Voltage control for Distributed Energy Resources - The value of coordination

Due to the large development and integration of renewable energy generators, voltage control in power distribution grids have become a very important topic for the energy automation systems. In this paper we present aspects regarding the design of local controllers and the overall stability of the control system. The results stem from analytical investigations and from measurements and experiments performed on a low voltage distribution grid. In the paper we will show that voltage asymmetry in the distribution grids cannot be neglected and consequently, the control of the voltage needs to be performed specifically for each phase. Decentralized local controllers can perform the control and, if designed correctly, they are highly efficient with respect to the use of reactive power.