Reactive Power Ancillary Service of Synchronous DGs in Coordination with Voltage Control Devices

Abstract

This paper presents an optimal way to control steady-state voltage in distribution feeders using reactive power ancillary service that is provided by synchronous distributed generators (DGs). Based on load forecasts provided one day in advance, DG reactive power is dispatched on the hour in coordination with the switching operations of an on-load tap changer (OLTC) and shunt capacitors (SCs). This aims to reduce not only distribution line power losses but also the number of switching operations of the OLTC and the SCs, which affect the feeder voltage quality and switching device lifetime. For the reactive power dispatch, a mixed-integer nonlinear optimization problem is formulated using a multiobjective function and solved using a particle swarm optimization (PSO) algorithm. Modules using evolutionary and dynamic programming are incorporated into the PSO algorithm to be less susceptible to becoming trapped in local optima and have a better chance of reaching global optimum. Simulation case studies using small- and large-scale distribution networks were performed using MATLAB to demonstrate that the coordinated reactive power support of the DGs, OLTC, and SCs can achieve the objective effectively, resulting in improved voltage quality.