Multi-objective day-ahead scheduling of cascade hydropower-photovoltaic complementary system with pumping installation

Cascade hydropower (CHP) is a promising resource to compensate for the randomness and variability of photovoltaic (PV) power generation. However, the flexibility of CHP might become insufficient due to increasing PV penetration. By constructing pump units to transform into mixed pumped-storage plants, the regulating flexibility can be further improved. Nevertheless, since the pump is usually installed between two adjacent reservoirs, the hydraulic coupling between CHP and pumps is strengthened, and it challenges the coordinated power dispatch of the CHP-PV complementary system with pumping installation. In this paper, a day-ahead dispatch strategy for the complementary system is established based on multi-objective stochastic optimization, which aims to reduce the variance of residual load, output deviation of complementary system and PV curtailment caused by PV uncertainties simultaneously. The normalized normal constraint method is employed to generate evenly distributed points on the Pareto frontier, which can present a fair tradeoff among multi-objectives. Hence, subjectivity arising from weight assignment can be eliminated and comprehensive decision support can be provided for the dispatch of the complementary system. Simulation studies are conducted on a real system in southwest China and the effectiveness of the proposed approach is validated. Compared to the case without pumping installation, the capability to compensate for PV fluctuations and the peak-shaving performance can be improved.