Considering a system based on hydroelectricity, with a significant penetration of renewables (wind and solar) and high barriers to build new dams and reservoirs; this paper presents the benefits that the installation of pumped-storage power plants (PSP) could add to such system, improving its efficiency and respecting the expanding boundaries. A case study was developed considering sixteen hydroelectric plants from a real cascade, one equivalent PSP and five wind farms. Through an evolutionary algorithm, the PSP operation was optimized focusing on minimizing the spillage that could be used to generate power in a convenient moment. To prove this concept, three different hydrologic scenarios were analyzed: wet, dry and medium seasons; based on the real water inflow of the river, according to historical measurements. This investigation makes possible to conclude that a PSP can effectively reduce the effects of intermittency of wind and solar generation, optimizing a subsystem having a topological structure commonly found in the Brazilian Interconnected System.