Photovoltaic generating units as reactive supply ancillary service providers

This paper addresses the issue of the application of PhotoVoltaic (PV) Distributed Generation (DG) units for supplying reactive power to the grid. In order to reach this aim, an advanced control scheme to suitably drive the injection of both active and reactive power into a MV radial distribution grid has been developed. Such algorithm allows a decoupled control of active and reactive power by properly adjusting the modulating signals of a PWM interface converter with the grid. A closed loop regulation scheme has been derived and guidelines for the choices of the reference quantities and for the design of the regulators are provided. The control algorithm has been applied to a real MV grid-connected PV power plant, which has been simulated in the PSCAD - EMTDC electromagnetic environment, in order to represent, with high detail, every system component and to thoroughly analyze the occurring electromagnetic transients. The positive effect of reactive power support to the grid from the PV unit has been highlighted, showing benefits on the grid current and voltage profiles with respect to the classical configuration, where the DG system behaves as a sole active power source. © 2008 The Berkeley Electronic Press. All rights reserved.