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Special Issue "Microgrids-2018"

A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (31 August 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Josep M. Guerrero
Highly Cited - Clarivate Analytics (formerly Thomson Reuters)

Microgrid Research Programme, Department of Energy Technology, Aalborg University Pontoppidanstraede 111, room 25, 9220 Aalborg, Denmark
Website | E-Mail
Interests: microgrids; minigrids; islanded energy systems; distributed generation; renewable energy; hierarchical control; distributed control; maritime microgrids, onboard grids

Special Issue Information

Dear Colleagues,

Microgrids are small-scale energy grids that can operate independently or autonomously from the main energy grid. They can contain generation, storage and consumption of any form of energy, including electricity, heat, etc. The concept is supposed to eliminate or reduce the use of energy transmission systems, to produce energy near consumption points, thus, constituting small distribution systems. This new energy paradigm is changing the way we conceive of electrical, thermal, gas, or water grids. This Special Issue includes, but is not limited, to the following topics:

  • AC, DC, and AC-DC hybrid microgrids
  • Power electronics-based microgrids
  • Small-scale renewable energies and storage for microgrids
  • Micro combined heat and power (CHP) systems for microgrids
  • Multiple microgrid clusters
  • Microgrids and nanogrids for rural areas and in developing countries
  • Microgrids for all/hybrid electrical ships and green ports
  • Microgrids for electrical vehicle charging stations
  • Advanced control techniques for microgrids
  • Smart metering and power quality for microgrids
  • The Internet of things and energy Internet for multiple microgrids
  • Reviews on the state-of-the-art in the area of microgrids

Prof. Dr. Josep M. Guerrero
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • microgrids
  • renewable energy

Published Papers (8 papers)

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Research

Open AccessArticle A Cost-Effective Decentralized Control for AC-Stacked Photovoltaic Inverters
Energies 2018, 11(9), 2262; https://doi.org/10.3390/en11092262
Received: 26 July 2018 / Revised: 23 August 2018 / Accepted: 24 August 2018 / Published: 28 August 2018
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Abstract
For an AC-stacked photovoltaic (PV) inverter system with N cascaded inverters, existing control methods require at least N communication links to acquire the grid synchronization signal. In this paper, a novel decentralized control is proposed. For N inverters, only one inverter nearest the
[...] Read more.
For an AC-stacked photovoltaic (PV) inverter system with N cascaded inverters, existing control methods require at least N communication links to acquire the grid synchronization signal. In this paper, a novel decentralized control is proposed. For N inverters, only one inverter nearest the point of common coupling (PCC) needs a communication link to acquire the grid voltage phase and all other N − 1 inverters use only local measured information to achieved fully decentralized local control. Specifically, one inverter with a communication link utilizes the grid voltage phase and adopts current control mode to achieve a required power factor (PF). All other inverters need only local information without communication links and adopt voltage control mode to achieve maximum power point tracking (MPPT) and self-synchronization with grid voltage. Compared with existing methods, the communication link and complexity is greatly reduced, thus improved reliability and reduced communication costs are achieved. The effectiveness of the proposed control is verified by simulation tests. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessFeature PaperArticle The Stability Analysis of a Multi-Port Single-Phase Solid-State Transformer in the Electromagnetic Timescale
Energies 2018, 11(9), 2250; https://doi.org/10.3390/en11092250
Received: 8 August 2018 / Revised: 20 August 2018 / Accepted: 23 August 2018 / Published: 27 August 2018
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Abstract
This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses
[...] Read more.
This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses the stability assessment of the MS3T in detail. First and foremost, the structure of the MS3T and its three stage control strategies are proposed. Furthermore, the stability analysis of each of the MS3T’s subsystems is achieved through the closed loop transfer function of each subsystem, respectively, including an AC-DC front-end side converter, dual active bridge (DAB) with a high-frequency (HF) or medium-frequency (MF) transformer, and back-end side incorporating DC-AC and dc-dc converters. Furthermore, the practical impedance stability criterion in the electromagnetic timescale, which only requires two current sensors and one external high-bandwidth small-signal sinusoidal perturbation current source, is proposed by the Gershgorin theorem and Kirchhoff laws. Finally, the overall stability assessment, based on a modified impedance criterion for the MS3T is investigated. The overall practical stability assessment of the MS3T can be validated through extensive simulation and hardware results. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle Optimal Energy Management within a Microgrid: A Comparative Study
Energies 2018, 11(8), 2167; https://doi.org/10.3390/en11082167
Received: 21 June 2018 / Revised: 19 July 2018 / Accepted: 16 August 2018 / Published: 19 August 2018
Cited by 2 | PDF Full-text (3795 KB) | HTML Full-text | XML Full-text
Abstract
In this work, we focus on optimal energy management within the context of the tertiary control of a microgrid operating in grid-connected mode. Specifically, the optimal energy management problem is solved in a unified way by using the optimal power flow (OPF) and
[...] Read more.
In this work, we focus on optimal energy management within the context of the tertiary control of a microgrid operating in grid-connected mode. Specifically, the optimal energy management problem is solved in a unified way by using the optimal power flow (OPF) and day-ahead concepts. The elements considered in the microgrid are a photovoltaic panel, a wind turbine, electric vehicles, a storage system, and a point of common coupling with the main grid. The aim of this paper consists of optimizing the economic energy dispatch within the microgrid considering known predictions of electricity demand, solar radiation, and wind speed for a given period of time. The OPF is solved using three different algorithms provided by the optimization toolbox of MATLAB® (R2015a, MathWorks®, Natick, MA, USA): the interior point method (IP), a hybrid genetic algorithm with interior point (GA-IP), and a hybrid direct search with interior point (patternsearch-IP). The efficiency and effectiveness of the algorithms to optimize the energy dispatch within the microgrid are verified and analyzed through a case study, where real climatological data of solar irradiance, wind speed in Almería city, photovoltaic system data, and room load from a bioclimatic building were considered. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle Model-Based Fault Detection of Inverter-Based Microgrids and a Mathematical Framework to Analyze and Avoid Nuisance Tripping and Blinding Scenarios
Energies 2018, 11(8), 2152; https://doi.org/10.3390/en11082152
Received: 1 August 2018 / Revised: 13 August 2018 / Accepted: 15 August 2018 / Published: 17 August 2018
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Abstract
Traditional protection methods such as over-current or under-voltage methods are unreliable in inverter-based microgrid applications. This is primarily due to low fault current levels because of power electronic interfaces to the distributed energy resources (DER), and IEEE1547 low-voltage-ride-through (LVRT) requirements for renewables in
[...] Read more.
Traditional protection methods such as over-current or under-voltage methods are unreliable in inverter-based microgrid applications. This is primarily due to low fault current levels because of power electronic interfaces to the distributed energy resources (DER), and IEEE1547 low-voltage-ride-through (LVRT) requirements for renewables in microgrids. However, when faults occur in a microgrid feeder, system changes occur which manipulate the internal circuit structure altering the system dynamic relationships. This observation establishes the basis for a proposed, novel, model-based, communication-free fault detection technique for inverter-based microgrids. The method can detect faults regardless of the fault current level and the microgrid mode of operation. The approach utilizes fewer measurements to avoid the use of a communication system. Protecting the microgrid without communication channels could lead to blinding (circuit breakers not tripping for faults) or nuisance tripping (tripping incorrectly). However, these events can be avoided with proper system design, specifically with appropriately sized system impedance. Thus, a major contribution of this article is the development of a mathematical framework to analyze and avoid blinding and nuisance tripping scenarios by quantifying the bounds of the proposed fault detection technique. As part of this analysis, the impedance based constraints for microgrid system feeders are included. The performance of the proposed technique is demonstrated in the MATLAB/SIMULINK (MathWorks, Natick, MA, USA) simulation environment on a representative microgrid architecture showing that the proposed technique can detect faults for a wide range of load impedances and fault impedances. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle Novel Distributed Optimal Control of Battery Energy Storage System in an Islanded Microgrid with Fast Frequency Recovery
Energies 2018, 11(8), 1955; https://doi.org/10.3390/en11081955
Received: 18 July 2018 / Revised: 18 July 2018 / Accepted: 27 July 2018 / Published: 27 July 2018
PDF Full-text (2584 KB) | HTML Full-text | XML Full-text
Abstract
Highly intermittent renewable energy sources pose new challenges to microgrid operation and control. Thus, many distributed control strategies have been proposed to solve this problem. However, for most previous studies, the system frequency fluctuation can be further controlled on the basis of the
[...] Read more.
Highly intermittent renewable energy sources pose new challenges to microgrid operation and control. Thus, many distributed control strategies have been proposed to solve this problem. However, for most previous studies, the system frequency fluctuation can be further controlled on the basis of the optimal control strategy. This paper proposes a novel distributed optimal control strategy of a battery energy storage system in an islanded microgrid to provide desired optimal control performance and fast frequency recovery. The proposed control strategy is implemented through a multi-agent system based on consensus algorithm, which only requires information collected through a local communication network. Furthermore, the measurement of supply–demand mismatch is replaced by the control signal obtained from a supplementary controller with the improved linear active disturbance rejection control algorithm. The stability of microgrid frequency can be greatly enhanced through this improvement. Finally, the validity of proposed method is demonstrated by various case studies which are given in this paper. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle A Multi-Agent System-Based Approach for Optimal Operation of Building Microgrids with Rooftop Greenhouse
Energies 2018, 11(7), 1876; https://doi.org/10.3390/en11071876
Received: 5 June 2018 / Revised: 4 July 2018 / Accepted: 17 July 2018 / Published: 18 July 2018
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Abstract
In this paper, an optimal energy management scheme for building microgrids with rooftop greenhouse is proposed. A building energy management system (BEMS) is utilized for the optimal fulfilment of energy demands in the building and the greenhouse. The exhaust heat generated due to
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In this paper, an optimal energy management scheme for building microgrids with rooftop greenhouse is proposed. A building energy management system (BEMS) is utilized for the optimal fulfilment of energy demands in the building and the greenhouse. The exhaust heat generated due to the operation of air conditioners in the building is used for fulfilling the cooling demands of the greenhouse via chillers. In addition to thermal and cooling demands, the four major control parameters (temperature, humidity, light intensity, and CO2 concentration) are also considered for optimal growth of crops in the greenhouse. A multi-agent system (MAS) is adopted to realize the interaction among several households of the building, the greenhouse, and the BEMS. The MAS comprises of several inner-level, intermediate level, and upper-level agents, which are responsible for their respective tasks. The performance of the proposed optimization strategy is evaluated for two seasons of a year, i.e., summer and winter. Numerical simulations have demonstrated the effectiveness of the proposed operation scheme for optimal operation of building microgrids with rooftop greenhouses. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle Impact of Demand Response Programs on Optimal Operation of Multi-Microgrid System
Energies 2018, 11(6), 1452; https://doi.org/10.3390/en11061452
Received: 10 May 2018 / Revised: 30 May 2018 / Accepted: 4 June 2018 / Published: 4 June 2018
Cited by 1 | PDF Full-text (2643 KB) | HTML Full-text | XML Full-text
Abstract
The increased penetration of renewables is beneficial for power systems but it poses several challenges, i.e., uncertainty in power supply, power quality issues, and other technical problems. Backup generators or storage system have been proposed to solve this problem but there are limitations
[...] Read more.
The increased penetration of renewables is beneficial for power systems but it poses several challenges, i.e., uncertainty in power supply, power quality issues, and other technical problems. Backup generators or storage system have been proposed to solve this problem but there are limitations remaining due to high installation and maintenance cost. Furthermore, peak load is also an issue in the power distribution system. Due to the adjustable characteristics of loads, strategies on demand side such as demand response (DR) are more appropriate in order to deal with these challenges. Therefore, this paper studies how DR programs influence the operation of the multi-microgrid (MMG). The implementation is executed based on a hierarchical energy management system (HiEMS) including microgrid EMSs (MG-EMSs) responsible for local optimization in each MG and community EMS (C-EMS) responsible for community optimization in the MMG. Mixed integer linear programming (MILP)-based mathematical models are built for MMG optimal operation. Five scenarios consisting of single DR programs and DR groups are tested in an MMG test system to evaluate their impact on MMG operation. Among the five scenarios, some DR programs apply curtailing strategies, resulting in a study about the influence of base load value and curtailable load percentage on the amount of curtailed load and shifted load as well as the operation cost of the MMG. Furthermore, the impact of DR programs on the amount of external and internal trading power in the MMG is also examined. In summary, each individual DR program or group could be handy in certain situations depending on the interest of the MMG such as external trading, self-sufficiency or operation cost minimization. Full article
(This article belongs to the Special Issue Microgrids-2018)
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Open AccessArticle A Communication-Free Decentralized Control for Grid-Connected Cascaded PV Inverters
Energies 2018, 11(6), 1375; https://doi.org/10.3390/en11061375
Received: 25 April 2018 / Revised: 18 May 2018 / Accepted: 25 May 2018 / Published: 29 May 2018
Cited by 3 | PDF Full-text (5214 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a communication-free decentralized control for grid-connected cascaded PV inverter systems. The cascaded PV inverter system is an AC-stacked architecture, which promotes the integration of low voltage (LV) distributed photovoltaic (PV) generators into the medium/high voltage (MV/HV) power grid. The proposed
[...] Read more.
This paper proposes a communication-free decentralized control for grid-connected cascaded PV inverter systems. The cascaded PV inverter system is an AC-stacked architecture, which promotes the integration of low voltage (LV) distributed photovoltaic (PV) generators into the medium/high voltage (MV/HV) power grid. The proposed decentralized control is fully free of communication links and phase-locked loop (PLL). All cascaded inverters are controlled as current controlled voltage sources locally and independently to achieve maximum power point tracking (MPPT) and frequency self-synchronization with the power grid. As a result, control complexity as well as communication costs are reduced, and the system’s reliability is greatly enhanced compared with existing communication-based methods. System stability and dynamic performance are evaluated by small-signal analysis to guide the design of system parameters. The feasibility and effectiveness of the proposed solution are verified by simulation tests. Full article
(This article belongs to the Special Issue Microgrids-2018)
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