Experimental Characterisation of Distributed Reactive Power Sharing under Communication-Induced Stress in Parallel Grid-Forming Inverters

TL;DR

This paper experimentally investigates how parallel grid-forming inverters share reactive power under communication delays and impedance mismatches, revealing stability limits and robustness of the control strategy in a microgrid setting.

Contribution

It provides an experimental analysis of reactive power sharing robustness and transient behavior under communication-induced stress in a microgrid with parallel inverters.

Findings

Reactive power sharing converges within 90 ms delay

Stability boundary is between 90 ms and 100 ms delay

Higher integral gain reduces stability margin

Abstract

Synchronisation of parallel grid-forming inverters is crucial for stable operation of future power systems. This includes accurate and robust reactive power sharing under realistic operating conditions such as impedance mismatch and communication constraints. In this work, reactive power sharing by virtue of a distributed control law is investigated under line impedance mismatch. Furthermore, robustness and transient behaviour of the proposed approach are experimentally evaluated under communication-induced stressors including a fixed 3% packet loss and communication delays ranging from 50 ms to 100 ms, artificially introduced through a software-defined overlay. The study is conducted in a low-voltage laboratory-scale microgrid comprising two parallel grid-forming inverters, an AC load, and a grid-following battery system acting as a reactive power injector. The results show reactive power sharing convergence up to 90 ms communication delay, with a stability boundary between 90 ms and 100 ms, which decreases with increasing integral gain.