2019
243
22042019
15092019
Universidad Cooperativa de Colombia, Colombia
Universidad Cooperativa de Colombia, Colombia
Universidad Cooperativa de Colombia. Medellin., Colombia
Abstract: —Generation and energy consumption are a major issue in different countries around the world. Nowadays, projects under development seek the modernization of electric power generation and distribution systems. One of the main strategies is the design of context-adaptable micro-grid architectures. The micro-grid concept focuses on a controlled, monitored and highly autonomous use of electric power supported on information technologies, for the optimization of energy transfer, minimize risks and increase the system’s quality, efficiency and reliability. This article, therefore, aims to identify, classify and compare different micro-grid architectures, based on their applicability and research trends. A systematic mapping study of micro-grid architectures is conducted to examine the experimental and theoretical contributions made by the scientific community. This article categorizes and quantifies the different studies related to the subject, identifying and analyzing the strengths and opportunities for improvement in the applicability of micro-grid architectures. The trends observed highlight five strategies as the most relevant, whose different characteristics contribute to an automated and intelligent organization of the distribution, control and supervision of electricity according to supply versus demand.
Keywords:Affordable and clean energyAffordable and clean energy,micro-grid applicationsmicro-grid applications,micro-grid architecturesmicro-grid architectures,regional developmentregional development,smart gridsmart grid,sustainable citiessustainable cities,sustainable development goalssustainable development goals.
Resumen: La generación y el consumo de energía son un problema importante en los diferentes países del mundo. Hoy en día, los proyectos en desarrollo buscan la modernización de los sistemas de generación y distribución de energía eléctrica. Una de las estrategias principales es el diseño de arquitecturas de micro-redes adaptables al contexto. El concepto de micro-red se centra en un uso controlado, monitoreado y altamente autónomo de la energía eléctrica apoyada en las tecnologías de la información, para optimizar la transferencia de energía, minimizar los riesgos y aumentar la calidad, eficiencia y confiabilidad del sistema. Este artículo, por lo tanto, tiene como objetivo identificar, clasificar y comparar diferentes arquitecturas de micro-red, en función de su aplicabilidad y tendencias de investigación. Se lleva a cabo un estudio de mapeo sistemático de las arquitecturas de micro-red para examinar las contribuciones experimentales y teóricas realizadas por la comunidad científica. Este artículo clasifica y cuantifica los diferentes estudios relacionados con el tema, identificando y analizando las fortalezas y oportunidades para mejorar la aplicabilidad de las arquitecturas de micro-red. Las tendencias observadas destacan cinco estrategias como las más relevantes, cuyas diferentes características contribuyen a una organización automatizada e inteligente de la distribución, el control y la supervisión de la electricidad de acuerdo con la oferta en función de la demanda.
Palabras clave: Aplicaciones de micro-redes, arquitecturas de micro-red, ciudades sostenibles, desarrollo regional, energía asequible y limpia, red inteligente, objetivos de desarrollo sostenible.
Eléctrica
A systematic mapping study of micro-grid architectures
Un estudio de mapeo sistemático de arquitecturas de micro-red
Received: 22 April 2019
Accepted: 15 September 2019
CURRENTLY, the conditions of climate change, greenhouse gases and other factors related to the production of electricity by sources such as coal, gas, oil and its derivatives, have created great concern around the world. As a response, renewable and non-conventional energies have gained strength for being considered as a desirable alternative[1]. Research on renewable energies has parallelly boosted the development of projects that seek the modernizing of energy generation and distribution systems by adapting and creating architectures of electric micro-grids with a higher rate of alternative or renewable energy use, and that offer a faster response to incidents or failures. The micro-grid concept was born in the industrialization age and it consists of a vast centralized network that support the provision of electric service for many consumers, from primary electric sources usually based on coal or oil.
The incorporation of renewable energies to the grid would be especially beneficial for municipalities or towns in rural areas that do not have access to utilities companies and electricity services called Non-Interconnected Zones (NIZ) [2],[3]. However, studies made by Gellings and Twidell have identified that implementing a large centralized network for generation and distribution of energy is not economically feasible in rural areas or NIZ [4],[5]. Instead, the use of small micro-networks is seen as a viable alternative with a high commercial potential, able to integrate renewable energies and effectively manage and control the energy consumption. Moreover, micro-grids are functionally unique systems able to respond to transmission or energy transfer needs. The network structure based on information technologies allows for highly autonomous monitoring and control processes, and the achievement of (1) optimization of energy transfer, (2) risk reduction and (3) increased system quality, efficiency and reliability.
By means of a mapping study, this article aims to identify and analyze the trends in the use of micro-grids as a mean for modernizing the consumption of energy [6].
The systematic mapping methodology is based on the formulation of research questions from a prior review of the state of the art of scientific contributions[7]. From these questions, the study unfolds in a way to offer a general overview of the research topic, as well as to categorize and quantify the different studies found. In here, scientific productions analyzed were limited to the past 4 years (2014 – 2018), period during which micro-grids architectures in renewable energy systems gained strength [8].
The methodological approach established by[9],[10] defines the following steps:
In this work, the previous steps are adapted as shown in Fig.1 for stablishing the final methodology to be followed [11].
The research scope of the mapping study is defined by the five research questions described below:
RQ1. What are the theoretical contributions of the scientific community to the application of micro-grids architectures in the field of electrical energy?
RQ2. What are the trends of experimentation and studies in the architectures of micro-grids?
RQ3. What technological factors are common in the design of micro-grids architectures?
RQ4. What are the applications of micro-grids architectures for renewable energies?
RQ5. Who are the main researchers in the topic of micro-grids architectures for renewable energies?
Each question is thought to scan different aspects in the topic of micro-grids as follows: Questions RQ1 and RQ2 aim to quantify and classify the contributions according to their type, purpose and context, in order to achieve a focused analysis on techniques and trends; Question RQ3 focuses on understanding different architectures’ design and modelling; finally, Question RQ4 and RQ5 add information linked to the object of the article.
The selection of the primary contributions that will build up the database of the mapping study is performed following the PICOC approach. This method focuses primarily on the population and, through different questions, it helps to identify essential key aspects in a research [12]. The description of the PICOC approach, acronym for Problem, Intervention, Comparison, Outcome and Context, is found in Table II.
The bibliographic databases used at the searching stage are: Science Direct, Dialnet, Scopus, Springer, Engineering Village e IEEE Explore, due to their compliance and ideal characteristics suitable for carrying out a mapping study.
The search is structured with the following keywords: “Smart grid”, “Architecture micro-grid”, “micro grids“, “trends micro-grid”, “renewables energies” and “technological factors”, which can be combined in different forms (permute) to give a total number of 720 possible different search parameters (6! = 6 · 5 · 4 · 3 · 2 · 1 = 720). In addition to the keywords, the search was refined to scope the period between 2014 to 2018.
This screening methodology delivered a total of 5,890 documents between book chapters, gray literature, technical reports and journal articles. In order to bring queries closer to the desired results, the use of search operators is considered, as [13] says: "An effective search equation would be the one formed by descriptors and their corresponding qualifiers combined with each other by means of the most appropriate Boolean operators" as OR; AND and NOT.
Table III. Shows the number of documents per database found. Nevertheless, although key words may be present in their content, they do not necessarily delve into the subject nor they help to answer the stablished research questions. To sort out the unrelated findings, an inclusion and exclusion criteria was defined and applied.
The Inclusion Criteria (IC) are:
IC-1: The document proposes an approach to the topic under study (method, technique, model, architecture, tool, methodological framework).
IC-2: The document proposes a solution, experiment or technical revision to architectures, systems, designs or models of micro-grids.
IC-3: The document mentions the application of micro-grids in the field of electrical energy.
IC-4: The document mentions applications of architectures in micro-grids for renewable energies.
The Exclusion Criteria (EC) are:
EC-1: Outcomes of interest have not been reported or are reported in an not appropriate, consistent manner.
EC-2: Title and abstract does not include any keyword
EC-3: Types of Publication: Editorial Material, Notes or Corrections are not considered
EC-4: The document does not propose an approach to the topic in its title, abstract and keywords.
The operators are applied with the use of the search string, under the following process:
After carrying out the process in 6 iterations, we obtain a total of 620 documents that meet the inclusion and exclusion criteria. The final number of documents found per scientific database is found in Table IV. These 620 documents are the base for the extraction and analysis of data needed to provide an answer to the research questions stablished before.
Preparation of data is performed using the software SPSS (Statistical Package for the Social Sciences) - IBM SPSS [14]. The first step is to encode the variables: name, type of data, length or width, in order to give relevance to the variables: author, title of the document, year of publication, source, content of document and architecture (See Fig. 2).
This step allows coefficients and indicators to be defined. Next, a series of analysis and calculations, i.e. linear, multivariate analysis [15], segmentation and crossed tables, confirm that the data are in optimal conditions for a statistical analysis and allow conclusions in trends to be drawn.
The verification of the data’s quality helps to recognize, eliminate and minimize errors present both in the data and results. The process consists of:
Lack or excess of data
Data that is not entered
Duplication of data
Typing error
Incorrect variable typing
In this case, the histograms, contingency tables and the summary of the statistics of each iteration are used.
The psychometric properties used in the mapping system, inclined towards the reliability and validity of the data, the following activities are applied:
Internal consistency analysis: Average the data altogether, getting each variable to measure a characteristic or portion of what it is wanted in the research process.
Discrimination capacity analysis: Elements are established in a way to reinforce the consistency of theone-dimensional character of the variables.
Factorial Study: the group structure is established, whose content and parameters allow to carry out a statistical analysis.
In sequence to the research questions, an analysis is made based on the results supported by IBM SPSS software. The results highlight five relevant architectures described in more detail below.
RQ1: What are the theoretical contributions of the scientific community to the application of micro-grids architectures in the field of electrical energy?
The scientific production around applications of micro-grids architectures for the energy sector has been experiencing a substantial increase due to major concerns that greenhouse gases and climate change arise, which sums to the need of implementing and integrating alternative energy sources.
SGAM is characterized by a neutral technological position. This architecture entails a set of interoperability layers that permits the interaction between conventional and renewable energies:
Business layer: Outlines the business objectives, regulatory and political framework, based on cases of use and micro-grid functions.
Information Layer: Structure and models data. A communications layer where protocols and regulations for communication are established.
Components Layer: Consist of location of domains - generation, transmission, distribution, distributed energy resources (DER), facilities for customers - and other areas - process, field, station, operation, company and marketing. From the compendium of options the architecture provides a comprehensive methodology for achieving a proper functioning micro-grid. The management of cases of use [17][18] allows the sharing of information between projects that implement similar cases, with different technical solutions. The result is the operation of a so-called intelligent network.
Table V. shows the description and operation of SGAM components [19].
It is based on the concepts of intelligent grids and has a micro-grid configuration, wich allows interoperability functions. It relies on three main layers that articulate the architecture’s operation:
Processes Layer: Where all business and regulatory processes are managed.
Station Layer: Where activities such as functional and non-functional procedures, registration, storage, protocols and guidelines of infrastructure, equipment and communications are established and where information is administered.
Operations Control Layer: Where monitoring, control and supervision is carried out. This layer has a centralized control that uses sensors and automated control systems for creating a distributed operating network capable of managing the micro-grid‘s electrical power and resources. It has an emphasis on detection and solutioning of failures. It is also characterized for the implementation of methodologies based on traditional and evolutionary processes. The application of agile methodologies to date for this type of architecture is not evident in the documents.
This architecture slightly breaks down the paradigm of layers or levels as there is a strong bidirectional combination of engineering, communication and management stages where architecture becomes a system that combines smart meters, communication grids and systems for data management. It is an interesting concept that allows us to understand the behavior of supply and demand management. Some documents mention the complex security risk situations due to possible data alteration. However, other documents argue that the solutions are within the reach of regulatory frameworks and public policies for the architecture’s adequate use and implementation [25], [26]. It is also worth highlighting AMI’s quick response to needs of demand, which is possible due to its principle of monitoring the distributed energy quality, the efficient use of electricity and the tendency to reduce environmental impact. Some of the projects highlight the application of technological development methodologies focused on the agility and response to the user, such as scrum [27] extreme program[28], lean [29] Kanban [30] among others [31],[32].
ADA architecture consists of bi-directional smart meters. An increase of energy distribution automation processes is possible with an integrated real time monitoring system that optimizes the efficiency of energy delivery. The overall result is the reduction of failures and interruptions, and a rise in the quality of service expectations. The architecture’s fundamental basis are a set of sensors, transducers and Smart Electronic Devices (SED), that work together to gather a large amount of information concerning the micro-grid behavior using a Scada system - supervision, control and data acquisition. The micro-grid is managed with greater speed, reliability and efficiency. CEATI reports - Centre for Energy Advancement through Technological Innovation [36], [37], define and show that for the grid to be intelligent it must include an automated monitoring system build up by sensors. This mechanism improves reliability, makes monitoring of equipment maintenance automatic and allows product monitoring to be based on a supply and demand analysis, all in all, to improve the quality of service.
Documents that mention ADA architecture explain that there are experiments and projects in progress in which ADA implementation demonstrates a reduction and control of the voltage force, a conservation and management of electric current flow or intensity, a detection of faults with greater accuracy, an analysis of the monitoring system and integrated supervision, and the obtaining of results and reports of the micro-grid operation.
This architecture seeks to promote the use of energy resources by optimizing operations with a proper planning and design of the energy network. For this, a distributed system of power generation is established. In planning, the analysis of geographic zones and the social and economic impact of the region are key [40]. An interesting feature of DER architecture is its adaptability to conventional electrical energy systems by means of sensors and a microgeneration system with connections and control of alternating current (AC) to direct current (DC) [41].
It is able to monitor, control and supervise the system for energy storage (ESS), which allows it to virtualize the use of load fluctuations by adapting to variables that influence supply and demand [42]. The DER approach possesses the advantage of: losses in the system, detect failures in real time, optimize the index of an interruption’s average duration, distribute energy more efficiently, account for an improved cost-benefit ratio.
In [43], the DER architecture integrates renewable (solar and thermal) and conventional energies to reduce greenhouse gas emissions and improve the use of electric power in a shopping center in Sydney, Australia. After the implementation, the author compares the results considering:
The results show a reduction of energy costs by 8.5% and carbon dioxide emissions by 29.6%. In addition, it is predicted that a greater investment in the construction of a DER micro grid that uses 90% of renewable energy can reduce carbon dioxide emissions by 72% and energy costs by 47%. In the authors’ words: "the study demonstrates effectiveness, efficiency and flexibility of the DER architecture for micro-grid in changing market conditions".
RQ2: What are the trends of experimentation and studies in the architectures of micro grids in the field of electrical energy?
The mapping study made evident a preference in the use of DER and ADA architectures in the past 2 years (2017 - 2018). This trend is clearly seen in Table VI where a comparison of number of published scientific production per architecture per year is made. DER and ADA architectures are the most used in experimentation, with real applicable projects in renewable energy.
From all the documents revised, we found that the mentioning of the architectures has been scarce and that the depth of the research is focused towards ADA and DER due to its characteristics and good results obtained. Apparently, the other architectures have been mildly investigated or perhaps their mention in documents is not very relevant because of the initial costs involved and the little research in this regard. The 43% of the documents assert that the application of each architecture depends on the context, accompaniment of the information and communication technologies and the automation processes.
RQ3: What technological factors are common in the design of micro grids architectures in the field of electrical energy?
The common technological factors in micro-grid architecture design for electrical energy are communication, control, supervision, maintenance, security and data storage, and distributed and automated systems [44].
There are non-technological factors, it is important to consider the flow of electricity as a bidirectional element, the analysis of supply vs. demand, storage capacity, use policies, flexibility, availability and cybersecurity.
ICT advances are also related to the opportunities for applying architectures in micro-networks, which is why cloud computing concepts, the internet of things, advanced sensors, data mining, business intelligence, among others, are relevant [45].
RQ4: What are the applications of micro grids architectures for renewable energies?
Micro-grids architectures were found to have greater relevancy in the fields of computer sciences, engineering and energies, as seen in Fig. 3. The aforementioned fields account for the higher percentages of publications reviewed in our mapping study. In addition, Micro-grids architectures have proven to be particularly beneficial for providing solutions to specific needs for specific organizations or communities, usually in non-interconnected areas[46].
A common factor is that once the planning is done, several alternatives are generated with a systematic model. Then, simulations are made using software such as HOMER, Vipor, Hybrid2, RETScreen, iHOGA, INSEL, TRNSYS, iGRHYSO, HYBRIDS, TRNSYS, iGRHYSO, HYBRIDS, RAPSIM, SOMES, SOLSOR, HySim, HybSim, IPSYS, HySys, Dymola / Modelica [47]
Software support allows additionally to run economic and technical analysis based on conditions obtained. However, the aforementioned software do not take into account social or political factors, which are relevant components that vary according to region and context, and should be considered for decision making.
RQ5: Which are the main researchers in the topic of micro grids architectures for renewable energies?
For this question, we selected as main criterion of evaluation the number of documents on which each author participate in every of the 620 documents in this study’s database. As evidenced in Fig. 4, Professors Josep M Guerrero and Juan Carlos Vásquez from the Aalborg University in Denmark, are the most published researchers in subjects related to architectures of micro grids in renewable energies.
The systematic mapping performed in this study clearly evidence the trends in micro electrical grid architectures. It is observed that 70% of the documents use architectures as a methodological approach for providing a solution to a specific problem. Architectures have also the ability to adapt to its context. According to the findings, the architecture is a fundamental base for the implementation of a micro grid and thus, needs to take into account political, economic, technical, environmental, social and cultural factors, demand response has already been proven to have great potential to contribute to increased system efficiency while bringing additional benefits, especially to consumers. [48]. Table 7 shows a set of general factors characterized in this study that helps determine the design, implementation and start-up of a micro grid architecture.
Significant advances have been made to standardize processes through micro-grid architectures for the integration of renewable and conventional energy, managed through distribution systems and distributed storage systems. Among these, there is ISA-95 which seeks the electrical distribution standard to provide intelligence and flexibility to micro-grids [49].
The development of this mapping study revealed that the number of associated topics and terminology in micro-grid architectures is broad. Despite the observable correlation between ICT and micro-grids, the link between quality assurance is limited. This is critical because all architectures talk about systematization of processes with the use of variables, functionalities, models, modules and interfaces. Therefore, the applicability of a quality testing process in software products will increase reliability within the life cycle of the project. [50][51]
Micro-grid architectures evolve in accordance with technological advances. Trends such as sensors, internet of things, big data, among others, become increasingly relevant for they incorporate flexibility and adaptability to architectures, hence becoming a determining factor for their development and implementation.
It is an indisputable fact that conventional and renewable electric power are fundamental for the development of any country, since it promotes the industrial and commercial sectors, as well as providing welfare and comfort to the population.[52]
The concern for climate change and the effects of greenhouse gases have allowed renewable energies to boom in the world. This has generated a transformation and evolution in the planning, design, implementation, monitoring and control of electrical energy networks through the search for new technologies and forms of connection. In this context, architectures for micro-grids appear as an efficient solution towards this transformation.
Getting to know the trends of use of architectures, their components and functionalities for the micro-grid, represent a fundamental element to provide solutions to communities or organizations not interconnected or with needs to efficiently manage the flow of energy and minimize the risks of environmental impact.
The studies, investigative processes and publications are contributions, as a motivating entity to future research works that allow to validate the real application of the architectures and their results.
In the academic field the publication of documents goes hand in hand with technological growth. The union of ICT to the concept of micro-grid contributes to the generation of strengthened architectural developments, which allow projects to have research and academic support, for optimal decision making.
After conducting the investigative process, it is concluded that there is a trend in the use of architectures for micro-grid, which along with the advances in the technological development for renewable energies and aims at the pursuit of achieving the objectives of sustainable development, for academic institutions a great research opportunity is presented.
This work was supported by research grant provide by Royal Academy of Engineering with Newton Fund in the project INV2309-E Identification of Knowledge Gaps in the Academia and Capacity Building for Aquatic Renewable Energy in Colombia; Universidad Cooperativa de Colombia ID 2210 " Smart technology management framework for research projects".
Research Professor of the Engineering Department of the Cooperative University of Colombia. Master in strategic telecommunications management and is currently studying a doctorate in projects with an ICT research line, his main research areas include telematic networks and services, architectures and software, energy and technological quality projects. He has worked as a co-researcher on national and international projects. Research Interests: Software quality, Smart cities, Information Technology Management, Data Analytics, Enterprise Architecture and IT Project Management.
National Head of Research in Engineering and Prof Dr at Universidad Cooperativa de Colombia. Scientific research in the energy sector through design and development of renewable energy, software development and environmental and economic models, simulation and modeling based on sustainability and multi-objective optimisation (i.e. exploratory techniques - genetic algorithms and expert systems - artificial intelligence). Simulation of conventional and renewable energy systems. Member of the European Network COST (European Cooperation in Science & Technology). Supervisor in MSc projects related to advanced simulation and optimisation. Principal investigator of international projects in partnership of the industry between Colombia, United Kingdom, Netherlands and European Union.
Received a Ph.D. degree in Systems Engineering and Computation from Universidad del Norte (2018), a master’s degree in Engineering (2011) and a bachelor degree in Systems Engineer (2005) from the Universidad Industrial de Santander. Professor/researcher in Universidad Cooperativa de Colombia, Campus Medellin. Professor of Postgraduate studies in: Information Technology Management and Information Management. She has published over 15 peer-reviewed articles in international journals and is currently Associated Researcher of COLCIENCIAS. Investigator of national and international projects in partnership of the industry between Colombia, United Kingdom, Netherlands and European Union. Research Interests: Smart cities, Information Technology Management, Data Analytics, Enterprise Architecture and IT Project Management.
