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About this book

This book presents intuitive explanations of the principles of microgrids, including their structure and operation and their applications. It also discusses the latest research on microgrid control and protection technologies and the essentials of microgrids as well as enhanced communication systems.

The book provides solutions to microgrid operation and planning issues using various methodologies including

planning and modelling;AC and DC hybrid microgrids;energy storage systems in microgrids; andoptimal microgrid operational planning.

Written by specialists, it is filled in innovative solutions and research related to microgrid operation, making it a valuable resource for those interested in developing updated approaches in electric power analysis, design and operational strategies. Thanks to its in-depth explanations and clear, three-part structure, it is useful for electrical engineering students, researchers and technicians.

Table of Contents

Frontmatter

Correction to: Microgrid Planning and Modeling

The original version of this book was published with an older version of the abstract in Chapter 2. This has now been corrected and updated.

Ali Jafari Aghbolaghi, Naser Mahdavi Tabatabaei, Morteza Kalantari Azad, Mozhgan Tarantash, Narges Sadat Boushehri

Microgrid Architectures and Power Electronics

Frontmatter

Chapter 1. Overview of Microgrid

The gradual decrement of fossil fuels, low energy efficiency and environmental problems met all over the world has led to several power system researches. These problems have promoted researches on alternative energy sources such as wind energy, solar photovoltaic, fuel cells, combined heat and power (CHP) systems, and micro turbines on the contrary of conventional resources. Moreover, the integration of renewable energy sources (RESs) to existing power grid is taken into account as a reliable and robust solution to aging generation, transmission and distribution systems. The innovative researches have brought a new concept as on-site generation or distributed generation at load sites. The utilized resources in this generation concept are later called as distributed energy resources (DERs) implying for a wide variety of power sources, and the generation type is named as distributed generation (DG). This chapter presents an introduction to microgrid concept by including distributed generation and active distribution networks, several DERs such as synchronous generator based and RES based resources, microgrid architectures, operation principles of microgrid, microgrid modeling studies, control and protection issues of microgrid.

Naser Mahdavi Tabatabaei, Ersan Kabalci, Nicu Bizon

Chapter 2. Microgrid Planning and Modeling

Due to the monetary and operational problems that have recently been faced with power plantsMicrogrid planning and modeling, the electric industry is deepening the future as the smart grid network to innovate these issues in the future. There will be significant differences in the conventional power system and smart network. When the demand increases, the system does not necessarily generate more electricity to meet consumption needs. In other words, power generation will not be directly dependent on consumption; instead, the function of reducing losses, managing user demand and cooperating with consumers in order to optimize the load. All of the proposed approaches, as already mentioned, ensure that the balance between generation and consumption is increased without creating an inevitable generation. The smart grid is capable of improving the operation of its components, reducing power costs, reducing additional charges, ensuring maintenance and saving costs of electricity generation, meeting demand and helping to protect the environment.

Ali Jafari Aghbolaghi, Naser Mahdavi Tabatabaei, Morteza Kalantari Azad, Mozhgan Tarantash, Narges Sadat Boushehri

Chapter 3. AC and DC Combined Microgrid, Modeling and Operation

In this chapter, we present modeling of a combined microgrid which is made by integration of two subsystems as AC bus microgridAC microgrid and DC bus microgrid. To the contrary of existing AC and DC microgridsDC microgrid the combined microgrid has advantages in efficient provision of local customers with ecologically clean, digital quality and reliable energy supply. This is achieved by special circuit design, whereby AC bus subsystem is connected with sources of power and loads which traditionally producing and consuming subsequently AC current. DC bus subsystem of combined microgrid connected with sources of power and loads which traditionally producing and consuming subsequently DC current. Both subsystems are interconnected by means of two-way inverter. In case of power deficiency in any of subsystems the control unit may change the direction of power flow and provide stable operation of combined microgrid using minimal number of conversion devices. Two study cases—for parallel operation of combined microgrid with Main grid as well as islanded operation of combined microgrid are presented. This chapter consists of the sections including introduction, structure of combined AC-DC microgridAC-DC microgrid, modeling of combined microgrid, energy storageEnergy storage, integration, conclusion, reference.

Nariman Rahmanovich Rahmanov, Ogtay Zaur oglu Karimov

Chapter 4. Distributed Energy Resources and Microgrid Infrastructure

Energy has an important part in the modern society. An increment in the amount of energy demand due to progress in different technologies, industrialization, etc. leads to developments in the energy sector. Electrical energy as the most important type, is the subject of so many researches. Environmental issues, deregulation of electrical systems, etc. have caused the arrival of distributed electrical generators better known as Distributed Energy ResourcesDistributed energy resources (DERs). However, penetration of DERs is accompanied with some problems. Formation of Microgrids (MGs) could lessen these issues. In this chapter, first different types of DERs alongside their models, would be discussed. Then, substructures for developing MGs would be presented.

Farid Hamzeh Aghdam, Navid Taghizadegan Kalantari

Chapter 5. Virtual Power Plants and Virtual Inertia

In a general way, the electrical networkElectrical network is the set of lines, transformers and infrastructures that carry electricity from generation centers to final consumers. The current networks were designed and are in operation since the mid-twentieth century and were conceived to cover a situation in which the main generation centers were far from the populations. The new energy model is totally different and is transforming the current system into a distributed system, in which any agent that is connected to the network has the possibility of providing energy, enabling the creation of microgenerators, so that there is no such direct dependence as with the current energy generation. Thanks to this type of network, it is possible to drastically reduce lossesLosses due to energy transport, facilitate the connection to the network of all types of renewable energiesRenewable energies and support energy storageStorage capacities. But this structure requires management systems and integration of the microgenerators in the electrical system and it is in this moment when the concept of Virtual Power PlantVirtual power plant (VPP) appears, which arises from the grouping of a series of small generators acting as a unit. Taking value from the energy microgeneration concept and the microgrids, a VPP connects many of these microgenerators to work together as a traditional plant through a centralized control system. A VPP achieves to interlink multiple concentrated sources in one area: wind, solar, storage batteries, biomass plants and conventional generation sources, and coordinate them through remote software. A Virtual Power PlantVirtual power plant is one of the main functions of the smart gridsSmart grid. Through it, various distributed generation resources are brought together, dispersed throughout the network, with the capacity to respond intelligently to demand controlDemand control and turn them into positions of active resources that function as a single centralized generating plant. In this way, the capacity of the virtual plant would be the sum of the powers of all the elements that make it up. We can say that VPPs use the Intelligent NetworkIntelligent network to enter the system and this can represent a reduction in demand and therefore affects the offer. It is called Virtual because it is in the digital world where, through telecommunicationsCommunication technologies and control networks, it can be linked to physical elements through software. For the virtual power plantVirtual power plant, sensors are used to collect data that are collected through a secure telecommunications infrastructure to convert them into information and be controlled by the system operator. The VPP is then a technical, operational and economic concept that is located in the digital part of the electrical networkElectrical network and provides facilities that allow greater flexibilityFlexibility of the electrical system. On the other hand, in recent years, within the electrical generation system, wind powerWind power has taken on great importance and has significantly increased its share of space in the generation market. This has implied an increasing value in the number of wind turbinesWind turbine connected to the network. This growing penetration of wind generation involves new factors to be taken into account in aspects such as frequency control, where the inertia of the system plays a determining role. The inertia of the system determines how the frequency will vary when a change occurs in the generation or in the power demand. The doubly-fed induction generatorDoubly fed induction generator wind turbines, the preferred choice for extensive wind farms, can reduce the effective inertia of the system. These variable speed wind turbinesWind turbine can emulate inertia by fast active power control. This virtual inertiaVirtual inertia can be taken as an important way for the control of the frequency.

Javier Bilbao, Eugenio Bravo, Carolina Rebollar, Concepcion Varela, Olatz Garcia

Chapter 6. Power Electronic Converters in DC Microgrid

There are not many sustainable sources of energyEnergy other than renewable energy sources (RES)Renewable energy, which are called solarSolar, windWind, water and various forms of biomassBiomass. The most effective way to increase the use of renewable energy sources is to make use of renewable energyRenewable energy systems in villages, townships or small island-shaped districts where there are significant amounts of energy consumers. For this reason, the microgridMicrogrid (MG) idea of small power system which is controllable, autonomous and balanced has been developed. Microgrids (MGs) playing a role of carrier for distributed generationDistributed generation resources (DGR), includes different distributed generationDistributed generation (DG) units, storage devices, energy converters, protection devices and load controlControl devices. A MG generally includes renewable small power sourcesPower sources consisting of interconnected distributed energyEnergy sources with capacity of providing sufficient and sustained energyEnergy for a significant portion of the load. Different architecture types of MGs are presented in the literature. In recent years, the use of MGs being able to operate in two different modes depending on the island and grid-connected, has been expanded for DGR integration. Direct currentCurrent (DC)Direct current microgrid has become an important subject of study in recent years as they have a more reliable and lower losses. A DC MG task distributes the DC power required by loads on a campus. Power generation in DC MG systems can be AC or DC; however, in most cases AC power supplies is converted to DC for distribution. The major advantage of DC microgridsMicrogrid when compared to AC systems is its property of unidirectional power flow. This allows power controlControl to be easily controlled by the power flow direction. In DC MG, the loads must be controllable to keep all loads at the DC range of the voltage in the default range and to regulate the voltage regulation. Besides voltage level and voltage regulation, the voltage ripple ratio should be kept as low as possible in DC microgridsMicrogrid. Therefore, power electronic converters are the most important part of the DC MG systems. There are although many studies published on MGs that controlControl strategy and power electronic circuits make their important portions. It is obvious that the development of power electronic circuits and controlControl methods has further enhanced the applicability of microgridsMicrogrid. In this study, the types, circuit structures and functions of power electronic converters used in DC microgridMicrogrid are discussed. Power electronicsPower electronics converters used in DC MGs are grouped and evaluated according to their targets. These power electronic converters have been detailed in terms of AC-DC rectifiers, inverters (for AC loads) and DC-DC converter circuit types. The simulation results of some topologies have been evaluated.

Ires Iskender, Naci Genc

Chapter 7. Power Electronic Converters in AC Microgrid

As the major worldwide infrastructure distribution systems are in AC, the chapter intends to review the main powerPower converterConverter types for Energy Sources integration. The requirements imposed by the existing standardsStandards are envisaged. An effective solution for injection of electrical power from Renewable Energy Sources (DC and AC power sources) into the grid is presented. Additionally, the efficiencyEfficiency improvement by means of the modulationModulation techniques is implemented and shown in this chapter. Due to the higher power energy in three-phaseThree-phase power systemsPower systems (PSs), despite of the AC single-phase PSs, the large energy storage systems are not necessary.

Marian Gaiceanu, Iulian Nicusor Arama, Iulian Ghenea

Chapter 8. Energy Storage Systems in Microgrid

The microgridMicrogrids represents a controllable electric entity that contains different loads into distributed energy resources. All typical microgrids use two or more sources by which electricity is generated, at least one of which is a renewable source. In this respect the main issues of the energy storage systemsEnergy storage system (ESS) are the enhancing of the stability of microgridMicrogrids and power balance. Also the insertion of the energy storage systemsEnergy storage system is beneficial for both operation modes of microgrids, grid connected and islanded. This chapter begins with an overview of the currentCurrent state of microgridsMicrogrids and ESS. The island operation mode of microgridsMicrogrids is based on the energy storage systemEnergy storage system . At the first level the control tasks during this mode of operation are to regulate the voltageVoltage and to maintain the frequency at the constant value. The power in each unit is shared among the storage units by secondary control of the energy storage systemEnergy storage system taking into account the energy level of each of them. Further, the authors present storage technologiesStorage technology of the electrical energy, i.e. converting it into mechanical, chemical, electrochemical, electromagnetic and thermal energy. The widespread mechanical energy storage technologyStorage technology is the pumped hydro (99% of the world total storage capacity) followed by the compressed air energyCompressed air energy and flywheelFlywheel . Afterwards, the fuelFuel cell, biomassBiomass and fossil fuel compose the chemical storageChemical storage domain. Batteries constitute the electrochemical storage technologyStorage technology . Electromagnetic and thermal energy storage technologiesStorage technology are represented by the super capacitors respectively the heat pumps. Both the features of the energy Storage technologiesStorage technology and the main properties will be presented. A comparison of the discharge time of the storage technologies by application is taken into account. The advantages and disadvantages of the storage technologies will be highlighted. The lack of the appropriate standardsStandard of interconnecting different kinds of energy sources and ESS to the microgridMicrogrids is a disadvantage in technology developing. Thereby the IEC/ISO 62264 standardsStandard refers to wind turbine technology, while the IEEE 2000 standard refers to photovoltaicPhotovoltaic (PV) interconnection power systemsPower systems . In order to reduce air pollution and mitigate climate change, in recent years the need to use renewable energy sources in microgrids has become important. In fact, technological development, public and political policies, availability of different renewable energy resourcesRenewable energy resources to be used in microgridsMicrogrids , are elements that create real perspectives in widespread development of renewable energies and their required ESS. The environmentalEnvironment impact and the costs of renewable energy resourcesRenewable energy resources have been estimated through the life cycle assessmentLife cycle assessment (LCA) methodology, which determines whether the use of renewable sources and ESS is sustainable. A case study regarding a PVPhotovoltaic (PV) system with and without batteries used into a microgrid that supply a wastewater treatment plant situated in Romania will be presented. Life cycle assessmentLife cycle assessment was used to quantify ecological sustainability and costs in both cases compared to a conventional supply of electricity from the grid. Conclusions and measures are drawn in order to increase the utilization of renewable sources and ESS in microgridsMicrogrids . Also the technically, economic and environmentalEnvironment benefits of inserting microgrids are discussed. The bibliographic references will be presented at the end of the chapter.

Horia Andrei, Marian Gaiceanu, Marilena Stanculescu, Paul Cristian Andrei, Razvan Buhosu, Cristian Andrei Badea

Chapter 9. Design and Experimental Investigations of an Energy Storage System in Microgrids

The continuous increasing in distributed renewable generation mainly based on wind and solar has complicated recently the normal grid operations. An accurate development in proper energy storage systemsEnergy Storage Systems (ESS) with high ability to store and supply energy on demand should effectively eliminate the potentially adverse negative impacts of actual grid operation technologies, such as severe power fluctuation provided by intermittent power generations and photovoltaic arrays. Therefore, the hydrogen economy is regarded as continuous research that can be understood as a significant effort to modify the actual energy system into a system that combines the hydrogen advantage of as energy carrier with high efficiency of proton exchange fuel cells (PEMFC) as electrochemical processes that converts energy power into electricity and heat. In this chapter an experimental investigation on the performance of an integrated microgrid, installed at the National Centre for Hydrogen and Fuel Cell, is presented. This system is equipped with specific components such as photovoltaic generator, solid polymer electrolyzerElectrolyzer producing 1 m3 h−1, 4.2 kW PEMFCPEM Fuel Cell and power conditioning system to develop different topologies. Experimental investigations of an energy storage system in microgrids were analysed under realistic scenarios in different environmental conditions. The water electrolyzerElectrolyzer stack is powered mainly by the solar PV energy source, then the produced hydrogen is stored in the hydrogen tank. The role of water electrolyzer is to generate hydrogen when the generated power by solar PV is greater than the power demand, and the role of PEMFC is to consume the generated hydrogenhydrogen from water electrolyzerElectrolyzer and to transform in electrical power energy. The target of the present work has been to assess the dynamic model of both systems to investigate the effect of these elements into the microgrid using measurements of the real systems. Modelling of the described system has been achieved using the MATLAB/Simulink. The model parameters have been acquired from manufacturer’s performance data-sheets. Based on above information, the proposed concept combining the PEMFC and water electrolyzerElectrolyzer hybrid sources could offer an important improvement for real time power imbalances. Therefore, this chapter take into account the control system based power conditioning and energy management of a controllable electrolyzerElectrolyzer in order to investigate the real time fluctuations of microgrid’s real power balance.

Mircea Raceanu, Nicu Bizon, Adriana Marinoiu, Mihai Varlam

Chapter 10. Energy Management Requirements for Microgrids

Load growth as a result of progress in technology, industrialization, environmental issues, etc. have caused the arrival of distributed energy resources and consequently formation of microgrids. Proper strategy for the operation of microgrid, could provide various economical, technical, social benefits and environmental benefits. One of the main units in the formation of a microgrid is its energy management center. It is responsible for right decisions about energy generations, consumptions and transactions. The bi-directional energy and data flows in microgrids, cause new challenges for energy management in microgrids. In this chapter, first the energy management system of a microgrid would be introduced. Then, its different parts would be illustrated. Finally, modelling and simulations for the energy management of a typical microgrid will be presented.

Farid Hamzeh Aghdam, Navid Taghizadegan Kalantari

Chapter 11. Energy Management of the Grid-Connected PV Array

Solar energy has an important place in the global energy context, this leading to an intense concern in the unconventional energies field. Even if the earth receives only a small fraction of the solar radiationSolar radiation emitted by the Sun (because the radiation suffers the phenomena of absorption and diffusion in the atmosphere) the solar energy has become one of the most important renewable sources. Solar energy can be captured and converted into electrical energy by using the photovoltaic technologies and/or thermal energy, through the use of various types of solar panels heat shields. In this context, the field of producing electricity with photovoltaic panelsPhotovoltaic panels is approached in this chapter. The photovoltaic panelsPhotovoltaic panels are devices that convert the solar energy into electrical energy. Depending on weather conditions, the generated renewable energy oscillates, being required an energy storage system to store the excess energy or to discharge energy during the lack of energy. The best solution applied for short-term storage of energy is the battery. On the other hand, the photovoltaic systemsPhotovoltaic systems only use a portion of the solar radiationSolar radiation and of certain wavelengths, in order to produce electrical energy. The rest of the energy received at the surface is converted into heat, leading to a rise in temperature of the cells components and reduction in yield. In conclusion, increasing productivity and energy efficiency of these facilities involves both the efficiency of their operation in the electric field and the study of the thermal phenomena that take place. In order to ensure a high degree of felicity of the electrical energy managementEnergy management atManagement the level of a microgrid type user, it is necessary to know the energy flows, the structure of the distribution network, and identification of the technical solutions depending on the field. In this chapter, the main functional parameters of the system considered will be analyzed, the quality parameters at the level of the electricity system of the user will be estimated, and the operating parameters of the system considered will be also analyzed. The objective of the chapter is to propose a technical solution to improve the efficiency of a photovoltaic power plantPhotovoltaic power plant within an area of seventy hectares through control, surveillanceSurveillance , meteringMetering and monitoring of the system from distance based on Supervisory Control and Data Acquisition (SCADA)Supervisory Control and Data Acquisition (SCADA) system. The photovoltaic power plant used to carry out the experiments is located in Romania. The location of the photovoltaic parkPhotovoltaic park is in a plain area where solar radiationSolar radiation is higher (over 1450 kWh/m2 year, in particular in the summer). With the help of the SCADASupervisory Control and Data Acquisition (SCADA) system, the energy managementEnergy management of the photovoltaic parkPhotovoltaic park can be achieved for: a short period (one day) or for a longer period (a week). The SCADA system offers information about: total energy delivered (kWh), day energy delivered (kWh), active inverter power (kW), percent of availability for photovoltaic power plantPhotovoltaic power plant , weather info (ambient temperature, plane radiation etc.), hourly graphs about plant production, alarms, current strings, energy meterEnergy meter (exported active-reactive power, imported active-reactive power), data about the weather station, inverter graphs, state of power transformers, breaker state, earthing state, month radiation, month exported active energy, currents variation (Ia, Ib, Ic), leakage current variation (Ig), and voltage variation (Va, Vb, Vc). The data stored by the system will allow the user to receive current information, but also these data can be compared with the data stored in the same period of the past years, in order to establish the productive efficiency of the photovoltaic power plantPhotovoltaic power plant .

Florentina Magda Enescu, Nicu Bizon, Ioan Cristian Hoarca

Chapter 12. PV Microgrids Efficiency: From Nanomaterials and Semiconductor Polymer Technologies for PV Cells to Global MPPT Control for PV Arrays

The chapter has to contribute to the part of electronic devices related to solar cells development, aided by new innovation technologies and new photovoltaic (PV) cells made by organic compounds and nanomaterials. Also, advances on the part of control techniques by presenting the results for Extremum Seeking Control (ESC)-basedExtremum Seeking Control (ESC) Global Maximum Power PointMaximum Power Point Tracking (GMPPT)Global Maximum Power Point Tracking (GMPPT) applied to PV microgridsPV Microgrids in partially shaded regimes are considered. The influence of the photovoltaic arrays topologies to multimodal characteristic of the PV power is also highlighted. Alternative new materials like ferrite Nano-Core-Shell (NCS) multilayer can be used to construct Thin Film Transistors (TFT)Thin Film Transistors (TFT) or can be applied for photovoltaic (PV) cells. Hence, the chapter firstly presents how the NCS technology generates nanomaterial layers. The ferrite core is self-assembled by an intermediary first shell to an organic shell represented by para-aminobenzoic acid (PABA). The fabricated nano-layers are investigated by Scanning Electron Microscopy technique (SEM) and also by Dynamic Lighting Scattering (DLS). These techniques find a hydrodynamic width for the ferrite NCS of 70.9 nm, besides to a zeta potential for these nanoparticles of 51.6 mV, proving an appropriate stability of the fabricated nanoparticles. Organic semiconductors are recently introduced for the transistor and Organic Solar Cell (OSC)Organic Solar Cell (OSC) manufacturing. Some Athena/Atlas simulations capture the better feature for the static characteristics for different electronic structures working as transistor or texturized solar cells. Either Nano-Core-Shell, Amorphous-Silicon or Polymers are suitable materials for PV microgridsPV Microgrids. The demonstration of current vectors traces and experimental static characteristics of the proposed electronic devices sustain these materials future use to enhance the PV arrays. Furthermore, the energy generated by the PV arrays can be fully harvested using GMPPT algorithmAlgorithms based on advanced ESC scheme.

Cristian Ravariu, Nicu Bizon, Elena Manea, Florin Babarada, Catalin Parvulescu, Dan Eduard Mihaiescu, Maria Stanca

Microgrid Control Systems

Frontmatter

Chapter 13. Control of Power Electronic Converters in AC Microgrid

The main advantage of AC microgrid is it has the compatibility with existing ac grid. The book chapter emphasizes on the current controlling strategies of power converters operating in different modes with AC microgrid system simplified structure. The challenging part to meet the defined output parameters for Distributed Energy Resources (DERs) with increased penetration of the same is also jagged with controlling strategies of power converters. DER and ESS are integral part of microgrid and for AC microgrid they require converter interface. Various converter topologies and their control is included. Microgrid requires extensive control strategy to meet with grid requirements and load requirements under verity of conditions. Control strategies of multilevel is used. Control methods related to primary control, secondary and tertiary control is discussed. The crucial parameter for selection of power converters control, selection of L, LC and LCL filters, according to application is included. Moreover, depending on the operating modes i.e. Grid Connection Mode and Stand-Alone Mode the respective control strategies are compared for the better understanding along with requirement of synchronization to estimate several grid parameters to achieve accurate control of the active and reactive power delivered to the grid.

Rajendrasinh Jadeja, Amit Ved, Tapankumar Trivedi, Gagandipsinh Khanduja

Chapter 14. DC Microgrid Control

The current challenges of the current power systemPower system are to face-up with the integration of the increased renewable energy sourcesrenewable energy sources, energy storagestorage systemsenergy storage system, access to the energy marketEnergy market in an optimaloptimal manner, reconfiguration under faultsfaults using microgridMicrogrid concept, being capable to assure more flexibility, and stabilitystability, through advanced controlcontrol. The chapter makes a modern introduction into the DC microgrid architecturesArchitecture and their control. As the most used control into the DC microgridsMicrogrid, the hierarchicalhierarchical control is presented. In order to guide the readers, the most used standards related to DC microgrids are presented. As case study, the advanced control of the utility converterutility converter has been developed and simulated in MatlabMatlab/Simulink. Nowadays, the securitysecurity protectionprotection of the energy network is a concern. An introduction to cyber-physical systemCyber-Physical System (CPS) (CPS) related to the power system field is presented.

Marian Gaiceanu, Iulian Nicusor Arama, Iulian Ghenea

Chapter 15. Hierarchical Control in Microgrid

It is required to utilize several control loops together to increase reliability and performance of microgrids. The current and voltage magnitudes, frequency and angle information, active and reactive power data provide the involved feedback for normal and island mode operations of microgrid. The hierarchical controlHierarchical Control structure of microgrid is responsible for microgrid synchronization, optimizing the management costs, control of power share with neighbor grids and utility grid in normal mode while it is responsible for load sharing, distributed generationDistributed Generation (DG), and voltage/frequency regulation in both normal and islanding operation modes. The load control of microgrid is performed by using more sophisticated electronic devices as well as regular circuit breakers. This regulation capacity could be improved since the ESS decreases the dependency to primary power sources. Although several improvements have been experienced in microgrid control strategies, the most intensive research areas are listed as decreasing the structural instability, improving the system performance to increase reliability, monitoring the harmonic contents, scaling the control infrastructure, enhancing the operation characteristics in error states, and implementing new control algorithms for normal and islanding operation. The microgrid system has hierarchical controlHierarchical Control infrastructure in different levels similar to conventional grids. The microgrid requires enhanced control techniques to manage any level of system. Safe operation of microgrid in both operation modes and connection and disconnection between microgrid and utility grid are depended to microgrid control techniques. The controllers should ensure to operate the system regarding to predefined circumstances and efficiency requirements. The hierarchical control methods and applications of microgrid infrastructure are presented in the proposed chapter.

Ersan Kabalci

Chapter 16. Distributed Control of Microgrids

The aim of this chapter discusses the relationship between hierarchical control and review of distributed control systems that is used in microgrids. The microgrids are differs from the conventional power systems. Because of the widespread use of advanced control technologies with features such as power electronics devices, detection/measurement applications, and communication infrastructures. These features of microgrids make it easier for renewable energy sources that are included in the power systems. Therefore, distributed control methods are applied in addition to centralized and de-centralized controls for reliable operation of the system in microgrids and between different microgrids. This section discusses the features of these methods.

Ahmet Karaarslan, M. Emrah Seker

Chapter 17. Intelligent and Adaptive Control

Intelligent and adaptive control is defined as a feedback control system that can adjust the character to the change in the environment in order to carry out the system optimally according to some specific criteria. An adaptive control system that overcomes the change in the environment over time is different from the optimal control system or feedback control systems. Feedback or optimal systems occur in the specified environment. If the changes in the environment are very sensitive, these systems cannot be designed in the manner requested by the designer. On the other hand, the adaptive system evaluates the environment. More accurately evaluates the performance of the system. It makes the necessary changes to the control characteristic to improve. Adaptive control includes the following three functions: identification, decision and change. In any adaptive control system, it is difficult to separate the system into its components. Conversely, these three functions must be present in the system for adaptation to occur. In this section, different intelligent and adaptive control systems are described.

Mehmet Zile

Chapter 18. Load Shedding, Emergency and Local Control

Nowadays, control of smart grids is of great importance in power networks. Considering loads and generations uncertainties is a paramount idea amongst researchers to illustrate real conditions of smart networks. Furthermore, special methods are being required to prevent cascading failures in emergency conditions whenever an islanded Microgrids (MGs)Microgrid tends to work independently. The first important factor is that loads demand are supposed to be completely catered in islanded MGs. Sometimes, shedding some unnecessary predetermined loads to attain systems previous balanced condition is common in electrical networks. In this chapter, we want to present an array of methods to control MGs in emergency conditions considering uncertainties. In this chapter, we focus our effort on developing a coordination control algorithm using Emergency Demand Response (EDR)Demand response resources and Under Frequency Load Shedding (UFLS)Load shedding methods considering various probabilistic scenarios. It is of supreme importance to design an optimal load shedding strategy in which customers and distribution companies’ rights are guaranteed.

Amin Mokari Bolhasan, Navid Taghizadegan Kalantari, Sajad Najafi Ravadanegh

Chapter 19. Smart Metering Based Strategies for Improving Energy Efficiency in Microgrids

In the last years, in the operation of electric distribution grids (EDGs), the optimization process is reduced to small size grids (namely microgrids)Microgrids for which the number of variables is much lower, and finding the optimal solution is not a problem. To better supervise and control each microgrid, the emergence of smart meteringSmart metering system (SMS) can be interpreted as a transformation in progress encountered at the level of majority of distribution grid operators (DGOs). In these conditions, distribution grid operators (DOGs) have possibility to obtain online data about the electricity consumption of customers, respectively the electricity amounts product by the renewable sources, which allows them to take some technical measures which enable the microgrids to operate more energy efficient and better plan their investments. A critical assessment of microgrids referring to improving the energy efficiencyEnergy efficiency brings out a series of problems partially unresolved due to the particularities of microgrids where they have been implemented. These problems are studied in this chapter and SMS-based new solutions are proposed for load modellingLoad modelling , phase load balancingPhase load balancing and voltage controlVoltage control . All approaches are tested using real microgrids, and the obtained results highlight the performances on the energy efficiency measures.

Gheorghe Grigoras, Ovidiu Ivanov, Bogdan Constantin Neagu, Pragma Kar

Chapter 20. Optimal Microgrid Operational Planning Considering Distributed Energy Resources

This chapter introduces an approach forOptimal microgrid operational planning Optimal MicrogridMicrogrid Operational Planning (OMOP) considering windWind and photovoltaic power generations, combined heat and powerCombined Heat and Power (CHP) generation units, electrical energy storages and interruptible loadsInterruptible Loads (ILs). The problem explores the optimal maintenanceMaintenance scheduling and operational planningOperational planning of a microgrid. A framework for OMOP is presented based on a two-level optimization procedure taking into account the system uncertainties. The formulated problem is modelled as a Mixed Integer Nonlinear Programming (MINLP)Mixed Integer Nonlinear Programming (MINLP) problem and a heuristic optimization method is utilized for the first level problem; meanwhile, a MINLP solver is used for the second level problem. This model is applied to the 9-bus and 33-bus test systems and the numerical results assess the effectiveness of the introduced method.

Mehrdad Setayesh Nazar, Ainollah Rahimi Sadegh, Alireza Heidari

Chapter 21. Self-healing: Definition, Requirements, Challenges and Methods

One of the most important issues in power gridsPower grid is the outageOutage problem that occurs due to weaknesses of the power system infrastructure or the occurrence of human or natural faults in the power system. The issue of complete deletion of power outages is unlikely due to unpredictable nature of major faults. After a fault, it is necessary to isolate the fault locationFault location as soon as possible. Thus, the energy path may be interrupted to some of the loads. However, new technologies or advanced methods can be used to reduce the interruptionsInterruption duration. By appearance of smart gridsSmart grid and developing its level of intelligence, it is possible to automatically detect a fault in the shortest time, isolate it from the system and feed healthy parts of the system on a different path. The set of automatic activities that occur after a fault occurrence to achieve previous goals is called self-healingSelf-healing. In other words, Self-healing of the distribution systemDistribution system means changing the distribution network structure after fault in order to feed disconnected loads while maintaining the network’s electrical constraints. Undoubtedly, self-healing is one of the main abilities of the smart gridsSmart grid with respect to traditional systems to automatically retrieve system after fault occurrence or keep away system from critical conditions. Self-healing usually consists of three steps: fault locationFault location, isolationIsolation and system restorationRestoration (FLISR). The large number of lines, branches, and equipment of the distribution network can complicate this process. In this chapter, definition, requirements and challenges of self-healing are introduced and various approaches which have been recently proposed by researchers are assessed. Also some tools and methods like demand responseDemand response, load sheddingLoad shedding, distributed energy resourcesDistributed energy resources and autonomous microgridsAutonomous microgrids which can facilitate self-healingSelf-healing process are assessed.

Ali Zangeneh, Mohammad Moradzadeh

Chapter 22. Various Droop Control Strategies in Microgrids

Droop controlDroop control is a well-known strategy to control active power in power systems without internal communication. It is usually implemented on the conventional power plantsPower plant to control the injected power of synchronous generatorsSynchronous generators to the grid. As this strategy is local, there is no need to communication systems. Thus, it reduces the complexity and cost of the system operation and improves the reliabilityReliability indices. Also, droop control has been used to control the active and reactive powerReactive power of distributed generationsDistributed generation in microgridsMicrogrid . FrequencyFrequency and voltage controlVoltage control of microgrid and proper power sharingPower sharing between DGs are the most important goals of droop control in the islanded modeIslanded mode of operation. The conventional droopConventional droop control has some disadvantages that limits their application in the modern microgrids. Slow transient dynamicsDynamic , load dependency of voltage and frequencyFrequency , low accuracy on power sharing, low power qualityPower quality for non-linear or unbalanced loads and circulating currentCirculating current between DGs are some of the main disadvantageous. Different methods have been proposed by researchers to overcome the problems, which are still an attractive subject for them. This chapter discusses different improved droop controllers, which have been used to overcome some of the problems.

Pegah Zafari, Ali Zangeneh, Mohammad Moradzadeh, Alireza Ghafouri, Moein Aldin Parazdeh

Chapter 23. Fuzzy PID Control of Microgrids

The purpose of this chapter is design and application of intelligent methods based on the fuzzy logic (FL) type PID controller for adaptive controlling of the microgrids. The traditional structure of the power systems is being changed continuously due to environmental limitations and depreciated infrastructures. The creation of distinct electrical boundaries between different areas of the power system with the ability to connect/disconnect and locating distributed generation (DG) resources near the load points has transformed the face of power systems. In this situation, power systems can be considered as a set of multiple microgrids that work in conjunction with each other in a coordinated manner. Although, in this case, the power system’s efficiency is increased, but its control is faced with bigger challenges. Coordination between microgrids, resource scheduling in the islanding and main utility-connected modes, exchanging power between different microgrids, and etc., are the reasons that necessitate the use of adaptive control methods for controlling such power systems. In this chapter, adaptive controlling mechanisms based on FL based PID control will be discussed in detail. FL based controllers are expanding due to their simple structure, easy implementation and adaptive behavior. This kind of controllers has a superb performance in controlling large-scale complex systems with high degree of nonlinearities by using their membership functions and fuzzy rules. Here, different control strategies based on Fuzzy PIDFuzzy-PID type controller will be described and discussed for controlling microgrids.

Hossein Shayeghi, Abdollah Younesi

Chapter 24. Adaptive and Online Control of Microgrids Using Multi-agent Reinforcement Learning

The primary aim of this chapter is the design and application of intelligent methods based on reinforcement learning (RL) for adaptive and online controlling the hybrid microgrids (HMGs). The traditional structure of the power systems is being changed continuously due to environmental limitations and depreciated infrastructures. The creation of distinct electrical boundaries between different areas of the power system with the ability to connect/disconnect and locating distributed generation (DG) resources near the load points has transformed the face of power systems. However, in this case, the power system’s efficiency increases, but its control is faced with bigger challenges. Coordination between HMGs, resource scheduling in the island and main utility-connected modes, exchanging power between different microgrids, and etc., are the reasons that necessitate the use of adaptive control methods in controlling such power systems. Reinforcement Learning is an adaptive control structure that is considered in this chapter. RL is a branch of multi-agent systems in the field of machine learning which is the main solution method for Markov decision process (MDP). In this chapter, based on RL features like an unpretentious structure, robust versus severe disturbances, and online behavior a novel method will be suggested for controlling different aspects of HMGs. The proposed control method uses the features of the RL and capabilities of the classical controllers to give an effective online controller with plain anatomy which is robust versus uncertainties and operating condition changes.

Hossein Shayeghi, Abdollah Younesi

Microgrid Protection Systems

Frontmatter

Chapter 25. Microgrid Protection

TheMicrogrid power system remained far beyond in adopting new technologies in key domains such as: automation, information technology and telecommunications. Globally, energy demand is constantly increasing and nowadays the power system has developed according to past and present needs. But, this has to be changed in order to adapt to the future rapid evolutions: today’s digitized society need efficient, scalable and resilient power systemsPower Systems , because, without it, our life style will reduce to an almost medieval existence. The difficulty and complexity of the power system transition from the traditional to the intelligent system consists in the fact that this must be done in order to solve the present problems and to prevent those which the system might face in the future by allowing the new technological innovations. All of this must take place while the system is in operation, without affecting the consumers. Among the risks associated with the traditional power system, based on a small number of large power stations, we mention the need to implement some power plants to take over the over-consumption (peaks), with major disadvantages. Some of the disadvantages can be summarized as follows: they only work temporarily; they do not easily depreciate their costs; low resiliencyResiliency (e.g. collapse of the system, for natural reasons, or a malfunction in the production or transport chain. Microgrids come with added value through protectionProtection , resilience and low cost due to the avoidance of power cuts which, with respect to each sector of activity, generate significant financial losses in case of occurrence. About these challenges and the link between the connectivityConnectivity of microgrids and the risks they are exposed to, the authors refer in the second paragraph of this chapter. Taking into account the technical requirements of the microgrids, protection solutions for both DCDC-Direct Current and AC currents will be presented. The level of pollution which our planet is facing imposes certain standardsStandard that change the approach of some industries. For example, in the transport sector, the authorities prohibit or impose extra-charges for cars with diesel engines and provide aid for the purchase of electric cars. Such a car raises the electricity needs of a home a few times, the colder winters and hotter summers put pressure on the system again, increasing the likelihood that the power system will crash. Therefore, reference will be made to the appropriate standards to which these protectionsProtection should be aligned. At the end of the chapter, development trends in this area will be mentioned. The microgrids solve many problems of the classic power system because a power system made up of a microgrids array acts as a whole and, in the event of a problem, it disconnects from the system without propagating up. The probability of the occurrence of a power cut is much diminished because, for example, as in the case of Denmark, the system is decentralized and a problem can be propagated at most on the local level, not nationally, and the energy storage component in the microgrids ensures good functioning during peak periods as well as in the event of a public network failure. Besides certain advantages of implementing microgrids, they come also with new threats from the cyber spectrum, with increased complexity, threats which other sectors have already faced and found solutions. Such examples are given in the fourth paragraph. The chapter ends with conclusions and a large number of references in the field of microgrids protection.

Horia Andrei, Marian Gaiceanu, Marilena Stanculescu, Ioan Marinescu, Paul Cristian Andrei

Chapter 26. Microgrid Protection and Automations

After the decision on devolution of electric power generation, a great number of dispersed storage and generation (DSG)Dispersed storage and generation units, which is mainly driven by renewable energy sources, has been connected to the power distribution networks. Existing of DSG units in the distribution network has converted the traditional distribution systems into active distribution networks, which are also called microgrids, and has created several technical difficulties from the operation points of view. Therefore, the conventional protection and control systems need to be improved to overcome these difficulties, and provide a reliable protection and control for microgrids operating in both grid connectedGrid connected mode and islanded modes. Today it is realized that partially developments in protection and control systems will not provide an ideal solution for the todays and future microgrids. Therefore, a full automated distribution network is certainly required for a proper protection and control of microgrids. This chapter will be deal with the protection and automation requirements of the microgrids, protection schemes and developments in the related fields.

Omer Usta

Chapter 27. Protective Systems in DC Microgrids

The aging power system causes to several grid problems such as intermittency, power quality issues, and blackouts since a few decades. Therefore, the power infrastructure requires serious troubleshooting studies in a wide manner. The distributed generation and integration of large photovoltaic (PV) plants to the existing utility have led to intensive interest on DC power grid infrastructure. The widespread use of DC based microgrids decreases significant power losses and facilitates operation and maintenance of microgrids. Besides, DC loads are easily supplied by DC microgrids that eliminate the requirement for power inverters. It is noted that elimination of DC-AC power conversion can prevent power losses of entire system between 7 and 15% that is remarkable ratio for a microgrid. In one hand, the DC microgrids provide increased interest due to their advantages such as power density and distribution efficiency comparing to AC power systems. On the other hand, short-circuit current capabilities of DC microgrids lead to significant hazards for users and properties. Moreover, it is not possible to overcome arc faults occurred in a DC microgrid by using regular circuit breakers since DC current do not draw a natural zero crossing waveform. The cost and bulky structure of DC circuit breakers is another important issue in this regard. The actual fault protection systems are based on over current detection for power electronic devices and improved circuit breakers, distributed generation source controllers, and several types of relays. This chapter deals with fault detection methods and protection devices in low voltage DC (LVDC), medium voltage DC (MVDC), and high voltage DC (HVDC) networks. Protection schemes and improved devices with circuit topologies are presented regarding to DC microgrids.

Ersan Kabalci

Chapter 28. Adaptive Protection Systems

SustainableAdaptive resources would replace traditional energy productionEnergy production solutions in the near future. There are determinant factors that force to adopt the changes in actual power systemPower system : environmental protectionEnvironmental protection , and the increasing price of natural gas, coal and oil. The chapter provides a short overview of protectionProtection functionsProtection functions in adaptiveAdaptive systemsAdaptive systems . Nowadays, the alternative energyAlternative energy sources forced the power system to support major transformations. The energy producers or medium voltageMedium voltage (MV) electricityElectricity market operatorsMarket operators through remoteRemote controllable line disconnectors achieve new technology in distribution power systemsDistribution power systems . The remote-controlledRemote-controlled recloserRecloser is one of the most important equipment used in MV distribution systemsDistribution systems . The chapter contains the most features of the remote-controlled recloser. The adaptive protection of a distributed system is based on the Loop AutomationLoop automation Scheme, described largely by the authors. The main advantage is the restorationRestoration of energy supply to consumersConsumers in minimum time. The chapter includes a case studyCase study in the Galati distribution operatorDistribution operator activity area (Romania).

Marian Gaiceanu, Iulian Nicusor Arama

Chapter 29. IEC 61850 Based Protection Systems

The IEC chapter includes protection XE “protection” power XE “power” systems Power systems based on the IEC IEC 61850 protocol XE “protocol” for data communication XE “communication” systems between substations XE “substation” . The IEC 61850 XE “IEC 61850” is adequate for real time communication between IED Intelligent Equipment Device (IED) based on GOOSE Generic Object Oriented Substation Event (GOOSE) messages XE “messages . The chapter includes the case study from the Romanian power systems: implementation of protection and remote control XE “remote control” system Remote control system in transformer XE “transformer” station Transformer station 110 kV/20 kV Laminor, using IEC 61850.

Marian Gaiceanu, Iulian Nicusor Arama

Chapter 30. Power Quality Issues and Mitigation Techniques in Microgrid

The most desirable characteristics of today’s power system with distributed energy resources (DER) forming the microgrid is the reliability of the power supply and immunity to various power quality(PQ) issues. It is important to examine PQ issues arising from the introduction of DER and behavior of microgrid with penetration of various loads. In this chapter, reader is introduced to major power quality issues in the microgrid. A number of solutions to tackle these issues and their operating principle are also explained. In addition to the conventional power quality issues, load pulses are frequently encountered and need to be tackled with great care in microgrid. Hence, the hybridization of Energy Storage System (ESS) with different power storage devices such as the ultracapacitors (UCs), Superconducting Magnetic Energy Storage (SMES) devices, and high speed Flywheel Energy Systems (FESs) is proposed to dynamically compensate the power flow balance.

Rajendrasinh Jadeja, Nicu Bizon, Tapankumar Trivedi, Amit Ved, Mrudurajsinh Chudasama

Chapter 31. Control and Protection of the Smart Microgrids Using Internet of Things: Technologies, Architecture and Applications

WithProtection the everyday technological growing and updates of the Internet of ThingsInternet of Things (IoT), smart microgrids, as the building foundations of the future smart grid, are integrating more and more different IoT architecturesArchitectures and technologiesTechnologies for applications intended to develop, controlControl, monitor and protect microgrids. A smart microgrid consists of a smaller grid that can function independently or in conjunction with the main power grid and it is suitable for institutional, commercial and industrial consumers and also for urban and rural communities. A microgrid can operate in two modes, stand-alone mode and grid-connected mode, with the possibility to switch between modes because of faults in the local grid, scheduled maintenance and upgrade, shortages and outages in the host grid or for other reasons. With various distributed energy resources (DER) and interconnected loads in the microgrid, IoT is intended to provide solutions for high energy management, security mechanisms and control methods and applications. The basic components of a microgrid refer to local generation, consumption, energy storage and point of coupling to the main power grid. Local generation consists of different energy resources that provide electricity to users, from single residential house to commercial and industrial centers, which represent consumption. Energy storage is where the power is stored and comes with multiple functions such as voltage and frequency regulation, power backup or cost optimization. A coupling point refers to the junction between a smaller smart microgrid and the main smart grid. The main purposes of this chapter are to show the role of Internet of Things in creating and developing smart microgrids including benefits, challenges and risks and to reveal a variety of mechanisms, methods and procedures built to controlControl and protect smart microgrids. Different technologies, architecturesArchitectures and applications using IoT, as the main key features, with the major goal of protecting and controlling innovative smart microgrids in line with modern optimization features and policies are intended to upgrade and improve efficiency, resiliency and economics. Microgrids represent a large IoT opportunity because they are composed of equipment that demands sensing, connectivity and analytics technologiesTechnologies to operate at the highest level.

Fernando Georgel Birleanu, Nicu Bizon

Backmatter

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