Cluster-type open-loop pumped storage power stations with hydraulic connections exacerbate water level fluctuations of conventional hydropower stations and alter hydropower flexibility

The redevelopment of conventional cascade hydropower stations (CCHS) incorporating pumped storage power stations (PSPS) offers a new approach to promoting renewable energy consumption. With this mode's growth, cluster-type open-loop PSPS with hydraulic connections are emerging. However, the operational characteristics and flexibility of complex PSPS remain under-researched. This study develops a multi-energy joint scheduling model including PSPS and conducts comprehensive analysis of PSPS. And this study uses the inclusion of Guinanwarang PSPS (GNPS) and Longyangxia-Laxiwa hybrid PSPS (LLPS) in Longyangxia (LYX) and Laxiwa (LXW) hydropower stations as examples. The results show that (1) The operating power of LLPS decreases with the increase of comprehensive utilization flow and the addition of GNPS, while GNPS is less affected by the flow and LLPS. (2) The addition of PSPS affects the magnitude of the water level fluctuations in CCHS, showing a distinct three-stage variation. (3) Compared to no PSPS, LYX power generation exhibits increases of 5 %–51 % with LLPS alone and 4 %–29 % with two PSPS. (4) Compared with no PSPS, PSPS can enhance the system's flexibility. When two PSPS are added, the increase is the greatest, with the daily average upward flexibility supply and downward flexibility supply improving by approximately 256 × 104kW and 304 × 104kW, respectively.