An important role in the management of the decarbonized electricity system can be played by pumped storage hydropower plants, both for their high storage capacity and their response speed.
A simulation and optimization model is presented to analyze the regulation capacity of a hybrid pumped storage plant and identify the most economically advantageous configuration in terms of control strategy parameters on the one hand and the hybrid components’ technology and size on the other hand. The model is able to simulate dispatching services such as primary, secondary, and primary ultra-fast frequency regulation (the last one, consistent with the Terna Fast Reserve pilot project). As a case study, a hypothetical reversible marine Pumped Storage Hydropower Plant (PSHP) is considered in Foxi Murdegu (Nuoro province), Sardinia, and hybridized with electrochemical storage systems (Battery Energy Storage System – BESS) and flywheel storage systems (Flywheel Energy Storage System – FESS).
Partially developed in the past, the model is completed with generalized pump-turbine characteristic curves and with the new Frequency Split control strategy, in addition to the Hydro Recharge. The set of configurations is also completed by adding PSHP+FESS to the previous PSHP+BESS and PSHP+BESS+FESS.
Starting from a list of candidate hybridization configurations, the optimization procedure is divided into two levels: i) optimization of the control parameters of each candidate hybridization configuration via a Particle Swarm Optimization (PSO) algorithm; and ii) choice of the hybridization configuration maximizing the Net Present Value (NPV).
For the typical year considered in the simulation, it turns out that the most economically advantageous hybridization of the Foxi Murdegu plant is with 25 MW of BESS, without FESS, due to the current high costs of this technology. The optimal hybridized plant was finally inserted into a simplified model of the 2030 Sardinian electrical system. Dynamic simulations have shown that, in case of a strong under/over-frequency, the frequency error is smaller than in the case of the non-hybridized plant. Furthermore, the PSHP hybridization avoids excessive mechanical stress to the hydraulic machine due to the services provided and allows the provision of an ultra-fast frequency service, opening the path to a greater profit from services.