Quantification and Regulation of Energy Reserves for Distributed Frequency and Voltage Control of Grid-Forming Inverters

TL;DR

This paper introduces a framework for quantifying and regulating energy reserves in grid-forming inverters within microgrids, enhancing hierarchical control and resource management.

Contribution

It proposes a novel BESS energy reserves framework and a modified DAPI controller for improved frequency, voltage regulation, and energy sharing in microgrids.

Findings

Effective frequency and voltage regulation demonstrated.

Improved power and energy sharing across inverters.

Controller performance validated via CHIL simulation.

Abstract

The introduction of Renewable Energy Sources (RES) and Distributed Energy Resources (DERs) has led to the formulation of Microgrids (MGs) and Networks of MGs (NMGs). MGs and NMGs can operate in islanded mode, transforming the grid into a more distributed system. This has led to extensive studies in the literature on distributed hierarchical control strategies. Previous works have proposed distributed secondary level frequency and voltage regulation control schemes for Battery Energy Storage System (BESS)-based Grid-Forming (GFM) inverters with State of Charge (SoC) balancing. However, links to tertiary level control in terms of service-based reserves and local resource adequacy in MGs are largely unexplored. Therefore, this paper proposes a BESS energy reserves framework, to quantify reserves for hierarchical control operation. Additionally, to partially regulate the proposed energy reserves, we propose the formulation of a modified Distributed-Averaging Proportional-Integral (DAPI) controller with regulation energy reserve consensus. Controller Hardware-In-the-Loop (CHIL) simulation is performed on an MG topologically based on the IEEE 13 bus test feeder system in MATLAB/Simulink. The proposed scheme results illustrate effective frequency and voltage regulation along with improved power and energy sharing across droop-controlled and Virtual Synchronous Machine (VSM) controlled inverters.