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Numrering	Referens	Omslagsbild	Hitta
1.	Ackermann, Thomas, et al. (författare) Distributed generation : a definition 2001 Ingår i: Electric power systems research. - 0378-7796 .- 1873-2046. ; 57:3, s. 195-204 Tidskriftsartikel (refereegranskat)
2.	Ackermann, Thomas (författare) Distributed resources and re-regulated electricity markets 2007 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 77:9, s. 1148-1159 Tidskriftsartikel (refereegranskat)
3.	Ahmad, Mohd Riduan, et al. (författare) Interference from cloud-to-ground and cloud flashes in wireless communication system 2014 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 113, s. 237-246 Tidskriftsartikel (refereegranskat)abstract In this study, cloud-to-ground (CG) flash and intra-cloud (IC) flash events that interfere with the transmission of bits in wireless communication system operating at 2.4 GHz were analyzed. Bit error rate (BER) and consecutive lost datagram (CLD) measurement methods were used to evaluate BER and burst error from 3 tropical thunderstorms on November 27, 28, and 29 during 2012 northeastern monsoon in Malaysia. A total of 850 waveforms from the electric field change recording system were recorded and examined. Out of these, 94 waveforms of very fine structure were selected which matched perfectly with the timing information of the recorded BER. We found that both CG and IC flashes interfered significantly with the transmission of bits in wireless communication system. The severity of the interference depends mainly on two factors namely the number of pulses and the amplitude intensity of the flash. The interference level becomes worst when the number of pulses in a flash increases and the amplitude intensity of pulses in a flash intensifies. During thunderstorms, wireless communication system has experienced mostly intermittent interference due to burst error. Occasionally, in the presence of very intense NBP event, wireless communication system could experience total communication lost. In CG flash, it can be concluded that PBP is the major. source of interference that interfered with the bits transmission and caused the largest burst error. In IC flash, we found that the typical IC pulses interfered the bits transmission in the same way as PBP and mixed events in CG flash and produced comparable and in some cases higher amount of burst error. NBP has been observed to interfere the bits transmission more severely than typical IC and CG flashes and caused the most severe burst error to wireless communication system.
4.	Ahmed, Kazi Main Uddin, 1989-, et al. (författare) Reliability Analysis of Internal Power Supply Architecture of Data Centers in Terms of Power Losses 2021 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 193 Tidskriftsartikel (refereegranskat)abstract The number of data centers and the energy demand are increasing globally with the development of information and communication technology (ICT). The data center operators are facing challenges to limit the internal power losses and the unexpected outages of the computational resources or servers. The power losses of the internal power supply system (IPSS) increase with the increasing number of servers that causes power supply capacity shortage for the devices in IPSS. The aim of this paper is to address the outage probability of the computational resources or servers due to the power supply capacity shortage of the power distribution units (PDUs) in the IPSS. The servers outage probability at rack-level defines the service availability of the data center since the servers are the main computational resource of it. The overall availability of the IPSS and the power consumption models of the IPSS devices are also presented in this paper. Quantitative studies are performed to show the impacts of the power losses on the service availability and the overall availability of the IPSS for two different IPSS architectures, which are equivalent to the Tier I and Tier IV models of the data center.
5.	Almas, Muhammad Shoaib, et al. (författare) Utilizing synchrophasor-based supplementary damping control signals in conventional generator excitation systems 2018 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 157, s. 157-167 Tidskriftsartikel (refereegranskat)abstract A supplementary function of Excitation Control Systems (ECSs) for synchronous generators is that of a Power System Stabilizer (PSS). The PSS implementation in these ECSs only allows the use of a limited type of pre-defined local input measurements and built-in PSS algorithms. To adapt existing ECSs to take advantage of synchrophasors technology, this paper proposes and implements a prototype wide-area damping controller (WADC) that provides synchrophasor-based damping input signals to existing ECSs. The developed WADC comprise (i) a real-time mode estimation module, (ii) synchrophasor’s communication latency computation module, and (iii) phasor-based oscillation damping algorithm executing in a real-time hardware prototype controller.Through Real-Time Hardware-in-the-Loop (RT-HIL) simulations, it is demonstrated that synchrophasor-based damping signals from the WADC can be utilized together with a commercial ECS, thus providing new options for selection of the best feedback signal for oscillation damping.
6.	Alvarez Perez, Manuel Alejandro, 1980-, et al. (författare) Reservoir-Type Hydropower Equivalent Model Based on a Future Cost Piecewise Approximation 2018 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 155, s. 184-195 Tidskriftsartikel (refereegranskat)abstract The long-term (LT) scheduling of reservoir-type hydropower plants is a multistage stochastic dynamic problem that has been traditionally solved using the stochastic dual dynamic programming (SDDP) approach. This LT schedule of releases should be met through short-term (ST) scheduling decisions obtained from a hydro-thermal scheduling that considers uncertainties. Both time scales can be linked if the ST problem considers as input the future cost function (FCF) obtained from LT studies. Known the piecewise-linear FCF, the hydro-scheduling can be solved as a one-stage problem. Under certain considerations a single segment of the FCF can be used to solve the schedule. From this formulation an equivalent model for the hydropower plant can be derived and used in ST studies. This model behaves accordingly to LT conditions to be met, and provides a marginal cost for dispatching the plant. A generation company (GENCO) owning a mix of hydro, wind, and thermal power will be the subject of study where the model will be implemented. The GENCO faces the problem of scheduling the hydraulic resource under uncertainties from e.g. wind and load while determining the market bids that maximize its profit under uncertainties from market prices. A two-stage stochastic unit commitment (SUC) for the ST scheduling implementing the equivalent hydro model will be solved.
7.	Archetti, Joao Antonio Guedes, et al. (författare) Real time validation of a control system for microgrids with distributed generation and storage resources 2023 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 223 Tidskriftsartikel (refereegranskat)abstract Faced with a scenario in which the increase in renewable energy generated near consumer centers can cause problems for the operation of the electrical network, the present work proposes a real-time simulation model for automation and control systems of electrical distribution networks with microgrids, distributed generation, and storage resources. The proposed model consists of a hardware-in-the-loop control with the aid of a simulation tool in conjunction with a Real-Time Digital Simulator (RTDS) and considers the dynamic behavior of switched elements and inverters. A communication platform using TCP/IP protocol between RTDS (power system) and MatLab/Simulink (optimization algorithms) allows the operation of the network in grid-connected and islanded mode, guaranteeing the computational time for experimental implementation. For the first mode, an algorithm is proposed to solve an optimal dispatch energy storage system problem. Second mode, an algorithm is proposed to solve a load shedding problem. The objective is to operate the microgrids optimally and evaluate the performance of a storage system based on real data from the state of Parana, in Brazil. Results show that the optimization algorithms are experimentally applicable, obtaining reasonable computational time to find optimal solutions and an assertive decision-making to meet the objectives. Thus, the proposed framework is a potential tool to validate algorithms for active management of microgrids in real-time simulation.
8.	Armendariz, Mikel, et al. (författare) Comparative Study of Optimal Controller Placement Considering Uncertainty in PV Growth and Distribution Grid Expansion 2018 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 155C, s. 48-57 Tidskriftsartikel (refereegranskat)abstract Distributed generation (DG) and especially grid-connected residential photovoltaic (PV) systems areemerging and high penetration levels of these can have an adverse impact on several low voltage (LV)distribution grids in terms of power quality and reliability. In order to reduce that effect in a cost-effectivemanner, the traditional distribution grid planning process is being reengineered by incorporating the gridcontrol operations and considering the uncertainties e.g., DG power, demand and urban/rural expansionplans. One of the challenges is to determine if the required technology deployment to operate the gridscan provide a better solution in terms of quality and cost than the traditional approach, which is prin-cipally based on cable reinforcement and change of transformers. In addition, if controllers were to bedeployed, it would be important to determine where they should be placed and at what stage of theexpansion planning, especially when the planning is assumed to be non-deterministic.Therefore, following this situation, in this paper we propose an optimal way to deploy and to operateutility’s controllable resources at the distribution grid and additionally we consider the uncertaintiesrelated to PV growth and distribution grid expansion. Thus, we include the non-deterministic multistageperspective to the controller placement problem. Furthermore, we perform a techno-economic analysis ofthe results and we show that an optimal controller placement allows removing the overvoltage problemsarising in the LV grid in a more cost-effective way compared to a typical traditional grid reinforcementapproach.
9.	Asef, P., et al. (författare) Load identification of different Halbach-array topologies on permanent magnet synchronous generators using the coupled field-circuit FE methodology 2018 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 154, s. 484-492 Tidskriftsartikel (refereegranskat)abstract In this paper, the influence of gap consideration on load identification under various Halbach-array-based topologies (HABOs) is investigated while the system is on-duty. The load characteristics of a radial flux generator with closed-slots and the exterior rotor topology is discussed, where the effect of eddy-currents are observed. This comparative study deals with the consideration of the combined moment of inertia calculation that demonstrates how electromagnetic-based post processing calculations are estimated without the aid of nominal machine parameter values. The analysis was performed using a 2-D finite-element simulation of different HABOs with the gap consideration between the segments. Additionally, a comprehensive comparison with no gap is considered. Also, the dynamic analysis using an uncontrolled conventional rectifier model is used to derive effected key output parameters such as torque, output power, power factor, and line-to-line voltage. The major objective of the study is to determine corresponding load results in order to employ the most suitable and capable magnetization topology from the load perspective in the PM synchronous generator (PMSGs). Accordingly, the maximum power (MP) point was carried out to maximize the output DC power. With respect to the combined moment of inertia estimation, the load parameter estimation is verified experimentally on a surface-mounted PMSG using different magnetization topologies. Furthermore, commercial and environmental issues of the project are considered to reduce CO2 emissions as part of green power generation development.
10.	Babazadeh, Davood, et al. (författare) Selection of DC Voltage Controlling Station in an HVDC Grid 2016 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 144, s. 224-232 Tidskriftsartikel (refereegranskat)abstract This paper proposes a real-time quantitative evaluation of HVDC converters’ in an HVDC grid to select the suitable DC slack converter. This real-time evaluation considers the strength of connecting AC grid and the converter's on-line capacity margin as selection metrics. The strength of AC grid is evaluated in real-time by the estimation of grid short circuit capacity using recursive lease square algorithm. Given these selection metrics, the credibility of HVDC stations in controlling the DC voltage can be offered to the system operator in real-time for further operational decisions. This paper also studies the practical aspect of the estimation algorithm regarding selection of the operating points. As major contribution, it suggests to intelligently use a naturally occurring droop response in HVDC grids as a second operating point in the estimation algorithm to calculate the short circuit capacity. The method has been tested through set of scenarios using a real-time co-simulation platform. This platform includes real-time power system simulator to model AC/DC grid, industrial HVDC controllers and corresponding ICT systems. The results show that the proper selection of DC slack station can improve the AC system response and DC voltage drops during disturbances.
11.	Babazadeh, Davood, et al. (författare) Study of Centralized and Distributed Coordination of Power Injection in Multi-TSO HVDC Grid with Large Off-shore Wind Integration 2016 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 136, s. 281-288 Tidskriftsartikel (refereegranskat)abstract This paper studies centralized and distributed schemes for the coordinationof power injection in an HVDC grid connected to large wind generation.This coordination of power injection aims to keep the power balanced withinthe HVDC grid especially during large wind disturbances. Furthermore, thecoordination tries to follow the converters’ schedules set by the connectingAC-TSOs every 15−minutes. This schedule comes from an overall combinedAC/DC economic dispatch calculation with lower resolution compared to thiscoordination. In this paper, the coordination of power injection has been formulatedas a non-linear constrained optimization problem for the centralizedarchitecture. Next, the centralized optimization problem is decomposed tosub-problems using the Auxiliary Problem Principle (APP) method for thedistributed architecture. This distributed optimization problem is solved byexchanging the required information between the AC TSOs. These two differentapproaches have been evaluated for a 5-terminal HVDC grid. Furthermore,a sensitivity analysis has been carried out to find the optimal updatingrate of power injection set-points. The result shows that the more frequentupdating of power injection coordination in the centralized architecture improvesthe generation reserves in each AC area.
12.	Bagheri, Azam, et al. (författare) Improved characterization of multi-stage voltage dips based on the space phasor model 2018 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 154, s. 319-328 Tidskriftsartikel (refereegranskat)abstract This paper proposes a method for characterizing voltage dips based on the space phasor model of the three phase-to-neutral voltages, instead of the individual voltages. This has several advantages. Using a K-means clustering algorithm, a multi-stage dip is separated into its individual event segments directly instead of first detecting the transition segments. The logistic regression algorithm fits the best single-segment characteristics to every individual segment, instead of extreme values being used for this, as in earlier methods. The method is validated by applying it to synthetic and measured dips. It can be generalized for application to both single- and multi-stage dips.
13.	Bano, Sayyeda Umbereen, et al. (författare) Maximum Lyapunov Exponent Based Nearest Neighbor Algorithm For Real-Time Transient Stability Assessment 2024 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 234 Tidskriftsartikel (refereegranskat)abstract In power systems, ensuring transient stability is paramount to prevent unforeseen blackouts and power failures. Transient stability assessment is crucial for the early detection and mitigation of instabilities, providing a rapid response to severe fault situations. The concept of the maximum Lyapunov exponent facilitates fast predictions for transient stability assessment after severe disturbances. This paper introduces an efficient maximum Lyapunov exponent algorithm for online transient stability assessment, representing the primary contribution of this work. This approach uses the time series data from the rotor angles of generators or the phase angles of generator terminal buses. Case studies are conducted on the Nordic Power System, with simulations performed in DigSilent PowerFactory. This study contributes by offering insights into the performance and adaptability of the proposed algorithm.
14.	Becerra Garcia, Marley, 1979-, et al. (författare) On the estimation of the lightning incidence to offshore wind farms 2018 Ingår i: Electric power systems research. - : Elsevier Ltd. - 0378-7796 .- 1873-2046. ; 157, s. 211-226 Tidskriftsartikel (refereegranskat)abstract Field observations have shown that the frequency of dangerous lightning events to wind turbines, calculated according to the IEC standard 61400-24:2010, is grossly underestimated. This paper intends to critically revisit the evaluation of the incidence of downward lightning as well as self-initiated and other-triggered upward flashes to offshore wind power plants. Three different farms are used as case studies. The conditions for interception of stepped leaders in downward lightning and the initiation of upward lightning is evaluated with the Self-consistent Leader Inception and Propagation Model (SLIM). The analysis shows that only a small fraction of damages observed in the analysed farms can be attributed to downward lightning. It is also estimated that only a small fraction (less than 19%) of all active thunderstorms in the area of the analysed farms can generate sufficiently high thundercloud fields to self-initiate upward lightning. Furthermore, it is shown that upward flashes can be triggered even under low thundercloud fields once a sufficiently high electric field change is generated by a nearby lightning event. Despite of the uncertainties in the incidence evaluation, it is shown that upward flashes triggered by nearby positive cloud-to-ground flashes produce most of the dangerous lightning events to the case studies.
15.	Belov, Vladimir, et al. (författare) Mathematical modelling of a wind power system with an integrated active filter 2009 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 79:1, s. 117-125 Tidskriftsartikel (refereegranskat)
16.	Blom, Evelin, et al. (författare) Performance of multi-scenario equivalent hydropower models 2020 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 187 Tidskriftsartikel (refereegranskat)abstract Simulations and analysis of large hydro-thermal power systems easily become computationally heavy without simplifications of the system at hand. Hydropower, in particular, presents a challenge as complex river systems add a large amount of variables and linked constraints to the analysis. A possible simplification is to use aggregated Equivalent models for different parts of the hydrosystem which give similar results, with respect to e.g. power production, as a more detailed description of the Original system. In this paper, novel linear multi-scenario Equivalent models for hourly simulations of nonlinear hydropower systems are developed and their performance investigated. The new models consider multiple scenarios for inflow, price and start resp. end content in the reservoirs as well as reserves for balancing capacity. The performance analysis is based on case studies over Swedish hydropower systems located in the electricity trading area SE1. The average relative error in power production is 9-15% and the computation time is reduced from 9 hours to between 0.4 and 36 seconds.
17.	Bollen, Math, et al. (författare) Characterization methods and typical levels of variations in rms voltage at the time scale between 1 second and 10 minutes 2020 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 184 Tidskriftsartikel (refereegranskat)abstract Voltage magnitude deviation from its nominal value varies over a range of time scales. This paper concentrates on the range between 1 s and 10 min as part of the long-term aim of obtaining a complete picture of voltage magnitude variations at time scales below ten minutes. Time series of voltage with 1-s time resolution are obtained at 57 locations around the world. The main contributions of the paper are: the definition of additional indices in the sub-10-minute time scale from the 1-s rms voltages; statistics on the values of these indices for different locations; identifying the need for further research through a set of recommendations to the research community. It is shown, among others, that for the available data set, the voltage typically varies between 0.5 V and 5 V within a 10-min window; a range exceeding 1 or 2 V is common; a range exceeding 5 V is uncommon.The need for the indices proposed in this paper is justified as equipment connected to the grid is changing and to help managing and for storing the huge amount of data resulting from power-quality measurements at many sites during several years.
18.	Bracale, A., et al. (författare) A new joint sliding-window ESPRIT and DFT scheme for waveform distortion assessment in power systems 2012 Ingår i: Electric Power Systems Research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 88, s. 112-120 Tidskriftsartikel (refereegranskat)abstract This paper proposes a novel scheme that jointly employs a sliding-window ESPRIT and DFT for estimating harmonic and interharmonic components in power system disturbance data. In the proposed scheme, separate stages are utilized to estimate the voltage fundamental component, harmonics and interharmonics. This includes the estimation of the fundamental component from lowpass filtered data using a sliding-window ESPRIT, of harmonics from a sliding-window DFT with a synchronized window, and of interharmonics from the residuals by applying the sliding-window ESPRIT. Main advantages of the approach include high resolution and accuracy in parameter estimation and significantly reduced computational cost. Experiments and comparisons are made on both synthetic and measurement data. Results have shown the effectiveness and efficiency of the proposed scheme.
19.	Bragone, Federica, et al. (författare) Physics-informed neural networks for modelling power transformer’s dynamic thermal behaviour 2022 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 211, s. 108447-108447 Tidskriftsartikel (refereegranskat)abstract This paper focuses on the thermal modelling of power transformers using physics-informed neural networks (PINNs). PINNs are neural networks trained to consider the physical laws provided by the general nonlinear partial differential equations (PDEs). The PDE considered for the study of power transformer’s thermal behaviour is the heat diffusion equation provided with boundary conditions given by the ambient temperature at the bottom and the top-oil temperature at the top. The model is one dimensional along the transformer height. The top-oil temperature and the transformer’s temperature distribution are estimated using field measurements of ambient temperature, top-oil temperature and the load factor. The measurements from a real transformer provide more realistic solution, but also an additional challenge. The Finite Volume Method (FVM) is used to calculate the solution of the equation and further to benchmark the predictions obtained by PINNs. The results obtained by PINNs for estimating the top-oil temperature and the transformer’s thermal distribution show high accuracy and almost exactly mimic FVM solution.
20.	Busatto, Tatiano, et al. (författare) Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations 2020 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 180 Tidskriftsartikel (refereegranskat)abstract Harmonic analysis studies of modern power systems commonly employ Norton and Thévenin equivalents at harmonic frequencies for the nonlinear devices. This approach neglects the so-called nonlinear interaction phenomenon. This paper addresses the difference between the results from the commonly-used model and the actual harmonic distortion measured in a low-voltage installation. A number of indices are introduced to quantify the nonlinear interaction. These indices allow a quantification of the extent to which the commonly-used model is also to predict harmonic voltages and currents in a modern low-voltage installation. The proposed model and the subsequent mathematical analysis are illustrated through measurements from different combinations of PV inverters and LED lamps using different technologies. The results show that deviation is dependent on the used technology, network impedance, and source voltage waveform. Other findings are that nonlinear interaction happens mainly in the low harmonic orders and impacts are more perceived on the harmonics phase angle. Possible explanations for these observations are discussed.
21.	Calil, Wílerson Venceslau, et al. (författare) Determining total cost of ownership and peak efficiency index of dynamically rated transformer at the PV-power plant 2024 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 229 Tidskriftsartikel (refereegranskat)abstract Dynamic rating of the transformer is a promising technology, which is suitable for various applications. Using dynamic rating for connecting renewable energy is believed to be beneficial for the economy and flexibility of the power system. However, to safely deploy such operation strategies, it is important to have more precise estimates for the total costs of owning such units and determine how effective such operation method is for a solar power plant. This study proposes a method for calculating total ownership costs (TOC) of dynamically rated transformers used for the connection of the solar power plant to the grid as well as analyzes its efficiency. The sensitivity analysis looks into the change in TOC and peak efficiency index (PEI) after considering reactive power dispatch. Results of this study also show how TOC, PEI, and load and no-load losses change depending on the transformer size.
22.	Cardoso, G., et al. (författare) Microgrid reliability modeling and battery scheduling using stochastic linear programming 2013 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 103, s. 61-69 Tidskriftsartikel (refereegranskat)abstract This paper describes the introduction of stochastic linear programming into Operations DER-CAM, a tool used to obtain optimal operating schedules for a given microgrid under local economic and environmental conditions. This application follows previous work on optimal scheduling of a lithium-iron-phosphate battery given the output uncertainty of a 1 MW molten carbonate fuel cell. Both are in the Santa Rita Jail microgrid, located in Dublin, California. This fuel cell has proven unreliable, partially justifying the consideration of storage options. Several stochastic DER-CAM runs are executed to compare different scenarios to values obtained by a deterministic approach. Results indicate that using a stochastic approach provides a conservative yet more lucrative battery schedule. Lower expected energy bills result, given fuel cell outages, in potential savings exceeding 6%.
23.	Carvalho, J. M., et al. (författare) Voltage sag index calculation: Comparison between time-domain simulation and short-circuit calculation 2008 Ingår i: Electric Power Systems Research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 78:4, s. 676-682 Tidskriftsartikel (refereegranskat)abstract This paper describes a case study where voltage sags indices are estimated using Monte Carlo approach combined with ATP (Alternative Transient Program) and short-circuit calculation program. Voltage sag magnitude and frequency are used to evaluate the correlation between both programs. The results indicate that time-domain simulation and short-circuit calculation gives similar voltage sag indices. Considering the high correlation between the results, short-circuit calculation programs are preferable over the time-domain simulation tools as the modelling for time-domain simulation is more complex, time consuming, and rarely covers the whole network. (C) 2007 Elsevier B.V. All rights reserved.
24.	Chandimal, Lasantha, et al. (författare) A field study on the energy dissipation associated with step and touch voltage in earthing systems encased in earth enhancing compounds 2024 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 231 Tidskriftsartikel (refereegranskat)abstract An extensive field experiment was conducted to investigate the effects of earth -enhancing compounds on earthing systems. Four identical vertical earth rods were installed, each encased in concrete, Bentonite, and two commercial enhancing materials. Lightning impulse signals were injected into all electrode arrangements, and the measured responses were used to analyse the associated risks of step and touch voltages. The peak voltage values and the corresponding energy dissipation for each measurement were calculated and compared to those of a reference electrode. The analysis of step voltage measurements and the corresponding energy dissipation demonstrated that the use of concrete exhibited greater advantages than the use of Bentonite. However, touch voltage measurements and the associated energy dissipation indicated that despite the lower touch voltage exhibited by Bentonite, its energy dissipation exceeded that of the reference electrode. Consequently, the unique findings reveal that specific variations of earth -enhancing compounds can exhibit reduced earth impedance and lower step or touch voltages while also yielding higher energy dissipation, introducing an unforeseen risk of injury.
25.	Cooray, Vernon, 1952-, et al. (författare) Current propagation type self-consistent leader-return stroke model 2023 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 217 Tidskriftsartikel (refereegranskat)abstract A current propagation type return stroke model which is consistent with the estimated distribution of the charge on the leader channel is described. The model takes into account the dispersion of the return stroke current along the return stroke channel. The model is capable of generating lightning return stroke electromagnetic fields that are in close agreement with experimental observations. The model could also be used to estimate the electric fields from the leader-return stroke combination at any given distance.
26.	Cooray, Vernon, 1952-, et al. (författare) Electromagnetic fields of accelerating charges : Applications in lightning protection 2017 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 145, s. 234-247 Tidskriftsartikel (refereegranskat)abstract Electromagnetic fields generated by accelerating charges can be utilized to evaluate the electromagnetic fields generated by systems where moving charges and/or propagating currents are present. The technique can be used easily to evaluate the electromagnetic fields generated by systems in which propagating currents are present. This is illustrated by utilizing the equations to derive expressions for the electromagnetic fields generated by systems in which current pulses injected by lightning flashes are propagating.
27.	Cooray, Vernon, 1952-, et al. (författare) Merging of current generation and current dissipation lightning return stroke models 2017 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 153:SI, s. 10-18 Tidskriftsartikel (refereegranskat)abstract Current generation and current dissipation return stroke models are engineering models based on the theory associated with the propagation of current pulses along transmission lines undergoing corona. However, neither of these models incorporates the complete theory associated with the phenomenon. One can make the physical scenario complete by combining the current generation concept with the current dissipation concept. In this paper how this can be done is demonstrated by creating a return stroke model which is a combination of these two model types. The new model encompasses the full theory associated with the pulse propagation along transmission lines under corona. The paper provides a full description of the model together with a description of the spatial and temporal variation of the return stroke current and the electric and magnetic fields generated at different distances as predicted by the model.
28.	Cooray, Vernon, et al. (författare) On the possible variation of the lightning striking distance as assumed in the IEC lightning protection standard as a function of structure height 2014 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 113, s. 79-87 Tidskriftsartikel (refereegranskat)abstract The effect of structure height on the lightning striking distance is estimated using a lightning strike model that takes into account the effect of connecting leaders. According to the results, the lightning striking distance may differ significantly from the values assumed in the IEC standard for structure heights beyond 30m. However, for structure heights smaller than about 30m, the results show that the values assumed by IEC do not differ significantly from the predictions based on a lightning attachment model taking into account the effect of connecting leaders. However, since IEC assumes a smaller striking distance than the ones predicted by the adopted model one can conclude that the safety is not compromised in adhering to the IEC standard. Results obtained from the model are also compared with Collection Volume Method (CVM) and other commonly used lightning attachment models available in the literature. The results show that in the case of CVM the calculated attractive distances are much larger than the ones obtained using the physically based lightning attachment models. This indicates the possibility of compromising the lightning protection procedures when using CVM.
29.	Cooray, Vernon, 1952- (författare) The influence of lightning conductor radii on the attachment of lightning flashes 2017 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 153:SI, s. 138-143 Tidskriftsartikel (refereegranskat)abstract The influence of the tip radius of lightning conductors on their lightning attractive distance as predicted by the self-consistent leader inception and propagation model (SLIM) is presented. The results show that in the absence of any glow corona from the tip of the conductor a smaller tip radius gives rise to a larger attractive radius than a larger radius. It is suggested that the reason for the experimental observations which show that blunt conductors are more efficient lightning receptors than sharp ones is the presence of glow corona at the tip of the sharp ones during the time of lightning strikes. Moreover, in a given background electric field, the probability of the inception of glow corona at the conductor tip increases with increasing conductor height and decreasing conductor radius. Thus, in a given electric field, as the conductor height increases its radius has to be increased to avoid the inception of glow corona at the tip. For this reason, the conductor radius that performs best as a lightning interceptor depends on the height of the conductor and the best performance shift from smaller radii to larger ones with increasing height of the conductor.
30.	Cooray, Vernon, 1952- (författare) Unification of engineering return stroke models 2021 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 195 Tidskriftsartikel (refereegranskat)abstract Engineering models burrow various features from transmission line theory and combine them using empirical data to create models that can predict the electromagnetic fields of lightning return strokes in space and time. At present, engineering models are the most successful in predicting the features of lightning electromagnetic fields in close agreement with the experimental data. Today, most scientists who are interested in lightning protection use engineering models in their studies. A large number of engineering return stroke models exist in the literature. Depending on the assumptions made they can be categorized as Current Propagation models (CP-models), Current Generation models (CG-models) and Current Dissipation models (CD-models). The goal of this paper is to describe the different approximations used in constructing these engineering return stroke models and to show that all these models are a special case of a more general model which we call Current model (C-model). We will show how various return stroke models can be precipitated from the C-model by neglecting different features associated with it.
31.	de Barros, Thiago Ribeiro, et al. (författare) Optimization algorithm associated with local and coordinated controls of distributed energy resources to meet technical and economic criteria 2024 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 226 Tidskriftsartikel (refereegranskat)abstract The present work proposes the development of a simulation platform that integrates the PSCAD software with python language, capable of portraying realistic and dynamic characteristics of the operation of an electrical system with high insertion of DERs. This work considers a scenario with high insertion of alternative sources, which are characterized by intermittent conditions of generation and consumption, therefore causing technical-economic challenges in the operation of the network. In this way, an electrical network will be created with photovoltaic systems, electric vehicles and batterys, in addition to local, coordinated and optimization controls. Local and coordinated controls act on network undervoltage and overvoltage problems. The optimized control, created in Python and based on a Predictive Control Model, determines the optimal operating curve for the batterys, reducing the energy cost of the system, being activated when the network does not present technical problems. Results showed a reduction of more than 16% in the energy cost of the network when enabling the optimized control, keeping the voltage profiles within regulatory limits. Thus, the proposed platform manages to carry out the technical-economic monitoring of the network, becoming a promising tool for the creation of active network management algorithms in dynamic simulations.
32.	de Medeiros, Marcial Guerra, et al. (författare) Minimum-time Secure Rollout of Software Updates for Controllable Power Loads 2020 Ingår i: Electric power systems research. - : Elsevier Ltd. - 0378-7796 .- 1873-2046. ; 189 Tidskriftsartikel (refereegranskat)abstract Generating minimum-time and secure software update schedules for controllable power loads in low-voltage distribution grids is a problem of increasing importance because of accelerating integration of renewable energy resources. In this paper, we call such a problem the software update rollout problem and present a mathematical framework for its modeling and solution. First, it is shown that this problem can be understood as a multi-resource bin packing problem. Then several approximate and exact solution schemes are discussed, the former using greedy approximate algorithms and the later using integer linear programming (ILP). These schemes are then evaluated on benchmark networks of realistic size (CIGRE-LV, TPC 83-bus distribution system). Experimental results show that both greedy and ILP approaches perform well for real-time purposes. In particular, the greedy approach can attain high-quality approximate solutions almost instantly while the ILP approach can not only provide solutions with certifiable optimality gaps but also include extra constraints (e.g., precedence) as needed.
33.	de Oliveira, Roger Alves, et al. (författare) Magnification of Transients at the Voltage Dips Starting and its Impacts on DFIG-based Wind Power Plants 2022 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 211 Tidskriftsartikel (refereegranskat)abstract This work shows that transients at voltage dips starting impact fault-ride-through of wind turbines. For fault-ride-through studies and manufacturer tests, it is therefore important to consider these transients and their magnification from the transmission grid through the collection grid to the wind turbines. Fault-ride-through studies in the literature do not consider the transient as a dip characteristic and employ overly-simplified models that do not consider the collection grid. This work studies in detail how the dip-starting transient changes during the propagation from the transmission grid to the wind-turbine terminals. It is also studied how this transient impacts the dynamic behaviour of the wind turbines in terms of the overvoltage on the DC-link of wind turbines based on doubly-fed induction generator (DFIG). The analyses are performed for several realistic configurations of a wind-power plant, all based on an existing installation. The results show that the magnitude of the transient is magnified when the resonant frequency of the collection grid is similar to the oscillation frequency of the transient. Moreover, the higher magnitude of the transient results in a significantly higher overvoltage on the DC-link. This work is the first in power quality literature to cover the collection and internal grid as a factor for the magnification of dip-staring transient. The main finding of this work is that the detailed models of the collection grid and the transients at the voltage dips starting must be not neglected when accessing the LVRT of wind turbines. It is strongly recommended to consider the details of the dip-starting transients and of the collection grid to assess the impact of dips on the wind turbines properly.
34.	Diaz, Oscar, 1980-, et al. (författare) Parameter variation in leader channel models used in long air gap discharge simulation 2016 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 139, s. 32-36 Tidskriftsartikel (refereegranskat)abstract Theoretical models have been developed to predict the 50% breakdown voltage of long air gaps arrangements, based on the physics of the discharge. These models are capable of estimating electric fields, leader and streamer region propagation, among others. An important parameter within this calculation is the leader model and its electric potential distribution along the discharge channel. In the present work, we compared engineering and physical leader models against experimental data recorded for a rod-to-plane electrode arrangement tested with switching-like voltage impulses. The analysis showed that the leader channel evolution depends strongly on the potential gradient assumed to sustain streamers.
35.	Díez-Maroto, L., et al. (författare) A WACS exploiting generator Excitation Boosters for power system transient stability enhancement 2017 Ingår i: Electric power systems research. - : Elsevier Ltd. - 0378-7796 .- 1873-2046. ; 148, s. 245-253 Tidskriftsartikel (refereegranskat)abstract Excitation Boosters (EB) are designed to improve transient stability of synchronous generators equipped with bus fed static excitation systems. They can be controlled using either local or remote signals following a disturbance. This paper explores how critical clearing times (CCT) can be improved by EBs controlled using remote signals. Particularly, Pseudo Center of Inertia (PCOI) and Dominant Interarea Path (DIP) signals derived from Phasor Measurement Units (PMU) within a Wide Area Control System (WACS) are used. Prototype controllers are tested by means of a Real Time (RT) Hardware-in-the-Loop (HIL) experimental setup.
36.	Duvnjak Zarkovic, Sanja, 1989-, et al. (författare) Onshore wind farm - Reliability centered cable routing 2021 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 196, s. 107201- Tidskriftsartikel (refereegranskat)abstract Designing an onshore wind farm is a complex planning process that requires various stages to be completed. The prime focus of this work is to assist planners and experts in finding the optimal cable layout of the onshore wind farm. The optimization algorithm is designed using mixed integer linear programming (MILP). The MILP algorithm takes into account system reliability, power transfer capacities and power quality issue. The novelty in this optimization algorithm is to simultaneously minimize cable installation cost and the cost of lost energy production and therefore maximize the reliability of the system. Additionally, the algorithm supports the optimal selection among different cable options, with different features, prices and capacities. By calculating voltage increase at the point of connection (POC), power quality issue is considered as well. The designed algorithm provides optimal results for four different wind farm layouts. Every layout is tested for three different case scenarios, where different number and type of cables are considered. The results show that more cable options contribute in lowering the total costs. Moreover, cables with higher capacity can help in improving the power quality issue.
37.	Edimu, M., et al. (författare) Analyzing the performance of a time-dependent probabilistic approach for bulk network reliability assessment 2013 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 104, s. 156-163 Tidskriftsartikel (refereegranskat)abstract The conventional sequential Monte Carlo Simulation (MCS) considers states in which a component is both in and out of service. Sequential MCS has been applied in different analyses whilst considering both symmetrical and asymmetrical probability distributions. The Beta distribution is however not one of the commonly recommended distributions for use in sequential MCS due to the complexity in deriving its inverse transform. A new sequential MCS technique that applies the Beta distribution is proposed in this paper. The technique is a time-dependent probabilistic approach (TDPA) that uses probability density functions (PDFs) to characterize stochastic network parameters in terms of their season- and time-dependency and simulates the component down (failure) states. The effect of this simulation approach on reliability calculations is analyzed using a published test network. The impact of dispersion and skewness in PDF based input models on a reliability analysis is also investigated. The results show that the TDPA can replicate the conventional sequential MCS analysis. The TDPA computation is also significantly faster. The simulation results of the TDPA also show that dispersion and skewness of component failure rate PDFs significantly influence a reliability analysis.
38.	Ehnberg, Jimmy, 1976, et al. (författare) Reliability of a small power system using solar power and hydro 2005 Ingår i: Electric Power Systems Research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 74:1, s. 119-127 Tidskriftsartikel (refereegranskat)abstract This paper studies the availability of the electricity supply when the sources consist of a combination of solar energy and a small hydro installation. Instead of flow-of-river, a small reservoir is used. By not using the hydro energy during sunny periods, the natural flow-of-river fills up the reservoir for later use. A model for global solar radiation is proposed with an astronomical part (deterministic) and a meteorological part (stochastic). The meteorological part is based on a Markov model of the cloud coverage. The solar model does not require solar radiation measurements, just cloud observations. A case study has been performed for Timbuktu (16.75degreesN, 0.07degreesW) in which generation availability is simulated for four different cases: solar power only; solar power with storage; solar and hydro power and solar and hydro, power with storage. To be able to use exclusively renewable energy sources, a combination of sources is needed to secure the reliability of the supply. Using solar cells in combination with a small reservoir is favorable. Even with a weak flow the affect of the flow on the day time reliability is minor, but great benefits can be found for reliability during low load hours (night time).
39.	Ekström, Rickard, et al. (författare) Lower order grid current harmonics for a voltage-source inverter connected to a distorted grid 2014 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 106, s. 226-231 Tidskriftsartikel (refereegranskat)abstract As a result of lower order grid voltage harmonics, the grid current injected by a voltage-source inverter will also be partially distorted. In large-scale applications, active harmonic filters or notch filters are used to reduce the grid current distortion. For small-scale units, this may not be economically viable. In this article, two different grid phase tracking methods are evaluated with respect to the grid current distortion. The first method uses the zero-crossing detection (ZCD) method together with a look-up table (LUT), to generate a perfectly sinusoidal voltage synchronized with the grid. The second method uses a single-phase phase-locked loop (PLL). This method will reflect the grid harmonics in the inverter output, resulting in either cancellation or superposition of the harmonics of the grid current. A theoretical expression for the grid current as a function of the grid voltage harmonics is derived. Individual grid current harmonics as well as the total harmonic distortion (THD) are experimentally evaluated for both ZCD and PLL, and compared with theory. Results are presented for different power flows into the grid and compared with grid codes.
40.	Elkington, Katherine, et al. (författare) On the stability of power systems containing doubly fed induction generator-based generation 2008 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 78:9, s. 1477-1484 Tidskriftsartikel (refereegranskat)abstract This article is concerned with the impact of large-scale wind farms utilising doubly fed induction generators on the stability of a general power system. Inspection of the eigenstructure of the power system provides a foundation for assessing the impact, which is then quantified by means of detailed numerical simulations. Simplified state-space models are used to describe the dynamics of the generators in a very simple system, whose network is described by algebraic relations. A third order model is derived for a doubly fed induction generator. Mathematical models are then used to identify the behavioural patterns of the system when it is subject to disturbances. Eigenvalue analysis reveals some interesting properties of the system for small disturbances, and shows that the addition to a power system of doubly fed generators, such as those in wind farms, improves the response of the system to small disturbances. However, numerical simulations show that it can have an adverse impact after larger disturbances.
41.	Eriksson, Robert, et al. (författare) Coordinated control of multiple HVDC links using input-output exact linearization 2010 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 80:12, s. 1406-1412 Tidskriftsartikel (refereegranskat)abstract This paper is concerned with the investigation of a new control technique for the conventional High Voltage Direct Current (HVDC) link. The proposed technique relies upon nonlinear state feedback linearization of the AC/DC power system. The idea in input-output exact feedback linearization is to algebraically transform nonlinear systems dynamics into a linear control problem using a nonlinear pre-feedback loop, and then for the linearized power system one can design another feedback loop using a well established technique such as a linear-quadratic regulator. The primary goal of the controller presented in this paper is to contribute to the enhancement of both the transient and the small-signal stability of the power system. Since the proposed state feedback linearization does not rely on the assumption that there is only small deviation of the states from an equilibrium, the enhancement of both is feasible. The simulation results obtained in the framework of the study show that the proposed controller is capable of stabilizing the system in various system operating conditions.
42.	Espín-Delgado, Ángela, et al. (författare) Diagnosis of supraharmonics-related problems based on the effects on electrical equipment 2021 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 195 Tidskriftsartikel (refereegranskat)abstract Supraharmonics (SH) have proliferated in low-voltage (LV) and medium-voltage (MV) grids due to the increasing use of technologies emitting distortion in the range 2–150 kHz. Currently, no recommended practices to assess the effects of SH on the electrical system exist. The propagation of SH through LV and MV grids leads to interference with the elements for power delivery and end-user equipment, e.g., light flicker, aging of capacitors and cable terminations, audible noise, and interruption of electric vehicle (EV) charging. As such incidents happen more often, the need for guidelines that facilitate the diagnosis of problems related to SH arises. Different features of the SH distortion are responsible for different interferences. This article introduces guidelines for the evaluation of the impact of SH based on the morphology of the interference. The evaluation is performed with easy-to-use methods and formulas directly related to the characteristics of the SH distortion. The adverse effects of SH considered are audible noise, light flicker, tripping of LV residual current devices (RCDs), and MV cable termination failure. This work interests field engineers and researchers facing problems related to SH; it also serves as a guide for further research.
43.	Espin Delgado, Angela, et al. (författare) Summation law for supraharmonic currents (2–150 kHz) in low-voltage installations 2020 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 184 Tidskriftsartikel (refereegranskat)abstract The development of methods to study the propagation of supraharmonics in LV and even MV grids is a current research topic among the power quality community, which has been motivated by the efforts to establish limits for non-intentional supraharmonic emissions and planning levels. The assessment of how much distortion a bulk use of power electronics devices can inject into the grid is necessary before stating emission limits and planning levels for supraharmonics. To address this issue, the development of suitable models that can predict the supraharmonic emission from a low-voltage installation as a whole is required. This article presents a comparison of models for the summation of supraharmonics. An improved model for the summation of supraharmonics is proposed, which is validated experimentally. It is shown that by using the proposed model, predictions of supraharmonic propagation can be accomplished. Furthermore, it is demonstrated experimentally that, with the increasing number of supraharmonic emitting devices, the supraharmonic current distortion injected into a grid by an installation increases up to a maximum value and then decreases due to the capacitive nature of power electronics appliances existing in low-voltage networks.
44.	Etherden, Nicholas, et al. (författare) Overload and overvoltage in low-voltage and medium-voltage networks due to renewable energy : some illustrative case studies 2014 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 114, s. 39-48 Tidskriftsartikel (refereegranskat)abstract This paper presents the use of curtailment to allow more wind or solar power to be connected to a distribution network when overcurrent or overvoltage set a limit. Four case studies, all based on measurements, are presented. In all cases the hosting capacity method is used to quantify the gain in produced energy for increased levels of distributed renewable energy resources. A distinction is made between “hard curtailment” where all production is disconnected when overcurrent and overvoltage limits are exceeded and “soft curtailment” where the amount of production to be disconnected is minimized. It is shown that the type of curtailment method used has a large impact on the amount of delivered energy to the grid. The paper further discusses details of the curtailment algorithm, alternatives to curtailment, the communication needs and risks associated with the use of curtailment
45.	Farrokhabadi, Mostafa, et al. (författare) An efficient automated topology processor for state estimation of power transmission networks 2014 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 106, s. 188-202 Tidskriftsartikel (refereegranskat)abstract A robust network topology processor that can be utilized in both traditional and PMU-based state estima- tors is developed. Previous works in the field of topology processing are scrutinized and their drawbacks are identified. Building on top of the state of the art, an algorithm covering the limitations of available topology processing approaches and including new features is proposed. The presented algorithm was implemented in MATLAB and tested using two different power networks with detailed substation config- urations (bus/breaker models) including a modified version of the IEEE Reliability Test System 1996. As the topology processor is intended to supply network topologies to a PMU-based Sate Estimator, the IEEE Reliability Test System 1996 is simulated in real-time using the eMegaSim Opal-RT real-time simulator which is part of “SmarTS Lab” at KTH Royal Institute of Technology. Testing is carried out through several test scenarios and computation times are calculated. It is shown that the computation times are adequate for supporting a PMU-only state estimator.
46.	Fernandes, Daniel Leocádio, et al. (författare) Distributed control on a multi-agent environment co-simulation for DC bus voltage control 2024 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 232 Tidskriftsartikel (refereegranskat)abstract Distributed control on a multi-agent format in co-simulation environment has been conceived in a client/server architecture for controlling a series of devices connected to a Direct Current (DC) bus. The implemented system aims for providing the communication infrastructure required for connecting the whole co-simulation environment. Power converters interact via a communication infrastructure orchestrated by a multi-agent system whose algorithm has been built for the proposed scenario. A virtual small village is supplied by a DC power system endowed by some photovoltaic arrays and energy storage by a battery bank. The use of Python, socket Transmission Control Protocol/Internet Protocol (TCP/IP) and Power Simulator (PSIM) with appropriate adaptation is meant to build the system in a lighter computational environment. The interaction among agents helped the co-simulation with a distributed control to maintain the DC bus stable in 180 Vdc and battery voltage oscillating within the state of charge (SoC) range, 99% and 97%, of 144 Vdc fed by a photovoltaic array under the coordination of the multi-agent system.
47.	Ferreira, Danton D., et al. (författare) A new power quality deviation index based on principal curves 2015 Ingår i: Electric power systems research. - : Elsevier BV. - 0378-7796 .- 1873-2046. ; 125, s. 8-14 Tidskriftsartikel (refereegranskat)abstract In this paper, a new power quality deviation index based on principal curves is proposed. The index provides a quantitative measure, which gives an idea of how much the monitored electrical signal has deviated from the nominal one. Differently of existing indices, the proposed index is a general index, i.e., it can be used for any type of disturbance in the monitored signal. In addition, the proposed index is used to perform a direct approach for detecting disturbances in power signals. This approach is able to detect the beginning and localize the disturbance by analyzing non-overlapping signal windows of one cycle of the fundamental component, leading to a simple method in terms of computational complexity
48.	Firouzi, Seyed Reza, et al. (författare) Interpreting and Implementing IEC 61850-90-5 Routed-Sampled Value and Routed-GOOSE Protocols for IEEE C37.118.2 Compliant Wide-Area Synchrophasor Data Transfer 2016 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 144, s. 255-267 Tidskriftsartikel (refereegranskat)abstract Flexibility and adaptability requirements of future electric power grids for integrating DERs call for the developmentof Wide-Area Monitoring, Protection And Control (WAMPAC) applications, utilizing synchrophasor measurementsprovided by the Phasor Measurement Units (PMUs).IEEE C37.118 is the most utilized protocol for real-time exchange of synchronized phasor measurement data. In orderto full some gaps not addressed in IEEE C37.118, and also to harmonize with the IEC 61850 power utility automationstandard, the IEC 61850-90-5 technical report has been developed. IEC TR 61850-90-5 introduces a mechanism fortransfer of digital states and time synchronized phasor measurement data over wide-area networks between PhasorMeasurement Units (PMUs), Phasor Data Concentrators (PDCs) and WAMPAC applications in the context of IEC61850.This work interprets the IEEE C37.118.2 and IEC 61850-90-5 Routed-Sampled Value and Routed-GOOSE protocolsand describes the design and implementation of a library named Khorjin with the functionality of (1) an IEEE C37.118.2to IEC 61850-90-5 gateway and protocol converter and, (2) an IEC 61850-90-5 subscriber and trac parser.The main contribution of this work is the development of Khorjin library using only standard C libraries (i.e.independent from any operating system). This is allowing the use of the library in dierent platforms.The design requirements and functionality of the Khorjin library has been tested in the KTH SmarTS Lab Real-TimeHardware-in-the-Loop (HIL) simulation environment to assess its conformance to the functional requirements of IEEEC37.118.2 and IEC 61850-90-5 standards.
49.	Ge, Chenjie, 1991, et al. (författare) Unsupervised deep learning and analysis of harmonic variation patterns using big data from multiple locations 2021 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 194 Tidskriftsartikel (refereegranskat)abstract This paper addresses the issue of automatically seeking and identifying daily, weekly and seasonal patterns in harmonic voltage from measurement data at multiple locations. We propose a novel framework that employs deep autoencoder (DAE) followed by k-mean clustering. The DAE is used for extracting principal features from time series of harmonic voltages. A new strategy is used for training the encoder in DAE from data at one selected location that is effective for subsequent feature extraction from data at multiple locations. To analyze the patterns, several empirical analysis approaches are applied on the clustered principal features, including the distribution of daily patterns over the week and the year, representative waveform sequences of individual classes, and feature maps for visualizing high-dimensional feature space through low-dimensional embedding. The proposed scheme has been tested on a dataset containing harmonic measurements at 10 low-voltage locations in Sweden for the whole year of 2017. Results show distinct principal patterns for most harmonics that can be related to the use of equipment causing harmonic distortion. This information can assist network operators in finding the origin of harmonic distortion and deciding about mitigation actions. The proposed scheme is the first to provide a useful analysis tool and insight for finding and analyzing underlying patterns from harmonic variation data at multiple locations.
50.	Gil de Castro, Aurora, et al. (författare) Light intensity variation (flicker) and harmonic emission related to LED lamps 2017 Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 146, s. 107-114 Tidskriftsartikel (refereegranskat)abstract This paper discusses two power-quality aspects of LED lamps: harmonics and flicker. Measurements have been performed of 24 different LED lamps: the harmonic current spectrum and light intensity variations have been measured. To enable an objective comparison, the light intensity variations were measured for all the lamps when exposed to the same voltage magnitude variations. Results show a large variety in harmonic emission between different LED lamps indicating that different technologies or different components are being used within the LED lamps. Moreover the results show a large variety in light intensity variations when different LED lamps are subjected to the same voltage fluctuations. A clear correlation was found between harmonic emission and sensitivity to voltage magnitude variations. Lamps with low light intensity variations are also the ones with the highest harmonic current emission. No clear relation between active power or price and sensitivity to voltage magnitude variations was found.

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