Special Issue "DC & Hybrid Micro-Grids"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy".

Deadline for manuscript submissions: 30 September 2019.

Special Issue Editors

Guest Editor
Prof. Dr. Sergio Saponara Website E-Mail
Department of Information Engineering (DII), University of Pisa, 56122 Pisa, Italy
Interests: electric/hybrid vehicles; autonomous and connected vehicles; smart energy systems; energy storage systems; predictive diagnostics
Guest Editor
Prof. Dr. Lucian Mihet-Popa Website E-Mail
Faculty of Engineering, Østfold University College, Kobberslagerstredet 5, 1671 Fredrikstad, Norway
Phone: +4792271353
Interests: modelling, simulations, control and testing of DER components (including BESS) in power distribution systems (micro-grids, smart grids); integration of DGs and renewable energy sources including PV, EV, and BESS; energy efficiency in smart buildings
Guest Editor
Prof. Dr. Roberto Saletti Website E-Mail
Department of Information Engineering, University of Pisa, V. Caruso 16, 56122 Pisa PI, Italy.
Interests: energy storage; battery managements systems; supercapacitors/Li-based batteries; digital electronics and embedded systems for smart grid

Special Issue Information

Dear Colleagues,

Microgrids are emerging as a suitable, reliable, and clean solution to integrate distributed energy sources, which include energy storage systems (ESSs) and active loads. Microgrids can include both AC and DC distribution lines, acting as a cluster of interconnected distributed energy resources (DERs). Although up to now the AC microgrid has been the most-used solution, thanks to the evolution in power electronics and in energy storage technology hybrid AC/DC microgrids are becoming the optimal approach. Indeed, they combine the main advantages of both AC and DC microgrids, with the integration of smart and digital grid devices and technologies in real-time operation. For example, with respect to AC approaches, DC-based microgrids allow for lower [DM1] issues, in terms of reactive power, frequency synchronization, and integration with an increasing number of DC loads.

To address this important topic, the proposed Special Issue calls for papers presenting:

  • -distribution and energy storage management/control systems for hybrid microgrids;
  • - recent advances in power electronics for microgrids and particularly in AC/DC, DC/DC and DC/AC converters and solid-state transformers;
  • - embedded systems and networking for microgrids towards the foundation of an “Internet of Energy”;
  • - predictive diagnostic and functional safety techniques for microgrids.

The latest developments and ongoing research and innovation activities related to microgrid controllers to improve the performance of distribution power grids are also welcome. Submissions about renewable energy systems or hybrid/electric vehicles, but with a relation to DC and/or AC microgrids, are also welcome.

Prof. Dr. Sergio Saponara
Prof. Dr. Lucian Mihet-Popa
Prof. Dr. Roberto Saletti
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 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

  • Distribution and Energy Storage Management Systems
  • Control Strategies for Microgrids
  • Power Electronics and Power Converters
  • Embedded Systems (MCU/PLC/FPGA/DSP) for Microgrids
  • Wireless Power Transfer
  • Recharge of Electric and Hybrid Vehicles
  • Networking for SmartGrid and Internet of Energy
  • DC and Hybrid Microgrids
  • Renewable Energy Systems Monitoring &Control
  • Predictive Diagnostic and Functional Safety for Microgrids

Published Papers (6 papers)

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Research

Open AccessArticle
Insulation Monitoring Method for DC Systems with Ground Capacitance in Electric Vehicles
Appl. Sci. 2019, 9(13), 2607; https://doi.org/10.3390/app9132607 - 27 Jun 2019
Abstract
Owing to the influence of ground capacitance in electric vehicles, in the traditional unbalanced electric bridge DC insulation monitoring (DC-IM) method, the voltage of positive and negative electric bridges changes slowly. To calculate the insulation resistances, sampling should be conducted once the voltage [...] Read more.
Owing to the influence of ground capacitance in electric vehicles, in the traditional unbalanced electric bridge DC insulation monitoring (DC-IM) method, the voltage of positive and negative electric bridges changes slowly. To calculate the insulation resistances, sampling should be conducted once the voltage of the bridge becomes stable, that will inevitably extend the monitoring cycle. To reduce the monitoring cycle, this study proposes a three-point climbing algorithm, namely, three-bridge voltage sampling with equal sampling intervals, to predict the evolution of the bridge voltage curve. However, due to the existence of sampling errors, the insulation resistances calculated by sampling values will deviate from the actual values. Then, this article also proposes the filter and correction methods of three sampled voltages to improve monitoring accuracy. Through experimental data, the influences of different parameters on the results are verified, and comparisons with the traditional method are shown in the back. The conclusion is that compared with the traditional method, the proposed method can monitor insulation resistance more quickly and ensure fixed monitoring cycles under different ground capacitance values and keep the similar monitoring accuracy. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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Open AccessArticle
Improved Control of Forest Microgrids with Hybrid Complementary Energy Storage
Appl. Sci. 2019, 9(12), 2523; https://doi.org/10.3390/app9122523 - 20 Jun 2019
Cited by 1
Abstract
In order to improve the power quality and the fault ride-through capability of islanded forest microgrids, a hybrid complementary energy storage control method is proposed. In this method, mode-based sectional coordinated control is adopted as the basic control scheme, whereas control of the [...] Read more.
In order to improve the power quality and the fault ride-through capability of islanded forest microgrids, a hybrid complementary energy storage control method is proposed. In this method, mode-based sectional coordinated control is adopted as the basic control scheme, whereas control of the hybrid energy storage, which includes the battery, the supercapacitor, and the wind turbine, utilizes the improved strategy. According to the characteristics of the energy storage units, adaptive control of batteries and supercapacitors are adopted to smooth the low-frequency power fluctuation in the long-term and to suppress the high-frequency component separately, in which predictive control of the converters is utilized to achieve rapid regulation. Furthermore, as a third energy storage unit, the wind power unit was investigated, utilizing the large rotating kinetic energy of the wind turbine to temporally suppress huge power disturbance and avoid load shedding. To verify the effectiveness of the proposed coordination control with hybrid complementary energy storage, simulations of the islanded DC microgrid in forest area were conducted in MATLAB/Simulink, with the results showing that, by utilizing the improved control method, the transient operation characteristics of the system were effectively enhanced. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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Open AccessArticle
An AC/DC Distribution Network DG Planning Problem: A Genetic-Ant Colony Hybrid Algorithm Approach
Appl. Sci. 2019, 9(6), 1212; https://doi.org/10.3390/app9061212 - 22 Mar 2019
Abstract
The planning problem of distributed generators (DG) accessing the AC/DC distribution network is a hot research topic at present. In this paper, a location and volume model of DG is established that considers DG operation and maintenance costs, DG investment costs, system network [...] Read more.
The planning problem of distributed generators (DG) accessing the AC/DC distribution network is a hot research topic at present. In this paper, a location and volume model of DG is established that considers DG operation and maintenance costs, DG investment costs, system network loss costs, fuel costs, pollution compensation costs, and environmental protection subsidies. Furthermore, voltage and power constraints are also considered in the model. To solve the proposed model, a hybrid algorithm called the GA-ACO algorithm is presented that combines the ant colony algorithm (ACO) and the genetic algorithm (GA). On one hand GA has good robustness, good adaptability, and quick global searching ability but it also has some disadvantages such as premature convergence and low convergence speed. On the other hand, ACO has the ability of parallel processing and global searching but its convergence speed is very low at the beginning. The IEEE-33 node distribution network is taken as a basic network to verify the rationale of the proposed model and the effectiveness of the proposed hybrid algorithm. Simulation results show that the proposed model is very in line with reality, the hybrid algorithm is very effective in solving the model and it has advantages in both convergence speed and convergence results compared to ACO and GA. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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Open AccessArticle
A Stability Preserving Criterion for the Management of DC Microgrids Supplied by a Floating Bus
Appl. Sci. 2018, 8(11), 2102; https://doi.org/10.3390/app8112102 - 01 Nov 2018
Abstract
Direct current (DC) distribution is one of the most important enabling technologies for the future development of microgrids, due to the ease of interfacing DC components (e.g., batteries, photovoltaic systems, and native DC loads) to the grid. In these power systems, the large [...] Read more.
Direct current (DC) distribution is one of the most important enabling technologies for the future development of microgrids, due to the ease of interfacing DC components (e.g., batteries, photovoltaic systems, and native DC loads) to the grid. In these power systems, the large use of controlled power converters suggests the need of a careful analysis of system stability, as it can be impaired in particular conditions. Indeed, in DC power systems, a destabilizing effect can arise due to the presence of inductor/capacitor (LC) filtering stages (installed for power quality requirements) and high-bandwidth controlled converters, behaving as constant power loads (CPLs). This issue is even more critical when the CPL is potentially fed only by the battery, causing the DC bus to be floating. In this context, Lyapunov theory constitutes a valuable method for studying the system stability of DC microgrids feeding CPLs. Such a theory demonstrates how the region of asymptotic stability (RAS) shrinks as the state of charge of the battery diminishes (i.e., as the bus voltage decreases). Once the accuracy of the RAS is validated by comparing it to the real basin of attraction (BA), numerically derived using continuation methods, a smart power management of the CPL can be proposed to preserve the system stability even in the presence of a low bus voltage. Indeed, a suitably designed criterion for limiting the load power can guarantee the invariance of RAS and BA for each equilibrium point. An electric vehicle was used herein as a particular DC microgrid for evaluating the performance derating given by the power limitation. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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Open AccessArticle
Multidimensional Optimal Droop Control for DC Microgrids in Military Applications
Appl. Sci. 2018, 8(10), 1966; https://doi.org/10.3390/app8101966 - 18 Oct 2018
Cited by 1
Abstract
Reliability is a key consideration when microgrid technology is implemented in military applications. Droop control provides a simple option without requiring communication between microgrid components, increasing the control system reliability. However, traditional droop control does not allow the microgrid to utilize much of [...] Read more.
Reliability is a key consideration when microgrid technology is implemented in military applications. Droop control provides a simple option without requiring communication between microgrid components, increasing the control system reliability. However, traditional droop control does not allow the microgrid to utilize much of the power available from a solar resource. This paper applies an optimal multidimensional droop control strategy for a solar resource connected in a microgrid at a military patrol base. Simulation and hardware-in-the-loop experiments of a sample microgrid show that much more power from the solar resource can be utilized, while maintaining the system’s bus voltage around a nominal value, and still avoiding the need for communication between the various components. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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Open AccessArticle
Energy Management Strategy for Rural Communities’ DC Micro Grid Power System Structure with Maximum Penetration of Renewable Energy Sources
Appl. Sci. 2018, 8(4), 585; https://doi.org/10.3390/app8040585 - 08 Apr 2018
Cited by 7
Abstract
The AC and DC power system structures need to be modernized to meet consumer demands. DC microgrids are suitably admired due to their high efficiency, consistency, reliability, and load sharing performance, when interconnected to DC renewable and storage sources. The main control objective [...] Read more.
The AC and DC power system structures need to be modernized to meet consumer demands. DC microgrids are suitably admired due to their high efficiency, consistency, reliability, and load sharing performance, when interconnected to DC renewable and storage sources. The main control objective for any DC microgrid is providing proper load–power balancing based on the Distributed Generator (DG) sources. Due to the intermittent nature of renewable energy sources, batteries play an important role in load–power balancing in a DC microgrid. The existing energy management strategy may be able to meet the load demand. However, that technique is not suitable forrural communities’ power system structure. This research offers an energy management strategy (EMS) for a DC microgrid to supply power to rural communities with solar, wind, fuel cell, and batteries as input sources. The proposed EMS performs the load–power balancing between each source (renewable and storage) in a DC microgrid for dynamic load variation. Here, the EMS handles two battery sources (one is used to deliver power to the priority load, and the other is utilized in the common DC bus) to meet the required demand. The proposed EMS is capable of handling load–power balancing using renewable energy sources with less consumption of non- conventional energy sources (such as a diesel generator). The performance of the system is analyzed based on different operating conditions of the input sources. The MATLAB/Simulink simulation model for the proposed DC microgrid with their EMS control system is developed and investigated, and their results are tabulated under different input and load conditions. The proposed EMS is verified through a laboratory real-time DC microgrid experimental setup, and the results are discussed. Full article
(This article belongs to the Special Issue DC & Hybrid Micro-Grids)
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