| 41. |
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| 42. |
- Leisse, Ingmar, et al.
(author)
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Coordinated voltage control in medium and low voltage distribution networks with wind power and photovoltaics
- 2013
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In: PowerTech (POWERTECH), 2013 IEEE Grenoble.
-
Conference paper (peer-reviewed)abstract
- Distributed Generation (DG) installations have been increasing during the last years. Wind power and photovoltaics are two of the most common renewable energy sources for DG typically connected to the distribution network (DN) originally planned and built to supply loads. DG units connected to the DN impact the voltage where customers are connected. Network voltage is an important quality criterion in DN. Voltage rise caused by DG units may become one of the limiting factors for the hosting capacity of wind power and photovoltaics in DNs. Increasing the hosting capacity by network rebuilding is possible but it is expensive and time consuming. Coordinated voltage control has been proposed to increase network capacity without the need of reinforcement. Simulations based on an existing medium and low voltage DN with wind power and photovoltaics are presented. It is shown that coordinated voltage control can increase the hosting capacity and avoid network reinforcement.
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| 43. |
- Leisse, Ingmar, et al.
(author)
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Electricity Meters for Coordinated Voltage Control in Medium Voltage Networks with Wind Power
- 2010
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In: Innovative Smart Grid Technologies Conference Europe (ISGT Europe), 2010 IEEE PES. - 9781424485086 - 9781424485093 ; , s. 1-7
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Conference paper (peer-reviewed)abstract
- During the last years the amount of electricity generated by Distributed Energy Resources (DER), especially wind turbines, has been increasing a lot. These Distributed Generation (DG) units are often connected to rural distribution networks, where they have a large impact on the voltage and the network losses. The network voltage at the customers point of connection is an important quality criteria and has to follow different standards as e.g. EN 50160. Therefore the voltage change caused by the integration of production units in the distribution network is an important aspect when integrating more DG in distribution networks and often a limiting factor for the maximum DG capacity which is possible to integrate into an existing network without reinforcement. Using the available voltage band more efficient by applying coordinated voltage control is a possibility to increase the hosted DG capacity in an existing distribution network without reinforcement of the network. To get the actual network status the new generation of electricity meters, which have the feasibility to communicate real time voltage measurements from the customers side to a network controller, give some benefits to a more flexible and coordinated voltage control in the network. The voltage range in the network will be used adapted to the actual load and generation situation instead of using worst case assumptions as it is good practice until now. A main part of the voltage control in medium voltage distribution networks is done by the on-load tap changer (OLTC) which takes the voltage at the consumers point of connection into account. A generic 10 kV distribution network with three typical types of feeders, as pure load, pure generation and mixed load and generation feeder, has been outlined. Coordinated voltage control is implemented by a central voltage controller. Simulations on the voltage and the network losses have been done and will be presented in this paper. The maximum DG capacity in the test system increases most when introducing coordinated control of the OLTC but also the use of reactive power adds some benefit. Further increase of the DG capacity by more extensive use of curtailment is always possible but due to economical aspects not favoured.
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| 44. |
- Leisse, Ingmar, et al.
(author)
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Increasing DG Capacity of Existing Networks through Reactive Power Control and Curtailment
- 2010
-
Conference paper (peer-reviewed)abstract
- Renewable energy sources (RES), especially wind turbines, have become more important during the last years. An increasing number of distributed generation (DG) units are connected to weak medium voltage distribution networks in rural areas where they have a large influence on the voltage and the line losses. Voltage rise is in this case often a limiting factor for the maximum amount of DG capacity. Already current wind turbines with a capacity of 2 MW can often not easily be connected to existing 10 kV feeders. To increase the DG capacity of existing networks without reinforcement DG units can be controlled. This paper proposes abandoning unity power factor used today and letting the converters used as network interface of many new wind turbine generators absorb reactive power to reduce the voltage level. Since reactive power has great influence on losses in the network the use of reactive power is limited. Line losses due to the transfer of reactive power are taken into account in this study. Furthermore the use of curtailment is analysed. Simulations of voltage change and line losses when using reactive power control by the connected wind turbines and curtailment in a simple test system are presented. Without reinforcement of the network it was possible to increase the DG capacity from 2;7MW to more than 4MW in the test network without violating voltage limits. Line losses increase but to a reasonable extent and lost energy due to curtailment is insignificant.
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| 45. |
- Liberg, Olof, et al.
(author)
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Monitoring of wolves in Scandinavia
- 2012
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In: Hystrix, the Italian Journal of Mammalogy. - 0394-1914 .- 1825-5272. ; 23, s. 29-34
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Journal article (peer-reviewed)abstract
- The Scandinavian wolf population is jointly monitored by Norwegian and Swedish authorities. Monitoring is made annually. Wolves are classified in different categories. Family groups (>= 3 animals sharing a territory), territorial pairs, other stationary wolves, and vagrants. Also number of reproductions are determined each year, and has the highest priority as national management goals for the wolf population in both countries are expressed as number of reproducing units. Three methods are used in combination. Tracking on snow is the basic method. Around 100 field workers are employed full time or part time to find and follow tracks of wolves during the monitoring season Oct. 1 - Feb 28. The second method is DNA-analysis, mainly based on wolf scats collected during tracking. DNA-analysis help verifying reproductions, identifying newly established pairs, differentiating between neighboring territories and for identifying new immigrants from the Finnish/Russian population. The third method is radio telemetry. 10-20 wolves are equipped with GPS-collars each year, and used for determining of territory extents and differentiating between neighboring territories. All monitoring data are recorded in national databases, and compiled each year in an annual monitoring reports. Annual budget for large carnivore monitoring in the two countries combined in 2011 was approximately 5.8 million Euro, of which approximately 1.5 million was spent on wolves.
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| 46. |
- Mernelius, Sara, et al.
(author)
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Compliance with hygiene guidelines : The effect of a multimodal hygiene intervention and validation of direct observations
- 2013
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In: American Journal of Infection Control. - : Elsevier. - 0196-6553 .- 1527-3296. ; 41:5, s. E45-E48
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Journal article (peer-reviewed)abstract
- BackgroundGood compliance with hygiene guidelines is essential to prevent bacterial transmission and health care-associated infections. However, the compliance is usually <50%.MethodsA multimodal and multidisciplinary hygiene intervention was launched once the baseline compliance was determined through direct observations in 4 departments of obstetrics and gynecology. Detailed evaluations of the compliance rates were performed at point of stability (at 80%) and follow-up (3 years after hygiene intervention). Validation of direct observations was performed using blinded double appraisal and multiappraisal.ResultsAt baseline, the compliance with barrier precautions and the dress code at the 4 departments were 39% to 47% and 79% to 98%, respectively. Point of stability was reached approximately 1 year after the hygiene intervention was launched. The compliance with barrier precautions was significantly higher at follow-up compared with baseline in 3 departments. In the validation by double appraisal, 471 of 483 components were judged identical between observers. In the multiappraisal, 95% to 100% of the observers correctly judged the 7 components.ConclusionIt is possible to improve compliance with hygiene guidelines, but, to ensure a long-lasting effect, a continuous focus on barrier precautions is required. Observation is a valid method to monitor compliance.
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| 47. |
- Rask, Olof, et al.
(author)
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Venös tromboembolism hos barn
- 2010
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In: Klinisk handläggning av venös tromboembolism. - 9789144053196 ; , s. 161-174
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Book chapter (peer-reviewed)
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| 48. |
- Safari Tirtashi, Mohammad Reza, et al.
(author)
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Control strategies for reactive shunts to improve long-term voltage stability
- 2013
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In: Power Engineering Conference (UPEC), 2013 48th International Universities.
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Conference paper (peer-reviewed)abstract
- Voltage collapse was one of the main causes for many recent blackouts. The direct link between voltage stability and reactive power balance in the system leads to more attention toward reactive power resources in the power systems. Shunt reactors and capacitors are used to balance reactive power in the power systems. The strategy to control them in both normal and emergency conditions is an important issue. This paper deals with two different strategies for automatic switching of shunt reactors and capacitors in the power systems. The first control strategy, called the local scheme, switches the shunt when the voltage at the local bus is outside the tolerance band. In the second control strategy, called neighboring scheme, local voltage as well as voltage at neighboring buses are used. Dynamic simulations of the NORDIC 32 test system show that the neighboring scheme improves voltage compared to the local one. In the simulated scenario a blackout is avoided by using the neighboring scheme. This is explained using PV curves for a new test system reflecting the key behavior of NORDIC 32.
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| 49. |
- Safari Tirtashi, Mohammad Reza, et al.
(author)
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Long-Term Voltage Collapse Analysis on a Reduced Order Nordic System Model
- 2014
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In: 2014 49th International Universities Power Engineering Conference (UPEC). - 9781479965564 ; , s. 1-6
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Conference paper (peer-reviewed)abstract
- This paper analyzes and explains the mechanism behind long-term voltage collapse in the NORDIC32 test system. For this purpose a simplified test system called N5area, reflecting the key voltage collapse characteristics of NORDIC32 is proposed. Applying control algorithms is much easier in N5area than in NORDIC32. Load recovery and generator excitation current limiter actions which are two important factors contributing to long-term voltage collapse are considered. Dynamic simulation results for a specified long-term voltage instability scenario are explained and discussed. The effect of generator current limiters is analyzed using PV curves. Furthermore, two different control strategies for controlling the shunt capacitors are applied as countermeasures to save the system. The two strategies are explained and compared and it is shown that control using the voltage at neighboring buses gives better performance.
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| 50. |
- Sotres, Javier, et al.
(author)
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AFM-based friction force spectroscopy : a novel methodology for the study of the strength and lateral diffusion of proteinaceous films
- 2012
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In: Proteins at Interfaces III State of the Art. - : American Chemical Society (ACS). - 9780841227972 ; , s. 129-151
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Book chapter (other academic/artistic)abstract
- We present a novel methodology for the study of proteinaceous films based on the friction force spectroscopy operation mode of the atomic force microscope. It provides information both on the strength at the nanoscale level and on the lateral diffusion properties of these systems. The usefulness of the data generated by this methodology are shown through its application to the study of different types of monolayers of model proteins, as well as to the study of the more complex and heterogeneous salivary films.
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