulation of variable-speed pumped storage units with a full-size converter (VSPSU with FSC) causes strong hydraulic disturbances in fixed-speed units (FSU) within shared pipelines. The influence of power command rates on the system has not been sufficiently quantified. Therefore, a model of pumped storage plant (PSP) containing VSPSU with FSC and FSU is constructed and validated against internationally used software SIMSEN. Influences of rates on dynamic characteristics are analyzed under turbine power reduction condition. An evaluation method is proposed to quantify power regulation performance for selecting optimal rates. Results indicate the following: (1) Advantage: the VSPSU-FSU demonstrates a superior power response compared to FSU-FSU under fast power control strategy. (2) Influence: overshoots of parameters show positive correlations with rates, while regulation time generally exhibits negative correlations. (3) Evaluation: Power regulation performance has a non-monotonic relationship with rates of VSPSU. Considering rapidity, safety, and stability comprehensively, the performance initially raises to a peak and then declines. Under 50% power reduction, the optimal power command rate is 0.1 p.u./s. The VSPSU–FSU active power regulation time is 4.9 s, significantly lower compared to FSU–FSU (45.17 s). This paper offers crucial insights for optimizing operation of PSPs with VSPSU and FSU.