Power-speed coupling response characteristics of variable speed pumped storage unit under pumping mode

Variable speed pumped storage unit (VSPSU) has the advantage of adjustable power under pumping mode, which can better meet the regulation demand of power grid. This paper aims to study the power-speed coupling response characteristics (CRCs) of VSPSU under pumping mode. Firstly, the model of VSPSU under pumping mode is established, and the power-speed CRCs are revealed. Then, the influence of regulating parameters on the power-speed CRCs is explored. Finally, the influence mechanism of power regulation of VSPSU is clarified. The results show that the VSPSU can realize power regulation by adjusting the speed through the frequency convertor. The transient response processes of power and speed are basically consistent in the overall trend, but the regulation quality of speed is better than that of power. The regulating parameters of the speed outer loop of frequency converter have obvious influence on the power-speed CRCs of VSPSU, but the regulating parameters of current inner loop of the frequency converter and the governor have little effect. With the decrease of initial speed or the increase of speed regulation amplitude, the power regulation amplitude increases, and the power regulation amplitude under decreased speed regulation scenarios is greater than that under increased speed regulation scenarios. When the power regulation amplitude is the same under different working heads, the speed regulation amplitude decreases with the increase of working head, and the speed regulation amplitude under decreased power regulation scenarios is smaller than that under increased power regulation scenarios.