Peak shaving model for multiple receiving power grids with large-scale cascade diversion-type hydro plants via HVDC transmission lines

Coordinated multigrid peak shaving utilizing large-scale cascade hydropower stations is important for power systems. With the planning and construction of cascaded serial diversion-type hydropower stations (CSDHS), effective multigrid peak regulation with CSDHS faces increasing challenges because of complex operational constraints such as upstream–downstream flow matching, multiple units sharing a diversion tunnel and operation constraints of high-voltage direct current (HVDC) transmission lines. To address these challenges, a novel multigrid peak regulation model for HVDC receiving ends powered by CSDHS is proposed in this paper. The innovative contributions of the model are as follows: (1) Minimization of peak-to-valley load differences across multiple grids by the CSDHS; (2) Quantification of hydraulic coupling effects through upstream–downstream flow matching of the CSDHS; (3) Integration of operational constraints for both hydropower plants and HVDC transmission lines; and (4) A vertical transmission strategy for integrated power delivery is proposed. A parallelogram approximation method combined with an iterative algorithm transforms the model into a tractable mixed-integer linear programming (MILP) formulation. Case studies of a specific CSDHS reveal the effectiveness of the model: During the dry season, the peak–valley load differences of the two grids are reduced by 16.6 % and 13.6 %, respectively, and by 50.6 % and 55.7 %, respectively, in the flood season. The vertical transmission strategy significantly reduces HVDC power regulation, decreases start–stop frequencies, and decreases vibration–zone crossings by 43 % and 39 % during the dry and flood seasons, respectively.