The actions for limiting the climate change are significantly affecting the electrical power system. Indeed, the increase in renewable power sources and the progressive shut off of coal-fired power plants are transitioning the generation from a centralized to a decentralized paradigm. The latter may cause issues in a grid that was originally designed taking as granted the presence of several big power plants to be used as actuators for the system control. Considering voltage control, the actual control architecture is based on a hierarchical structure applied to a given set of rigidly subdivided control areas. Although such architecture is currently capable of maintain voltage control on the grid, the increase in converter interfaced generators (due to renewables exploitation) and the decrease of the buses short circuit powers (due to high power plants shut-off) may decrease its effectiveness in the future. To this aim, in this paper a coordinated decoupling voltage control is proposed, capable of using all the available reactive power sources on the grid as actuators. The issue of controlling a system with a variable number of actuators (due to generators connection and disconnection) is taken into account, proposing a suitable solution for avoiding transients during the switch between controllers having different output dimension. A brief discussion about communication (among actuators and controller) performances required for implementing the proposed control in the power system is also given.
