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Micro-grid architecture design is the basis of the micro-grid construction. It is necessary to follow certain design principles when designing micro-grid architecture, which differs from traditional distribution network designing. This paper describes several micro-grid architecture design principles, taking into consideration in the partition and...
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... HMG combines AC and DC networks in the same DS through Interlinking Converters (IC) and has been conventionally implemented based on radial distribution schemes with satisfactory results [4]. However, the high 2 DER penetration can cause voltage increases [5]. High load demand can cause a significant voltage to decrease at the end of the line and, at the same time, overload distribution lines and connected transformers [6]; thus, voltage regulation is challenging, especially for long feeders [7]. ...
Smart Transformer (ST)-based Meshed Hybrid AC/DC Microgrids (MHM) are a feasible alternative to increase the performance of conventional microgrids (MG) and to increase the penetration of Distributed Energy Resource (DER) at the same time, active and reactive power dispatch on the system. Despite this, MHMs present challenges in managing resources under uncertainties and controlling electronic converters associated with the ST and DER, making it complex to achieve optimal system performance. In this paper, a Data-Driven Distributionally Robust Optimization (DDDRO) for Day-Ahead Operation Planning of an ST-based MHM considering the reactive power dispatch of the DER that minimizes network losses, voltage deviations, and operation cost simultaneously, considering uncertainties of Photovoltaic Generators (PVG) and demand, is proposed. The Column and Constraint Generation (C&CG) algorithm and Duality-Free Decomposition (DFD) method are adopted. Besides, the original mixed-integer non-linear planning problem is converted into a Mixed-Integer (MI) Second-Order Cone Programming (SOCP) problem through second-order cone relaxation and positive octagonal constraint method. Simulation experiments and results with a connected MHM system demonstrate the effectiveness and performance of the proposed model. Finally, we observe the effect of the meshed structure of MG and the positive impact of integrating the ST to form MHM, taking advantage of the degrees of freedom of this multi-stage converter for optimal energy management under uncertain conditions.
... In the AC-DC hybrid microgrid, the fundamental equipment for connecting the AC and DC sides is the interlinked power converter (ILC). According to the actual needs of the grid, the ILC can work in the rectifier or inverter mode [77,78,79]. It allows the power exchange between the AC and DC sides while maintaining the energy balance. ...
... It allows the power exchange between the AC and DC sides while maintaining the energy balance. References [78,79,80] propose an investigation on the influence of EVs on the of hybrid microgrids including storage systems. Reference [81] provides a review and classification of different hybrid AC-DC microgrid topologies. ...
This paper is an overview of fast charging for electrical vehicles. Specifically, it analyzes the impact of Ultra-Fast Charging Stations (UFCSs) on the distribution grid and their role in the smart grids. Moreover, the paper defines the framework of UFC, its diffusion and the associated new trends. The most frequently used converters in the conversion stages of DC charging stations with integrated generation are analyzed. To achieve this goal four active front end AC-DC converters (unidirectional and bidirectional), three isolated DC-DC converters as well as two control architectures are explored. In comparing the targeted configurations, the main target is set on categorizing them based on supply voltage level, type of smart grid, and power flow of the converters. Further, the paper outlines a broad overview of main standards for UFCSs and evaluation of the reliability, data collection, and operation of UFCSs. The paper aims to to link the needs of the designers of charging stations to preferences of the commercial market.
... MGs are small-scale EPSs consisting of hybrid RESs, ESSs, PCs, AC-DC buses, AC-DC loads, control units, system monitoring, and software interfaces [27]. They can operate in island mode and connected mode, where all grid setpoints are assumed [28][29][30][31][32][33][34][35][36][37][38][39]. Several national and international MG projects that consider different RESs have been successfully completed with generation capacities ranging from a few kW to hundreds of MW, as shown in Tables 1 and 2. A brief discussion of the different hybrid RES combinations is presented in these tables. ...
Microgrids (MGs) are systems that cleanly, efficiently, and economically integrate Renewable Energy Sources (RESs) and Energy Storage Systems (ESSs) to the electrical grid. They are capable of reducing transmission losses and improving the use of electricity and heat. However, RESs presents intermi ent behavior derived from the stochastic nature of the renewable resources available on site. This can cause power-quality issues throughout the electrical grid, which can be solved by different optimization techniques and/or control strategies applied to power converters. This paper offers a detailed review of the literature regarding three important aspects: (i) Power-quality issues generated in MGs both in islanded mode and grid-connected mode; (ii) Optimization techniques used in the MGs to achieve the optimal operating conditions of the Energy Management System (EMS); and (iii) Control strategies implemented in the MGs to guarantee stability, mitigation of power-quality issues, power balance, and synchronization with the grid. It is worth mentioning that in this paper, we emphasize hybrid MGs (HMGs) since they combine the benefits of AC-MGs and DC-MGs while increasing system reliability. As the utility grid moves toward an optimal design of MG structures, this paper will serve as a foundation for future research, comparative analysis , and further development of novel techniques regarding HMGs.
... The hybrid microgrid structure shown in Figure 3 is one of the possible topologies. Other structures differ in the way AC-DC microgrids are connected, using one or two static switches connected in parallel [55,61,62]. In addition, they can use power routers, solid-state transformers, and smallsized flexible AC transmission systems. ...
... Refs. [14,21,24,61] listed the following challenges faced by hybrid microgrids: ...
The development of AC distribution systems provides for the seamless integration of low-voltage microgrids with distributed energy resources (DERs). This poses new challenges for the control of normal, emergency, and post-emergency states of microgrids, calling for the creation and development of information and communications technology infrastructure. Power converters/inverters that are used to integrate renewable DERs lack inertia. Along with them, fossil fuel-fired generation units are also being integrated into microgrids. These include gas generator sets, diesel generator sets, and microturbines, having small (up to 1–2 s) values of mechanical inertia constants—Tj. This leads to an increase in the rate of transients by a factor of 5–10. Under these conditions, the technical requirements for the speed of automatic power flow control systems, as well as the methods they rely on, have to be reconsidered. Microgrids include DC microgrids, AC microgrids, and hybrid (AC-DC) microgrids. In the case of hybrid microgrids, DERs are connected to the DC grid and are integrated into the AC grid through a common inverter. The complexity of the task of microgrid control is due to the need to choose properly the type and extent of control actions so as to prevent the emergence and development of accidents. The employed control methods must ensure the reliable power supply to consumers and the quality of power in microgrids, as well as the reliable operation of the external distribution systems into which they are integrated. The article gives an overview of control methods for low-voltage AC and AC-DC microgrids, which allow one to tackle effectively solve the tasks.
... However, incorporating these elements into the common DC bus makes voltage control complex and power-sharing algorithms are necessary [17] [18]. AC/DC Hybrid Microgrids (HMGs) appear as a typology of great interest since they combine the main advantages of AC and DC MGs [16] [19] [20], with a high degree of reliability, flexibility, and economy [21]. This MG allows combining AC and DC networks in the same distribution network through Interlinking Converters (ICs), which helps the integration of DER, ESSs, AC/DC loads, and V2G with minimal DS modifications, reducing the overall cost [22] [16]. ...
... These MG configurations have been conventionally implemented based on radial distribution schemes with satisfactory results. However, they might show low reliability regarding power supply since DER can cause voltage increases and exceed the limit [19]. In contrast, high load demand can cause a significant voltage to decrease at the end of the line and, at the same time, overload distribution lines and connected transformers [23]. ...
Microgrids are considered an adequate alternative to overcome the challenges involving integrating distributed energy resources in distribution systems to contribute to the ’Three D’ trend in the electricity sector, i.e., decentralize, decarbonize, and digitize electricity. This paper reviews the most relevant works to establish a baseline for the advancement and development of smart transformer-based meshed hybrid microgrids and energy management systems. First, the structure of the solid-state transformers as smart transformers and their potential application as an energy router in a microgrid is discussed. Then, the principle of conformation of meshed hybrid microgrids based on a smart transformer and the topologies reported in the literature are reviewed. Finally, power management systems integrated into smart transformers-based meshed hybrid microgrids are studied. According to the findings and conclusions, it is considered that smart transformers-based meshed hybrid microgrids operated by an optimal energy management system under uncertainty are a potentially feasible technological alternative for the adequate penetration of distributed energy resources into local distribution systems.
... Various architectures for renewable rich microgrids are studied in [7]. Though a lot of research has been carried out for DC/DC microgrids due to increasing penetration of renewables and battery energy storage systems (BESS), it is not a suitable solution for AC dominated electric utility grid in Singapore [8]. ...
... Though a lot of research has been carried out for DC/DC microgrids due to increasing penetration of renewables and battery energy storage systems (BESS), it is not a suitable solution for AC dominated electric utility grid in Singapore [8]. Hybrid AC/DC microgrid structures and their implementation have been studied over the past few years [7], [9], [10], and they provide a suitable solution for a cluster-of-commercialbuildings microgrid due to financial and power conversion efficiency related benefits, as repeated DC/AC and AC/DC conversion requirements can be eliminated. ...
... Compared to the single-ring, multiple-ring, complimentaryring and feeder type AC/DC hybrid microgrid structures [7], the typical hybrid microgrid stucture with intermediate tieconverters, as shown in Fig. 1 provides a better solution due to low complexity of interconnection and operation, as well as better reliability in case of grid contingency events. The authors have demonstrated a testbed experimental setup for such a hybrid microgrid and the benefits are explained in [11], [12]. ...
... Selection of an appropriate DCMG topology is very important as it influences the vital aspects of an EPS, such as robustness, reliability, resiliency, controllability, flexibility, and cost of the project [30][31][32]. The voltage level required for the system under development is a crucial factor while making a choice on the DCMG topology to be deployed. ...
This article presents an up-to-date systematic review of the status, progress, and upcoming advancement regarding DC-microgrid. In recent years, the attention of researchers towards DC-microgrid has been increased as a better and viable solution in meeting the local loads at consumers' point while supplementing to stability, reliability, and controllability of a given power system. The topology, configuration, protection challenges, and issues with DC- microgrid are very much different compared to those of AC-microgrid. Moreover, the grounding requirement and its configuration are also playing an important role in DC-microgrid compared to AC-microgrid. Therefore, a separate study on DC-microgrid with a 360⁰ angles of view is necessary. In this regard, this paper has tried to accumulate all recent advancements on the DC-microgrid domain in addition to traditional deeds. By this process, the authors have adopted a review strategy comprised of few specific tasks, for example (i) preparation of article database related to microgrid protection; (ii) designing inclusion/exclusion criteria to filter out the required and important articles (iii) analysing each articles based on critical viewpoints. In general, this article presents an extensive survey and analysis of methods proposed by different researchers dealing with DC microgrid protection and grounding issues. At the end, this article has also suggested a few recommendations and questions regarding future studies. We hope that the outcomes of this review paper will definitely help the readers working on a similar domain and found to be an encouraging research field.
... Power network systems affect other aspects, such as maintenance costs, robustness, durability, device management and hierarchy, efficiency , quality, resource use and market versatility [18][19][20][21][22].Specific basic considerations should be taken into account in determining the configuration of the IOP Publishing doi:10.1088/1757-899X/1070/1/012098 4 network, i.e. effects on the environment, capacity accessible at various stages, optimal usage of energy and possible scalability [23][24].A variety of topologies have been documented in the literature and it is observed that six styles of structures may cover almost all structures [25]. ...
In the evolving era, microgrid wins the heart in all power fields. Among that DC
configuration achieved more demand because of its less complex structure, low cost, more
reliability and more power quality and last but not the least the control scheme is less complex
than AC microgrid. Management of power and energy are the evolving traits adopted by
researchers now a days. This paper mainly aims at the comparative analysis of different
topologies, structure, and operational mode of DC microgrid. Despite the global energy crisis
and the increasingly atmospheric pollution, distributed generation integration with renewable
energy is becoming a potential trend in technology. Finally, attention has been paid to the recent
challenges to the DC microgrid system.
... MGs have become the latest attraction in the scientific community not only because of its ability of integrating the distributed generation into the Main Grid in a reliable and cleaner way (with the reduction of emissions), but also due to its high reliability and capacity to operate before natural phenomena. Consequently, MGs provide active distribution grids, less energy losses in transmission and distribution (T&D) and less time in its construction and investment [1,6,11,12]. ...
... Figure 2 lists a summary of different topologies used in MGs. As shown, the MGs operate in parallel to the main electrical grid, in islanded mode (autonomous power) and in interconnected mode (uses the Main Grid reference) [1,3,6,9,11,24,27,32,42,43,44,45]. ...
Microgrids (MG) treat local energy supply issues effectively and from a point of view of the distribution grid, may be a power supply or virtual load. Despite holding a myriad of benefits, MGs also bear a set of challenges, including a higher fault rate. Currently, many articles focus on control techniques; however, little has been written about the techniques of control, hierarchical control, and fault-tolerant control (FTC) applied to MGs, which is the motive of this bibliographic revision on control systems. A brief comparison of the different approaches in the field of present-day research is carried out primarily addressing hierarchical control and fault tolerance. The objective of this investigation is to attract the interest of researchers to the field of control and fault tolerance applied to MGs, such as: modeling, testbed, benchmark systems, control and hierarchical control strategies, fault diagnosis and FTC.
... In the first architecture, the secondary side of the step-down transformer is used as a common AC bus where each load is connected to the bus via independent AC/DC stages. In the second architecture, a single AC/DC stage is configured to provide a common DC bus service for the system load [21,22]. ...
... Thus, this chapter presents an overview of various configurations of charging stations and control topologies that can be utilized for the proper management of EV charging stations. 21 This chapter has three main objectives: (i) to determine the applicability of the common alternating current (AC) and direct current (DC) bus system in the EV charging stations; (ii) to analyze the integration of renewable energies into the charging systems (such as solar charging systems), the overall control and management framework, and the methods that can be employed including their impediments and sustainability; (iii) to identify the large-scale interaction of EVs with the grid and their charging schedule mechanisms. ...
... In [21,102], the influence of EVs on the internal characteristics of the micro-grid and the storage system has been investigated under the hybrid micro-grid structure. [57,103], have been examined the battery SoC and the random charging demand of the EV user. ...
Higher penetration of electric vehicles (EV) and plug-in hybrid electric vehicles requires efficient design of charging stations to supply appropriate charging rates. This would trigger stress on conventional grid, thus increasing the cost of charging. Therefore, in this scenario the use of on-site renewable sources such as photovoltaic (PV) energy alongside to the conventional grid can increase the performance of charging station. In this thesis, a PV source is used in conjunction with grid to supplement EV load. However, the PV is known for its intermittent nature that is highly dependent on geographical and weather conditions. So, to compensate the intermittency of PV, a battery storage system (BSS) is combined with the PV in a grid-tied system, providing a stable operation of hybrid PV based charging station.Generally, hybrid sources based charging station should be cost effective, efficient, and reliable to supplement the variable needs of EVs load in different scenarios. In this thesis, efficient hierarchical energy management strategy is proposed and applied to maximize on-site PV energy, to meet the variable load of EVs using quick response of BSS and putting less stress on grid. This strategy overall improves the performance and is reliable and cost-effective.An efficient bidirectional power conversion stage is introduced for BSS in the form of interleaved buck-boost converter to ensure the safe operation of BSS and reduce the losses during conversion stage. This topology has characteristics to improve the current ripples and therefore, increase the power quality drastically. Similarly, to extract the maximum power from PV system under intermittent weather conditions, MPPT is used alongside with interleaved boost converter to ensure the continuity of power from PV source. Similarly, for vehicles charger stage, to meet the dynamic power demands of EVs; while, keeping the balance between available generation amounts, interleave converter is proposed combined to sub-management strategy. Particularly, this conversion stage and management addresses the low utilization of grid sources for charging purpose when, peak load is present at grid side. This charging behaviour greatly decreases the stress on grid especially at peak hours and therefore, improves the performance of system in overall.To operate whole system under desirable conditions, an online energy management strategy is proposed. This real-time strategy works in hierarchical manner, initializing from maximized utilization of PV source, then using BSS to supplement power and utilizing grid during intermittent conditions or when there is low amount of PV. The management strategy ensure reliable operation of system, while maximizing the PV utilization, meeting the EVs demand and maximizing the life the BSS.In this thesis, a hybrid charging system based on PV, BSS and conventional grid is proposed to support the needs of EVs load. Efficient energy conversion stage has been proposed using interleave buck-boost converters to improve the quality of power and at the end, an online management strategy is developed to maximize the renewable energy utilization, inserting lesser stress on grid and improving the utilization of BSS to improve its life.
