Hasil untuk "Distribution or transmission of electric power"

Mohammed N. Khamees, Kai Sun

The primary goal of Optimal Power Flow (OPF) is to optimize the operation of a power system while meeting the demand and adhering to operational constraints. This paper presents a new approach for AC OPF. First, the approach constructs a Voronoi diagram by distributing multiple sample points representing potential solutions throughout the search space. Then, it recursively adds new sample points including a tentative optimal point from the continuous gradient-projection method, a point in the most sparsely populated region to ensure high fidelity, and the connecting point, until the stopping criterion is met. The proposed approach is illustrated in detail using the IEEE 9-bus system and then validated on the IEEE 39-bus and 118-bus systems to verify the quality of the obtained solution.

Mohamad Nassereddine

Easir Arafat, Babak Porkar, Mona Ghassemi

As global electricity demand continues to rise, innovative transmission line designs are being developed to enhance efficiency and reliability. Recent studies emphasize the urgent need for advanced structures that improve transmission capabilities. In this context, optimally designed unconventional lines with higher natural power emerge as potential game changers. Various electrical, mechanical, and structural aspects must be studied for a new overhead line design. Among them, evaluating these new transmission line designs against established safety standards is crucial, particularly concerning low-frequency (50 or 60 Hz) electric fields generated under these new lines. This paper comprehensively analyzes the electric fields generated by conventional and unconventional overhead transmission lines. By calculating the electric field for each sub-conductor individually, we offer a detailed comparison highlighting the differences in field distribution between these two line types. Our findings indicate that the unconventional transmission lines exhibit a more favorable electric field profile and comply with current exposure limits set by regulatory agencies. This research underscores the potential of unconventional designs to improve safety and minimize environmental impact while addressing the challenges posed by increasing electricity demands.

Lina He, Shiwen Yu

Existing grid-forming inverter control schemes for distributed energy resources (DERs) primarily rely on active power (P)-frequency (f) and reactive power (Q)-voltage (V) droop mechanisms that are tailored for highly inductive transmission grids. However, in weak distribution grids where P and Q are highly coupled due to their resistive network characteristics, these control schemes cannot provide independent and accurate f and V regulation. This will further deteriorate the dynamic and stability performance, potentially resulting in inverter and load tripping during disturbances. To address this challenge, this paper proposes an innovative decoupling grid-forming control scheme, which is designed based on a systematic perspective that considers the inherent coupling characteristic of the entire distribution grid. The small-signal stability of the proposed controller is analyzed by varying controller parameters and the grid strength. The effectiveness of this controller is comprehensively verified using both MATLAB and OPAL-RT platforms by comparing it with existing grid-forming control strategies. The results show that the proposed controller can effectively decouple P and Q regulation in weak distribution grids. It enables DERs to provide independent, accurate, and autonomous f and V regulation, thus improving grid stability and dynamics. The proposed control strategy is cost-effective, communication-free, and can be easily commercialized due to its straightforward and robust circuit design.

Mattia Deriu, Michela Migliori, Corrado Gadaleta et al.

Abstract The diffusion of offshore wind power plants (OWPPs), useful to fulfil renewable diffusion policy targets, implies several technological challenges for integration in power transmission network. The definition of the OWPP connection to the transmission network affects possible exploitation of the assets, involves an evaluation of active power losses and loadability and points out the need for compensation devices, in order to comply with connection rules fixed by the grid operator. This paper proposes a methodology to determine the most suitable electric connection for an OWPP based on high‐voltage alternating current (HVAC) cables, for providing indications for transmission system operators. In particular, different HVAC connection schemes for OWPPs are analysed, focusing on new 66 kV standard voltage and high‐voltage levels, providing technical insight on transmission cable optimal operation conditions. An economic analysis is carried out by proper estimation of construction costs and production forecast, accounting for active power losses and reliability impact. The most suitable connection solution depending on OWPP size and distance in Italian framework is evaluated by means of synthetic techno‐economic indicators, further analysing possible sensitivities of energy price and capacity factor.

Zhen Dai, Shouyu Liang, Yachen Tang et al.

The seamless integration of swift and precise topological analysis with state estimation is crucial for ensuring the dependability, stability, and efficiency of the power system. In response to this need, this paper introduced a novel approach to constructing a spatiotemporal “Power Grid One Graph” model using a graph database, enabling rapid topological analysis and state estimation. Initially, a spatiotemporal power grid model was created by merging grid topology with dynamically updated telemetry and telesignaling data. Subsequently, utilizing the graph model and entity mapping, the spatiotemporal node-breaker graph model was obtained and the corresponding bus-branch model was generated. Based on the node-breaker graph model, topological error identification was conducted, and a fast topological analysis optimization algorithm, considering component functionality, was applied to update the bus-branch graph model, facilitating graph-based state estimation. Finally, the proposed method was validated on a real power system, and its application, along with performance enhancements of the spatiotemporal power grid model considering topological changes, was investigated. The presented method provides both theoretical and practical support for the digital transformation of the power system and the advancement of the digital twin power grid.

Arslan Ahmad, Ian Dobson

We focus on large blackouts in electric distribution systems caused by extreme winds. Such events have a large cost and impact on customers. To quantify resilience to these events, we formulate large event risk and show how to calculate it from the historical outage data routinely collected by utilities' outage management systems. Risk is defined using an event cost exceedance curve. The tail of this curve and the large event risk is described by the probability of a large cost event and the slope magnitude of the tail on a log-log plot. Resilience can be improved by planned investments to upgrade system components or speed up restoration. The benefits that these investments would have had if they had been made in the past can be quantified by "rerunning history" with the effects of the investment included, and then recalculating the large event risk to find the improvement in resilience. An example using utility data shows a 12% and 22% reduction in the probability of a large cost event due to 10% wind hardening and 10% faster restoration respectively. This new data-driven approach to quantify resilience and resilience investments is realistic and much easier to apply than complicated approaches based on modeling all the phases of resilience. Moreover, an appeal to improvements to past lived experience may well be persuasive to customers and regulators in making the case for resilience investments.

Le Zheng, Jiajie Zheng, Chongru Liu

This paper presents a Generalized Modal Analysis (GMA) concept for the small-signal stability analysis of power systems with high penetration of Converter-Interfaced Generation (CIG). GMA quantitatively assesses interactions between various elements in the power system, offering intuitive and transparent physical interpretations. The method's versatility in selecting physical quantities at different input and output ports makes it broadly applicable. Based on the concept of GMA, the study further defines interaction quantification indices by selecting voltage ports, examining the impact of grid disturbances on power sources and the support from the power sources to the grid at connection points. Numerical simulations on modified 14-bus and 68-bus systems validate GMA's effectiveness in capturing the coupling of the dynamic characteristics between grid elements. This research provides a theoretical foundation and analytical framework for future analyses of power system stability with diverse power sources.

Lusha Wang, J. Kwon, N. Schulz et al.

Electric vehicles (EVs) are becoming a promising source of grid ancillary services due to the temporal and spatial charging flexibility, quick response and storage capability. Such advantages are increasing with government policy promotion and technology improvement. However, the exploration of EV flexibility requires the coordination of both transmission system operators (TSOs) and distribution system operators (DSOs), to ensure the safe and reliable operation of power network. In this paper, we propose a coordinated evaluation method that determines the optimal utilization of EV temporal flexibility without compromising EV owners’ usage. At the distribution level, DSOs first evaluate EV aggregators’ operational boundaries to exploit distribution level services. At the transmission level, TSOs then determine EV charging schedules and ancillary service capacity simultaneously, taking into account the requirement from DSOs. We validate the model in a case study using the IEEE 123 node test feeder and EV charging sessions obtained from a transportation simulation tool that uses real-world data.

Zhaotian Yan, H. Xie, Yong Li et al.

The domino-resonator wireless power transfer system is designed in this work to harvest energy from the magnetic field around a 110-kV high voltage transmission line and supply power to the online monitoring device continuously over 1.1 meters insulation distance. Each domino resonator is evenly spaced and is embedded inside sealed insulation discs. The theoretical analysis shows that the constant voltage (CV) mode and the constant current (CC) mode can be realized by adjusting the receiver's switch state, which can meet the battery's CV and CC charging requirements. Such a method cancels the communication between the transmitter and the receiver. The finite-element simulation results show that the influence on the electric and magnetic field intensity distribution near the insulator can be negligible. Finally, a 30 W prototype with an output voltage of 7 V is built. The experimental results show that the fluctuation of output voltage (CV mode) and output current (CC mode) is less than 6% and 7%, respectively. The maximum efficiency is higher than 40% when the transmission distance is 1.1 m, and the number of coils is 12.

P. Reddy, M. S. Gupta, S. Nundy et al.

The photovoltaic (PV) system is one of the most promising technologies that generate benevolent electricity. Therefore, fossil fuel-generated electric power plants, that emit an enormous amount of greenhouse gases, can be replaced by the PV power plant. However, due to its lower efficiency than a traditional power plant, and to generate equal amount of power, a large land area is required for the PV power plant. Also, transmission and distribution losses are intricate issues for PV power plants. Therefore, the inclusion of PV into a building is one of the holistic approaches which reduce the necessity for such large land areas. Building-integrated and building attached/applied are the two types where PV can be included in the building. Building applied/attached PV(BAPV) indicates that the PV system is added/attached or applied to a building, whereas, building integrated PV (BIPV) illustrates the concept of replacing the traditional building envelop, such as window, wall, roof by PV. In India, applying PV on a building is growing due to India’s solar mission target for 2022. In 2015, through Jawaharlal Nehru National Solar Mission, India targeted to achieve 100 GW PV power of which 40 GW will be acquired from roof-integrated PV by 2022. By the end of December 2019, India achieved 33.7 GW total installed PV power. Also, green/zero energy/and sustainable buildings are gaining significance in India due to rapid urbanization. However, BIPV system is rarely used in India which is likely due to a lack of government support and public awareness. This work reviewed the status of BIPV/BAPV system in India. The BIPV window system can probably be the suitable BIPV product for Indian context to reduce the building’s HVAC load.

B. Ardila, E. Soto, J. Zamora

V. Torres-Garcia, N. Solis-Ramos, N. Gonzalez-Cabrera et al.

Nowadays, many modern electrical power systems are designed for transmission and distribution using underground systems. Such systems minimize visual impact, reduce congestion, and increase security and reliability. However, the technology utilized has increased the capacitance effect, which can lead to the system being more susceptible to the occurrence of the ferroresonance phenomenon. Ferroresonance can cause dielectric or thermal damage and consequently makes the system susceptible to faults in the electrical power equipment and installations. This paper analyzes the ferroresonance phenomenon after switching maneuvers in a real underground distribution feeder to detect possible conditions of ferroresonance. The analysis is carried out in a typical underground distribution system with distribution transformers connected in wye-grounded/wye-grounded (Ynyn), and modeled using the ATP/EMTP software.

Sasan Pirouzi

Abstract Energy management of a virtual power plant (VPP) that consists of wind farm (WF), energy storage systems and a demand response program is discussed in the present study. The introduced strategy is realized at the electrical power transmission level and takes into account the collaboration between VPPs in day‐ahead energy and reserve markets. One notable feature of the proposed strategy is attempting to make the revenue of VPPs close to the operating cost of generating units as much as possible. The objective function is subjected to the network‐constrained unit commitment model, up and down reserve requirements and the proposed VPP constraints. This method is taking into account the uncertainty in system and VPP loads, day‐ahead market energy and reserve price and WF power generation. This strategy is applied as hybrid stochastic‐robust scheduling to the VPP at the electrical power transmission level, where the scenario‐based stochastic programming models the uncertainty of day‐ahead market prices, and the bounded uncertainty‐based robust optimization has been adopted to model the uncertainties related to the load and WF power. Scheme has been tested on IEEE systems. According to the obtained results, the proposed coordination of VPPs in the mentioned markets demonstrates capability of suggested strategy.

Hamed Jalalat, Sahand Liasi, Mohammad Tavakoli Bina et al.

Abstract Various Flexible Alternating Current Transmission System (FACTS) devices are used to improve the power quality and reliability of power system. In addition to the technical constraints, the installation and maintenance costs limit the exploitation of such devices. To maximize the efficiency of FACTS, the least possible number of devices must be placed optimally in the network. In this vein, many types of research have been conducted to offer optimal placement solutions. Although these methods lead to optimal placement, they usually suffer from a huge amount of computational burden. Therefore, here, an intelligent optimal placement approach is presented, focusing on reducing computational volume. For this aim in the suggested method, the monitoring buses are limited, while monitoring other buses is carried out using an estimation approach. To avoid increasing calculations for this selection, applying the worst fault condition instead of all fault types, the least number of monitoring buses are selected. Moreover, high‐risk zones are indicated for each monitoring bus so that by applying different fault conditions in only these areas, the study is conducted, which results in an additional decrement in computational burden. Finally, the optimal placement problem is solved by employing the genetic algorithm.

Badrzadeh Babak, Matevosyan Julia, Emin Zia et al.

Abstract Power systems around the world are rapidly transitioning to much higher shares of inverter‐based resources (IBRs) with few synchronous generators remaining online. IBRs and synchronous generators have fundamentally different dynamic performance characteristics resulting in a difference in the overall power system dynamic performance. IBRs are generally more flexible and controllable than synchronous generators; however, at the same time they exhibit significantly more complex control systems. Furthermore, new and emerging capabilities are being developed progressively and in particular the so‐called grid‐forming inverters (GFM). GFM offer several new capabilities not previously possible with conventional grid‐following inverters (GFL). However, they are not well understood currently when applied in a mega scale and moving forward when they will likely take over the role synchronous generators have been performing for several decades as the workhorse of system security support. Key questions currently in the technical community include the extent to which GFM shall be similar or different to each of the synchronous machines and conventional GFL, and how various control strategies can assist in maximising the grid support capabilities sought and minimise or ideally eliminate any adverse impacts. The objective of this special issue is to provide insights into some of these unknowns.

Rahmat Khezri, Salah Bahramara, Amin Mahmoudi

Abstract Cloud energy storage (CES) in the power systems is a novel idea for the consumers to get rid of the expensive distributed energy storages (DESs) and to move to using a cloud service centre as a virtual capacity. Although the different characteristics and applications of the energy storages are reviewed in some papers, there is no review study on the CES concepts, formulations, applications, and challenges. Therefore, the main contribution of this paper is to review the applications of the CES and its technical challenges in the power systems. For this purpose, the concept and fundamentals of the CES, as well as their role in supporting the consumers and the power network, are described first. The flow of information in a CES is then discussed, and the roles of the operator, consumers, and facilities, as the main sectors of the CES are explained. The existing studies are classified and discussed regarding the different applications of the CES in the power systems and their drawbacks are highlighted. The operation and planning (feasibility) problems of the CES are investigated. Reviewing the existing studies shows that comprehensive models are required to address the energy management (EM) and feasibility analysis of the CES applications. To address this challenge, the general formulations are presented for the planning and the operation scheduling problems of the CES. In addition, addressing different CES applications in the power systems leads to some technical challenges which are described. Finally, future directions are suggested for potential researchers to continue the studies on the CES integration and application.

Arash Dehghani, Mostafa Sedighizadeh, Farhad Haghjoo

Abstract The issue of resilience in electrical distribution systems has been proposed increasingly with the frequent occurrence of natural disasters in recent years and the imposition of high costs due to widespread power outages. To date, various resilience indices have been proposed, some of which have been improved upon over time by extensive research, leading to more comprehensive indices. However, a standard index has not yet been approved and presented in this regard by international committees, despite the efforts made. The issue of resilience in electrical networks was examined by curve analysis index in more detail compared to other proposed indices, although it is not yet complete and should be investigated from various aspects and its shortcomings be eliminated. The present study aims to evaluate some fundamental obstacles in the “curve analysis” index and correct it in a new index called “Combining Investment and Reform” (CIR) index. Two issues of “costs in terms of investment and repairs imposed by the event” and “need to separate critical and non‐critical loads” are considered simultaneously in the proposed index. Finally, the capabilities of the proposed index are evaluated and compared in a sample electrical network in the face of events with different intensities.

Chenglong Jia, Penghao Chu, Wenbin Zhao et al.

Abstract The gas‐insulated switchgear (GIS) is a vital component of a power system, and understanding the shock wave characteristics of its internal discharge is crucial to ensure the safe and stable operation of the entire system. In this study, a high‐speed shadowing technique is employed to obtain the shadowgraphs of a typical flow‐field evolution of sulfur hexafluoride (SF6) gas following the breakdown of a pin–plate gap inside a GIS. Experimental data were used to derive parameters, including the Mach number, propagation speed, distance of the discharge shock wave, and the temperature, pressure, density, and velocity of the SF6 gas after wave generation. With a 0.2‐mm discharge gap and 0.4‐MPa pressure, the discharge generates a spherical shock wave, centred at the contact between the discharge channel and electrodes, that propagates in all directions. The shock wave gradually weakens after 20 μs, propagating at near‐sonic speed, and its Mach number decreases from 2.92 to 1.15; similarly, its post‐wave parameters sharply decrease during the first 20 μs. Additionally, a significant reflection occurs when the shock wave propagates to the metal wall. The authors’ findings provide a valuable reference for detecting and diagnosing the internal discharge in GISs.

Muhammad Zubair Khan, Oleg E. Peil, Apoorva Sharma et al.

In the rapidly expanding field of two-dimensional materials, magnetic monolayers show great promise for the future applications in nanoelectronics, data storage, and sensing. The research in intrinsically magnetic two-dimensional materials mainly focuses on synthetic iodide and telluride based compounds, which inherently suffer from the lack of ambient stability. So far, naturally occurring layered magnetic materials have been vastly overlooked. These minerals offer a unique opportunity to explore air-stable complex layered systems with high concentration of local moment bearing ions. We demonstrate magnetic ordering in iron-rich two-dimensional phyllosilicates, focusing on mineral species of minnesotaite, annite, and biotite. These are naturally occurring van der Waals magnetic materials which integrate local moment baring ions of iron via magnesium/aluminium substitution in their octahedral sites. Due to self-inherent capping by silicate/aluminate tetrahedral groups, ultra-thin layers are air-stable. Chemical characterization, quantitative elemental analysis, and iron oxidation states were determined via Raman spectroscopy, wavelength disperse X-ray spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Superconducting quantum interference device magnetometry measurements were performed to examine the magnetic ordering. These layered materials exhibit paramagnetic or superparamagnetic characteristics at room temperature. At low temperature ferrimagnetic or antiferromagnetic ordering occurs, with the critical ordering temperature of 38.7 K for minnesotaite, 36.1 K for annite, and 4.9 K for biotite. In-field magnetic force microscopy on iron bearing phyllosilicates confirmed the paramagnetic response at room temperature, present down to monolayers.