Power Electronic Loads as Providers of Reactive Power Ancillary Service to the Grid: Analytical and Experimental Study

Reactive power injection has been the common practice to stabilize and support the voltage in electric power systems and its provision was traditionally considered to be part of the duties of the units dispatching active power. This article proposes the provision of reactive power by electric loads which are interfaced to the grid by active rectifiers that enable them to inject reactive current to support the electric grid voltage locally. The reactive power characteristic at the point of load connection in a distribution system was analytically obtained and experimentally verified in a reduced scale laboratory model. The obtained reactive power curves are used to determine the required rating of the converter interfacing the load, for consideration of stability and operability margins, effect on power factor, impact of distributed compensation and for operation after transients. Relevance of the curves is also discussed for Low Voltage Ride Through (LVRT) operation of the converters interfacing the loads. Influence of the type of line (X/R >1, X/R=1, X/R