Characterization and Validation of Hybrid Energy Storage Systems Formed by Li-Ion Batteries and Supercapacitors for Their Installation in Hydroelectric Power Plants

Abstract

Hydroelectric power plants suffer from wear and tear of the different mechanical parts when participating in frequency control ancillary services. In a paradigm where the needs of providing frequency control are continuously growing, the lifespan of hydroelectric power plants is being compromised. In this sense, hybridizing the hydro with energy storage systems, specifically Li-ion batteries (Li-ion BESS) has been proven to be a good solution. However, Li-BESS suffer from ageing, and a combination of hydro, Li-BESS, and supercapacitors (SCs) seems to be promising for protecting both the hydro and Li-BESS from an excessive aging (Project HYBRIDHYDRO). CIEMAT’s facilities account for a Hardware-In-the-Loop (HIL) installation to test this configuration, with prototypes of Li-BESS, SCs and a HIL platform that emulates the hydro. This paper presents the models, characterization and validation tests for real prototypes of Li-BESS and SCs. They are needed to develop hybrid control strategies that reduce the aging of Li-BESS and the hydro. Starting from selecting proper semi-empirical models, laboratory tests have been performed for finding the parameters. Then, the models are compared to the manufacturer datasheet, reaching errors below 3% for the voltage/runtime and thermal model of the Li-BESS, as well as for the frequency domain and thermal model of the SCs. In addition, the time delay introduced by the power electronic converters when imposing a reference to the Li-BESS and SCs have been tested in laboratory, and thereby modeled. Hence, the complete behavior of the facility is taken into account when developing hybrid control strategies, resulting in an optimized techno-economical operation which will include both Li-BESS and hydro aging considerations.