Distributed Optimal Voltage Control for Three Phase Unbalanced Distribution Systems with DERs

Abstract

Traditionally, electric utilities have used local (non-optimal) or centralized (optimal) approaches for voltage control in electric distribution grids. However, with increased penetration of distributed energy resources (DERs), voltage control has become increasingly challenging for distribution grid operators. This is mainly due to intermittency and variability in power injections of DERs. Digitalization and automation driven by smart grid development provides an opportunity to find balance between non-optimal local and complex but optimal centralized voltage control. Distributed optimization approaches enabled by automation utilize DERs to mitigate such voltage issues in optimal and resilient manner. This paper proposes an optimal distributed voltage control algorithm for three phase unbalanced distribution systems using augmented Lagrangian multiplier theory and primal-dual gradient algorithms. The algorithm requires local voltage measurements and communication among neighbouring buses while meeting hard limits on reactive power injections on voltage control devices and DERs. Developed algorithm is validated for both single phase and three phase unbalanced distribution systems voltage control using OpenDSS.

Additional details