Stri Ab

Gothenburg, Sweden
Gothenburg, Sweden
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Yang K.,Lulea University of Technology | Bollen M.H.J.,Stri Ab | Larsson E.O.A.,Lulea University of Technology
IEEE Transactions on Power Delivery | Year: 2015

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 to the origin of the complex plane. For integer harmonics, this center is offset 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. © 1986-2012 IEEE.

Etherden N.,Lulea University of Technology | Etherden N.,Stri Ab | Bollen M.H.J.,Lulea University of Technology | Bollen M.H.J.,Stri Ab
IEEE Transactions on Sustainable Energy | Year: 2013

Energy storage can potentially allow for more production from renewable resources into existing grids. A methodology to quantify grid limitations and dimension battery energy storage systems is presented in this paper. By use of grid consumption and production data, the hosting capacity methodology is developed as a general framework for storage dimensioning that can be applied by grid operators. The method is successfully applied to an existing subtransmission grid; actual hourly production and consumption data during a two-year period is used. The role of a storage system compared to other means to handle overloading is studied. It is found that about one third of overloading instances are suitable to handle with a battery energy storage system. After this, diminishing returns per unit of storage capacity are shown to occur. © 2010-2012 IEEE.

Ronnberg S.K.,Lulea University of Technology | Bollen M.H.J.,Lulea University of Technology | Bollen M.H.J.,Stri Ab | Wahlberg M.,Lulea University of Technology | Wahlberg M.,Skellefteä Kraft Elnät AB
IEEE Transactions on Power Delivery | Year: 2011

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. © 2011 IEEE.

Wang Y.,Sichuan University | Bollen M.H.J.,Lulea University of Technology | Bollen M.H.J.,Stri Ab | Xiao X.-Y.,Sichuan University
IEEE Transactions on Power Delivery | Year: 2015

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. © 2014 IEEE.

Larsson E.O.A.,Lulea University of Technology | Bollen M.H.J.,Lulea University of Technology | Bollen M.H.J.,Stri Ab | Wahlberg M.G.,Lulea University of Technology | And 3 more authors.
IEEE Transactions on Power Delivery | Year: 2010

This paper presents different methods to describe voltage and current distortion in the frequency range 2 to 150 kHz. The timefrequency 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. © 2010 IEEE.

Yang K.,Lulea University of Technology | Bollen M.H.J.,Lulea University of Technology | Bollen M.H.J.,Stri Ab | Larsson E.O.A.,Lulea University of Technology | And 2 more authors.
Electric Power Systems Research | Year: 2014

This paper presents harmonic measurements from three individual wind turbines (2 and 2.5 MW size). Both harmonics and interharmonics have been evaluated, especially with reference to variations in the active-power production. The overall spectra reveal that emission components may occur at any frequency and not only at odd harmonics. Interharmonics and even harmonics emitted from wind turbines are relatively high. Individual frequency components depend on the power production in different ways: characteristic harmonics are independent of power; interharmonics show a strong correlation with power; other harmonic and interharmonic components present various patterns. It is concluded that the power production is not the only factor determining the current emission of a wind energy conversion system. © 2013 Elsevier B.V.

Bollen M.H.J.,Lule University of Technology | Bollen M.H.J.,Stri Ab
Synthesis Lectures on Power Electronics | Year: 2011

This book links the challenges to which the electricity network is exposed with the range of new technology, methodologies and market mechanisms known under the name "smart grid." The main challenges will be described by the way in which they impact the electricity network: the introduction of renewable electricity production, energy efficiency, the introduction and further opening of the electricity market, increasing demands for reliability and voltage quality, and the growing need for more transport capacity in the grid. Three fundamentally different types of solutions are distinguished in this book: solutions only involving the electricity network (like HVDC and active distribution networks), solutions including the network users but under the control of the network operator (like requirements on production units and curtailment), and fully market-driven solutions (like demand response). An overview is given of the various solutions to the challenges that are possible with new technology; this includes some that are actively discussed elsewhere and others that are somewhat forgotten. Linking the different solutions with the needs of the electricity network, in the light of the various challenges, is a recurring theme in this book. Copyright © 2011 by Morgan & Claypool.

Bracale A.,Parthenope University of Naples | Carpinelli G.,University of Naples Federico II | Gu I.Y.-H.,Chalmers University of Technology | Bollen M.H.J.,Stri Ab | Bollen M.H.J.,Lule University of Technology
Electric Power Systems Research | Year: 2012

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. © 2012 Elsevier B.V. All rights reserved.

Gutman I.,Stri Ab | Dernfalk A.,Stri Ab
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2010

There are no standardized methods available at present for artificial pollution testing of polymeric insulators. Modified Salt Fog and Solid Layer tests based on procedures described in IEC 60507, intended for ceramic insulators, are thus often applied. Among methods evaluated for polymeric insulators made of hydrophobicity transfer materials (HTM), a modified Solid Layer test with preconditioning by dry powder is considered as being representative and most promising for future standardization. Further, the proposed procedure allows for testing at different hydrophobic states of the polluted insulators via the introduction of defined time between the application of pollution and voltage test. Finally, if the 50% flashover voltage is determined using e.g. the up-anddown method, results of the tests can be directly applied for insulator selection and dimensioning by means of statistical or deterministic methods. © 2010 IEEE.

Gutman I.,Stri Ab | Lundengard J.,Stri Ab | Vosloo W.,Eskom
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2014

The Rapid Flashover pollution test method (RFO) exposes energized polluted insulators to fog and uses step changes of voltage to identify a minimum flashover voltage. The RFO method reduces test time by a factor of three or more compared to up-and-down voltage application method and is thus time- and cost-effective. In this paper the results from RFO on five ceramic and composite station insulators (line, post and hollow) with median 4.7 m leakage distance are compared closely with duplicate tests using up-anddown procedure. The tests on hydrophobic composite insulators used the preconditioning principles from CIGRE Brochure 555. Full-scale withstand testing of the same five but 420-kV class voltage insulators with median leakage distance 13.3 m are also presented. It is indicated that the flashover test results of RTV-coated station insulators should be specially analyzed and treated. © 1994-2012 IEEE.

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