Optimal Design of Volt/VAR Control Rules for Inverter-Interfaced Distributed Energy Resources

TL;DR

This paper presents a novel, scalable method for customizing Volt/VAR control rules for inverter-interfaced DERs, optimizing voltage regulation and stability on distribution feeders using a gradient-based algorithm.

Contribution

It introduces a new methodology for designing and adjusting Volt/VAR rules per bus that guarantees stability and improves voltage profiles in distribution grids.

Findings

Method effectively improves voltage regulation.

Guarantees stability of nonlinear grid dynamics.

Scalable to real-world distribution feeders.

Abstract

The IEEE 1547 Standard for the interconnection of distributed energy resources (DERs) to distribution grids provisions that smart inverters could be implementing Volt/VAR control rules among other options. Such rules enable DERs to respond autonomously in response to time-varying grid loading conditions. The rules comprise affine droop control augmented with a deadband and saturation regions. Nonetheless, selecting the shape of these rules is not an obvious task, and the default options may not be optimal or dynamically stable. To this end, this work develops a novel methodology for customizing Volt/VAR rules on a per-bus basis for a single-phase feeder. The rules are adjusted by the utility every few hours depending on anticipated demand and solar scenarios. Using a projected gradient descent-based algorithm, rules are designed to improve the feeder's voltage profile, comply with IEEE 1547 constraints, and guarantee stability of the underlying nonlinear grid dynamics. The stability region is inner approximated by a polytope and the rules are judiciously parameterized so their feasible set is convex. Numerical tests using real-world data on the IEEE 141-bus feeder corroborate the scalability of the methodology and its explore the trade-offs of Volt/VAR control with alternatives.