A Two-Stage Coordinative Zonal Volt/VAR Control Scheme for Distribution Systems with High Inverter-based Resources

TL;DR

This paper introduces a fast, rule-based two-stage voltage control scheme for distribution systems with high inverter resources, coordinating IBR and VR to improve voltage regulation efficiently using minimal measurements.

Contribution

The paper proposes a novel two-stage zonal Volt/VAR control method that reduces measurement needs and retrofitting, enhancing voltage regulation in unbalanced distribution systems.

Findings

Effective voltage regulation demonstrated on real distribution feeders.

Significant reduction in VR tap changes and voltage fluctuations.

Fast, measurement-efficient control algorithm suitable for real-time deployment.

Abstract

This paper presents a two-stage zonal Volt/VAR control scheme for coordinating inverter-based resources (IBR) with utility-owned voltage regulators (VR) to regulate voltage in unbalanced 3-phase distribution systems. First, correlations between nodal voltages are derived from nodal voltage sensitivity studies. Then, the feeder is partitioned into non-overlapping, weakly-coupled voltage control zones based on nodal voltage correlations. IBR are used in the first stage to regulate voltage changes continuously and VR are used in the second stage to regulate large voltage deviations. An online VR voltage setpoint tuning strategy is developed to reduce excessive tap changes and avoid large voltage fluctuations without retrofitting existing VR controllers. In addition, the proposed algorithm uses real-time voltage measurements only from the critical nodes (typically less than 4% of total nodes) to reduce the sensing and communication needs. Actual distribution feeder topologies and load and PV time-series data are used to verify the performance of the algorithm. Because the method is a rule-based approach, it runs extremely fast, requires fewer measurements, and requires no retrofit to the existing VR control mechanisms. Simulation results show that the performance of the proposed method in terms of voltage control results and average numbers of VR tap changes are satisfactory.