Smart rural grid pilot in Spain

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Smart rural grid pilot in Spain 1

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Francesc Girbau-Llistuella , Andreas Sumper , Ramon Gallart-Fernandez 2 , Santi Martinez-Farrero 2 1 Polytechnic University of Catalonia (BarcelonaTech), Spain; 2Estabanell Energia, Barcelona, Spain

Chapter Outline 14.1 14.2

Introduction 316 Social impact of smart grid technologies in rural societies

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14.2.1 Introduction to the digital divide 317 14.2.2 Societal expectations 318 14.2.3 Risks 319

14.3

Smart grid technologies in rural distribution networks

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14.3.1 Introduction to distribution networks 320 14.3.2 Rural distribution networks 321 14.3.3 The new electric paradigm: smart grids 322

14.4

Smart rural grid project

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14.4.1 14.4.2 14.4.3 14.4.4

Introduction to the smart rural grid project 323 The smart rural grid pilot network 325 Intelligent distribution power router 325 Integration of smart grid technologies in a smart rural grid 328 14.4.4.1 Promotion of distributed generation 328 14.4.4.2 Inclusion of new protection devices 328 14.4.4.3 Back-up resources 330 14.4.4.4 New telecommunications network 330 14.4.4.5 New control and management agents 331 14.4.5 New operation functionalities and potential of the pilot area 334 14.4.5.1 Operational circumstances for the pilot network 334 14.4.5.2 Particular goals for each of the agents of the pilot network architecture 334 14.4.6 Smart rural grid outcomes 338

14.5 Conclusions References 343

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The Energy Internet. https://doi.org/10.1016/B978-0-08-102207-8.00014-X Copyright © 2019 Elsevier Ltd. All rights reserved.

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14.1

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Introduction

Many electricity companies as well as many types of multiutilities around the world have recently begun to deploy the so-called Smart Grid (SG) to modernize their existing grids. This is happening either by a legal mandate (e.g., the rollout of smart meters) or because the technology is ready and mature enough to raise the expectations of new business models that can deliver future profits to the companies who embrace such a technological challenge. The SG can be defined as an electricity network that can integrate in a cost-efficient manner the behavior and actions of all users connected to itdgenerators, consumers, and those that do bothdto ensure an economically efficient and sustainable power system with low losses and high levels of quality, safety, and a secure supply. This will allow consumers to improve their energy efficiency as a result of the real-time information on the energy impact arising from their activities, all thanks to the deployment of a number of specific sensors and power electronics. Rural distribution networks (DNs) are in general more vulnerable than urban distribution grids. The aged infrastructure of rural DNs combines with the other usual challenges in these locations, such as lower quality indices and difficulty of access after faults, and these require novel technical solutions and cutting-edge technologies to face them. The increasing penetration of distributed power plants can be understood as a threat, but it can also contribute to overcoming these weaknesses. To do so, the flow of the locally generated electric energy must be controlled for optimal use of the available energy. The Smart Rural Grid (SRG) project emerges to face those challenges and it helps in responding to the different technical and operational issues in the particular case of rural grids, doing so by exploiting the convergence between electricity and telecommunications networks. This work aims to highlight how utilities can operate more efficiently by using their available resources and it describes how to interconnect energy prosumers for enabling multidirectional energy flow. It also examines the best way to make the transition from the present rural DN to a new electric operational framework by SG technologies while neither losing sight of the corresponding new business concepts associated with this transition nor failing to be respectful of the environment. In the European Union, 950 SG projects have been launched since 2002 [1]. Germany, United Kingdom, Denmark, and Spain are the countries where major number of Research and Development (R&D) and demonstration projects are carried out [1]. It is important to highlight that Germany, United Kingdom, and Denmark are countries where there is a favorable national or regulatory environment, whereas Spain is the opposite case. Furthermore, the major part of funding has come from private investment. The most important cofunding instruments are framework programs, from fifth to Horizon 2020. In case of Spain, 79 demonstrations and 99 R&D projects have been executed since 2002. The major part of these projects are private DNs in that are connected to the main grid at a single point, and most of them can work connected or isolated [2].

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This project has been funded by the European Union (European Union’s Seventh Framework Programme for research, technological development, and demonstration under grant agreement no. 619610) and comprises a consortium of eight partners. The partners have developed a set of devices, services, and energy managers that assist in the operation of the aforementioned SRG pilot. These cutting-edge technologies are intended to increase the interoperability, resilience, efficiency, and robustness of the existing rural DN through the utilization of new SG technologies: (1) an Intelligent Distribution Power Router (IDPR), which is an active power electronic device that operates at low voltage (LV) in rural distribution grids with the aim of reducing losses and enabling voltage and reactive power control; (2) a new Power Line Communications (PLC) technology for a rural DN; (3) a robust communication network that allows managing distributed energy resources and IDPRs; (4) data and energy control systems that manage local microproduction and IDPR units; (5) energy storage systems that enable new operation modes and increase continuity of supply; and (6) a pilot area that integrates all the novel features. This book chapter is organized as follows. The present section introduces the reader to the topic. Section 14.2 gives a social view of the impact of SGs in rural areas. Expectations and risks are discussed. Section 14.3 gives a general overview on SG technologies for rural DNs. Section 14.4 details the project SRGs, focusing mainly on the technology and architecture used, and it presents the results of the project. Section 14.5 discusses the conclusions of this chapter.

14.2

Social impact of smart grid technologies in rural societies

14.2.1 Introduction to the digital divide The term Digital Divide (DD) is used to describe a gap between, on the one hand, those who have ready access to information and communication technologies as well as the skills for making use of those technologies; and, on the other, those who have neither the access nor skills for using those same technologies within a geographic area, society, or community. This economic and social inequality that exists between groups of people is not limited to the original division between the “haves” and “have-nots” of informationdat least, not as it was considered at the beginning of the 21st century [3] before being immediately reconsidered [4] and described as a technical and social issue [5]. What this means is that the only issue is not connectivity, which should be considered a human right [6], but speed, which determines the usability of the technology. Based on the existing technologies, the backbone of any kind of digital grid is limited by geographical and economic constraints, as the regions with low population density and difficult orography are usually rejected by the utilities when deciding on their investments, due to the high deployment costs and low returns. This could lead to a new DD for anything related to energy management, meaning that citizens

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outside the SG regions would continue to use energy just as they did in previous decades, which can be translated into lower quality of service, higher costs, and less flexibility. This DD would be based on the haves and have-nots because the new capacities will be available only if the infrastructures are resilient and meshed enough for guaranteeing a certain level of quality. It is well known that rural DNs are tree-shape deployed without redundancy in most cases, whereas the telecom networks (TNs) are either tree-shaped or simply unavailable. This is an important difference between the urban and rural environments, i.e., network redundancy versus infrastructure resilience. By way of example, an urban consumer (the red circle in Fig. 14.1(a)) is supplied by other service points (the green circles). This implies that if any one of them fails, others can contribute to proper operation, thus improving the system’s quality of service. On the other hand, a rural customer (the red circle in Fig. 14.1(b)) is supplied by only one service point. This implies that if the closest service point fails, the consumer will be disconnected. In the case of rural environments, performance is low and the quality of service is less than in urban settings. In addition, rural environments are typically in remote locations, where some other technical and logistical issues arise during processes of restoring voltage or repairing damage. The fact of having a tree-shaped networkdand thus the lack of a properly meshed griddis a technological and economic constraint against assuring a reliable SG in rural areas.

14.2.2

Societal expectations

It is expected that a society evolves toward a new paradigm in which citizens want to be empowered and participate in domains that were reserved for the political arena or for large corporations. The energy sector is also exposed to the winds of change, and new active consumers want to become prosumers so that they can make their own choices in terms of costs and energy mix. But even for consumers who either are unwilling to become prosumers or lack any possibility of doing so, there is an extended wish to know and understand the impact of their actions so that they may aim for more sustainable behavior in terms of energy consumption, thus reducing consumption and cost while maintaining their level of comfort. According to Rifkin [7] these

(a)

A meshed network

(b)

A shape-tree network

Figure 14.1 Network topology in urban and rural areas (a) A Meshed network. (b) A Shape-tree network.

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expectations converge into the Energy Internet. Energy Internet provides a smart, reliable, efficient, responsive, and decentralized network of energy and information. Society is asked what it could expect from belonging to an Energy Internet and an SG. If the SG and the Energy Internet guarantees sustainable development and a future based on low carbon technologies and economies along with active and informed consumers, the society could choose how to consume or produce its energy as well as how to share it with its neighbors while paying attention to retail prices and the environmental costs. In addition, thanks to the implementation of the Internet of Things (IoT), intelligent and connected appliances will minimize the time invested in domestic affairs, thus opening new windows of time for investing in e-learning and socialization. The new IoT data will be converted into information thanks to powerful data mining systems and intelligent algorithms, offering to each citizen a basic set of records according to their actual needs and therefore optimizing the quality of the inputs. The new IoT needs to be accommodated in the electrical infrastructure. Therefore, the Energy Internet integrates these IoTs into Smarts Grid. However, this will not happen on day one of being connected to an SG but only after a well-organized learning curve, when different layers of society will have incorporated it into their daily lives. Once the SG is generously deployed and has been socially accepted, an explosion of new services can be expected, just as what happens when any organization opens up its data and makes them available to citizens. Therefore, consumers can expect to see their level of comfort improve more quickly than the related costs will rise, all without having to invest any of their valuable time. Therefore, all electrical system operators must also take into consideration the Rifkin proposition that “the decentralization of the energy system will create new opportunities, but also new ways of doing business, since the competition will be replaced by cooperation schemes” [7]. Thus, businesses and strategies will be disrupted, making the establishment either adapt its ways of doing business or die. Finally, citizens will take ownership of the SG. There are certainly scientific and technical challenges to solve, but once this is done we can expect plug-and-play systems that will make the technology socially acceptable.

14.2.3 Risks If the SG is limited to a city affair, this will increase the DD and limit the possibilities of citizens living and/or working outside the boundaries of the SG. The investment cost is huge, but the return on investment also increases in parallel with costs, thanks to the possibility of offering new services to consumers and to the reduction in the system’s operational costs. These new services will help consumers improve the way they use energy, allowing them to efficiently manage their electrical consumption and generation. They could, for the first time ever, choose their energy mix and cost, which could possibly provide a net income to families. Therefore, the risk lies in creating a DD where the population density is low, such as in rural areas where SG technologies are not deployed due to the impossibility of recovering the investment.

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Because of the need for reaching the 20e20e20 targets [8], most experiences involving SGs around the world have focused on smart cities, most of them with limited scope and a lack of coordination. Most of the smart city exercises are limited to the deployment of sensors and meters in restricted city areas, with the aim of testing the management of demand response actions. There is a risk arising from the name “smart city,” which may thus limit the intelligence of the grids and their benefits to cities and their inhabitants, as the rural world may be considered to be the backyard of the cities. According to Ref. [9], almost 32% of the European citizens are currently living in what are considered rural areas so there is a need for controlling the implementation of new technologies that can enhance existing regional unbalances. In addition, an important aspect of the SG is that it should include the rural surroundings not only as a place for the weekends, if not as a perfect place for balancing one’s personal and professional life, but also for reaching sustainability goals. Therefore, there is a need for extending work opportunitiesdof any kinddfar away from the cities. Finally, the SG will produce a huge volume of data that must be managed and transformed into useful information. This information could contribute to building up smart communities, promoting e-governments, efficient buildings, e-mobility, and sustainability. However, it is necessary to ensure the protection of data privacy.

14.3 14.3.1

Smart grid technologies in rural distribution networks Introduction to distribution networks

For many decades, there have been essentially no changes in the structure of the electrical power system. The electricity flow has been unidirectional, from large generation plants to small end-consumers through very high voltage transport networks until the distribution reaches the consumers. As Distributed Generation (DG) is introduced, consumers also become generators or prosumers and two threats merge against the traditional electrical system: the bidirectionality of the electricity flow and the unpredictability of small-scale generation based on renewable energy, which is typically sun and wind. Most electrical distribution companies commonly need to correctly and strategically plan their electrical distribution system. Therefore, a good planning strategy that incorporates different solutions should be defined to avoid any issues. In addition, demand and the natural growth of the network entails resizing the electrical infrastructure and finding an economic balance between investment costs and quality of service. Such planning strategies depend on the type of distribution systems, which can be categorized as in the following ways. (1) An industrial distribution system is characterized by a very high rate of power and energy consumption per area (kW/km2 and kWh/km2) with a small number of large consumers. They are typically supplied directly from the medium voltage (MV) network, and a part of them generates

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some of their own energy through cogeneration processes. (2) A commercial distribution system is also characterized by a high rate of power and energy consumption per area with a moderate number of consumers who have a wide range of power. Typically, it corresponds to banks, supermarkets, schools, and hospitals, among others. They can be supplied directly from a medium- or low-voltage network, and some of them typically require external electrical support in cases of emergency. (3) An urban distribution system has a moderate or high rate of power and energy consumption per area, with a very high number of small consumers. They are usually supplied by LV. (4) A rural distribution system has a small rate of power and energy consumption per area due to a small number of scattered consumers with low consumption.

14.3.2 Rural distribution networks Focusing on the rural systems, the majority of rural Distribution Networks comprise long overhead MV lines that are operated between 1 and 36 kV [10,11] with bare cables [12]. From these MV lines, overhead LV lines feed customers up to few hundred meters away by crossing valleys, mountains, and forests. Furthermore, because of the orography, these networks are difficult to access, which is aggravated by adverse meteorological conditions. Both line types can basically be considered resistive. Historically, overhead lines with bare cables were erected because they are the most cost effective way to provide power supply to rural and remote areas [12]. This type of electrical line is critical, because the majority of failures suffered in rural distribution systems occur precisely in overhead bare lines during severe weather conditions. In particular, according to Ref. [12], about 62% of all middle voltage network faults are caused by nature; with adverse weather conditions, this figure increases up to 92%. Moreover, the rural distribution circuits are sized according to their mechanical factors rather than according to voltage drops or maintaining the continuity of supply to a number of large consumers. Accordingly, Distributed System Operators (DSOs) have been replacing the low-voltage overhead bare lines with overhead or underground three- or four-wire cables, which are more reliable but more expensive. However, the majority of MV lines are still overhead bare conductors. The typical topology of rural systems is radial [10,11,13] and usually connects dispersed consumers across a wide territory. This yields important variations in voltage levels between the feeder and the different consumption points [12]. In contrast to the urban DNs, the capacity of rural lines is limited by the important voltage drops and mechanical requirements, not by the thermal rating of the conductor [10,14,15]. In addition, the rural DNs lack strong interconnections with transmission systems, thus converting rural DNs into weak systems [10]. The configuration of rural systems cannot be easily changed because there are few switches and disconnectors, in addition to being manual and in remote locations [12,16]. The electrical protections are also weak because they are sacrificial protections such as fuses [12,16]. In contrast to urban, industrial, and commercial mesh networks, the rural ones usually have only an upstream protection device that disconnects the whole system in case of any eventuality. This greatly reduces the network resilience

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and increases the number of hours without supply to the consumers. Therefore, it is recommended to improve the resilience and performance of the system by sectionalizing the network with recloser switches, including back-up distribution substations, and by deploying DG and fault indicators [12]. Rural DNs are more vulnerable than other distribution grids. The aged infrastructure of a rural DN combines with the other usual challenges in this kind of location, where we can find lower-quality indices (number or time of interruptions), difficulty of access after electrical contingencies, voltage variations, grid congestion, tree pruning, and scattered consumption. All of this requires updated solutions and cutting-edge technologies for facing them. Traditionally, electrical utilities have solved these issues by building new secondary substations (SSs), lines, and other electrical infrastructures. Even in specific cases, capacitors are deployed to compensate reactive power flows and reduce voltage drops. In addition, the new DGs have exacerbated the issues mentioned above, demanding more static and nonflexible reinforcement of the network. When combined with advanced communication and control technologies, this increasing penetration of small distributed power plants, electrical storage systems, and electric vehicles can contribute to overcoming these weaknesses while defining a new electric paradigm. In this new electric paradigm, new local electric generation and distributed electrical storage is controlled for its optimum purpose. Therefore, now is the time for defining a new proper rural network with a highquality power supply that has neither electrical interruptions nor sudden voltage drops. With the addition of a reliable and robust telecommunications infrastructure, all of this will provide incentives to rural producers and small enterprises for investing there.

14.3.3

The new electric paradigm: smart grids

This new paradigm is SGs, which must make it possible to manage a relevant number of different electrical resources while guaranteeing system stability with the least investment. The DSO has to take care of the stability of the electricity by supplying a stable voltage, which is what makes appliances and machinery work properly. Therefore, a collection of new equipment is required along with new operation strategies and new agents who can predict changes in the electrical system and react efficiently in an automated way. On the one hand, the European Commission has been issuing a number of Directives and Regulations, which force the DSO to deploy the needed technology to reach the technological goal of having a functioning SG. At the same time, the National Regulators have created a proper system of incentives to give companies the motivation to go ahead with the R&D for coping with such a relevant challenge. On the other hand, DSOs have begun their technological path to the SG with so-called automated meter reading, which is based on unidirectional telecommunications. Initially, it was only used simply as a method for reading consumer meters, thus improving the billing system and making it more reliable. Nevertheless, some utilities have also implemented two-way communication that is also called the automated

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metering infrastructure, thus allowing companies to offer demand response options to their customers and improve outage detection and distribution automation. In summary, new SGs requires a collection of sensors and interfaces that provide detailed data of the system in real time, distributed energy resources such as DGs and electrical storage, new devices based on power electronics technology, an appropriate communications network, new predictions, management, and control algorithms. Fulfilling these requirements will convert the rural DN into a microgrid (or quasi-grid) that ensures network operation and will lead to a new marketenvironment. A quasi-grid concept refers to the alternative of the traditional network expansion (through new SSs, lines, or other electrical equipment), which is based on DGs, electrical storage, power electronics, and control algorithms. To conclude, the major benefits of SG technologies in distributed systems, especially in rural DNs are the following: 1. SG technologies contribute to supporting and updating the aged infrastructure, especially in rural networks. 2. SG technologies reinforce the system against outages, blackouts, and surges, especially in rural networks. 3. The advanced control and management make efficient and optimum operation possible. 4. SG technologies contribute to the predictive maintenance and self-healing capabilities while providing knowledge about the operation of the system and equipment and about errors and strange phenomena. 5. Smart meters and other SG technologies offer the opportunity to motivate active consumers toward a rational and sustainable use of energy, thus changing their consumption habits. 6. SG technologies facilitate the use of electric vehicles in societies and provide them new roles and capacities, such as those that arise from the vehicle-to-grid strategy. In this sense, they also facilitate the deployment of distributed storage by DSOs and end-users. 7. SG technologies allow the demand-sideemanagement programs to save money for generators and end-users, thus decongesting the system. 8. SG technologies considerably reduce barriers to DG, thus facilitating their integration, control, and billing system. In addition, new DG can enhance system performance by reducing the distance between generation and consumption. 9. SG technologies also improve system relativity by reconfiguring the grid and promoting islanded operation to isolate the damaged part, especially in rural environments where networks are long and radial. 10. SG technologies need a stable and robust telecommunications network, which provides new services and options to DSOs and end-users.

Additionally, according to Refs. [17,18], SGs provide the adequate background for the Energy Internet, an open, robust and reliable environment where consumers, prosumers, and more agents interact at each other.

14.4

Smart rural grid project

14.4.1 Introduction to the smart rural grid project As indicated above, the aged infrastructure of rural DNs require updated solutions and cutting-edge technologies. In addition, the increasing DG penetration can contribute to

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overcoming these weaknesses and thus define a new electric paradigm. However, the flow of the locally produced electric energy must be controlled for the optimal use of available energy “credits.” The particular conditions and operation boundaries of rural distribution grids need a new type of thinking that includes assisting technologies to enhance operations [19e21]. The SRG project emerges to face those challenges and help answer the different technical and operational issues for the particular case of rural grids. In this sense, the SRG project explores and shows how to exploit the convergence between electricity and telecommunications networks. The work being undertaken aims to point out how utilities can operate more efficiently by using their available electric resources, and it highlights how to interconnect energy prosumers to enable a multidirectional energy flow [22]. It also examines the best way to make the transition from the present rural DN to a new electric operational framework by using SG technologies without losing sight of the correspondingly associated business concepts [23,24]. The EU-funded SRG project defines a novel system architecture for SRGs. It has been deployed as part of EyPESA’s DN in Vallfogona, Catalonia, Spain. EyPESA, which is the project leader, combines the roles of DSO and retailer. EyPESA cooperates with (1) CITCEA-UPC, which is devoted to research, innovation, and the technological transfer to industry in the fields of mechatronics and enertronics; (2) ZIV Communications, which is a Spanish manufacturer with a complete variety of PLC communications systems, digital protection, and control equipment for lowto high-voltage electric power networks; (3) XOC, which provides fiber optic services in Catalonia; (4) KISTERS, which offers leading technology solutions and standard software for the energy market; (5) SWRO, which distributes electricity, gas, water, and district heating, measures the electricity, bills other suppliers, and manages electricity market communications; (6) CGA, which is a leading supplier of control and automation solutions, services, and products for monitoring and controlling power transmission and distribution across various market sectors; and finally (7) SMARTIO, which is a cluster of enterprises and academic institutions that carry out the SRG integration and the dissemination in the control center room [25]. Thanks to the expertise of the SRG consortium, the SRG project has developed a set of devices, services, and energy managers that assist in the operation of the cited SRG pilot. These cutting-edge technologies are intended to increase the interoperability, resilience, efficiency, and robustness of the existing rural DN through the utilization of new SG technologies [24]: (1) IDPRs; (2) new PLC technology for a rural DN; (3) a robust communications network that allows managing distributed energy resources and IDPRs; (4) a data and energy control system that manages local microproduction and IDPR units (these systems are based on bidirectional powers and information flows that redispatch power generation and optimize the whole system.) [26,27]; (5) an energy storage system that enables new operation modes and increases continuity of supply; and (6) a pilot area that integrates all the novel features. Thanks to the aforementioned challenges, the involved technology helps achieve the technological and economic feasibility in rural areas [24].

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14.4.2 The smart rural grid pilot network The SRG pilot network is focused on a real rural distribution grid with substantial potential for improving efficiency, in particular in terms of continuity of supply [15]. The DN where the project is carried out is the final part of 5-kV DN in a rural zone on the EyPESA network. EyPESA is a DSO that operates a DN in Catalonia (Spain). EyPESA provides service to around 56,000 customers along its 1500 km of lines [28].The principal particularity of the EyPESA network is that about 50% of the network is deployed in a rural environment where over two-thirds of the customers are from the domestic and service sectors. The EyPESA DN is connected to the transmission system at 220 kV through two fully automated primary substations. Internally, the DSO transports the electricity at 40 kV, distributing to smaller DNs at 20, 5, and 3 kV through automated SSs. Finally, the DSO distributes to its clients using LV networks through SSs that are mostly not unautomated. The Pilot Network (PN) chosen here concerns an area with a low population density, barely 25 customers distributed across four low-level SSs (see Fig. 14.2) and who are residential and agrarian. The PN is characterized as a nonmanageable radial grid, where operational safety is guaranteeddas in traditional networksdthrough manual switch-disconnectors and fuses. Furthermore, failure detection and access is complicated by the fact that the MV lines of the grid cross valleys and mountains, exposing them to adverse weather conditions. As seen in the right-upper part of Fig. 14.2, the electrical scheme of the PN is depicted. An overhead bare line comes from a substation that interconnects to a 40-kV subtransmission system located several thousand meters from the PN. In the PN, the overhead bare line covers from several hundred to a few thousand meters, constituting the pilot MV network. In the pilot MV network, three manual switch-disconnectors can be tripped during maintenance tasks (see Fig. 14.2). The MV lines end at the three-phase circuit breakers of each SS. The three-phase circuit breakers are directly connected to the SS transformer. Following the SS transformer are the LV lines, which are four-wire braided cables that are protected by single-phase fuses, providing passive protection in case of overcurrent. Finally, the SS LV networks supply customers dispersed around the rural area. Each of them is equipped with a smart meter and a power switch that limits maximum power consumption and provides protection against grid eventualities (though it does not actively manage the load). Most of the clients in the PN demand a single-phase power supply, and this is translated into an unbalanced load through the three-phase DN.

14.4.3 Intelligent distribution power router The biggest challenge of the SRG project has been the development of an IDPR. This device comprises an innovative electronic-based power conversion system. The IDPR enables the integration of DG, renewable sources, domestic and industrial loads, and electric vehicles into the distribution systems. Moreover, it favors the integration of energy storage devices and, finally, it improves the power quality and grid support [29]. The IDPR is designed to be connected in parallel with the LV grid and an energy storage device (see Fig. 14.3). In terms of performance, the power stage implements an

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Figure 14.2 Pilot network in a rural area.

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Figure 14.3 Secondary substation with an IDPR.

extremely compact transformerless topology based on the new highly efficient silicon carbide power semiconductor devices. Moreover, the control system of the IDPR is easily managed by the system operator set points as well as a permanent monitoring of the power flow upstream and downstream of its coupling point via Modbus RTU. On the one hand, the IDPR functionalities include power quality improvement as a result of the active compensation for current harmonic, reactive power, and unbalance on the current demand side. At the same time, active and reactive power can be dispatched because of its 4-quadrant operation. A normal operation mode is conceived for converting the entire system downstream to an aggregated bidirectional load that can be regulated to match the upstream requirements of the system operator in terms of stability and energy management. This is how the IDPR is aimed at being a powerful element for integrating DG or renewable sources, domestic or industrial loads, and electric vehicles. Therefore, in this operation mode (so-called slave), the voltage and frequency in the coupling point of the IDPR is provided by the main grid, by an auxiliary generator or by another IDPR. The IDPR, while operating in slave mode, is controlled as a current source for delivering or consuming power, according to exogenous setpoints. It is required that the grid has to be under normal operating conditions in regard to voltage and frequency levels while the IDPR is balancing the circulating currents. Therefore, the local consumption is seen by the grid upstream as aggregated consumption, and this compensates the reactive power while canceling harmonic content, which in fact minimizes losses in the distribution system.

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In case of grid failure or a scheduled disconnection, the IDPR is able to restore the LV grid in isolated mode. This grid-disconnected operation provides a voltage reference to the system to supply loads, DGs, and/or storage systems. Therefore, the developed IDPR is able to work while fixing the voltage and frequency of the local area. At the moment this mode is put into operation (so-called master mode), the main grid has to be decoupled from this area, and no other IDPRs can be connected in master mode. The master mode starts from a zero voltage situation with a progressive local grid energization consisting of a voltage ramp. After that, when the grid is stabilized up to its nominal values, consumers, DGs, and slave IDPRs allocated inside the same area can be progressively connected and configured to assure that the master IDPR is able to guarantee system stability. This mode is disabled if no storage device is installed in the IDPR.

14.4.4

Integration of smart grid technologies in a smart rural grid

After deploying the innovative grid architecture and addressing the adoption of both new management tools and technologies, the PN will become deeply transformed, resulting in the scheme depicted in Fig. 14.4. Next, the above actions for upgrading the rural grid are listed [30,31], and the following subsections go deeper into describing the above updates for developing the rural grid: (1) promoting the DG (detailed in Section 4.4.1); (2) including new protection devices (detailed in Section 4.4.2); (3) installing back-up resources (detailed in Section 4.4.3); (4) deploying a proper telecommunications network (detailed in Section 4.4.4); and (5) developing new control and management agents (detailed in Section 4.4.5).

14.4.4.1 Promotion of distributed generation The presence of renewable generation in power networks is progressively gaining more and more importance [14]. The growth of DGs in the PN will improve the security of supply to customers and increase the energy efficiency of the grid. For the adopted PN, the maximum generation capability of DGs for end-use customer is high because the legal ceiling is about 64 kW, according to Spanish Regulations [32], whereas the consumption peak is below 30 kVA. The latter, along with the availability of space that rural consumers have to install DGs, yields a tremendous potential for decarbonizing the rural grid. Photovoltaics is the most usual DG technology, offering the lowest levelized cost of energy among the eligible options [33]. However, there are other technologies such as wind, gasification, and biomass, which are also attractive to rural areas, thanks to the availability of farm and forestry residues [14]. In addition, the DSO has carried out strategies to apply a curtailment to these DGs when necessary.

14.4.4.2 Inclusion of new protection devices As previously indicated, the protection elements of the PN are not equipped with automatic reclosing, thus they are able to isolate only part of the electrical grid in

LC

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SS 928 Photovoltaics facility 6 kWp

Consumer MV line at 5 kV LV line at 0.4 kV LV line at 0.23 kV

Com. device IDPR BESS Aux. batteries RTU Industrial PC Gen. controller

~

Fuse Power switch (ESE) Aut. switch disconnector (ESE) Electrical measurament unit (EMU) Equivalent LV load line Equivalent LV generation line

BESS DG GS IDPR LC LEMS RTU TC

Battery energy storage system Distributed generation Gen set Intelligent distribution power router Local controller Local energy management system Remote terminal unit Transfomer controller

LEMS

SS 010

TC

SS 730

TC

SS 734

TC

SS 928

LC TC GS

~

DG

~

~

DG

~

DG

~

329

Figure 14.4 Electrical scheme of pilot network with new elements after reinforcement.

DG

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case of an eventuality. Modern rural grids require a certain degree of flexibility to offer new electrical configurations and new modes of operation [16]. For instance, they should allow isolated operation and reconnection of some or any parts of the grid when various grid eventualities occur [27]. To do so, the overload LV lines should be independently managed to energize the islands through back-up energy resources. Therefore, it is proposed that the LV fuses of LV feeders be replaced with automated and remotely controlled power breakers. This in turn impacts the selectivity of LV lines during grid eventualities. Moreover, it is indispensable to have selectivity at the MV level to disconnect the PN from the External Grid (EG) and also to have the possibility of creating different electrical configurations. Consequently, some manual switch-disconnectors are automated and remotely controlled. To integrate and remotely manage the new protection devices, a new element is included: the so-called Remote Terminal Unit (RTU). The RTU is a solution for substation automation, protection, and control, which delivers information to the Supervisory Control And Data Acquisition (SCADA) of the DSO grid and offers full capability for integrating and controlling devices through different communications protocols. Therefore, four RTUs are installed in each SS to integrate all new control and protection devices.

14.4.4.3 Back-up resources Diverse types of back-up resources can be adopted so as to improve the security of supply in electrical networks. One option is the inclusion of diesel generators (GS). Such systems enable the islanded operation of the network, even in the absence of DGs and storage. Alternatively, one could opt for power electronic-based solutions. In this regard, the SRG project developed the IDPR [34,35]. The IDPR, like the GS, enables islanded operation of the system in case of eventuality [36,37]. Thus, the IDPR is a device located at strategic nodes of the DN and its main goal is to control power flows. As can be seen in Fig. 14.4, the PN comprises three IDPRs. There are only two IDPRs equipped with a Battery Energy Storage System (BESS), because of space limitations in SSs. Also, the GS is set up in SS 010, thus enabling islanded operation in the absence of DGs and storage. Note also in Fig. 14.4 that in the case of protection devices, the back-up resources are integrated into the PN through RTUs.

14.4.4.4 New telecommunications network The SRG project explores the convergence between electricity and TNs. A new telecom infrastructure is proposed with the aim of guaranteeing the efficient integration and management of DGs, new back-up resources and new protection and control devices through RTUs. The TN is presented in Fig. 14.5. As mentioned previously, the TN comprises two different environments: an inner TN and an outer TN for the PN. The solution adopted for inner TN implements a wireless area at the SS level, thus enabling DGs to connect directly to control devices. In particular, the Worldwide

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331

WiMAX

WiMAX

GPRS

Ripoll interconnection point to MPLS network

WiMAX

SS 010 antena

WiMAX

SS 010 router

WiMAX

Radiolink

XOC interconnection point to FO network

SS 734 antena

SS 730 antena PLC

PLC

Milany repeater

Inner telecoms network

SS 730 router

SS 928 antena

PLC

SS 928 router

SS 734 router

First channel Second channel Wired Wireless

Outer telecoms network

EyPESA router

EyPESA SCADA

Bellmunt repeater

Figure 14.5 Telecommunications network.

Interoperability for Microwave Access (WiMAX) is the wireless technology chosen for creating this wireless area [38,39]. In a second step, a primary channel that employs the PLC technology will be set up, allowing communications between SSs. Then, the wireless network can be used as a secondary point-to-point channel if the primary channel is incapacitated [38]. The solution adopted for the outer TN, which communicates the PN with the SCADA and other exogenous agents, is based on two communications channels. The first channel connects the PN with the SCADA through WiMAX and FiberOptic (FO) communications. The SCADA interfaces with other external agents to the PN. The second channel also uses wireless technology to connect to the wired network. The eventual back-up for the proposed wireless technology is based on General Packet Radio System (GRPS) communications, which have less capacity than WiMAX. The GPRS communications interconnect the PN with the SCADA through a different communications channel, a MultiProtocol Label Switching (MPLS) network. The coexistence of such a heterogeneous group of technologies is justified by two main reasons: the existence of certain communications infrastructures, such as FO and MPLS network, at the time of modernizing the project; and geographical constraints that make it difficult to deploy wired communications in some parts of the PN.

14.4.4.5 New control and management agents The previous sections presented diverse new SG technologies for modernizing the DN [40]. Some of them, such as IDPRs, switch-disconnectors, power breakers, and DGs, need to be managed externally and coordinated for grid operation optimization. To efficiently manage the grid, diverse management agents are defined. They interact with one another by exchanging data and commands. From a bottom-up approach,

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GEMS 3

Ref.

2 1

an

ds

SCADA m

4

D

SO

co

m

5

7

LEMS

6

8 10

9

LC 13

TC

TC

1 2 3 4 5 6 7 8 9 10 11 12 13

Data GEMS setpoints (DN) GEMS forecast (DN) SCADA data (DN) GEMS setpoints (PN) GEMS forecast (PN) SCADA commads (PN) LC data (PN) LEMS setpoints (PN) SCADA commands (LEMS) LC data (PN) LEMS setpoints (SS) SCADA commands (SS) TC data (SS)

1211

TC

TC

Data Commands Setpoints

Figure 14.6 New control and management agents.

the management hierarchy is configured by the so-called Transformer Controller (TC), the Local Controller (LC), the Local Energy Management System (LEMS), the SCADA and, finally, at the top of the management structure is the Global Energy Management System (GEMS) [40]. The hierarchy and relationships are depicted in Fig. 14.6. In detail, the TC is the software that is executed in each RTU (see Fig. 14.4). As the bottom-end of the management architecture, it directly exchanges information and setpoints with the back-up resources and DGs, as well as with control and protection devices, which are connected to each SS. TCs supply the commands and setpoints to the abovementioned network components and collect their data and alerts through Modbus RS-485 and other wired communications. Above the TCs is the LC. This software configures the second level of the management architecture and is implemented in one RTU. The LC is responsible for managing all the TCs in the PN. It transfers to the TCs the commands and setpoints provided by, respectively, the SCADA and the LEMS. On the one hand, commands refer to PN configuration orders, such as those for the process of turning on/off switchable elements or devices and for incrementing or decrementing the transformer’s tap changer. On the other hand, setpoints refer to active and reactive power control signals for network operation. Finally, the LC is responsible for collecting all data from TCs via the IEC-60870-5-104 protocol over Transmission Control Protocol (TCP) and Internet Protocol (IP). Altogether, the LC acts as a bridge between upper management agents, i.e., SCADA and LEMS, and TCs. Although the TCs and LC ensure proper supervision and protection, the LEMS enables the operational optimization of the PN. The LEMS calculates on a minuteby-minute basis the setpoints to back up resources and DGs, doing so by using data collected by the LC, the SCADA constraints and commands, and the GEMS setpoints

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and forecasts. The PN data comes from LC via Modbus TCP/IP each minute, although SCADA constraints and commands are updated asynchronously through the LC. Conversely, GEMS setpoints and forecasts come through the SCADA via File Transfer Protocol (FTP). Furthermore, the LEMS records the most relevant information of the PN so that it can be checked when there is an eventuality. The LEMS is the last level of the management architecture included in the PN environment. Because of the complexity of the calculations carried out by LEMS, it is implemented in an industrial PC (see Fig. 14.4). This has been selected because it has high computing power and also an extended temperature range, which means it needs no fans and is thus compact in design, protecting it from dirt, dust, and humidity while enduring the harshest conditions. The SCADA is just above the PN. There is only one SCADA for the whole DN. Thus, it monitors the status not only of the PN but also of the system the PN is connected to. Eventually, the SCADA will allow remote operation of some network elements such as switches, transformers, capacitor banks, etc., for maintenance and the eventual maneuvering of the network. Therefore, the SCADA is the element that delivers commands to the LC via the IEC-60870-5-104 protocol over TCP/IP. These commands are conventionally determined by the network operator at its convenience. The SCADA is not a new element to the management architecture of networks, but for the innovative approach proposed for the PN operation it offers new functionalities beyond the state of the art. Specifically, these new functionalities are transferring to the GEMS all the system data via FTP each 15 min and to transferring to the LEMS the GEMS setpoints and forecasts via FTP. So, in general terms, the SCADA acts as a bridge between inner and outer management agents of the PN. In the same way as the SCADA, the GEMS is in an outer environment of the PN. The GEMS calculates a series of active and reactive power setpoints for managing the whole DN. This means that GEMS provides control setpoints for each IDPR and DG within the PN. It is divided into two modules. One module forecasts the consumer’s consumption and DG production, according to the DN data that are provided by SCADA, as well as data from other inputs such as meteorological and calendar data. The second module generates the DG and IDPR setpoints to increase the performance of the network. Data are exchanged between GEMS and SCADA every 15 min via FTP. The management agents presented above comprise a novel management architecture, which allows controlling the newly installed SG technologies, e.g., DGs, back-up resources and new protection devices. One remarkable advantage of the architecture is that it decentralizes the operation of the system according to its electrical configuration (e.g., whether the grid is connected or isolated). Another advantage is that it enhances the potential scalability of the system, making it possible to replicate the same architecture throughout the whole DN. Furthermore, this decentralization increases the reliability of the system because not everything depends on the decision of the SCADA. Instead, intelligence is allocated also to other agents that can act even autonomously in case of any eventuality. Such advantages go beyond the typical working practices of grid operators in weak rural systems.

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14.4.5

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New operation functionalities and potential of the pilot area

On completion of the reinforcements carried out to develop the PN, this results in a highly flexible system that offers various operational capabilities, which are described in this section. To this aim, this section first identifies the different operational circumstances for the PN (in Subsection 14.4.5.1). Second, the section defines duties for each of the agents composing the novel management architecture proposed in this study (in Subsection 14.4.5.2).

14.4.5.1 Operational circumstances for the pilot network It is known that the PN falls within one of the three following different circumstances: (1) Circumstance 1 (C1) is the most usual, and this occurs when the PN, or at least part of it, is supplied by the EG without experiencing grid eventualities; (2) Circumstance 2 (C2) is when the PN, or at least part of it, operates islanded from the EG without experiencing grid eventualities (this means that back-up resources, such as a IDPR or a GS, ensure the security of supply for consumers and the power balance of the PN, or part of it.); (3) finally, Circumstance 3 (C3) is when the PN, or part of it, experiences a grid eventuality, e.g., a blackout or a short-circuit (including also situations when the PN, or part of it, is not supplied because it is undergoing scheduled maintenance tasks). According to the presented operational circumstances and the disposition of the switches and back-up resources in the PN (see Fig. 14.4), the grid can be divided into three sectors, as depicted in Fig. 14.7 [27,30,31]. Sectors 1 (S1) and 3 (S3) can be operated in isolated mode because they are equipped with IDPRs (including a BESS) and a GS. For instance, by being able to operate isolated they can fall under the operational circumstances C1 and C2. Conversely, Sector 2 (S2) can only operate while connected to the EG or with the support of other sectors because this sector is not equipped with IDPRs or a BESS. Table 14.1 collects all possible scenarios for the PN, according to the operationality of the sectors and the state of links between them [27,30,31].

14.4.5.2 Particular goals for each of the agents of the pilot network architecture The operational scenarios were defined in previous subsection, and they mainly comprise operational circumstances for sectors that consider them to be isolated (C2) or connected to the EG (C1). Depending on whether a sector is connected or not to the EG, there can be different optimization goals for its operation. This subsection precisely describes the role of the two Energy Management Systems (EMS) that handle the PN, the GEMS, and LEMS while keeping in consideration the abovementioned operational circumstances [27,30,31]. As has been previously mentioned, these two EMS determine the series of active and reactive power setpoints for managing the whole DN, and they calculate on a minute-by-minute basis the setpoints to back-up resources and DGs using data collected by the LC, SCADA constraints and commands, and forecasts. Both EMSs optimize, insofar as possible, the operation of the PN. Such optimization is solved

-EG

Link S1

Lin

kS

IDPR

1-

S2

Sector 2 SS 730

GS IDPR

GS DG

GS

DG

SS 734

Distributed generation (DG) Sector or independent area

IDPR

DG

Secondary substation (SS) Consumer MV line at 5 kV LV line at 0.4 kV LV line at 0.23 kV Intelligent distribution power router (IDPR) Battery energy stroage system (BESS) Gen set (GS)

Smart rural grid pilot in Spain

SS 010

Sector 1

Link S2-S3

SS 928

Sector 3 GS GS

~

IDPR

DG

DG

~

Figure 14.7 PN with sectors or areas. 335

336

Table 14.1 PN scenarios depending on state of links and operationality of sectors Links between sectors

Operationality

EGeS2

S1eS2

S2eS3

S1

S2

S3

Circumstances

Connected

Connected

Connected

Operating

Operating

Operating

C1

Connected

Connected

Operating

Operating

Connected

C1 þ C3 C1 þ C3

Operating Connected

Connected

Connected Connected Connected

Operating

Operating

Operating

C2

Operating

Operating

Operating

C2

Operating

Operating

Operating

C2

Operating

Operating

Connected

Operating Operating

C2 þ C3 Operating

C2 þ C3

Operating

C2 þ C3 C2 þ C3

Operating

Connected

Connected

Connected

C2 þ C3

Operating

Operating

Operating

C1 þ C2

Operating

Operating

Operating

C1 þ C2

Operating

C1 þ C2 þ C3

Operating

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Connected

Connected

Operating

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in two steps. The first optimization, called economic optimization hereinafter, solves an optimal economic dispatch and thus addresses the market aspects such as the availability and cost of the DGs as well as back-up resources. The second optimization relies on the inputs of the first to adjust active and reactive dispatches for the DGs and back-up resources while considering technical aspects such as power losses, thus allowing it to perform an Optimal Power Flow (OPF). Depending on the operational circumstance, i.e., grid connected (C1) or isolated (C2), the abovementioned optimizations are global or local. The global optimizations comprise the whole network. The horizon for the economic optimization is 24 h, whereas the horizon for the OPF is a few hours. For both global optimizations, the time step is 15 min. It is worth noting that to successfully solve the economic optimal dispatch, the applied algorithm requires forecasts that exceed the 24-h horizon. Conversely, the local optimizations comprise just the PN, as it is not connected to the EG. The horizon and the time step for both the economic and OPF optimizations is 1 min. The required forecasted data for economic optimization are 1 day ahead. Table 14.2 summarizes the roles that GEMS and LEMS adoptddepending on the operational circumstances for the PNdwhile executing above described optimizations. Table 14.2 Roles of GEMS and LEMS, depending on the operational circumstance GEMS

LEMS

C1

1. Generates the consumption and generation forecasts for the whole system. 2. Executes the global economic optimization, function of the global market aspects, availability and cost of DGs and back-up resources. 3. Executes the global OPF, function of the global economic optimization setpoints and network features. 4. Provides the global setpoints file for the following 24 h, in time steps of 15 min.

1. Adjusts the global setpoints on a 1-min basis while considering other technical eventualities. 2. Provides the adjusted global setpoints to the DGs and back-up resources.

C2

1. Generates the consumption and generation forecasts for the PN. 2. Provides the forecast file for the following 24 h, in time steps of 15 min.

1. Executes the local economic optimization, function of the local market, availability and cost of DGs and back-up resources. 2. Executes the local economic optimization, function of the local market, availability and cost of DGs and back-up resources. 3. Provides the local setpoints to DGs and back-up resources.

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14.4.6

Smart rural grid outcomes

One of the results of the SRG project is the developed IDPRs for the PN. The IDPR power cell and cabinet are shown in Fig. 14.8. In any case, controlled current source power cells (depicted in photo (a) in Fig. 14.8) are allocated to the left part of the IDPR cabinet (see photos (b), (c), and (d) in Fig. 14.8). In addition, the IDPR cabinet includes all control boards, an Ethernet switch, an extra DC-link, and a 48 Vdc UPS system, AC and DC switchgear elements, a thermal magnetic and residual circuit breaker, the precharger components, safety relays, RTUs (reserved allocation in upper right part), PLC communications device, an industrial PC where LEMS is implemented (reserved

(a)

(b)

IDPR installed in SS 010 The controlled current source power cell

(d)

(c)

IDPR installed in SS 730

IDPR installed in SS 928

Figure 14.8 The power cell and three developed IDPRs. (a) The controlled current source power cell. (b) IDPR installed in SS 010. (c) IDPR installed in SS 730. (d) IDPR installed in SS 928.

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Table 14.3 IDPR-rated values for the three final pilot units Parameter

SS 010

SS 730

SS 928

IDPR rated power

39.8 kVA

17.3 kVA

34.6 kVA

Rated AC side current

100 A

25 A

50 A

Rated AC side Voltage

230 V

400 V

400 V

Rated AC side frequency

50 Hz

50 Hz

50 Hz

Maximum AC Voltage

253 V

440 V

440 V

Minimum AC Voltage

195.5 V

340 V

340 V

Maximum AC frequency

51 Hz

51 Hz

51 Hz

Minimum AC frequency

48 Hz

48 Hz

48 Hz

Rated DC side current

60 A

e

60 A

Rated DC side Voltage

320 V

e

320 V

Maximum DC Voltage

275 V

e

275 V

Minimum DC Voltage

365 V

e

365 V

allocation in upper right part, only in the IDPR SS 010), electromagnetic interface filters and, finally, ACeDC connection ports. Also their specifications are detailed in Table 14.3. In addition, a User Interface Console (UIC) is implemented in the LEMS. Fig. 14.9 represents the console that presents data from the IDPRs. In particular, the Point of Common Coupling (PCC) voltages and frequency is depicted on the middle part of the console, the RST active and reactive LV power flows from the consumer side is depicted on the right side, and the upper part shows the resultant RST active and reactive flows. Moreover, the IDPR information is depicted on the lower part, where there are also the management actuators. In particular, there are three actuators, from right to left: the first actuator allows enabling or disabling the harmonic current compensation (Enable H); the second actuator enables or disables the balancing of RST phases (Enable UB); and the third actuator activates or deactivates the reactive power compensation (Enable Q). Just under these three actuators is the power package service, which allows sending active (if there is a battery) and reactive power packages to loads or the EG. In addition, the state of the IDPR is incorporated on the left of the console in the diagram. Finally, the performance of the IDPR in the LV grid is presented. The UIC manages the IDPR and shows RMS voltages and currents as well as average activeereactive power. Nevertheless, to check the instant values of the voltage and current, an oscilloscope is used to record data at a higher sampling rate. Then, the obtained data are analyzed with mathematical software (Matlab). Three different scenarios are proposed to test the IDPR’s contribution to power quality: in case (1), the IDPR balances active phase currents and compensates reactive

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The Energy Internet IDPR selector Pr (kW)

Qr (kvar)

Ps (kW)

Qs (kvar)

Pt (kW)

Qt (kvar) Y-Yn 5 kV–230 V

State: Turn off

Stand by

IDPR fault

Reset

(0 × 01)

(0 × 40)

Alarms

MV grid

(0 × 80)

LV grid Turn off

Error

Turn off

Operation Precharge

Ur (V) Us (V)

(0 × 02)

Ut (V)

BusOK

F (Hz)

Ready

PCC

(0 × 04)

Qr (kvar)

Ps (kW)

Qs (kvar)

Pt (kW)

Qt (kvar)

Loads

Stop Slave mode

Pr (kW)

Master mode

(0 × 08)

(0 × 10)

P* (kW) Q* (kvar)

master

Grid fault (0 × 20)

State diagram

Pr (kW)

Qr (kvar)

P (kW)

Ps (kW)

Qs (kvar)

U (V)

Pt (kW)

Qt (kvar)

IDPR

SoC (%)

BAT

Figure 14.9 The User Interface Console of the IDPRs from the SRG.

power; in case (2), the IDPR cancels harmonic currents; and case (3) combines cases (1) and (2) and dispatches 12 kvar. The three-phase LV waveforms are depicted on the left side of Fig. 14.10 while the right side shows the three line currents. Regarding the voltage case, it should be noted that all waveforms are sinusoidal and about 230 V phase-to-phase. However, looking in detail at the voltage plots (a) and (b) in Fig. 14.10, a 2.5 V average voltage variation (considering all phases) can be computed. This value can be used to compute the grid impedance module, thus obtaining about 0.18 U. Conversely in regard to current waveforms, it can be deduced from plot (b) in Fig. 14.10 that, when current balancing is disabled, the rural grid presents important unbalances (a gain shift difference of 2p/3 rad). Thereupon, the IDPR contributes to reducing the asymmetrical losses by helping to diminish the operational stress on the distribution transformer. Moreover, it should be remarked that although the IDPR is balancing the grid currents in plot (a) of Fig. 14.10, it is possible to observe irregular peaks. This is the effect of the rural end-user load type. Finally, to validate with commonly used criteria the capabilities and contributions of the IDPR to the voltage and current Total Harmonic Distortion (THD), we compute the Power Factor (PF) and the current’s Degree of Unbalance (DU) by contrasting cases (1) and (2). Note that DU is defined as the part of the total current that correspond to each phase. Table 14.4 shows the voltage and current THDs when the harmonic current compensation is enabled or not. Note that the THD of voltages fulfills the power quality requirement EN 50160. After the harmonic current is compensated, the obtained

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(a)

Phase R

Phase S

200

50

150

40 30 20

50

Current (A)

Voltage (V)

100

0 –50

10 0 –10 –20

–100

–30

–150 –200

Phase T

–40 0

10

20 Time (ms)

30

–50

40

0

10

20 Time (ms)

30

40

Balancing current and compensating reactive power consumption: case (1)

(b)

Phase R

Phase S

200

50

150

40 30

100

20 Current (A)

Voltage (V)

50 0 –50

10 0 –10 –20

–100

–30

–150 –200 0

Phase T

–40 10

20 Time (ms)

30

–50 0

40

10

20 Time (ms)

30

40

30

40

Harmonic compensation: case (2)

(c)

Phase S

Phase R

200

50

150

40 30 20

50

Current (A)

Voltage (V)

100

0 –50

10 0 –10 –20

–100

–30

–150 –200 0

Phase T

–40 10

20 Time (ms)

30

40

–50

0

10

20 Time (ms)

Combination of case (1) & (2) plus dispatching 12 kvar: case (3)

Figure 14.10 Phase to neutral voltage and line currents to demonstrate the IDPR’s contributions to power quality. (a) Balancing current and compensating reactive power consumption: case (1). (b) Harmonic compensation: case (2). (c) Combination of case (1) and (2) plus dispatching 12 kvar: case (3).

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Table 14.4 Total harmonic distortion Phase R (%)

Phase S (%)

Phase T (%)

Initial voltage

1.66

2.52

2.09

Initial current

12.42

17.09

15.83

Final voltage

1.46

1.50

1.50

Final current

6.44

6.54

6.77

Table 14.5 Power factor Phase R

Phase S

Phase T

Initial

0.9949

0.8380

0.6005

Final

0.9999

0.9982

0.9910

Table 14.6 Power factor Phase R (%)

Phase S (%)

Phase T (%)

Initial

35.5

43.3

18.2

Final

33.6

34.0

32.4

values are better, at around 1.5%. Nevertheless, the current THD is higher and the current harmonic compensation has a significant impact on the THD, reducing the initial situation to 6.5%. This contribution indirectly causes the reduction of voltage THDs. In addition, Table 14.5 shows the PF values where the evolution of the PF is reflected. Improvement of the PF value from phase S and T is especially notable. Finally, Table 14.6 shows the initial and final DUs. It is noteworthy that the IDPR allows proper balance of the grid currents.

14.5

Conclusions

In this book chapter we presented the SRG project and its results. It has been shown that the technological development toward SGs in electrical networks has an important impact on society. In especially rural areas, there is a risk of being literately unconnected from the SG and thus having no possibility to take advantage of novel business models and pursuing economic development. This phenomenon is called the Digital Divide. The SRG project has developed special tools and technology to overcome these technological and societal challenges. Its goal is to upgrade and automate the electricity infrastructures for accommodating consumers and prosumers for the Energy

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Internet of the future. One key technology that has been developed is the IDPR. This versatile power electronic device enables rural grids to perform in operational modes that differ from the traditional radial supply. This introduces new degrees of freedom in the operation of these grids, allowing utilities to find solutions for blackouts, natural disasters, overloads, and reduced power quality, among others. The developed IDPR is based on advanced power electronic technologies, namely Silicon Carbide semiconductor switches that increase the overall efficiency of the inverters. The high switching frequency of this technology delivers good control performance, which enables the same device to compensate harmonics, balance the phases, compensate reactive power, and inject or consume active power. In addition, the IDPR facilitates new business models based on a local approach. The IDPR solution needs to be integrated into a TN while taking into account the special characteristics of rural areas. Challenges such as low bandwidth and large distances have been overcome by using the multiple IDPR system under the orchestration of an SCADA system in combination with local and global EMSs. This system has been built and validated in the pilot test region of Vallfogona in the Catalan Pyrenees of Spain. The experimental results show that the system improves the power quality of the grid increases the hosting capability of renewable energy resources. The islanding capability increased not only the availability of the rural grid but also the quality of service. Future works regarding scalability of this system and the heterogeneous grouping of storage devices are planned by the authors. Further, the next challenges of SRG project are focused on the IPDR industrialization and exploitation. The key objectives to carry out this are bringing down costs, increasing the rated power per unit, decreasing volume of the unit, and enhancing the global efficiency of device. Moreover, another related key point is the electrical storage, which is essential for the IDPR operation. The overall results show that such technology can beat the DD of SG development in rural areas, thus granting all people the advantage of reaping its rewards.

References [1] Smart Grid Projects Outlook 2017 j JRC Smart Electricity Systems and Interoperability, 2017 (Online). Available: http://ses.jrc.ec.europa.eu/smart-grids-observatory. [2] A. Díaz Gallo, Microgrids Opportunities Within Spain’s Smart Grids initiatives, 2017 (Online). Available: https://building-microgrid.lbl.gov/sites/all/files/santiago_diaz.pdf. [3] W.A. Leighton, Broadband Deployment and the Digital Divide, Policy Anal., No. 410, 2001, pp. 1e34. [4] P. Dimaggio, E. Hargittai, Working Paper Series, 15 from the ‘Digital Divide’ to ‘Digital Inequality’: Studying Internet Use as Penetration Increases, 2001. [5] W. Chen, B. Wellman, W. Dutton, B. Kahin, A. Wyckoff, S. Bae, V. Hung, K. McEldowney, C. Scheel, H. Waki, A. Board, B. Forsythe, S. Russ, P. Moorhead, Charting Digital Divides: Comparing Socioeconomic, Gender, Life Stage, and RuralUrban Internet Access and Use in Eight Countries, 2004.

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[6] J.J. Barry, Crossing the Digital Divide: Is Access to the Internet an Economic Right?, 2013. [7] J. Rifkin, The Third Industrial Revolution : How Lateral Power Is Transforming Energy, the Economy, and the World, Palgrave Macmillan, 2013. [8] 2020 Climate & Energy Package j Climate Action, 2017 (Online). Available: https://ec. europa.eu/clima/policies/strategies/2020_en. [9] Urban-Rural Typology - Statistics Explained, 2017 (Online). Available: http://ec.europa. eu/eurostat/statistics-explained/index.php/Urban-rural_typology. [10] A. G
omez-Exp
osito, A.J. Conejo, C. Ca~nizares, Electric Energy Systems: Analysis and Operation, CRC Press, 2008. https://www.crcpress.com/Electric-Energy-Systems-Analysisand-Operation/Gomez-Exposito-Gomez-Exposito-Conejo-Conejo-Canizares-Canizares/ p/book/9780849373657. [11] I. Zubia, I. Arrambide, O. Azurza, P.M. García, J.J. Ugartemendia, Rural smart grids: planning, operation and control review, Renewable Energy and Power Quality Journal 11 (2013). [12] M. Zviedritis, A. Gavrilovs, A. Kutjuns, Power supply reliability vs profitability in rural distribution networks, in: Electric Power Quality and Supply Reliability Conference (PQ), 2014, 2014, pp. 335e340. [13] P. Kundur, N.J. Balu, M.G. Lauby, Power System Stability and Control, vol. 7, McGrawhill, New York, 1994. [14] T. Ackermann, G. Andersson, L. S€oder, Distributed generation: a definition, Electric Power Systems Research 57 (3) (2001) 195e204. [15] B. Saint, Rural distribution system planning using Smart Grid Technologies, in: Rural Electric Power Conference, 2009. REPC’09. IEEE, 2009, p. B3. [16] C. Puret, E/CT, MV Public Distribution Networks Throughout the World, vol. 155, 1992. [17] L.H. Tsoukalas, R. Gao, From smart grids to an energy internet: assumptions, architectures and requirements, in: 2008 Third International Conference on Electric Utility Deregulation and Restructuring and Power Technologies, 2008, pp. 94e98. [18] H. Jiayi, J. Chuanwen, X. Rong, A review on distributed energy resources and MicroGrid, Renewable and Sustainable Energy Reviews 12 (9) (2008) 2472e2483. [19] A. Zomers, The challenge of rural electrification, Energy for Sustainable Development 7 (1) (March 2003) 69e76. [20] H. Farhangi, The path of the smart grid, IEEE Power and Energy Magazine 8 (1) (January 2010) 18e28. [21] A.C. Tobar, H.U. Banna, C. Koch-Ciobotaru, A. Cabrera Tobar, H. Ul Banna, C. KochCiobotaru, Scope of electrical distribution system architecture considering the integration of renewable energy in large and small scale, in: Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), 2014 IEEE PES, 2014, pp. 1e7. [22] Smart Grid Library, Prosumers, 2016. [23] V. Buehner, P. Franz, J. Hanson, R. Gallart, S. Martinez, A. Sumper, F. Girbau-Llistuella, Smart Grids for Rural Conditions and E-Mobility-Applying Power Routers, Batteries and Virtual Power Plants, 2016. [24] The Anatomy of the Project - Smart Rural Grid Project, 2016 (Online). Available: http:// smartruralgrid.eu/the-anatomy-of-the-project/. [25] Smart Rural Grid, Smart Rural means. Cachign the Future Bringing Ubran Electricity Quality to Rural Areas, 2016. [26] P.H. Nguyen, W.L. Kling, P.F. Ribeiro, Smart power router: a flexible agent-based converter interface in active distribution networks, IEEE Transactions on Smart Grid 2 (3) (Sep. 2011) 487e495.

Smart rural grid pilot in Spain

345

[27] F. Girbau-Llistuella, A. Sumper, R. Gallart-Fernandez, V. Buehner, Operation of rural distribution grids with intermittent generation in connected and island mode using the open source EMS solver SCIP, in: 2015 International Conference on Renewable Energy Research and Applications (ICRERA), 2015, pp. 983e988. [28] Estabanell Energia, Els orígens d’Estabanell Energia, 2016. [29] D. Heredero-Peris, D. Montesinos-Miracle, et al., Inverter design for four-wire microgrids, in: Power Electronics and Applications (EPE’15 ECCE-Europe), 2015 17th European Conference on, 2015, 2015, pp. 1e10. [30] Project Deliverables - Smart Rural Grid Project, 2016 (Online). Available: http:// smartruralgrid.eu/archive_category/project-deliverables/. [31] F. Girbau-Llistuella, F. Díaz-Gonz
alez, A. Sumper, R. Gallart-Fern
andez, D. HerederoPeris, Smart grid architecture for rural distribution networks: application to a Spanish Pilot Network, Energies 11 (4) (2018) 844. http://www.mdpi.com/1996-1073/11/4/844. [32] vol. BOE n
um. 2. Real Decreto 842/2002, Ministerio de Ciencia y Tecnologia, Reglamento electrotécnico para baja tensi
on, 2 de agosto, 2002. [33] K. Branker, M.J.M. Pathak, J.M. Pearce, A review of solar photovoltaic levelized cost of electricity, Renewable and Sustainable Energy Reviews 15 (9) (2011) 4470e4482. [34] F. Girbau-Llistuella, J.M. Rodriguez-Bernuz, E. Prieto-Araujo, A. Sumper, Experimental validation of a single phase intelligent power router, in: Nnovative Smart Grid Technol. Conf. Eur. 2014 IEEE PES, 2014, pp. 1e6. [35] J.-M.M. Rodriguez-Bernuz, E. Prieto-Araujo, F. Girbau-Llistuella, A. Sumper, R. Villafafila-Robles, J.-A.A. Vidal-Clos, P. Joan-Marc Rodriguez-Bernuz, E. PrietoAraujo, F. Girbau-Llistuella, A. Sumper, R. Villafafila-Robles, J.-A.A. Vidal-Clos, Experimental validation of a single phase intelligent power router, Sustainable Energy, Grids and Networks 4 (2015) 1e15. [36] D. Heredero Peris, C. Chill
on Ant
on, M. Pages Giménez, G.I. Gross, D. Montesinos Miracle, et al., Grid-connected to/from off-grid transference for micro-grid inverters, in: PCIM 2013-International Exhibition & Conference for Power Electronics, Intelligent Motion, Power Quality, 2013, pp. 1629e2636. [37] D. Heredero-Peris, C. Chillon-Anton, M. Pages-Gimenez, G. Gross, D. MontesinosMiracle, et al., Implementation of grid-connected to/from off-grid transference for micro-grid inverters, in: Industrial Electronics Society, IECON 2013-39th Annual Conference of the IEEE, 2013, pp. 840e845. [38] V.C. G€ung€or, D. Sahin, T. Kocak, S. Erg€ut, C. Buccella, C. Cecati, G.P. Hancke, Smart grid technologies: communication technologies and standards, IEEE Transactions on Industrial Informatics 7 (4) (2011) 529e539. [39] J.G. Andrews, A. Ghosh, R. Muhamed, Fundamentals of WiMAX: Understanding Broadband Wireless Networking, Pearson Education, 2007. [40] Smart Rural Grid, Archive j Project Deliverables, 2016.