Hierarchical voltage regulation of transmission systems with renewable power plants: An overview of the Italian case

Hierarchical automatic voltage regulation is implemented in several power systems using the reactive power capabilities of controlled alternators in transmission networks. With the introduction of power plants based on Renewable Energy Sources (RES), in the transmission network there are new possible participants to the voltage regulation which replace in part the traditional large alternators. The paper reviews the actual situation in Italy for the participation of renewable power plants to the transmission network voltage regulation.