1,721,130 research outputs found
Grid-Listening and Grid-Ringing: Alternative Concepts for Grid-Following and Grid-Forming within Power Systems Frequency Transients
Full text linkThe paper introduces the concepts of grid-listening and grid-ringing as alternative ways to interpret the classes of converter control commonly known as grid-following and grid-forming. The intrinsic nature of these two controls define their interaction within the frequency transients in power systems, and in particular with the disturbance propagation and the synchronization process. The grid-following interacts with the oscillations in the system just detecting them: for that, it can be regarded as grid-listening. The grid-forming interacts with the power-frequency oscillations contributing to them: for that, it can be regarded as grid-ringing. This conceptual revisiting is illustrated with a representative system, and further discussed with some examples on a benchmark power syste
Adaptive and dynamic Ant Colony Search algorithm for optimal distribution systems reinforcement strategy
No full textComparative Analysis of Charging Station Technologies for Light Electric Vehicles for the Exploitation in Small Islands †
Full text linkThe worldwide growing adoption of Light Electric Vehicles (LEVs) indicates that such technology might in the near future be decisive for improving the sustainability of transportation. The segment of LEVs has some peculiar features compared to electric mobility in general, which then deserve a devoted investigation. Stakeholders are called to implement the most appropriate technology depending on the context, by taking into account multi-faceted factors, which are the investigation object of this work. At first, a methodology is formulated for estimating the power and energy impact of LEVs recharging. Based on this, and assessed that the load constituted by LEVs is in general modest but might create some problems in lowly structured networks, it becomes conceivable to develop Charging Station (CS) technologies which are alternative to the grid connection at a point of delivery. Yet, it is fundamental to develop accurate methodologies for the techno-economic and environmental analysis. This work considers a use case developed at the University of Brescia (Italy): a CS operating off-grid, powered by PhotoVoltaics (PV). Its peculiarity is that it is transportable, which makes it more appealing for rural/remote areas or when the charging demand is highly not homogeneous in time. On these grounds, this work specializes to a context where the proposed solution might be more appealing: small isolated islands, in particular Favignana in Sicily (Italy). It is estimated that the adoption of the proposed off-grid CS is by far advantageous as regards the greenhouse gases emissions but it is more economically profitable than the grid connection only if the number of users per day is less than order of 200. Hence this work provides meaningful indications on the usefulness of off-grid CS powered by PV in peculiar contexts and furnishes a general method for their techno-economic and environmental assessment
A General Methodology for Short-circuit Calculations in Hybrid AC/DC Microgrids
Full text linkIn this paper, the issues related to short-circuit calculations in hybrid AC/DC microgrids are discussed. The reference standard for short-current calculations in DC systems is the IEC 61660, which provides a mathematical formulation of the problem. The standard only includes radial DC grids and does not consider a more complex system, such as meshed DC systems or a hybrid AC/DC microgrid. This paper proposes a generalized approach that can be used independently of the characteristics of the hybrid system. The proposed approach is applied to four test microgrids with different distributed sources and number of nodes and the results are compared with those obtained simulating the same grids with Neplan 360®
Legal Liability of Professional Engineers: The Case of a Fire at a Shopping Center
No full textIn this paper, the authors discuss the legal liabilities of the professional engineer as both the engineer of record of a project and the construction site manager. In particular, this paper analyzes the case of a fire at an end-user MV/LV substation of a shopping center in Italy, occurred a few years after maintenance works on the electrical installation. The professional engineer who had designed and overseen the construction of the substation was accused of criminal negligence. The authors through the examination of applicable technical standards, as well as of safety regulations, demonstrate that the professional engineer had acted diligently and that there was no ground for the negligence charges. The forensic analysis of the substation fire is provided, and the importance of the chain of custody, the chronological documentation, and the secure storing of all the artefacts and fire-damaged evidence are stressed. The authors believe that this paper can be a useful reference for electrical forensics engineers, investigating similar accidents
Forensic Analysis of Fire in a Substation of a Commercial Center
Full text linkIn this article, the authors discuss the legal liabilities of the professional engineer as both the engineer of record of a project and the construction site manager. In particular, this article analyzes the case of a fire at the end-user medium voltage-low-voltage (MV-LV) substation of a shopping center in Italy, which occurred a few years after the maintenance works on the electrical installation. The professional engineer who had designed and overseen the construction of the substation was accused of professional negligence. The authors through the examination of applicable technical standards, as well as of safety regulations, demonstrate that the professional engineer had acted diligently and that there was no ground for the negligence charges. The analysis of the substation fire is provided, and the importance of the chain of custody, the chronological documentation, and the secure storing of all the artifacts and fire-damaged evidence is discussed. The authors believe that this article can be a useful reference for electrical forensics engineers, investigating similar accidents
Energy Management System in Grid-Connected Small Scale AC/DC Microgrids Including Renewable Sources and Flexible Loads
No full textThe growth of small scale microgrids with diverse distributed generations has drawn attention to their effective energy management. In this paper, for various energy scenarios, an energy management system is adopted to minimize the energy purchased by a hybrid AC/DC microgrid from the upstream grid due to high peak-hour energy prices and maximise generation from renewable sources, while adjusting the most optimal charge/discharge control strategies for flexible loads such as electric vehicles and storage systems, and the supply of non-controllable loads. In addition, peak shaving is simultaneously implemented in this proposed model without considering minimum power deviation as an objective function. Simulation of the methodology on a real-world solar car park in the campus of the University of Palermo shows its effectiveness and practicality for microgrids operators
A stochastic approach for self-healing capability evaluation in active islanded AC/DC hybrid microgrids
No full textThis paper aims to implement a resilience assessment in AC/DC hybrid microgrids using a stochastic simulation approach. Self-healing measures including load shedding, control of distributed generation and flexible devices, like Energy Storage Systems (ESS) and Electrical Vehicles (EVs), are simulated to enable AC/DC hybrid microgrids to supply critical loads in islanded mode, assuming a disconnection of these microgrids from the main AC grid due to a fault. To perform this analysis, a two-stage process is proposed: first, a Monte-Carlo simulation-based stochastic approach is adopted to generate samples to simulate intermittent loads, power generation from Renewable Energy Sources (RESs), and fault occurs in the upstream grid; second, for each sample indicating islanded mode, a grid-connected daily Optimal Power Flow (OPF) is formulated in Mixed-Integer Linear Programming (MILP) form based on minimizing operation cost to withdraw the State of the Charge (SoC) of stationery and traction batteries and electrical vehicles before microgrids may go to islanded mode. Finally, resilience of islanded microgrids are evaluated through some indices. In addition, different strategies are considered for modeling the behavior of both two types of electrical vehicles V1G and V2G. Simulations results show distributed generation and flexible devices might improve resilience in islanded microgrids, optimal daily planning in grid-connected mode could affect it adversely though, due to the low energy available of flexible devices at the islanding moment
A Secure and Distributed Method for Energy Communities' optimal operation
No full textIn this paper, we represent a secure distributed method to allow collaboration between the users of an energy community while guaranteeing their privacy. By aggregation of distributed optimizers in users' property, members are enabled to choose their strategies to maximize their own benefit. The summation of players' strategies leads to a collective consumption behavior with associated reward and these collective actions of members are modified during consecutive rounds of a game depending on the others' strategies to reach the optimum point. The distributed scheme of this method splits the computational burden among all users and makes it appropriate to be implemented on low-cost devices. Furthermore, the proposed method gives the opportunity to the users to have their preferences beside the energy community's global objective. The assessment of the method on a 10-user Energy Community proves that after few rounds of the game, users reach an optimum equilibrium point that not only maximizes each users benefit, but also meets the community target
Short-circuit Calculations in Hybrid AC/DC Microgrids
Full text linkIn this paper, the issues related to short-circuit calculations in hybrid AC/DC microgrids are discussed. The reference standard for short-current calculations in DC systems is the IEC 61660, which provides a mathematical formulation of the problem. The standard only includes radial DC grids and does not consider a more complex system, such as meshed DC systems or a hybrid AC/DC microgrid. This paper proposes a generalized approach that can be used independently of the characteristics of the hybrid system. The proposed approach is applied to two test microgrids and the results are compared with those obtained simulating the same grids with Neplan 360
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