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  • 1.
    Alvarez, Manuel
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Jabr, Rabih
    American University of Beirut.
    Cossent, Rafael
    Universidad Pontificia de Comillas.
    Frías, Pablo
    Universidad Pontificia de Comillas.
    Zhong, Jin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Capacity Mechanisms for Distribution Network Expansion Planning2019Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208Artikkel i tidsskrift (Fagfellevurdert)
  • 2.
    Axelberg, Peter G V
    et al.
    Unipower.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gu, Irene Y H
    Chalmers University of Technology.
    Efficient trace of flicker sources by using the quantity of flicker power2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 465-471Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Industries that produce flicker are often placed close to each other and connected to the same power grid system. This implies that the measured flicker level at the point of common coupling (PCC) is a result of contribution from a number of different flicker sources. In a mitigation process it is essential to know which one of the flicker sources is the dominant one. Therefore this paper proposes a method to determine the flicker propagations and trace the flicker sources by using flicker power measurements. Flicker power is considered as a quantity containing both sign and magnitude. The sign determines if a flicker source is placed downstream or upstream with respect to a given monitoring point and the magnitude is used to determine the propagation of flicker power throughout the power network and to trace the dominant flicker source. This paper covers the theoretical background of flicker power and describes a novel method for calculation of flicker power that can be implemented in a power network analyzer. Also a conducted field test based on the proposed method is described in the paper.

  • 3.
    Axelberg, P.G.V.
    et al.
    Unipower AB, Alingsås.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    An algorithm for determining the direction to a flicker source2006Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 21, nr 2, s. 755-760Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes an algorithm for calculating the direction to a flicker source with respect to a monitoring point. The proposed algorithm is based on sampling of both the voltage and current. The low-frequency fluctuations in voltage and current are recovered from the input signals by demodulation, and passed through a bandpass filter as described in IEC 61000-4-15. A new quantity - flicker power - is defined from the output signals of the two filters. The direction to a flicker source is obtained from the sign of this flicker power. The proposed algorithm has been validated by simulations and several field measurements

  • 4.
    Axelberg, P.G.V
    et al.
    University College of Borås.
    Gu, I.Y.H
    Chalmers University of Technology.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Support vector machine for classification of voltage disturbances2007Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, nr 3, s. 1297-1303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The support vector machine (SVM) is a powerful method for statistical classification of data used in a number of different applications. However, the usefulness of the method in a commercial available system is very much dependent on whether the SVM classifier can be pretrained from a factory since it is not realistic that the SVM classifier must be trained by the customers themselves before it can be used. This paper proposes a novel SVM classification system for voltage disturbances. The performance of the proposed SVM classifier is investigated when the voltage disturbance data used for training and testing originated from different sources. The data used in the experiments were obtained from both real disturbances recorded in two different power networks and from synthetic data. The experimental results shown high accuracy in classification with training data from one power network and unseen testing data from another. High accuracy was also achieved when the SVM classifier was trained on data from a real power network and test data originated from synthetic data. A lower accuracy resulted when the SVM classifier was trained on synthetic data and test data originated from the power network.

  • 5.
    Bagheri, Azam
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gu, Irene Y.H.
    Department of Electrical Engineering, Chalmers University of Technology.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Balouji, Ebrahim
    Department of Electrical Engineering, Chalmers University of Technology.
    A Robust Transform-Domain Deep Convolutional Network for Voltage Dip Classification2018Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 33, nr 6, s. 2794-2802Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a novel method for voltage dip classification using deep convolutional neural networks. The main contributions of this paper include: (a) to propose a new effective deep convolutional neural network architecture for automatically learning voltage dip features, rather than extracting hand-crafted features; (b) to employ the deep learning in an effective two-dimensional transform domain, under space-phasor model (SPM), for efficient learning of dip features; (c) to characterize voltage dips by two-dimensional SPM-based deep learning, which leads to voltage dip features independent of the duration and sampling frequency of dip recordings; (d) to develop robust automatically-extracted features that are insensitive to training and test datasets measured from different countries/regions.

    Experiments were conducted on datasets containing about 6000 measured voltage dips spread over seven classes measured from several different countries. Results have shown good performance of the proposed method: average classification rate is about 97% and false alarm rate is about 0.50%. The test results from the proposed method are compared with the results from two existing dip classification methods. The proposed method is shown to out-perform these existing methods.

  • 6.
    Basu, Supratim
    et al.
    Bose Research (P) Ltd., Bangalore.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    A novel common power factor correction scheme for homes and offices2005Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 20, nr 3, s. 2257-2263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper explores the approach of having a common Power Factor Correction circuit for domestic and commercial loads. This leads to lower harmonic distortion without the need to install (expensive) active rectifiers in each end-user device. The need for power-factor correction as well as a number of design options is discussed in this paper. The design and cost estimation of a common Power Factor Correction scheme and some reliability issues are discussed

  • 7.
    Bollen, Math
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gu, I.Y.H.
    Characterization of voltage variations in the very-short time-scale2005Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 20, nr 2, s. 1198-1199Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter presents a method for characterizing the fast voltage variations that occur on a time scale between the subsecond fluctuations covered by the flickermeter standard and the 10-min values covered by standards like EN 50160 The method is fully compatible with IEC 61000-4-30 class A. The new characteristic is correlated to small switching actions, such as domestic load switching and transformer tap-changer operation.

  • 8.
    Bollen, Math
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Gu, I.Y.H
    Chalmers University of Technology, Department of Signals and Systems.
    On the analysis of voltage and current transients in three-phase power systems2007Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, nr 2, s. 1194-1201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a method for analyzing measurements of voltage transients in three-phase systems. The method is based on the Clarke transform introduced in 1950 for calculations of travelling waves along three-phase transmission lines. The proposed method also shows close similarities with the classification of three-phase unbalanced voltage dips. After extracting the actual transient (e.g., by using a notch filter centered on the power-system frequency), the three signals are decomposed into seven components. From the relation between these seven components, the dominant component is identified. The method is successfully applied to a number of measured transients. The paper also identifies the limitations of the method and gives suggestions for future work

  • 9.
    Bollen, Math
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ribeiro, Paulo
    Calvin College, Grand Rapids, MI.
    Larsson, Anders
    Lundmark, Martin
    Limits for voltage distortion in the frequency range 2 to 9 kHz2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 3, s. 1481-1487Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper addresses voltage distortion in the frequency range 2 to 9 kHz, above what is normally considered in harmonic studies. By extrapolating the voltage-distortion limits that exist in international standards for distortion up to 2 kHz, it is concluded that 0.5% of nominal voltage per 200-Hz band is a safe limit. This limit is next used to estimate the number of small generator units (1-10 kW) that can be connected to a low-voltage grid. It is concluded that in some cases the connection of one or just a few units already leads to a distortion level above the limit.

  • 10.
    Bollen, Math
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Styvaktakis, Emmanouil
    Chalmers University of Technology, Department of Signals and Systems.
    Gu, Irene Yu- Hua
    Chalmers University of Technology, Department of Signals and Systems.
    Categorization and analysis of power system transients2005Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 20, nr 3, s. 2298-2306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power system transients are power-quality disturbances that can be harmful to electronic equipment. This paper contributes and provides some solutions to the following issues: 1) to introduce a new way to identify different categories of power system transients based on their underlying causes; 2) to propose a model and analysis tool for oscillatory transients, where emphasis is on finding phenomena and characteristics associated with the underlying causes of transients. A model-based approach, ESPRIT, is applied to a number of simulated voltage waveforms to extract the parameters of oscillatory transients, and the results may be used for identifying and understanding the causes of transients by correlating the major components in transients with the phenomena that may appear in different types of transients and some a priori knowledge of power system settings

  • 11.
    Bollen, Math
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Verde, Paola
    University of Cassino.
    A framework for regulation of RMS voltage and short-duration under and overvoltages2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 4, s. 2105-2112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a general approach for voltage-quality regulation. The same framework covers voltage-amplitude variations, dips, and swells. The framework uses the difference between power-quality events and power-quality variations to introduce a "responsibility-sharing curve" distinguishing between normal operational voltage for which equipment should be immune and events that are subject to voltage-quality regulation. It is further proposed to use equipment immunity requirements as a basis for the responsibility-sharing curve.

  • 12.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Including Uncertainties from Customer Connections in Calculating Low-Voltage Harmonic Impedance2019Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 34, nr 2, s. 606-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method is proposed in this paper to determine the harmonic impedances in low-voltage networks in a stochastic way. The consequences of resonances for harmonic propagation and stability of power converters are summarized. By using Monte Carlo simulation, the method includes the uncertainties in customer impedances, specifically due to electronic loads and local generation. The uncertainty in customer impedance is included by considering probability distribution for the resistive, inductive and capacitive parts of the impedance. The concept of transfer impedance is used for phase-to-neutral connections. A method is developed and applied to two existing low-voltage networks in Sweden. Results show that, for these two networks, the resonant frequencies decrease around 28 % once PV panels are installed. The paper includes a discussion of some of the practical aspects of applying the proposed method.

  • 13.
    Du, C
    et al.
    ABB AB, HVDC System, Ludvika.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Agneholm, E
    Sannino, A
    ABB AB, Corporate research.
    A new control strategy of a VSC-HVDC System for high-quality supply of industrial plants2007Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, nr 4, s. 2386-2394Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a control strategy for a VSC-HVDC for improving the quality of power supply to industrial plants. The new idea of this control strategy is to give high priority to keep up the ac voltage and slightly decrease the frequency during disturbances. The motivation for choosing this strategy is that the sensitive processing industries are much more sensitive to voltage drops as compared with frequency deviations. In order to test this control strategy, the dynamic performance of a VSC-HVDC supplied industrial plant is investigated during sudden load disturbances, balanced and unbalanced faults from the grid. Simulation results obtained using PSCAD/EMTDC show that with the use of the proposed control strategy, the system can ride through disturbances such as motor starting and faults by slightly decreasing the frequency. The current limit of the VSC-HVDC converters has a significant influence on the dynamics of the system. An increase of the current limit significantly improves the power quality of the system. The comparison of the behavior between a pure ac supplied industrial plant and a VSC-HVDC supplied industrial plant clearly shows the capability of the VSC-HVDC to mitigate voltage dips during faults.

  • 14.
    Ekman, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Wisten, Åke
    Experimental investigation of the current distribution in the couplings of moving trains2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 1, s. 311-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transport of iron ore from the Swedish mining areas to the harbors is carried out by electric trains. In 2003, there was a dramatic increase in the number of bearings discarded due to electric current corrosion. No evident reason to this increase could be found and a project was initiated measuring electrical currents in engines and couplings as well as position and velocity of the train in an attempt to find countermeasures to the excess currents in the bearings. The RMS-magnitudes of the currents have been recorded and compared for different positions on the train, for different train configurations, and at different driving conditions. The results showed substantial electrical currents going through the couplings and much higher currents in modern trains with 30 tons axle load compared to old trains with 25 tons axle load.

  • 15.
    Enohnyaket, Mathias
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Ekman, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Analysis of air-core reactors from DC to very high frequencies using PEEC models2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 2, s. 719-729Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Faced with the challenges of increasing operational frequencies and switching rates of modern power electronics devices used in power systems, there is need for high frequency models (up to a few megahertz) for power components like reactors, capacitors banks and transformers. This paper presents the application of PEEC theory forthe creation of high frequency, electromagnetic models for air-core reactors. The electromagnetic field couplings are separated in mutual partial inductances and mutual coefficients of potential giving a correct solution from DC to a maximum frequency determined by the meshing. The PEEC models are validated by comparing simulation results, for both time and frequency domain analysis, against measurements and other established modeling methods, and show good agreement. The model created by PEEC theory, could be helpful in the design and diagnostics of air-core reactors and other power system components.

  • 16.
    Filho, J.M.C.
    et al.
    Itajuba Federal University, Brazil.
    Leborgne, R.C.
    Federal University of Rio Grande do Sul (UFRGS), Porto Alegre.
    Abreu, J.P.G de
    Itajuba Federal University, Brazil.
    Novaes, E.G.C
    Petrobras, Rio de Janeiro.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Validation of voltage sag simulation tools: ATP and short-circuit calculation versus field measurements2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 3, s. 1472-1480Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two methods to calculate voltage sags are validated against actual measurements. One of the methods is a short-circuit calculation program resulting directly in sag magnitude during the fault. The other is an electromagnetic transient program resulting in voltage waveform as a function of time. Individual sag characteristics and system performance obtained by deterministic simulation and measurement are compared. The influence of the random variables (prefault voltage, fault location and fault impedance) is investigated.

  • 17.
    Fomari, Frederica
    et al.
    University of Genova, Department of Electrical Engineering.
    Procopio, Renato
    University of Genova, Department of Electrical Engineering.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    SSC compensation capability of unbalanced voltage sags2005Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 20, nr 3, s. 2030-2037Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, the capacity of a static series compensator (SSC) to compensate for voltage sags is discussed, and a complete analysis of the effects of unbalanced Sags on the SSC compensation capability is carried out. Expressions are obtained for the missing voltage during unbalanced voltage sags. These expressions are used to estimate how often a voltage sag occurs where the missing voltage exceeds the injection capability of the SSC. The method is applied to a typical Italian network configuration

  • 18.
    Gu, I.Y.H.
    et al.
    Chalmers University of Technology.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Estimating interharmonics by using sliding-window ESPRIT2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 1, s. 13-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method is proposed for estimating interharmonic frequencies in power system voltage and current signals. The method is based on a spectrum-estimation method known as "estimation of signal parameters via rotational invariance techniques" (ESPRIT). To allow for a more reliable spectral estimation and to cover nonstationarity in the signal, a sliding-window version of ESPRIT is introduced. This paper describes the basic ESPRIT method as well as sliding-window ESPRIT. The paper discusses the application of the method to one synthetic signal and three measurement signals. It is shown that the method allows for very accurate frequency estimation of interharmonic components. The limitations of the methods, such as line splitting and spurious components, can be overcome by using the coherent information obtained from the sliding-window method. A number of remaining issues are also discussed in this paper.

  • 19.
    Larsson, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Wahlberg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Lundmark, Martin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Measurements of high-frequency (2-150 kHz) distortion in low-voltage networks2010Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 25, nr 3, s. 1749-1757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents different methods to describe voltage and current distortion in the frequency range 2 to 150kHz. The time-frequency domain was shown to give additional information next to the time- and frequency-domain representations. Measurements of different devices and at different locations showed remnants of the switching frequency of the power electronics as well as lower frequency oscillations around the current zero crossing to be present in voltage and current. The voltage distortion is shown to vary a lot during the day and between locations.

  • 20.
    Leborgne, R.C
    et al.
    Chalmers University, Elteknik.
    Olguin, G
    ABB Corporate Research.
    Filho, J.M. Carvalho
    Itajuba Federal University, Brazil.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Differences in voltage dip exposure depending upon phase-to-phase and phase-to-neutral monitoring connections2007Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 22, nr 2, s. 1153-1159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Voltage dip indices are estimated for a set of simulated and measured events. The simulated dips are obtained applying the method of fault positions on a large transmission network and the measured dips come from a one-year survey. The indices estimated to compare phase-to-phase and phase-to-neutral dips are SARFI-90, SARFI-70, SARFI-ITIC, and average voltage dip amplitude. Furthermore, the results are analyzed in terms of the cumulative distribution frequency of the voltage dip amplitude. The comparison of phase-to-phase and phase-to-neutral indices indicates that, at transmission level, phase-to-neutral dips are more frequent and more severe than phase-to-phase ones. However, these differences are reduced at the load connection level, where the phase and line voltages show similar performance for the monitored system

  • 21.
    Milanovic, J. V.
    et al.
    School of Electrical and Electronic Engineering, The University of Manchester.
    Meyer, J.
    Institute of Electrical Power Systems and High Voltage Engineering, Technische Universitaet Dresden.
    Ball, R. F.
    National Grid, Warwick Technology Park, Warwick.
    Howe, W
    Electric Power Research Institute (EPRI), Boulder, CO.
    Preece, R.
    School of Electrical and Electronic Engineering, The University of Manchester.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Elphick, S.
    Australian Power Quality and Reliability Centre, University of Wollongong.
    Čukalevski, N.
    Institue “Mihailo Pupin,” Belgrade.
    International Industry Practice on Power Quality Monitoring2014Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 29, nr 2, s. 934-941Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monitoring of voltages and currents at system buses gives the network operators information about the performance of their network, both for the system as a whole and for individual locations and customers. There is also demand from the customers and the regulatory agencies to provide information on the actual power-quality (PQ) level. Developments in enabling technology have made it possible to monitor at a large scale and to record virtually any PQ parameter of interest. While many network operators are installing monitoring equipment and while more and more monitors are available, there is a lack of knowledge and agreement on a number of aspects of the monitoring process and on processing the recorded data. As a response to this lack of uniformity in approach, data acquisition, and processing, in February 2011, CIGRE and CIRED established the Joint Working Group C4.112: “Guidelines for Power quality monitoring—measurement locations, processing and presentation of data.” In order to identify the current international industry practice on PQ monitoring, the group carried out a survey in 43 countries across the world. This paper summarizes the key findings from 114 responses to the questionnaire and identifies prevalent industrial practice in PQ monitoring around the world.

  • 22.
    Oliveira, Thiago Cle de
    et al.
    Universidade Federal de Itajubá.
    Filho, Jose Maria de Carvalho
    Universidade Federal de Itajubá.
    Leborgne, Roberto Chouhy
    Universidade Federal do Rio Grande do Sul.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Voltage sags: validating short-term monitoring by using long-term stochastic simulation2009Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 3, s. 1344-1351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a procedure to validate voltage sag results based on a short-term monitoring program and stochastic assessment of voltage sag characteristics. The main practical use of this methodology is to analyze the accuracy of sag characteristics obtained from short monitoring periods. With a Monte Carlo Simulation approach, probabilistic models of several factors are taken into account: lines and busbars fault rate, pre-fault voltage, fault-type distribution, fault-location uncertainty, and fault resistance distribution. Confidence intervals based on the percentile method and hypothesis tests are the statistical tools selected to perform the validation of voltage sags magnitude and frequency. A case study based on the evaluation of a six-month monitoring period shows the applicability of the proposed methodology.

  • 23.
    Ravindran, Vineetha
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Busatto, Tatiano
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Meyer, Jan
    Institute of Electrical Power Systems and High Voltage Engineering, Technische Universitaet Dresden, Dresden, Germany.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Time-varying interharmonics in different types of grid-tied PV inverter systems2019Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Widely existing circuit topologies and inverter control strategies for PV systems allow customer flexibility but also introduce different kinds of interharmonics into the grid. A complete understanding of interharmonics from PV systems, with reasons behind their origin, remains needed. In addition, the timevarying nature of interharmonics and the potential impacts on other equipment are yet to be understood. In this paper, laboratory and field measurements are presented of seven different inverter types at multiple locations. A comprehensive analysis is performed to understand the existence, persistence, and propagation of interharmonics in PV systems on the DC side as well as grid side for different power levels. The origins of the interharmonics are established with experimental evidence and through a comparative analysis. A rural low voltage 6 customer network, with two different impedance profiles caused by the installation of PV, is considered to show the potential impact on customer voltage. To address the time-varying nature of interharmonics, a sliding window ESPRIT method is preferred over FFT based methods

  • 24.
    Renders, Bert
    et al.
    Department of Electrical Energy, Systems and Automation (EESA), Ghent University.
    Gussemé, Koen De
    Department of Electrical Energy, Systems and Automation (EESA), Ghent University.
    Ryckaert, Wouter
    Department Industrieel Ingenieur, Katholieke Hogeschool Sint-Lieven, Ghent.
    Stockman, Kurt
    Department Provinciale Industriële Hogeschool, Hogeschool West-Vlaanderen, Kortrijk.
    Vandevelde, Lieven
    Department of Electrical Energy, Systems and Automation (EESA), Ghent University.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Distributed generation for mitigating voltage dips in low-voltage distribution grids2008Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 23, nr 3, s. 1581-1588Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of synchronous and induction generators has a positive effect on the retained voltage (the lowest rms voltage during the event) during voltage dips in high voltage networks. The impact of converter-connected distributed-generation (DG) units has been reported to be negligible, as most converters operate at unity power factor, and the currents injected in the grid are limited to the nominal current of the converter. However, the impact of DG units on the distorted grid voltage is strongly dependent on the voltage level, and thus the grid impedance, of the concerned grid. This paper investigates and compares the effects of converter-based DG units, synchronous and asynchronous generators on the retained voltage during voltage dips in low voltage distribution grids.

  • 25.
    Rönnberg, Sarah
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Wahlberg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Interaction between narrowband power-line communication and end-user equipment2011Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 26, nr 3, s. 2034-2039Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper discusses some of the electromagnetic-compatibility issues concerning the use of power lines for communication. Based on a series of measurements performed in a laboratory environment and in the field, five different types of interactions between communication and end-user equipment are distinguished. Measurement examples are shown for several of these types. It is concluded that the creation of a low-impedance path by end-user equipment is the main cause of interference.

  • 26.
    Schwanz, Daphne
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Möller, Friedemann
    Technische Universität Dresden.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Meyer, Jan
    Institute of Electrical Power Systems and High Voltage Engineering, Technische Universitaet Dresden, Technical University Dresden, Dresden University of Technology.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Stochastic Assessment of Voltage Unbalance due to Single-Phase-Connected Solar Power2017Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 32, nr 2, s. 852-861, artikkel-id 7488998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stochastic method is presented in this paper to estimate the future voltage unbalance in a low-voltage distribution network with high-penetration of single-phase photovoltaic inverters (PVIs). Location and phase allocation of the PVIs are considered as input parameters for the stochastic simulation. The method has been applied to three different low-voltage networks: two in Sweden and one in Germany. In the Swedish networks, for 6-kW single-phase PVIs, it is likely that the contribution from single-phase photovoltaic inverters to the voltage unbalance exceeds 1%. The 2% value is unlikely to be exceeded. In the German network, for 4.6-kW single-phase PVIs the voltage unbalance is between 1.35% and 2.62%.The risk of high voltage unbalance can be reduced by a combination of controlled distribution over the phases and reduction of the maximum size for a single-phase PVI.

  • 27.
    Sorrentino, Elmer
    et al.
    Universidad Simón Bolívar, Caracas.
    Alvarez, Manuel
    Universidad Simón Bolívar, Caracas.
    Multipliers to shift the through-fault protection curve for various connections of distribution transformers2011Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 26, nr 3, s. 2055-2057, artikkel-id 5725148Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the multipliers to shift the through-fault protection curve for various connections of distribution transformers. Cases with a secondary center tap and with secondary open delta were analyzed as well as the effect of using single-phase units with different short-circuit impedances. © 2011 IEEE.

  • 28.
    Wang, Ying
    et al.
    College of Electrical Engineering and Information Technology, Sichuan University.
    Bagheri, Azam
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Xiao, Xian-Xong
    College of Electrical Engineering and Information Technology, Sichuan University.
    Single-Event Characteristics for Voltage Dips in Three-Phase Systems2017Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 32, nr 2, s. 832-840, artikkel-id 7496837Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper compares different methods for voltage-dip characterization. Those methods are based on earlier proposed algorithms for extracting three-phase characteristics (dip type, characteristic voltage, and so-called “PN factor”). The difference between the 12 methods being studied in this paper is in the way in which the time variation of those characteristics is treated to result in single-event characteristics. The methods are applied to 259 measured voltage dips and the performance of the different methods is compared. It is found that small differences in method can result in big difference in results. From the comparison, two methods are selected and recommended for inclusion in international standards.

  • 29.
    Wang, Ying
    et al.
    College of Electrical Engineering and Information Technology, Sichuan University.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Xiao, X. Y.
    College of Electrical Engineering and Information Technology, Sichuan University.
    Calculation of the phase-angle-jump for voltage dips in three-phase systems2015Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 30, nr 1, s. 480-487, artikkel-id 6899711Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase-angle-jump is defined in this paper as another single-event characteristic of voltage dips, besides residual or characteristic voltage and duration. This paper proposes and compares six methods to calculate the phase-angle-jump for measured voltage dips in a three-phase system. This paper also studies the details of the calculation: correcting frequency and transition segments. The six proposed methods have been applied to 235 sets of measured voltage dips and a statistical comparison has been made. It is recommended that two of the methods be included in IEEE Standard 1564 and IEC 61000-4-30.

  • 30.
    Yang, Kai
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Aggregation and Amplification of Wind-Turbine Harmonic Emission in a Wind Park2015Inngår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 30, nr 2, s. 791-799, artikkel-id 7042349Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents measurements of harmonic and interharmonic current (with 5 Hz frequency resolution) in the complex plane. The complex currents are spread around a center point. For interharmonics this center corresponds with the origin of the complex plane. For integer harmonics this center is off-set from the origin. A goodness-of-fit test reveals that phase angles of most interharmonics are uniformly distributed. A Monte-Carlo simulation based on the measurements has been performed to study the aggregation of the emission from individual turbines to the public grid. Low-order integer harmonics show less cancellation compared to high-order harmonics. Interharmonics aggregate close to the square-root rule for uniform phase angles.

1 - 30 of 30
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