| 1. |
- Karlsson, Elinor K, et al.
(författare)
-
Genome-wide analyses implicate 33 loci in heritable dog osteosarcoma, including regulatory variants near CDKN2A/B
- 2013
-
Ingår i: Genome Biology. - : Springer Science and Business Media LLC. - 1465-6906 .- 1474-760X .- 1474-7596. ; 14:12
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Canine osteosarcoma is clinically nearly identical to the human disease, but is common and highly heritable, making genetic dissection feasible.RESULTS: Through genome-wide association analyses in three breeds (greyhounds, Rottweilers, and Irish wolfhounds), we identify 33 inherited risk loci explaining 55% to 85% of phenotype variance in each breed. The greyhound locus exhibiting the strongest association, located 150 kilobases upstream of the genes CDKN2A/B, is also the most rearranged locus in canine osteosarcoma tumors. The top germline candidate variant is found at a >90% frequency in Rottweilers and Irish wolfhounds, and alters an evolutionarily constrained element that we show has strong enhancer activity in human osteosarcoma cells. In all three breeds, osteosarcoma-associated loci and regions of reduced heterozygosity are enriched for genes in pathways connected to bone differentiation and growth. Several pathways, including one of genes regulated by miR124, are also enriched for somatic copy-number changes in tumors.CONCLUSIONS: Mapping a complex cancer in multiple dog breeds reveals a polygenic spectrum of germline risk factors pointing to specific pathways as drivers of disease.
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| 2. |
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| 3. |
- Abid, Fahim, et al.
(författare)
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Intermodulation due to interaction of photovoltaic inverter and electric vehicle at supraharmonic range
- 2016
-
Ingår i: 2016 17th International Conference on Harmonics and Quality of Power. - Piscataway. NJ. - 9781509037926 ; , s. 685-690
-
Konferensbidrag (refereegranskat)abstract
- Advent of power electronic switching is introducing more and more non-linear loads in the low voltage grid. Besides harmonic current generation in the frequency range below 2 kHz, these non-linear loads are also responsible for current emission in the range of 2 kHz to 150 kHz, commonly known as supraharmonic emission. Supraharmonic currents mainly flow between nearby appliances and heavily influence the overall emission of neighboring devices. This paper presents an analysis of supraharmonic interaction between a photovoltaic inverter and an electric vehicle. It has been noticed that intermodulation distortion arises as a result of interaction between different switching frequencies used by the devices. Later, additional household equipment were added to photovoltaic and electric vehicle to observe their effect on intermodulation distortion. All the measurements were conducted in a controlled laboratory environment imitating a domestic customer.
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| 4. |
- Ahmed, Kazi Main Uddin, 1989-, et al.
(författare)
-
Electrical Energy Consumption Model of Internal Components in Data Centers
- 2019
-
Ingår i: Proceedings of. - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- In the context of modern information technology (IT) industry, cloud computing is gaining popularity for big data handling. Therefore, IT service providers like Google, Facebook and Amazon are expanding their technical resources by building data centers to improve the data processing and data storage facilities under cloud service pattern. However, data centers consume a large amount of electrical energy. In recent years, a lot of research has been done to reduce the electrical energy consumption of data centers by high performance computing. However, very few researchers have focused on the electrical energy consumption by the electrical components inside the data center. In this paper, a component based electrical energy consumption modelling approach is presented to identify the losses of different components as well as their interactions to the total electrical energy consumption of the data center. The electrical energy consumption models of servers and other components are presented as a function of server utilization.
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| 5. |
- Alvarez, Manuel, 1980-, et al.
(författare)
-
A Capacity Mechanism Design for Distribution Network Expansion Planning
- 2018
-
Ingår i: 2018 IEEE International Conference on Environment and Electrical Engineering and 2018 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe). - 9781538651865 - 9781538651872
-
Konferensbidrag (refereegranskat)abstract
- Capacity remuneration mechanisms have been originally oriented to ensure availability and continuity of supply on the power generation pool. Equivalent generation-based capacity mechanisms could be implemented to enhance and prolong the usability of the distribution grid. In particular, such capacity mechanisms would provide an alternative to traditional expansion options leading to investment deferral. In this work, a distribution capacity mechanism to fit within a distribution network planning methodology will be proposed and discussed. The capacity mechanism will be outlined following similar guidelines as for the design of capacity mechanisms used in the energy only market. The result of the design is a volume based capacity auction for a capacity-constrained system, oriented to both the active and the reactive power provision.
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| 6. |
- Alvarez, Manuel, et al.
(författare)
-
A Smart Distribution Toolbox for Distribution System Planning
- 2015
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Konferensbidrag (refereegranskat)abstract
- The distribution system planner should be able to coordinate smart grid solutions in order to find cost effective expansions plans. These plans should be able to deal with new added system uncertainties from renewable production and consumers while guaranteeing power quality and availability of supply. This paper proposes a structure for distribution systems planning oriented to help the planner in deciding how to make use of smart solutions for achieving the described task. Here, the concept of a system planning toolbox is introduced and supported with a review of relevant works implementing smart solutions. These are colligated in a way that the system planner can foresee what to expect with their combined implementation. Future developments in this subject should attempt to theorize a practical algorithm in an optimization and decision making context.
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| 7. |
- Alvarez Perez, Manuel Alejandro, 1980-, et al.
(författare)
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A Generic Storage Model Based on a Future Cost Piecewise-Linear Approximation
- 2019
-
Ingår i: IEEE Transactions on Smart Grid. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3053 .- 1949-3061. ; 10:1, s. 878-888
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents a generic storage model (GSM) inspired by the scheduling of hydraulic reservoirs. The model for steady state short-term (ST) operational studies interlaces with the long-term (LT) energy scheduling through a piecewise-linear Future Cost Function (FCF). Under the assumption that a Stochastic Dual Dynamic Programming (SDDP) approach has been used to solve the energy schedule for the LT, the FCF output from that study will be processed to obtain an equivalent marginal opportunity cost for the storage unit. The linear characteristic of a segment of the future cost function (FCF) will allow a linear modeling of the storage unit production cost. This formulation will help to coordinate the renewable resource along with storage facilities in order to find the optimal operation cost while meeting end-point conditions for the long-term plan of the energy storage. The generic model will be implemented to represent a battery storage and a pumped-hydro storage. A stochastic unit commitment (SUC) with the GSM will be formulated and tested to assess the day-ahead scheduling strategy of a Virtual Power Plant (VPP) facing uncertainties from production, consumption, and market prices.
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| 8. |
- Alvarez Perez, Manuel Alejandro, 1980-, et al.
(författare)
-
A Hydro-Reservoir Generic Storage Model for Short-Term Hydrothermal Coordination
- 2017
-
Ingår i: IEEE PES PowerTech Manchester 2017: towards and beyond sustainable energy systems, 2017. - Piscataway, NJ : Institute of Electrical and Electronics Engineers (IEEE). - 9781509042371
-
Konferensbidrag (refereegranskat)abstract
- This work presents a linear solution for the short-term hydro-thermal scheduling problem linked to long-term conditions through a piecewise-linear Future Cost Function (FCF). Given end-point conditions to conform long-term water releases, and given actual reservoir conditions, a segment of a pre-built piecewise future cost function will be chosen. The linear characteristic of the FCF segment will allow a linear modeling of the hydro-power plant, in a similar fashion as a thermal unit with an equivalent marginal opportunity cost. A short-term hydro thermal coordination problem will be formulated considering parallel and cascaded hydro-reservoirs. Three study cases involving different reservoir configurations and scenarios will be computed to test the model. The results of this model mimics coherently the future-cost hydro-thermal coordination problem for the different configurations tested. Given similarities with other forms of energy storage, a new theoretical model for generic storage will be proposed and discussed.
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| 9. |
- Alvarez Perez, Manuel Alejandro, 1980-, et al.
(författare)
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Regulatory Matters Affecting Distribution Planning With Distributed Generation
- 2017
-
Ingår i: CIRED - Open Access Proceedings Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 2515-0855. ; 2017:1, s. 2869-2873
-
Tidskriftsartikel (refereegranskat)abstract
- Under the present European directive concerning common rules for the internal market in electricity, distribution companies are not allowed to own distributed generation (DG) but encouraged to include it as a planning option to defer investment in traditional grid reinforcements. Distribution system operators (DSOs) have used the provision of capacity contracted to DG as a viable alternative under current regulatory arrangements. Here, the topics bonding DSOs and DG owners under the present regulation will be explored and a planning structure that considers distribution capacity contracts as a planning option will be proposed. This will serve as a road map for DSOs to implement its preferred planning tools in an optimisation context, considering costs of investment, reliability, operation, and capacity provision while complying with current regulation.
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| 10. |
- Alvarez Perez, Manuel Alejandro, 1980-, et al.
(författare)
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Remuneration Assessment of a VPP Providing Distribution Capacity Services
- 2017
-
Ingår i: IEEE PES PowerTech Manchester 2017. - Piscataway, NJ : Institute of Electrical and Electronics Engineers (IEEE). - 9781509042371
-
Konferensbidrag (refereegranskat)abstract
- A Distribution System Operator (DSO) might consider a capacity contract as a planning alternative to defer grid investments. A Virtual Power Plant (VPP) might be able to provide such capacity and change its production as requested by the DSO. This article presents an assessment of the impact of this type of distribution capacity contract (DCC) on VPP's remuneration. This assessment is done by comparing the optimal production / bidding strategy which maximize its profit, under presence or absence of these contracts. The impact of intermittent generation and storage while evaluating these scenarios will be investigated as well. A stochastic unit commitment will be used to determine the VPP's strategy under uncertainties from wind power, load, market prices, and the requested power by the DSO. The model showed that the VPP involvement in distribution capacity contracts can improve its remuneration when certain types of Distributed Energy Resources (DER) are used to provide the service.
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| 11. |
- 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.
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| 12. |
- Alvarez Perez, Manuel Alejandro, 1980-
(författare)
-
Stochastic Planning of Smart Electricity Distribution Networks
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The penetration of intermittent Distributed Generation (DG) brought additional uncertainty to the system operation and planning. To cope with uncertainties the Distribution System Operator (DSO) could implement several strategies. These strategies range from the inclusion of smart technologies which will increment system’s flexibility and resiliency, to improvements in forecasting, modeling, and regulatory pledge that will facilitate the planning activity. Regardless of the nature of the solutions, they could be collected in a sort of toolbox. The planner will access the toolbox to conform cost effective plans, better able to deal with any uncertainty. The present work will address the problem of distribution system planning under uncertainties, considering smart solutions along with traditional reinforcements, in the short-term lead time up to 3 years ahead. The work will be focused on three aspects that are the cornerstones of this work: • A planning facilitating strategy: Distribution Capacity Contracts (DCCs). • A flexibility enabler technology: Energy Storage. • A binding methodology: Multistage Stochastic Programming. Stochastic dual dynamic programming (SDDP). Under the present directive of the European Parliament concerning common rules for the internal market in electricity, distribution companies are not allowed to own DG but entitled to include it as a planning option to differ investment in traditional grid reinforcements. An evaluation of the regulatory context will lead this work to consider DCCs as a planning alternative available in the toolbox. The impact of this type of contract on the remuneration of the DG owner will be assessed in order to provide insight on its willingness to participate. The DCCs might aid the DSO to defer grid i ii investments during planning stages and to control the network flows during operation. Given that storage solutions help to match in time production from intermittent sources with load consumption, they will play a major role in dealing with uncertainties. A generic storage model (GSM) based on a future cost piecewise approximation will be developed. This model inspired by hydro-reservoirs will help assessing the impact of storage in planning decisions. This model will be tested by implementing it in short-term hydro scheduling and unit commitment studies. To trace a path towards the future of this research work, a discussion on the planning problem formulation, under consideration of the lead time, the expansion options, the smart strategies, and the regulatory framework will be presented. Special focus will be given to multistage stochastic programming methods and in particular to the SDDP approach.
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| 13. |
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| 14. |
- Andersson, Marcus, et al.
(författare)
-
Interfering signals and attenuation : potential problems with communication via the power grid
- 2006
-
Ingår i: Proceedings of Nordic Distribution and Asset Management Conference.
-
Konferensbidrag (refereegranskat)abstract
- This paper will give a general overview of the potential problems associated with remote-meter reading via the power grid and describe some of the technologies available. A comparison will be made between the power grid as a communication channel and other, dedicated and shared, channels. Examples will be given of practical cases in which the communication channel does not function in the intended way.
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| 15. |
- Blanco, Ana Maria, et al.
(författare)
-
Impact of flat-top voltage waveform distortion on harmonic current emission and summation of electronic household appliances
- 2018
-
Ingår i: The Renewable Energies and Power Quality Journal. - : EA4EPQ-European Association for the Development of Renewable Energy, Environment and Power Quality. - 2172-038X. ; 1:16, s. 698-703
-
Tidskriftsartikel (refereegranskat)abstract
- Electronic household appliances are non-linear loads and emit harmonics into the low voltage networks. Usually, these loads are simply modelled by constant current source models, which only represent the harmonic emission of the appliances for a single supply voltage distortion, mostly sinusoidal conditions. Measurements have shown that the harmonic currents emitted by electronic devices can significantly depend on the circuit topology and the existing supply voltage distortion. This paper studies the impact of supply voltage distortion, which can be typically found in public low voltage networks (so-called flat-top voltage waveform), on the harmonic current emission of individual devices with different circuit topologies as well as the impact of supply voltage distortion on the harmonic summation of these devices.
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| 16. |
- Bollen, Math, et al.
(författare)
-
A Measurement-Based Definition of Phase-Angle for Negative-Sequence Unbalance
- 2020
-
Ingår i: IEEE Transactions on Power Delivery. - : IEEE. - 0885-8977 .- 1937-4208. ; 35:5, s. 2561-2564
-
Tidskriftsartikel (refereegranskat)abstract
- This letter proposes a measurement-based definition for the phase-angle of the negative-sequence voltage that fits in the general approach used in the IEC standard for power-quality measurements, IEC 61000-4-30. The definition is based on an expression that is obtained during a derivation of the classical expression for calculating the negative-sequence voltage from the rms values of the three line-to-line voltages. The definition can be applied to the 10/12 cycle, 150/180-cycle and 10-minute values.
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| 17. |
- Bollen, Math, et al.
(författare)
-
A wind park emitting characteristic and non-characteristic harmonics
- 2010
-
Ingår i: 2010 14th International Power Electronics and Motion Control Conference (EPE/PEMC 2010). - Piscataway, NJ : IEEE Communications Society. - 9781424478569 ; , s. S14-22-S14-26
-
Konferensbidrag (refereegranskat)abstract
- This paper shows measurements of the emission of harmonics by a small windpark. The spectrum consists of the characteristic harmonics associated with six-pulse converters and a broadband spectrum covering frequencies at which emission normally is not present. These frequencies are caused by the switching pattern of the power-electronics converters. Similar spectra have been reported by other authors and for other types of modern converters. Whereas the actual emission is small, the presence of emission at non-characteristic frequencies could result in voltage distortion limits being exceeded.
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| 18. |
- 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.
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| 19. |
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| 20. |
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| 21. |
- Bollen, Math, et al.
(författare)
-
Consequences of Smart Grids for Power Quality Overview of the Results from CIGRE Joint Working Group C4.24/CIRED
- 2018
-
Ingår i: 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT-Europe 2017. - New York : Institute of Electrical and Electronics Engineers (IEEE). - 9781538619537
-
Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of the expected unintended (negative) consequences for power quality of several on-going developments in the power system. Four developments directly related to smart-grid technology are covered: microgrids; advanced voltage control; feeder reconfiguration; and demand-side management. Four developments indirectly related are also covered: new sources of electricity production; increased used of active power-electronic converters; shift from overhead lines to cables; and new types of lighting. The paper summarizes the discussions in an international working group and presents the main findings are recommendations.
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| 22. |
- Bollen, Math, et al.
(författare)
-
Future work on harmonics : some expert opinions part I – wind and solar power
- 2014
-
Ingår i: Proceedings - International Conference on Harmonics and Quality of Power. - : IEEE. - 1540-6008 .- 2164-0610. ; , s. 904-908
-
Tidskriftsartikel (refereegranskat)abstract
- A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. The results of this discussion are summarized in this paper and some of the issues are discussed in more detail in this paper and in its companion paper. This paper discusses emission from wind and solar power as well as advantages and disadvantages of active and passive filters.
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| 23. |
- Bollen, Math H J, et al.
(författare)
-
Harmonics and Wind Power Installations
- 2021
-
Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : IEEE. ; , s. 648-652
-
Konferensbidrag (refereegranskat)
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| 24. |
- Bollen, Math, et al.
(författare)
-
Harmonic and interharmonic distortion due to a windpark
- 2010
-
Ingår i: IEEE Power and Energy Society General Meeting. - Piscataway, NJ : IEEE Communications Society. - 9781424465491 - 9781424483570
-
Konferensbidrag (refereegranskat)abstract
- This paper discusses two aspects of the impact of windparks on the waveform distortion in the power system: emission and resonances. The paper gives a general overview of the emission and shows measurement results from a small but modern windpark connected to a 10-kV feeder and estimates the need for network strength to limit the resulting voltage distortion. The paper also gives a general overview of harmonic resonances associated with windparks and illustrates this by means of two numerical examples. Important conclusions from this paper are than harmonic resonances are more likely to be a concern that the emission from windparks, and that the interharmonic emission and the emission at non-characteristic harmonics are more prominent than with existing installations.
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| 25. |
- Bollen, Math, et al.
(författare)
-
Harmonic emission from installations with energy-efficient lighting
- 2011
-
Ingår i: Proceeding of the International Conference on Electrical Power Quality and Utilisation, EPQU. - Piscataway, NJ : IEEE Communications Society. - 9781467303798 ; , s. 797-802
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the results from a number of measurements of the harmonic emission from installations that contain a large number of energy-efficient lamps. Two of the measurements concern the replacement of incandescent lamps with CFL and LED; the other measurement concerns an installation with up to 48 fluorescent lamps with high-frequency ballasts. The paper also contains a discussion on why the (total) power factor is not a good measure to quantify the performance of lamps or installations containing large numbers of lamps
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| 26. |
- Bollen, Math, et al.
(författare)
-
Hosting Capacity of the Grid for Photovoltaic Installations : a Stochastic Approach Applied to Single-phase Connections
- 2018
-
Ingår i: DIGITAL PROCEEDINGS. - : Energynautics GmbH.
-
Konferensbidrag (refereegranskat)abstract
- This paper discusses the voltage rise due to PV installations connected to a low-voltage network. The connection of individual installations is studies for both single-phase and three-phase connection. A stochastic method is presented to estimate the hosting capacity. This method is illustrated for random and coordinated connection of single-phase installations. It is shown, in a number of ways, that the installation of large (e.g. 6 kW) single-phase connected units can easily result in unacceptable overvoltages.
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| 27. |
- Bollen, Math, et al.
(författare)
-
Hosting Capacity of the Power Grid for Renewable Electricity Production and New Large Consumption Equipment
- 2017
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 10:9
-
Tidskriftsartikel (refereegranskat)abstract
- After a brief historical introduction to the hosting-capacity approach, the hosting capacity is presented in this paper as a tool for distribution-system planning under uncertainty. This tool is illustrated by evaluating the readiness of two low-voltage networks for increasing amounts of customers with PV panels or with EV chargers. Both undervoltage and overvoltage are considered in the studies presented here. Probability distribution functions are calculated for the worst-case overvoltage and undervoltage as a function of the number of customers with PV or EV chargers. These distributions are used to obtain 90th percentile values that act as a performance index. This index is compared with an overvoltage or undervoltage limit to get the hosting capacity. General aspects of the hosting-capacity calculations (performance indices, limits, and calculation methods) are discussed for a number of other phenomena: overcurrent; fast voltage magnitude variations; voltage unbalance; harmonics and supraharmonics. The need for gathering data and further development of models for existing demand is emphasised in the discussion and conclusions
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| 28. |
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| 29. |
- Bollen, Math, et al.
(författare)
-
Modelling and simulation issues resulting from extended measurements
- 2015
-
Ingår i: 2015 IEEE Power & Energy Society General Meeting. - Piscataway, NJ : IEEE Communications Society. - 9781467380409
-
Konferensbidrag (refereegranskat)abstract
- Presents a collection slides covering the following topics: supraharmonics propagation; measurement modeling; grid supply terminals; device terminals; secondary emission; primary emission; voltage measurement and capacitor
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| 30. |
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| 31. |
- Bollen, Math, et al.
(författare)
-
Power Quality Concerns in Implementing Smart Distribution-Grid Applications
- 2017
-
Ingår i: IEEE Transactions on Smart Grid. - : IEEE. - 1949-3053 .- 1949-3061. ; 8:1, s. 391-399
-
Tidskriftsartikel (refereegranskat)abstract
- This paper maps the expected and possible adverse consequences for power quality of introducing several smart distribution-grid technologies and applications. The material presented in this paper is the result of discussions in an international CIGRE-CIRED joint working group. The following technologies and applications are discussed: microgrids; advanced voltage control; feeder reconfiguration; and demand-side management. Recommendations are given based on the mapping.
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| 32. |
- Bollen, Math, et al.
(författare)
-
Primary and Secondary Harmonics Emission : Harmonic interaction - A set of definitions
- 2016
-
Ingår i: 2016 17th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Computer Society. - 9781509037926 ; , s. 703-708
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes a set of definitions to simplify the discussion about the different contributions to the harmonic currents at the terminals of a device or an installation. Definitions are given, and explained, for 'primary harmonic emission', 'secondary harmonic emission', and 'harmonic interaction'
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| 33. |
- Bollen, Math, et al.
(författare)
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Spread of high frequency current emission
- 2013
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Ingår i: 22nd International Conference and Exhibition on Electricity Distribution (CIRED 2013). - Red Hook, NY : Curran Associates, Inc.. - 9781849197328
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the spread of the high frequency current emission between devices of different size and the grid. The impact of the EMC filter, either LCL or CLC configuration, has been considered from a simplified model. The high frequency current emission, produced by a large device, can potentially cause a relatively large current flowing through a nearby small device. An important conclusion from the study is that current amplification can occur due to harmonic resonances between different types of filters.
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| 34. |
- Bollen, Math, et al.
(författare)
-
Standards for supraharmonics (2 to 150 kHz)
- 2014
-
Ingår i: IEEE Electromagnetic Compatibility Magazine. - 2162-2264. ; 3:1, s. 114-119
-
Tidskriftsartikel (refereegranskat)abstract
- There is a serious interest from the international standard-setting community in knowledge about voltage and current distortion in the frequency range 2 to 150 kHz, referred to as supraharmonics. At the same time, research is ongoing at a number of locations, but the knowledge about supraharmonics remains limited. This paper compares some of the properties of harmonics and supraharmonics. An increase in supraharmonics for individual devices is observed in association with a decrease in harmonic emission (i.e. below 2 kHz). A proposal is made for setting limits in this frequency range. The proposal is based on existing standards and is meant to be for discussion. The authors strongly encourage an open discussion about the proposed limits. There are a number of differences between harmonics and supraharmonics that are not covered by the proposed set of limits. A substantial amount of further research is needed to extend the standard framework for supraharmonics such that this can be covered by standards
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| 35. |
- Bollen, Math, et al.
(författare)
-
Typical harmonic levels and spectra with low-voltage customers
- 2019
-
Ingår i: CIRED 2019 Proceedings. - : AIM.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents levels of harmonic voltage distortion with low-voltage customers during 2017 and 2018. Measurements were obtained over a period between one hour and one day per location. Results are presented for the harmonics in the phase-to-neutral voltage at 163 locations; the highest 10-minute values per location have been used for presenting the results. For harmonics in the neutral-to-ground voltage, 1-second values at 88 locations have been used. The harmonic levels showed to be well below the limits in EN 50160 and IEC 61000-2-2 for almost all locations and for all harmonics with exception of harmonics 9, 15 and 21. The dominating frequencies at most locations are harmonics 5 and 7.
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| 36. |
- Busatto, Tatiano, et al.
(författare)
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Comparison of Models of Single-Phase Diode Bridge Rectifiers for Their Use in Harmonic Studies with Many Devices
- 2022
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Harmonic modeling of low-voltage networks with many devices requires simple but accurate models. This paper investigates the advantages and drawbacks of such models to predict the current harmonics created by single-phase full-bridge rectifiers. An overview is given of the methods, limiting the focus to harmonic analysis. The error of each method, compared to an accurate numerical simulation model, is quantified in frequency and time domain considering realistic input scenarios, including background voltage distortion and different system impedances. The results of the comparison are used to discuss the applicability of the models depending on the harmonic studies scale and the required level of detail. It is concluded that all models have their applicability, but also limitations. From the simplest and fastest model, which does not require a numerical solution, to the more accurate one that allows discontinuous conduction mode to be included, the trade-off involves accuracy and computational complexity.
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| 37. |
- Busatto, Tatiano, et al.
(författare)
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Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations
- 2020
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Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 180
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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.
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| 38. |
- Busatto, Tatiano, et al.
(författare)
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Experimental Harmonic Analysis of the Impact of LED Lamps on PV Inverters Performance
- 2019
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Ingår i: 2019 Electric Power Quality and Supply Reliability Conference (PQ) & 2019 Symposium on Electrical Engineering and Mechatronics (SEEM). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- It is known for instance that voltage waveform distortion and network impedance have a significant impact on PV inverter current emissions. Because this, much research is still required to better understand their behavior and impact when multiple common household devices are placed to operate together in the same low-voltage installation. In particular, this paper addresses the harmonic impact of LED lamps on PV inverters performance considering different technologies and number of lamps. The analysis has been carried out with different scenarios considering two types of LED lamps, with and without power factor correction feature, and three different PV inverter technologies. The evaluation of the impacts is simply performed by frequency and time domain analysis, establishing the correlation between the devices current harmonics. The results obtained from the experiments have shown that LED lamps are prone to add a significant impact on the PV inverter current harmonics, and this impact is mainly dependent on the devices used technology.
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| 39. |
- Busatto, Tatiano, et al.
(författare)
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Including Uncertainties from Customer Connections in Calculating Low-Voltage Harmonic Impedance
- 2019
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Ingår i: IEEE Transactions on Power Delivery. - : IEEE. - 0885-8977 .- 1937-4208. ; 34:2, s. 606-615
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 40. |
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| 41. |
- Busatto, Tatiano, et al.
(författare)
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Stability Analysis of PFC Converters Under Different Source Impedances and Its Consequences on Zero-Crossing Distortion
- 2022
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Ingår i: IEEE Transactions on Power Delivery. - : IEEE. - 0885-8977 .- 1937-4208. ; 37:4, s. 3235-3244
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Tidskriftsartikel (refereegranskat)abstract
- In the presence of multiple power converters in a power system the total current may exhibit zero-crossing distortion in the form of recurrent damped oscillations with high magnitude. These oscillations are synchronized with the power system frequency. This paper presents a comprehensive analysis of the input current of single-phase ac-dc converters fitted with power factor correction (PFC) controllers. Emphasis is given on the impacts of the source impedance, and on how the number of converters connected to a common coupling point (PCC) impacts the PFC controller’s performance. A system model is developed followed by simulation and measurements in a real installation with electronic ballasts used to drive fluorescent lighting tubes. Results show that the recurrent damped oscillations originating from PFC controllers are close to the harmonic range and with a very low level of cancellation between devices. The magnitude therefore increases proportionally with the number of devices. As the source impedance increases, instability may occur. Possible explanations for these observations are discussed.
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| 42. |
- Busatto, Tatiano, et al.
(författare)
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Supraharmonics Emission Assessment of Multi-level Converters Applied for Photovoltaic Grid-Connected Inverters
- 2017
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Ingår i: The Renewable Energies and Power Quality Journal. - Spain : EA4EPQ-European Association for the Development of Renewable Energy, Environment and Power Quality. - 2172-038X. ; 1:15, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- Topologies for different DC-AC converters used on grid-connected photovoltaic (PV) inverters are analysed and compared within this paper. The main focus is to evaluate the supraharmonic emission in the frequency range 2 to 150 kHz. For this study three topologies are evaluated: Neutral Point Clamped (NPC), the Cascaded H-bridge (CHB) and the Flying Capacitor (FC). To approximate the operation closer to a real scenario, the converters are analysed under the presence of voltage waveform distortion in the power supply. The simulation is performed using PSpice for the converters and Simulink for the grid. The characterization is made by the quantification of harmonics and supraharmonics, and also by the frequency domain analysis of the output current. Finally, a comparison of the chosen technologies is carried out, given a better understanding on the elements which exert influence on this type of emission.
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| 43. |
- de Oliveira, Roger Alves
(författare)
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Applications of Unsupervised Deep Learning for Analysing Time-Varying Power Quality Big Data
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Continuous power quality monitoring allows grid stakeholders to obtain information about the performance of the network and costumer facilities. Moreover, the analysis of continuous monitoring allows researchers to obtain knowledge on power quality phenomena. Power quality measurements result in a large amount of data. Power quality data can be classified as big data, not only for its volume, but also for the other complexities: velocity, variety, and veracity. Manual analysis of power quality data is possible but time-consuming. Moreover, data reports based on standardized indexes and classical statistical techniques might hide important information of the time-varying behaviour in power quality measurements. Artificial intelligence plays a role in providing automatic tools for proper analytics of big data. A subset of artificial intelligence called machine learning has enabled computers to learn without explicit programming. Driven by the huge improvements in computer processing, a subset of machine learning based on multiple layers of artificial neural networks has been developed to tackle increasingly complex problems. The so-called deep learning applications teach themselves to perform a specific task by automatically extracting essential features from the raw data. Despite the possibilities of automatic feature extraction, most applications of deep learning to power quality are still the same as expert systems or earliest machine learning tools. Moreover, most of the applications are based on synthetic generated data and supervised techniques. In this context, the main motivation of this thesis is providing a new tool based on unsupervised deep learning to handle analytics of time-varying power quality big data. The unsupervised deep learning method proposed in this thesis combines a deep autoencoder with clustering for extracting patterns and anomalies in power quality big data. The deep autoencoder maps the original data to a compressed format that contains the principal features of the data. Automatic results are provided by the deep learning, and inferences can be obtained without requiring prior knowledge of deep learning. The outputs from unsupervised deep learning can serve as a guide for further data analysis, highlighting important time steps within large power quality datasets. By following these indications from the deep learning results, experts gain valuable insights into power quality phenomena, which can be referred to as "learning from deep learning". The interpretation of the deep learning results in this thesis allowed to making proper inferences for patterns and anomalies. For power quality measurements synchronised with 24-h, the results allowed making inferences concerning daily variations, seasonality, and the origins of power quality disturbances. For power quality measurements non-synchronised with 24-h, the results could be interpreted visually through the distribution of the patterns in a physical variable, such as the dynamic operating conditions of an electrical railway power system.An important contribution of this thesis concerns the physical interpretation of the phenomena is related to the anomalies in harmonics caused by geomagnetically induced currents. An interesting finding by applying the deep anomaly detection to measurements in the Swedish transmission grid is the damping of the anomalies caused by geomagnetically induced currents in the winter due to the heating load. This thesis also demonstrated that the signatures for anomalies in harmonic measurements in a Swedish transmission location are similar to the ones found in a low-latitude transmission location at the South Atlantic Anomaly due to geomagnetically induced currents. Moreover, by cross-checking the anomalies at the South Atlantic Anomaly with protection trips with undetermined causes, this thesis demonstrated that anomaly harmonics due to geomagnetically induced currents can cause protection mal trips.This thesis demonstrates that unsupervised deep learning can serve as an additional tool for compressing time-varying power quality big data into a more interpretable form. Despite the application of an unsupervised method, power quality experts remain significant in power quality studies. The main conclusion of this thesis is that unsupervised deep learning enhances the understanding of power quality experts and provides a complementary approach for analysing and extracting insights from time-varying power quality big data.
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| 44. |
- de Oliveira, Roger Alves, et al.
(författare)
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Deep Learning For Pattern Recognition Of Interharmonics In Time-Series And Spectrograms
- 2021
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Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 738-741
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Konferensbidrag (refereegranskat)abstract
- This work applies an unsupervised deep feature learning to finding patterns of interharmonics. The main objectives of this work are to provide an additional graphical tool to handle two distinct data inputs: (a) individual interharmonics components in time-series; (b) broadband spectrum by employing spectrograms. Both data inputs are analysed employing an autoencoder based on convolutional neural networks followed by clustering. The application of the method results in the most common patterns in time-series or spectrograms. Two study cases are presented by applying the method to measurements from solar installations in Finland and Sweden. The results show the usefulness of the method to recognize interharmonics in a single frequency and broadband spectrum.
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| 45. |
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| 46. |
- de Oliveira, Roger Alves, et al.
(författare)
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Deep Learning Method With Manual Post-Processing for Identification of Spectral Patterns of Waveform Distortion in PV Installations
- 2021
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Ingår i: IEEE Transactions on Smart Grid. - : IEEE. - 1949-3053 .- 1949-3061. ; 12:6, s. 5444-5456
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a deep learning (DL) method for the identification of spectral patterns of timevarying waveform distortion in photovoltaic (PV) installations. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. This paper shows that the DL method can be used as a starting point for further data analysis. The main contributions of the paper include: (a) providing a novel DL method for finding patterns in spectra; (b) guiding the manual post-processing based on the patterns found by the DL method; and (c) obtaining information about the emission from four PV installations.
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| 47. |
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| 48. |
- de Oliveira, Roger Alves, et al.
(författare)
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Third Harmonic and its Relation to Solar Elevation Angle in a PV Installation with Solar Tracking Systems
- 2022
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Ingår i: 2022 20th International Conference on Harmonics & Quality of Power (ICHQP) Proceedings. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This paper shows an application of a deep learning method to a solar installation with a solar tracking system. The method consists of a deep autoencoder followed by clustering. The deep learning method allows defining the most dominant component in harmonic spectra during long-term measurements. Power Quality measurements were accessed over two years in 3ϕ PV installation of 6 kVA with 2-axis tracking in northern Sweden. The deep learning results indicate that the third harmonic of current is the component that changes most over the two years. This paper demonstrates that there is a correlation between the daily and seasonal variations of the third harmonic with the solar elevation angle at the location. The main conclusion for this cause was associated with the operation of the solar tracking systems which are based on single-phase motors. The paper also discusses the possibility of correlation of the third harmonic with cloud coverage, snow on the panels, and reactive power unbalance.
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| 49. |
- De Souza Salles, Rafael, et al.
(författare)
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Interharmonic Analysis for Static Frequency Converter Station Supplying a Swedish Catenary System
- 2022
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Ingår i: 2022 20th International Conference on Harmonics & Quality of Power (ICHQP) Proceedings. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- The paper aims to present a waveform distortion analysis focused on interharmonics in measurements from a 70 kV busbar feeding a traction supply substation with four static frequency converters (SFC). The substation supplies a Swedish catenary system from 50 Hz public grid to 15 kV 16 ⅔ Hz. The paper assesses the interharmonics for different scenarios regarding the point of a connection configuration between the traction substation and the upstream grid, as well as a change in the number of SFCs connected in the substation. The IEC 61000-4-7 grouping method and spectrograms were used to illustrate the issue. The significant presence of interharmonics calls attention to the subject in railway application. The total indexes help to evaluate the broad picture of the phenomena. The work contributes to the waveform distortion and interharmonics in railway systems studies.
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| 50. |
- De Souza Salles, Rafael, et al.
(författare)
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Waveform Distortion Emission Assessment on Pantograph Measurements from Low-Frequency Railway Electrification
- 2022
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Ingår i: 2022 20th International Conference on Harmonics & Quality of Power (ICHQP) Proceedings. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- The paper aims to provide a waveform distortion assessment on pantograph current measurements. The data analyzed is regarding a 15 kV 16.7 Hz catenary system from Switzerland. The paper provides a characterization of the rolling stock emission content for different operation modes during a commercial utilization of the vehicle, approaching traditional harmonics, interharmonic and supraharmonic phenomena. In addition, the work provides an adaptation on the interharmonic processing proposed by the IEC 61000-4-7 regarding the 16.7 Hz fundamental frequency. The results contribute to the waveform distortion emission on pantograph measurements subject and railway systems investigation in general.
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