Since the adoption of the "Energy Strategy 2050" by the Federal Council in 2017, Switzerland has been looking for new energy alternatives to the nuclear sector and ways to reduce its greenhouse gas emissions, in particular by promoting the development of renewable energies. The national hydroelectric park, which represents 59% of total energy production, has an essential place in this context of upheaval in electricity supply. In the coming years, more and more existing power plants will come to the end of the concession. In this transitional period, they must be the subject of interventions to adapt their installations and operations to future economic, energy, legislative and environmental contexts. The main objective of the project is the development of a methodology to identify and promote technical solutions to increase winter energy production and operating flexibility. It consists of a first step of diagnosing the installations reference state and then a second step of generating and analysing renewal variants. It is then applied to the case study of the Forces Motrices de Conches (GKW) and the Forces Motrices Valaisannes (FMV) power plants in Haut-Valais.