Abstract
This paper proposes a modified version of the power-based control (MPBC) applied to microgrids (µGs) with multiple points of connection (i.e., utility grid itself or any other neighboring µG). Using the MPBC, single-phase distributed energy resources (DERs) arbitrarily connected between the phases share the amounts of balanced power, while the unbalanced and homopolar power are steered only to the line-to-neutral inverters. The control technique is based on a three-level hierarchical control using narrow bandwidth, low data rate communication that properly coordinates the DERs connected to three-phase four-wire µGs. The MPBC allows the DERs to steer power flow at any of the multiple points of common coupling of a multi-PCC dispatchable µG. The modified control proposed herein is evaluated through simulation results using MATLAB/SIMULINK considering a real urban distribution grid with typical operational elements and conditions. When compared to the original power-based control (PBC), results show that a meshed µG may reach power benchmarks with accommodation time 80% lower when applying MPBC. Moreover, it may also lead to significant power loss reduction (about of 5%) in some studied cases.
Highlights
The microgrid model appears as a versatile structure to allow the interconnection of several distributed energy resources (DERs), loads and energy storage systems (ESSs) into a flexible grid topology [1]
If μG coordinated control is not well managed the ac bus may suffer from power quality (PQ) issues, such as voltage deviation, frequency variation, protection mistriggering etc., which can drive the system to instability [5,6]
Some utility companies are already starting to adopt projects with μG clusters (μGCs), such as the Commonwealth Edison, which is developing a μGC using the Bronzeville μG and the campus μG at the Illinois Institute of Technology in Chicago [9]. μG cluster is defined as the interconnection of two or more μGs capable of connecting to the utility grid and exchanging power among them through their points of common coupling (PCCs) [6,10]. μGCs can offer various ancillary services, including power flow control, energy trading, sharing of energy storage systems, corrective maintenance, frequency and voltage regulation in a larger geographic area of the electrical system, which allows for better system operation under contingency conditions [11]
Summary
The microgrid (μG) model appears as a versatile structure to allow the interconnection of several distributed energy resources (DERs), loads and energy storage systems (ESSs) into a flexible grid topology [1]. Several references demonstrate that the μG model can increase grid efficiency, reliability and improve system stability [2,3]. If a μG is dispatchable in terms of power, it can contribute to increase the hosting capacity of a distribution system [4]. Energy management and coordination of μGs become a challenge, since several uncertainties are involved in this assessment (e.g., intermittency in electricity sources, such as wind speed variation and solar shadowing, as well as variable load demand). If μG coordinated control is not well managed the ac bus may suffer from power quality (PQ) issues, such as voltage deviation, frequency variation, protection mistriggering etc., which can drive the system to instability [5,6]. A single μG has shortcomings to ensure resilience against disturbances at a certain point in the distribution grid [7]
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