Superposition control of extreme water levels in surge tanks of pumped storage power station with two turbines under combined operating conditions

• Published in: Journal of energy storage 2022-12, Vol.56, p.105894, Article 105894
• Main Authors: Cui, Zilong, Guo, Wencheng, Zhang, Tianyu
• Format: Article
• Language: English
• Subjects: Combined operating conditions; Extreme water levels; Pumped storage power station; Superposition control; Surge tanks; Two parallel turbines
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2022.105894

This paper investigates the superposition control of extreme water levels (EWLs) in surge tanks of pumped storage power station (PSPS) with two turbines under combined operating conditions (COCs). Firstly, for PSPS with upstream and downstream surge tanks (UDST) and two turbines, the model and ten COCs are presented. The superposition control strategy of EWLs in UDST is designed. Secondly, the most favourable superposition time and the most unfavourable superposition time under COCs, i.e. superposition control moments, are determined. The concepts of initial gradient and superposition gradient are proposed to reveal the control mechanisms. Finally, the influences of tunnel parameters on superposition control moments are analyzed. The results show that tangential points for water level - flow velocity curves of initial operating condition and superposition operating condition are not the superposition control moments. For ten COCs, the most favourable superposition time is the moment of minimum superposition gradient, and the most unfavourable superposition time is contrary. With the increase of sectional area and decrease of length for tunnel, the superposition control moments decrease. Because the initial gradient and superposition gradient are mainly affected by tunnel parameters, the hydraulic coupling oscillations of UDST have no effect on superposition control moments. •Model of PSPS with UDST and two turbines is established.•Superposition control strategy of EWLs in UDST is designed.•Superposition control moments under ten COCs are determined.•Superposition mechanisms are revealed by initial and superposition gradients.•Influences of tunnel parameters on superposition control moments are analyzed.