Model Reduction for Inverters with Current Limiting and Dispatchable Virtual Oscillator Control

TL;DR

This paper develops reduced-order models for grid-forming inverters with current limiting and virtual oscillator control, enabling efficient analysis while capturing current-limiting effects in resistive and inductive networks.

Contribution

It introduces novel reduced-order models that incorporate current-limiting actions, tailored for networks with resistive and inductive lines, using analytical and singular perturbation techniques.

Findings

Reduced models accurately approximate higher-order models.

Models demonstrate computational efficiency in simulations.

Effective in capturing current-limiting effects in various network types.

Abstract

This paper outlines reduced-order models for grid-forming virtual-oscillator-controlled inverters with nested current- and voltage-control loops, and current-limiting action for over-current protection. While a variety of model-reduction methods have been proposed to tame complexity in inverter models, previous efforts have not included the impact of current-reference limiting. In addition to acknowledging the current-limiting action, the reduced-order models we outline are tailored to networks with resistive and inductive interconnecting lines. Our analytical approach is centered on a smooth function approximation for the current-reference limiter, participation factor analysis to identify slow- and fast-varying states, and singular perturbation to systematically eliminate the fast states. Computational benefits and accuracy of the reduced-order models are benchmarked via numerical simulations that compare them to higher-order averaged and switched models.