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About this book

This book provides a comprehensive overview on the latest developments in the control, operation, and protection of microgrids. It provides readers with a solid approach to analyzing and understanding the salient features of modern control and operation management techniques applied to these systems, and presents practical methods with examples and case studies from actual and modeled microgrids. The book also discusses emerging concepts, key drivers and new players in microgrids, and local energy markets while addressing various aspects from day-ahead scheduling to real-time testing of microgrids. The book will be a valuable resource for researchers who are focused on control concepts, AC, DC, and AC/DC microgrids, as well as those working in the related areas of energy engineering, operations research and its applications to energy systems.Presents modern operation, control and protection techniques with applications to real world and emulated microgrids;Discusses emerging concepts, key drivers and new players in microgrids and local energy markets;Addresses various aspects from day-ahead scheduling to real-time testing of microgrids.

Table of Contents


Operation of Microgrids


Chapter 1. An Introduction to Microgrids, Concepts, Definition, and Classifications

Microgrids are self-sufficient energy ecosystems designed to tackle the energy challenges of the 21st century. A microgrid is a controllable local energy grid that serves a discrete geographic footprint such as a college campus, hospital complex, business center, or neighborhood. It connects to the grid at a point of common coupling that adopting voltage with the main grid in normal and can break off automatically or manually and works as an island using its local energy generation units in times of crisis. The microgrid concept assumes a cluster of loads and combination of distributed energy resources units such as solar panels, wind turbines, combined heat and power, energy storage systems such as batteries and also electric vehicle charging stations. Microgrids contribute to modify flexibility, reliability, and resiliency, accessibility of green and safe energy with ability to participate in demand response, cost optimization and grid-balancing programs. Microgrids can be categorized via different aspects ranging from the structure such as DC, AC, or hybrid to control scheme such as centralized, decentralized or distributed. This chapter reviews briefly the microgrid concept, its working definitions and classifications.
Maryam Shahbazitabar, Hamdi Abdi, Hossein Nourianfar, Amjad Anvari-Moghaddam, Behnam Mohammadi-Ivatloo, Nikos Hatziargyriou

Chapter 2. Operation Management of Microgrid Clusters

This chapter deals with the most significant characteristics of networked microgrid clusters (NMCs). The NMCs operation improves the reliability and resiliency through self-healing, enables the best utilization of DERs, and power exchange between MGs. In this chapter, in addition to the advantages and challenges of NMCs, the main objectives, architecture, control strategies, and operation of NMCs are described. Also, the overview of energy management strategies, modeling, and solution methods in the NMCs are presented. Finally, the energy management of NMCs by 24-hour scheduling, consisting of several distributed generations and loads in three scenarios, is tested on a standard case study. The simulation results are validated by MATLAB software and with the PSO algorithm. These results show that NMCs can decrease total cost and prevent load shedding by reducing the power dependence through exchanging power between MGs.
Meisam Moradi, Asghar Akbari Foroud

Chapter 3. Energy Management Systems for Microgrids

Energy management system (EMS) has a vital role in the operation of a microgrid (MG) in the hourly or minute-by-minute time-scales. EMS coordinates with the other systems such as advanced metering infrastructure (AMI), maintenance scheduling, outage management, distribution management, and weather forecasting systems to gather an extensive amount of data on a real-time horizon. The gathered data is precisely processed to generate appropriate control signals to achieve the predetermined economic or technical goals. However, it is a hierarchical decision making including daily, hourly, and real-time scheduling. In this chapter, the performance of EMS is analyzed in both normal state and contingency conditions. Normal operation mainly focuses on economic aspects, whilst in the contingency state, EMS should guarantee the security of the system. This chapter presents a conceptual explanation on this topic along with the mathematical modelling and some examples.
Seyed Mohsen Hashemi, Vahid Vahidinasab

Chapter 4. Optimal Dispatch and Unit Commitment in Microgrids

Optimal managing the operational schedule of energy sources of the microgrid has a high effect on the performance of the microgrid. On the other hand, increasing the interest of consumers for optimal controlling the consumption using demand response programs improves the efficiency of the microgrid. For these reasons, the optimal dispatch and unit commitment in microgrids in the presence of a demand response program is investigated in this chapter. Micro turbine and fuel cell are nonrenewable units of the microgrid while renewable distributed generations are wind turbine and photovoltaic panel. An energy storage system is another type of energy source of the microgrid. Moreover, the microgrid can buy/sell energy from/to the upstream network when the produced power of energy sources of the microgrid is lower/more than the demand of the microgrid. The combination of multi-objective grey wolf optimization algorithm and fuzzy decision-making method is utilized to find the best operational schedule of energy units. The considered objective function consists of economic and environmental indices. Ultimately, the proposed unit commitment method is implemented in the sample microgrid. The numerical results demonstrate the high effect of the proposed method on improving the economic and environmental indices of the microgrid.
Hossein Shayeghi, Masoud Alilou

Chapter 5. The Role of Energy Storage Systems in Microgrids Operation

Generally, a microgrid can be defined as a local energy district that incorporates electricity, heat/cooling power and other energy forms, and can work in connection with the traditional wide area synchronous grid (macrogrid) or “isolated mode”. Additionally, with the trend of transportation electrification, the concept of microgrid has been gradually expanded to many mobile cases, such as electric vehicles, electric aircraft and all-electric ships. Different from conventional land-based microgrids, those mobile microgrids usually operate in isolated states and cannot exchange energy with the main grid. In recent years, microgrids have gradually become an important interface to integrate multiple energy sources, such as various renewable energy, which further presses the integration of energy storage systems into microgrids.
This book chapter focuses on the role of energy storage systems in microgrids. In Sect. 1, current types of different microgrids are described, such as the land-based microgrids and mobile microgrids. In Sect. 2, current energy storage technologies are reviewed to show their technical characteristics. In Sect. 3, the applications of energy storage systems in microgrids are summarized as load leveling and power quality.
Sidun Fang, Yu Wang

Chapter 6. Microgrids and Local Markets

Today’s electricity grids are being challenged by profound changes in operational conditions, shifting from centralized generation, served by transmission and distribution networks, to one with embedded distributed energy resources (DERs). Without appropriate operational and control layers, DERs can impose power quality and stability challenges. Conversely, coordinated and controlled use of DERs can provide substantial benefits for networks such as deferring or avoiding investments in the electricity network, and providing ancillary services. There are currently limited opportunities for DERs to provide these additional benefits to networks, or to be rewarded for providing these benefits. The increasing penetration of DERs aligned with grid digitization are changing electricity grids from a centralized structure to a decentralized one with geographically distributed generation resources. Due to various barriers, it is challenging to design a centralized market that could serve customers in distributed locations. The concept of the local market is an auspicious option to manage DERs locally and to handle local problems associated with the integration of DERs. Microgrids could provide a framework for establishing local markets in order to actively involve prosumers and consumers in a local energy system through financial incentives. The microgrid is a promising approach to help DERs to participate in different markets and to access the value from the services they provide to broader grids. Local markets in microgrids improve microgrid customers’ and operators’ capacity to access the economic values of controlling their distributed energies. This chapter reviews the concept of local markets for microgrids. In particular, different definitions of local markets are reviewed, and benefits and services which can be provided by local market are discussed. Then, three different models for local markets are presented, followed by a discussion on market settlement methods in local markets. Case studies are employed to demonstrate different attributes of local markets. The chapter is concluded with remarks and challenges for microgrids markets that can be explored in future.
Mohsen Khorasany, Reza Razzaghi

Chapter 7. An Economic Demand Management Strategy for Passive Consumers Considering Demand-Side Management Schemes and Microgrid Operation

In a modern power system, a consumer can economically meet its demand by choosing the right strategy. The first and most convenient option, but obviously not the economic one, is to buy energy directly from the different electricity markets. The next choice, to minimize costs, is to supply electricity using the local generations. The latter can evoke the concept of microgrid if self-sufficiency exists. Meanwhile, alongside these choices, demand-side management (DSM) schemes are efficient supplementary solutions in the economic provision of demand. In fact, the efficient strategies of microgrids and DSM can be applied to the customer side to enhance loads flexibility. Despite the provision of significant advantages, the economic operation of microgrids is one of the most critical challenges in the power system. In response to this challenge, DSM, which is an efficient strategy that has provided considerable potentials in the restructured power systems, can be the resolution. In this chapter, the impact of customers’ participation level in demand response (DR) programs alongside its operation in the form of microgrid are investigated from the economic point of view. An approach is proposed to evaluate the installation and operation costs of a microgrid versus DR cost to opt an economic demanding strategy for a large-scale consumer. Two DR programs including price-based DR (PDR) and incentive-based DR (IDR) are considered in the studies. The proposed model is implemented in three real case studies that are investigated through simulations to study the different aspects of the problem. The results illustrate significant benefits that are obtained by applying the proposed economic management.
Mohammad Esmaeil Honarmand, Vahid Hosseinnezhad, Barry Hayes, Behnam Mohammadi-Ivatloo, Pierluigi Siano

Chapter 8. Real-Time Perspective in Distributed Robust Operation of Networked Microgrids

The increasing distributed energy resources' penetration at the edge of distribution systems create multiple energy communities in as microgrids. In this chapter, a distributed robust operation method for networked multiple microgrid has is presented. Combination of alternating direction method of multipliers and robust optimization methods is implemented on the proposed operation problem. The presented method by coordinating decisions which are made in the individual microgrid provides robust strategies for the participating in day-ahead and real-time markets. The strategies are determined using appropriate forecasts of renewable energy resources' generation power, load and market prices by implementing long short term memory technique with exogenous variables. By using proposed real-time method, the operation schedules would be determined before the day-ahead and the real-time markets' clearing times. The objective function is to minimize the operation costs of distributed energy resources and day-ahead and real-time markets' transaction costs which is decomposed using alternating direction method of multipliers. Coordination between microgrid operators and forecasting are simulated in MATLAB. Finally, through a linkage between MATLAB and GAMS optimization software, mixed integer linear programming based problems are solved using CPLEX over the GAMS. Numerical studies are established based on realistic test system and the efficiency of robust operation is confirmed with after-the-fact analysis.
Mehdi Jalali, Manijeh Alipour, Kazem Zare

Chapter 9. Application of Heuristic Techniques and Evolutionary Algorithms in Microgrids Optimization Problems

Despite all achievements of the microgrids, planning a cost-effective structure is a complicated process due to the different parameters that should be taken into account at any decision level. This chapter will focus on recent progresses in the application of computational intelligences and heuristic techniques in Microgrids that can cover different challenges of this area including the sizing and management optimization, predictive maintenance, estimation of exploitable energy, real-time self tuning system, siting, operation scheduling, and variety of other applications. Using these methods leads to a reliable network partitioning with less CPU effort and save the operating costs of the distributed nodes and interruption costs. Also, they provide more mobility to add extra restrictions to the aforementioned issues such as sizing and scheduling of power generation sources. To demonstrate the efficiency of the evolutionary algorithms (EAs), a comparison is carried out between the EA methods and conventional energy management system such as interval linear programming and mixed-integer.
Amir Aminzadeh Ghavifekr

Control of Microgrids


Chapter 10. Conventional Droop Methods for Microgrids

As the number of distributed generators (DGs) is increasing, the droop control methods are becoming more important. The droop control, which is also known as the primary control of hierarchical system in microgrid, has been widely used because it enables the stable power sharing among multiple generators in parallel operation. In particular, the droop control methods can be applied to the DGs to regulate the active and reactive powers for maintaining the grid frequency and voltage with the steady-state characteristic of generators based on the relationships of active power (P)–frequency (f) and reactive power (Q)–voltage (V). The regulation of output powers from renewable energy sources (RESs) is difficult due to their stochastic and intermittent behaviors. Therefore, the use of energy storage system (ESS) is necessary in microgrid to reduce the uncertainty and variability from RESs, particularly when it has very high renewable penetrations. In addition, the interest in DC microgrids has been recently rising because of their connectivity and high efficiency. In DC microgrid, the droop control is also used effectively like in AC microgrid. In this book chapter, the comprehensive overview of conventional droop control methods in both AC and DC microgrids will be firstly presented. Then, their different characteristics and features will be described for several DGs such as diesel generators, RESs, and ESSs while focusing on their proper applications to the DGs depending on the different operating conditions of microgrid.
Kwang Woo Joung, Jung-Wook Park

Chapter 11. Distributed Control Approaches for Microgrids

Microgrids (MGs) as controllable and small-scale electric power systems are the main building blocks of smart grids. The unique feature of MGs is their ability to operate in both grid-connected and islanded modes. The MG control system plays a critical role in accommodating its reliable operation in both operating modes. The MG control system deploys a hierarchical control structure including primary, secondary, and tertiary control levels. These control hierarchies are responsible for the voltage and frequency control and regulation as well as the optimal operation of the MG. In this chapter, these control hierarchies are elaborated. The MG control system can either adopt a centralized or distributed control structure. The distributed control structure has rendered more advantages compared to the centralized one in terms of reliability and resilience. In a distributed control structure, Distributed Generators (DGs) can communicate with each other through a distributed communication network and make consensus-based control decisions to satisfy a specific MG control target. This chapter addresses the distributed control of both AC and DC MGs and covers the distributed control techniques utilized for voltage/frequency control as well as active/reactive power sharing.
Tohid Khalili, Ali Bidram

Chapter 12. On Control of Energy Storage Systems in Microgrids

In high renewable penetrated microgrids, energy storage systems (ESSs) play key roles for various functionalities. In this chapter, the control and application of energy storage systems in the microgrids system are reviewed and introduced. First, the categories of energy storage systems utilized in microgrids and the power electronic interface between energy storage systems and microgrid systems are introduced. Then a comprehensive review of control methods of ESSs in islanded microgrids is reviewed. The functionalities include SoC balancing among multiple ESSs, coordination among renewable energy resources and ESSs, etc. In grid-connected microgrids, the utilization of ESSs for grid ancillary services, especially frequency and voltage regulation are introduced. The future research trend and opportunities are also discussed.
Yu Wang, Sidun Fang, Yan Xu

Chapter 13. Microgrid Stability Definition, Analysis, and Examples

The voltage and frequency of microgrid systems are changed when imbalances occur between power generation and demand. Thus, an important issue for systems is the operation in islanded mode. To solve this problem, a robust controller can be used to improve the stability responses of voltage and frequency. Accordingly, this study develops a novel adaptive fuzzy proportional-integral-derivative (AFPID) controller to regulate the voltage and frequency oscillations of islanded microgrids. The controller has two parts that operate in parallel to ensure the proper performance against uncertainties. The first part is a simple PID controller with constant gains that are obtained in nominal operation, and the second part is a fuzzy logic-based online mechanism for tuning PID gains against uncertainties. The non-dominated sorting improved differential evolution (NSIDE) algorithm is applied in the design of the AFPID controller to avoid the need for trial-and-error attempts and overcome the challenges presented by fuzzy design. The Analytical Hierarchy Process (AHP) mechanism is used in the optimization process that involves the optimal tuning of gains, membership functions and rule bases to ensure excellent decision making regarding solutions. The combination of fuzzy theory features and the NSIDE algorithm is intended to guarantee robust voltage/frequency control in islanded microgrids and simplicity in terms of process and structure. Ultimately, the data of the Himmerlands Elforsyning power system in Aalborg, Denmark is utilized to compare the effectiveness of the proposed AFPID controller, the conventional fuzzy PID controller and the classical PID controller against different disturbances and load uncertainties. The comparison is based on the integral of squared time multiplied by square error, maximum overshoot, maximum undershoot and settling time. Simulation results demonstrate that the proposed AFPID controller is robust against disturbances and load uncertainties; thus rendering it is an excellent choice for application in the actual islanded microgrids.
Hossein Shayeghi, Hamzeh Aryanpour, Masoud Alilou, Aref Jalili

Chapter 14. Voltage Unbalance Compensation in AC Microgrids

Environmental problems of the conventional power generation result in a tendency to increase the use of renewable energy, which in turn has altered the electrical power system. The increasing use of distributed generations over the last decade has led to the concept of Microgrids (MGs). MGs can operate in grid-connected or islanded mode. In the islanded condition, there is a greater probability of the power quality loss due to the lack of a main grid support. Harmonic distortion and voltage imbalance can be considered as two of the most important power quality disturbances. For this reason, this chapter involves the control methods that proposed to compensate unbalanced voltage and harmonic distortion. The performance of these methods are evaluated analytically, and its effectiveness and feasibility is illustrated at the end of the chapter by simulating a simple islanded MG.
Shahram Karimi, Mehdi Norianfar, Josep M. Guerrero

Chapter 15. WAM-Based Hierarchical Control of Islanded AC Microgrids

This chapter presents a wide area measurement system (WAMS) based hierarchical control of islanded AC microgrids (IACMGs) with static and dynamic loads. The proposed WAMS-based hierarchical controller consists of a lower-level decentralized controller, for each inverter-interfaced distributed generation (IIDG) unit, accompanied by an upper-level multi-input-multi-output (MIMO) centralized controller. Furthermore, this chapter also analyzes the impact of signal transmission time delays on the performance of the proposed WAMS-based hierarchical controller by performing simulation study on its application to the typical IACMG system.
E. S. N. Raju P, Trapti Jain

Protection of Microgrids


Chapter 16. Fault Ride Through and Fault Current Management for Microgrids

Over the recent years, the distributed energy resource (DER) generation and integration with utility grid became the most widely used worldwide. Thereon, the integration of distributed energy resources to the power grid and their dynamics during grid faults had become a critical issue in the new grid code requirements. In line with this, the fault ride through (FRT) capability control of grid-connected DER became the most important issue related to grid codes. There is growing interest in the industry in the application of microgrids (MGs) to take advantage of the proliferation of DER to address planning objectives such as improving resiliency and efficiency. In order to fulfill the FRT requirements imposed by grid codes, various approaches have been proposed in the last years. This chapter presents an overview of several existing FRT capability enhancement approaches during grid fault conditions and presents an FRT strategy specific for MG with an inverter-based interface (IB-MG) to maintain power exchange with distribution networks during network faults or disturbances. A uniqueness of this chapter is to outline a detailed fault current management strategy specific for MG FRT to coordinate with area utility grid, which is limiting the inverter fault current contributions and impacts on the distribution networks protection during faults or disturbances. A hardware-in-the-loop platform is proposed in this chapter for implementation and validation of MG FRT control algorithm.
Wei Kou, Sung-Yeul Park

Chapter 17. Microgrid Protection

In recent years, the installation of renewable generation sources (RASs) has undergone a great deal of growth, the horizontal structure of electrical networks has led to the formation of micro grids (MGs). These electrical networks have operational benefits, since the power of the load is local and the problems of network congestion, power losses are mitigated, hence reducing the operation and generation costs. These networks also have the characteristic that they integrate highly dynamic elements with significant limitations on controllability. The early detection of faults and the security of not operating falsely under normal operating conditions in highly dynamic networks, pose a challenge to the security of protection schemes. The application of multi agent systems for adaptable solutions and on-line protection schemes can offers a viable solution.
Arturo Conde Enríquez, Yendry González Cardoso, José Treviño Martínez

Chapter 18. A New Second Central Moment-Based Algorithm for Differential Protection in Micro-Grids

There are different definitions for Smart Grid, one of them is: Smart Grids is that it employs a wide variety of distributed energy resources (DER). In such conditions, the increasing local generation requires a new type of approach for protection. Ensuring the function of a relay to satisfy the requirements of the development of the smart grid and perform the protection task with high reliability, involves solving different technical aspects. In order to remove the fault with a minimum area of interruption, it requires the setup of multiple protection relays and their technical coordination. In order to meet the above requirements, protection devices based on various hardware platforms, different techniques and the on-site operational management of these devices have been proposed. An interesting feature proposed for the Smart Grid is self-healing. This means that the system is capable of continuing the power supply after any kind of disturbances. Self-healing is, in fact, a broad concept including the stability of transmission grids, but here the focus is on the protection of MV distribution networks. In this context, one way to achieve the self-healing functionality is to switch over to island operation in case of a fault in some parts of the network. The successful use of the local generation for achieving controlled island operation in some fault cases requires the use of suitable telecommunication between different parts of the system. In addition to this, there is a need to adapt the protection configuration to the system state. Especially critical in this respect is the power generated by the local sources and the loading in various parts of the network. Depending on the load/generation balances the size of suitable islands to be used in fault cases may be different at different times.
Ernesto Vázquez, Héctor Esponda, Manuel A. Andrade

Chapter 19. Microgrid Protection with Conventional and Adaptive Protection Schemes

One of the driving force of the Microgrid research in the past decade has been to accelerate the integration of renewable energy sources (RES) including wind and photovoltaic (PV) based generation into distribution networks. The islanded mode of Microgrids on the other hand would not only increase the reliability of existing distribution networks but also increase the security of supply for geographically islanded systems. But as a matter of fact, wind and PV systems are inherently intermittent resources so there is always need of some kind of energy storage to smooth out the power fluctuations caused by weather related intermittency. It is also a fact that most of the well-established renewable energy generators and energy storage technologies are coupled to the distribution networks using power electronic converters. The power electronics converters are, on the one hand very flexible and quick to operate, but on the other hand lacking inertial response and very limited fault current providers. Present day protection schemes rely on single setting group which becomes ineffective with increasing penetration level of distributed energy resources (DERs) including renewable energy sources and energy storages. During faults in grid-connected mode of Microgrids a high magnitude fault current of 10–50 times the nominal current will be expected from the main grid but in islanded mode only limited fault current magnitude of 1–2 times the nominal current will be available due to converter-based generators. The conventional single setting overcurrent protection causes the immediate disconnection of DERs during faults in grid-connected mode and does not allow any islanded mode operation of DERs due to safety reasons. An adaptive protection will be necessarily required for grid-connected Microgrids to continue operation even in islanded mode after disconnection from the main grid due to faults. An adaptive overcurrent protection will have at least two reliable settings groups, one for grid-connected and other for islanded mode of Microgrid. The adaptive setting group of islanded mode overcurrent protection will have to be more sensitive as compared to grid-connected mode considering the reduced fault current contribution of DERs in islanded Microgrid. The adaptive setting groups could be changed from one setting group to other based on the status of Microgrid connecting switches. The status of switches and thus Microgrid mode (grid-connected or islanded mode) information can be exchanged through for example IEC 61850 GOOSE communication protocol with centralized or decentralized communication architecture or through offline communication-less local measurements for example local voltage magnitude.
Aushiq Ali Memon, Hannu Laaksonen, Kimmo Kauhaniemi

Chapter 20. Fault Identification, Protection Schemes, and Restoration Requirements of Microgrids

Integration of distributed energy resources (DERs) in demand side territories ends in microgrid (MG) concept as a miniature version of traditional power grids, which facilitates realizing sustainable electrification. In this regard, power supply restoration, as an important issue in MGs, calls the need for meeting transient stability and fault ride-through (FRT) of DERs by devising apt protection systems and also enhancing fault detection and isolations solutions. By doing so, the unintentional disconnection of DERs is annihilated and continuity of electricity supply is preserved in MGs. Likewise, enhancing fault detection and isolations solutions offers fast and better restoration of MGs following probable events. Although contemplating restoration requirements in MG protection is of importance, it should be noted that the developed methods should be confined to inexpensive schemes with commercialized protective devices. Therefore, in this chapter, effective protection schemes are investigated for protecting MG based on commercialized protective devices with a special focus on restoration requirements. These schemes should be able to protect the network with a mesh structure, too. Accordingly, the challenges associated with direction detection, blinding issue, and possible mal-operations is met where techno-economic requirements are considered. If properly aligned with fault indicators, the existing protection devices could be jointly deployed for fast restoration of MGs, fast restoration of DERs, improving equipment health, and enhancing the reliability of MG.
Amin Yazdaninejadi, Amir Hamidi, Sajjad Golshannavaz, Daryoush Nazarpour

Chapter 21. Real-Time Testing of Microgrids

The need for clean energy for development and growth gave rise to power electronic interfaced local renewable generation and microgrids. Researchers across the world have been working on a spectrum of issues pertaining to the field of microgrids, ranging from control, operation and management aspects for the islanded, grid connected modes and the seamless transition aspects, to the protection and the power quality issues. These proposed solutions need rigorous testing under a wide range of dynamic conditions, before actual field deployment under diverse environments. Thus there needs to be a focus to develop fast, safe, accurate and reliable testing methods. Accuracy, flexibility, scalability, compactness, ease of implementation and economic viability are some of the common parameters which are used in the benchmarking of a testing methodology. These objectives are mostly in conflict with each other and thus need fresh out of the box solutions for the design and development of the testing methodologies. The chapter presents the fundamentals of and a comparison between the various testing techniques - ranging from off-line to real-time (RT) simulations, rapid controller prototyping, hardware in the loop (HIL): both the signal level (CHIL) and power level (PHIL), RT power level emulation, test-bed platforms, hybrid approaches/combinations of these techniques and novel solutions such as digital twin, blockchain and internet of things (IoT) based approaches. The future challenges in the area of microgrid testing are also discussed.
A. S. Vijay, Suryanarayana Doolla


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