A Framework to Utilize DERs' VAR Resources to Support the Grid in an Integrated T-D System

TL;DR

This paper proposes a framework leveraging inverter-based DERs as distributed VAR devices to enhance grid support, using a novel optimization approach and co-simulation to evaluate system impact.

Contribution

It introduces a new D-OPF formulation and a co-simulation method to quantify DERs' VAR support in an integrated T-D system, improving grid flexibility.

Findings

DERs can provide significant local VAR support without compromising distribution performance

The proposed framework accurately estimates maximum VAR support at various operating points

Co-simulation demonstrates the positive impact of DER VAR support on grid stability

Abstract

Increasing penetration of inverter-based distributed energy resources (DERs) opens up interesting opportunities for the transmission systems. We present a hypothesis that the numerous DERs in var control mode can be seen as geographically distributed var devices (mini-SVCs) and if controlled properly, can be exploited to increase system flexibility by providing local var support to the grid as an ancillary service. Based on this premise, a var support framework is proposed in this paper. It utilizes a novel D-OPF formulation for unbalanced three-phase feeders enabling the estimation of the maximum var support that can be provided by the DERs to the grid at different operating points without compromising the distribution network performance. Further, a co-simulation method is developed to investigate the true impact of the proposed DER var support on the grid in an integrated Transmission-Distribution (T-D) system.