Small-Signal Analysis of the Microgrid Secondary Control Considering a Communication Time Delay

TL;DR

This paper analyzes the stability of an islanded microgrid's secondary control considering communication delays, using small-signal modeling, root locus analysis, and validation through simulations and experiments.

Contribution

It introduces a small-signal model for microgrid secondary control that accounts for communication time delays and validates it with comprehensive simulations and experiments.

Findings

System stability is affected by communication delays.

Control parameters influence the system's dynamic response.

The proposed model accurately predicts system behavior under delay variations.

Abstract

This paper presents a small-signal analysis of an islanded microgrid composed of two or more voltage source inverters connected in parallel. The primary control of each inverter is integrated through internal current and voltage loops using PR compensators, a virtual impedance, and an external power controller based on frequency and voltage droops. The frequency restoration function is implemented at the secondary control level, which executes a consensus algorithm that consists of a load-frequency control and a single time delay communication network. The consensus network consists of a time-invariant directed graph and the output power of each inverter is the information shared among the units, which is affected by the time delay. The proposed small-signal model is validated through simulation results and experimental results. A root locus analysis is presented that shows the behavior of the system considering control parameters and time delay variation.