Islanded Network Research Articles

Krasovskii and shifted passivity based output consensus

Motivated by current sharing in power networks, we consider a class of output consensus (also called agreement) problems for nonlinear systems, where the consensus value is determined by external disturbances, e.g., power demand. This output consensus problem is solved by a simple distributed output feedback controller if a system is either Krasovskii or shifted passive, which is the only essential requirement. The effectiveness of the proposed controller is shown in simulation on an islanded DC power network.

Capacity Market for Distribution System Operator – With Reliability Transactions – Considering Critical Loads and Microgrids

Conventional distribution system (DS) asset planning methods consider energy only from transmission systems (TS) and not from distributed energy resources (DER), leading to expensive plans. Newer transactive energy DS (TEDS) asset planning models, built on capacity market mechanisms, consider energy from both TS and DERs, leading to lower-cost plans and maximizing social welfare. However, in both methods the cost of higher reliability requirements for some users are socialized across all users, leading to lower social welfare. In this article, a novel transactive energy capacity market (TECM) model is proposed for DS asset planning. It builds on TEDS incremental capacity auction models by provisioning for critical loads to bid and receive superior reliability as a service. The TECM model considers these reliability transactions, in addition, to selling energy transactions from TS and DERs, buying energy transactions from loads, and asset upgrade transactions from the network operator. The TECM model allows for islanded microgrids and network reconfiguration to maximize social welfare. The TECM model is assessed on several case studies, demonstrating that it achieves higher social welfare and a lower plan cost.

A cold island connectivity and network perspective to mitigate the urban heat island effect

Many studies have proposed strategies to mitigate the urban heat island effect from the perspective of landscape patches, yet few studies have mitigated the urban heat island effect from the perspective of cold island connectivity and network. This study proposes a new method (Combined cooling pattern) to connect cold islands: surface (Cooling sources) - line (Networks)- point (Cooling spaces, heating spaces). Initially, the cooling sources are identified by the morphological spatial pattern analysis method and connectivity analysis. Then, to enhance the connectivity of the cooling sources, we applied circuit theory to construct the cooling network and identify the critical nodes. Finally, three levels of cooling strategies are developed. Taking Wuhan as an example, the results show that 27 cooling sources, 58 cooling corridors, 69 cooling spaces and 26 heating spaces are identified. A regional cooling network should be constructed to mitigate the urban heat island effect, and effective cooling measures should be implemented in key node areas. The method adopted can provide new ideas for sustainable urban development and urban climate adaptation planning.

Pulse width dependent operations of a Ag2S island network reservoir

The rapid growth in demand for edge artificial intelligence increases importance of physical reservoirs that work at low computational cost with low power consumption. A Ag2S island network also works as a physical reservoir, in which various physicochemical phenomena contribute to a reservoir operation. In this study, we investigated its frequency dependence and found that diffusion of Ag+ cations in a Ag2S island, which has a relaxation time of about 100 μs, plays a major role when performance is improved. Modified National Institute of Standards and Technology (MNIST) classification task using an input pulse width of 100 μs resulted in the accuracy of 91%. Iterative operations up to 10 million cycles revealed a small enough standard deviation of output, suggesting a potential for practical use of a Ag2S island network as a reservoir.

Effective Utilization of Distributed Power Sources under Power Mismatch Conditions in Islanded Distribution Networks

The integration of distributed generation (DG) into a power distribution network allows the establishment of a microgrid (MG) system when the main grid experiences a malfunction or is undergoing maintenance. In this case, the power-generating capacity of distributed generators may be less than the load demand. This study presents a strategy for the effective utilization of deployed active and reactive power sources under power mismatch conditions in the islanded distribution networks. Initially, the DGs’ and capacitors’ optimal placement and capacity were identified using the Jaya algorithm (JA) with the aim to reduce power losses in the grid-connected mode. Later, the DG and capacitor combination’s optimal power factor was determined to withstand the islanded distribution network’s highest possible power demand in the event of a power mismatch. To assess the optimal value of the DG–capacitor pair’s operating power factor (pfsource) for the islanded operation, an analytical approach has been proposed that determines the best trade-off between power losses and the under-utilization of accessible generation. The test results on 33-bus and 69-bus IEEE distribution networks demonstrate that holding the islanded network’s load power factor (pfload) equal to pfsource during the power imbalance conditions allows the installed distributed sources to effectively operate at full capacity. As expected, the proposed strategy will assist the utility companies in designing efficient energy management or load shedding schemes to effectively cope with the power mismatch conditions.

Assessment of Voltage Fluctuations for Battery Storage Systems Providing Frequency Response Services

This paper investigates voltage fluctuations caused by the operation of battery energy storage (BES) units which provide frequency response (FR) and fast frequency response (FFR) services using a test network based on a typical part of the United Kingdom (UK) mainland system. This paper provides an overview of current FR/FFR services currently used in the UK, and a summary of their typical modes of operation. Using DIgSILENT Powerfactory, the paper introduces a simple frequency disturbance generator to mimic typical frequency disturbances that would occur in the UK network, and then subsequently uses a representative test distribution network to show how voltage disturbances associated with BES units can develop across the electrical network. The paper provides a contribution to knowledge by creating a systematic approach for assessing voltage disturbance and flicker concerns for BES units on island networks, using a simple control algorithm and novel frequency disturbance generator.

Ag2S island network reservoir that works with direct optical signal inputs

A physical reservoir that accepts direct light irradiation as input was developed using a Ag2S island network. Short-term memory and nonlinearity required for reservoirs are achieved by the diffusion of Ag+ cations in each Ag2S island and the growth of Ag filaments between Ag2S islands. We found that direct light irradiation to Ag2S islands changes local conductivity in a reservoir, which enhances the performance in short-term memory and nonlinearity of the reservoir. Using the effect, we performed a pattern classification of light that was irradiated to a Ag2S island network reservoir through a rectangular slit, which resulted in the accuracy of over 95%.

A Copula-Hammersley approach for probabilistic analysis of integrated power and heat networks

As the interaction between the electrical and district heating networks have been increased due to the wide utilization of combined heat and power units, the interest in providing an appropriate tool to analyze these integrated systems dramatically grows. Besides, the installation of renewable energy power plants, such as wind turbines, is increased because of their clean power generation. However, the amount of their generated power is uncertain since wind speed is not exactly determined. In this regard, deterministic approaches cannot be employed to solve the power flow problem, and it is necessary to use a probabilistic viewpoint. This paper presents a probabilistic power flow framework for the integrated power and heat networks based on a novel Copula-Hammersley technique. The proposed method is able to consider various system uncertainties along with the existed interaction between the heat and power networks to successfully solve the power flow problem. Simulations on a case study of Barry Island networks demonstrate the applicability and effectiveness of the proposed methodology. The superiority of this technique is verified by studying various indices and characteristics of the obtained results in comparison with some other conventional approaches. It is verified that the proposed technique reduces the average mean and standard deviation errors by approximately 45% and 72% compared to traditional methods, respectively. Furthermore, the efficiency ratio of the proposed approach is 15% higher than that of the conventional methods which shows that it is faster and more accurate than those techniques.

Multi-period optimal scheduling framework in an islanded smart distribution network considering load priorities

Multi-period optimal scheduling framework in an islanded smart distribution network considering load priorities

Adaptive Droop Control Strategy for Load Sharing in Hybrid Micro Grids

Energy management becomes essential when distributed energy sources such as solar, wind, and fuel cell are connected in a micro-grid. In this paper, using a combination of two powerful neural network tools and fuzzy logic, intelligentization, and adaptation of droop control along with voltage and current control as one of the most common methods of decentralized control is done. One of the essential features of this method is its fast performance and the need for telecommunication infrastructure. In this paper, we provide a comprehensive control system that enables proper operation in both upstream and island network modes for both AC and DC microgrids. The proposed method is simulated to evaluate its effectiveness. The proposed structure, by adapting the control system by ANFIS structure, can properly distribute power between distributed products in a brilliant way and without the need for operators and costly telecommunications infrastructure in the face of severe disturbances such as change. The state between the connection and the island or fault occurrence ensures the stability of both the AC and DC parts of the microgrid. The results show the effectiveness of the proposed method.

基于MSPA模型的新型城市热景观连通性分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于MSPA模型的新型城市热景观连通性分析 DOI: 10.5846/stxb202109172619 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 湖南省科技创新计划湖湘青年英才项目（2021RC3104）；湖南省研究生科研创新基金项目（CX20210895）；株洲云龙示范区生态廊道专项规划项目（HNHXZZ-20171109） Analysis connectivity of urban heat island in a new-type urbanization based on MSPA model Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于土地利用景观格局对城市热岛效应的影响研究较多，但准确识别对城市热岛效应具有重要影响的关键斑块和节点方面的研究亟待开展。以新型中小城市株洲云龙示范区为例，以城市热岛网络构建为切入点，应用形态学空间格局分析（Morphological Spatial Pattern Analysis，MSPA）与景观连通性模型识别城市发展进程中核心热景观斑块和关键节点，并分析其时空演变特征。研究结果表明：（1）2007-2018年云龙示范区热岛斑块趋于集中，热岛面积较研究初期有明显增加，从地表温度空间分布上体现为城区与周边农村的温度对比更加鲜明，表明城市化进程中建设用地呈聚集扩散趋势。（2）研究期间热岛核心区占热景观面积比最大，且比例有明显上升趋势。而边缘、支线、孤岛、桥接、环线以及孔隙形态类型面积占比均呈现出不同程度的下降趋势，表明热岛斑块之间聚集程度不断提高。（3）识别出景观连通度重要性值较高的前20热景观斑块，其中前3斑块的重要性值和面积占比较大，属于极重要与重要两个热岛核心斑块重要性等级，值得重点关注与优化。（4）对重要性值高的热岛核心区域可优先采取降温措施，可以打断节点之间连接减缓整个区域的热岛效应。本研究结果对我国中小城市规划和可持续发展具有重要的实践指导意义。 Abstract:Many previous studies have concerned with the effects of land use/land cover changes and landscape patterns on the urban heat island. However, accurate identification of key patches and nodes with high contribution to urban heat island need to be urgently studied. Using Yunlong Demonstration Zone of Zhuzhou, a new-type city, as the case study area based on morphological spatial pattern analysis (MSPA) and landscape connectivity model, this study constructed an urban heat island network to identify the spatio-temporal dynamic characteristics of core thermal landscape patches and nodes in process of urban development. The results showed that:(1) from 2007 to 2018, heat island patches tended to be concentrated in Yunlong Demonstration Zone, and the area of heat island increased significantly compared with the initial stage of the study. From the spatial distribution of land surface temperature, the contrast between urban area and surrounding countryside was more distinct. (2) During the study period, the area of heat island core class was the largest, and the area proportion showed an obviously rising trend. While the area proportion of edge class, branch class, islet class, bridge class, loop class and perforation class showed a decreasing trend to varying degrees, which was largely related to the increase of aggregation degree between heat island patches. (3) The top 20 thermal landscape patches with higher importance value of landscape connectivity were identified, and the importance value and area of the top 3 patches were relatively large, which should be deserved more attention and optimization. (4) Patch-based cooling measures adopted to avoid the connection between node could effectively alleviate the heat island effects in the whole region. The results of this study have important practical significance for the planning and sustainable development of small and medium-sized cities in China. 参考文献 相似文献 引证文献

Volt/Var control and energy management in non-interconnected insular networks with multiple hybrid power plants

This paper proposes a sensitivity-based optimization approach for the energy management and volt/var control of islanded networks powered by a thermal generator and several hybrid power plants (HPPs). Specifically, the method optimizes, in a 24-hour horizon, the active and reactive power of the HPPs, the output voltage of the thermal generator, as well as the settings of local voltage controllers e.g., step voltage regulators, capacitor banks, in order to minimize the generation cost of thermal generators and satisfy the following constraints: a) the technical limits of the diesel generators, b) the maximum direct penetration limits of the renewables, c) the state of charge limits of energy storage systems, d) the three-phase voltage limits of all the buses of the network. Simulations were executed in a modified islanded version of the IEEE 8500-node network, consisting of a diesel generator and multiple HPPs with various renewable generators and storage devices. According to the simulations, the proposed method minimizes the generation cost of diesel generators, while satisfying all the aforementioned technical constraints. In contrast to the existing optimization methods e.g., PSO, MINLP, which are practically inapplicable in large networks with a 24-hour optimization horizon, the proposed method presents very low computation time.

Quantum Coherence in Loopless Superconductive Networks.

Measurements indicating that planar networks of superconductive islands connected by Josephson junctions display long-range quantum coherence are reported. The networks consist of superconducting islands connected by Josephson junctions and have a tree-like topological structure containing no loops. Enhancements of superconductive gaps over specific branches of the networks and sharp increases in pair currents are the main signatures of the coherent states. In order to unambiguously attribute the observed effects to branches being embedded in the networks, comparisons with geometrically equivalent-but isolated-counterparts are reported. Tuning the Josephson coupling energy by an external magnetic field generates increases in the Josephson currents, along the above-mentioned specific branches, which follow a functional dependence typical of phase transitions. Results are presented for double comb and star geometry networks, and in both cases, the observed effects provide positive quantitative evidence of the predictions of existing theoretical models.

Utilization of Common DC Systems for Petrochemical Applications

For more than four decades, Adjustable Speed Drives (ASDs) have been used in petrochemical and other industrial applications. Many papers have been written about various applications and issues related to ASDs. This article will expand on previous papers and will look more specifically at the design considerations for low voltage (LV) high horsepower ASDs that reside on a common dc bus, expanding on application considerations for creating a large dc bus and the effects on the rest of the power system. This article will include a case study of a particular application having a diesel generator supplying an islanded network feeding multiple rectifiers with a common dc bus that spanned several hundred feet.

Modernization of Dense Wavelength Division Multiplexing (DWDM) Route Surabaya-Bangil To Increase Optical Network Capacity

Along with the increasing demand for data networks, on the Java island network traffic, especially the Surabaya - Bangil link, the operator increases the channel capacity by modernizing DWDM (Dense Wavelength Division Multiplexing) technology in its transmission equipment. At that time, the DWDM technology was DWDM 6800 with a maximum capacity of one port that could only accommodate 10 Gbit/s, while using DWDM 9800, the maximum capacity of one port could accommodate up to 100 Gbit/s. Modernization of DWDM 6800 to DWDM 9800 technology uses the cross-connect method so that it does not require many costs and can be done within a short duration of time so that network performance can be adequately maintained. As a result, after modernization, the network has sufficient reserves to cover demand for the next few years.

Examining the Asian American leadership gap and inclusion issues with federal employee data: Recommendations for inclusive workforce analytic practices.

In April 2021, a coalition of employee resource groups called the Federation of Asian American, Native Hawaiian, and Pacific Islander Network, or FAN, was established at the National Institutes of Health (NIH). The coalition aims to be a unifying voice that represents and serves these diverse communities. Discussion within the group centered around the persistent inequities and the lack of inclusion that the Asian American communities have long endured. Two common themes emerged from these discussions: (1) a leadership gap for Asian Americans in senior leadership and managerial positions, and (2) the everyday experience of exclusion. Asian Americans represent nearly 20% of the NIH permanent workforce yet make up only 6% of the senior leadership positions. These two issues reflect the sentiment that Asian Americans often feel invisible or forgotten in the discourse of structural racism and organizational inequities, especially in organizations in which they are numerically overrepresented. The purpose of this manuscript is to raise awareness of Asian American concerns in the federal workforce and how current employment and workforce analytic practices in this domain might contribute to the invisibility. To accomplish this goal, we will (1) describe relevant historical and contemporary contexts of Asian American experience undergirding their inclusion and visibility concerns; (2) present data analyses from available data sources to provide a deeper understanding of the Asian American leadership gap and lack of inclusion concerns; (3) highlight data availability and analytic challenges that hinder the ability to address the inequity and invisibility issues; and (4) recommend practices in data collection, measurement, and analysis to increase the visibility of this community in the federal workforce.

A Three-Phase Sensitivity-Based approach for smooth Line-Switching in islanded networks

This paper deals with a new smooth line-switching method that facilitates the network reconfiguration of islanded networks. Its distinct features include the ability to handle network asymmetries and to minimize the line current during the switching action. This is attained by developing a three-phase sensitivity-based method to determine the operating set-points of distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as to the negative- and zero-sequence currents of DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.

Islands of Connectivity [communications - networks and services

Stunning coastlines and verdant mountain scenery make the Cook Islands a popular tourist destination. This tourism industry has contributed to a decade of economic growth, and in 2021 the government of this nation in the South Pacific introduced the SMART Economy Initiative to create 'smart' island networks. Around the world, the Internet of Things (IoT) is used for energy metering, road traffic management, street lighting operation and environmental controls. Not all IoT nodes need the fast data transfer of a 5G network, and in the Cook Islands, the tropical and mountainous terrain means installation is not practical. LoRaWAN (long-range wide area network) technology was selected for the Cook Islands' Smart Island project. The low-power protocol uses the unlicensed industrial, scientific, and medical (ISM) frequency band for bi-directional communication.

Contingency reserve estimation of fast frequency response for battery energy storage system

The large-scale renewable energy integration faces a challenge of frequency stability due to low inertia in weak power grids. One solution to mitigate this issue is via the fast frequency response service provided by battery storage systems so that the overall grid response during a large power outage can be improved. The battery power reserve is crucial to ensure the frequency ancillary services provision. However, grid operators currently investigate the contingency reserve of batteries through inefficient processes, such as extensive simulations or trial-and-error methods. Therefore, this paper proposes a semi-analytical methodology to quantitively determine the minimum required battery power reserve for preventing under-frequency load shedding when a severe generation trip occurs. This minimum reserve is derived from the time-variant kinetic energy of a given dispatch case. Case study results of the Mexican network demonstrate that the calculated battery power reserve can provide a cost-effective fast frequency response for a real islanded network. The research outcomes offer valuable insights for battery management and grid ancillary services requirement estimation in the transition to power networks dominated by converter-interfaced renewable energy resources.

Modeling and Simulation of Basochhu Hydropower Plant: Islanding Operation Using Real-Time Performance Data

This paper presents the dynamic modeling and simulation of the 64 MW Basochhu Hydro investigation of its island mode operation and network restoration. A robust real-time simulation model is necessary to analyze the static and dynamic control and operating characteristics of hydropower plant, which can be empirically modeled based on real-time performance measurements. The schematic layout of the BHP from the reservoir (pond) to the turbine is divided into sub-components, each of which is represented by mathematical differential-integral equations. The composite model was then validated by comparing the simulated and real-time measured responses. The paper also examined the preliminary test results of island mode operation and restoration to grid connection. The midnight load of Thimphu was arranged for island operation taking into account of the minimal power disruption. At the instant of grid disconnection, the active power of the test unit fell freely from 13 MW to 9 MW, activating the deflector control instantly cutting off the water jets proportional to the power drop. The measurements and simulation results confirmed that the Basochhu Hydropower Plant has robust governor control systems, and it can withstand the island mode operation, and reliably feed the local load without the need for grid interconnection.