| 1. |
- Besnard, Francois, et al.
(författare)
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An Optimization Framework for Opportunistic Maintenance of Offshore Wind Power System
- 2009
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Ingår i: 2009 IEEE BUCHAREST POWERTECH, VOLS 1-5. - NEW YORK : IEEE. - 9781424422340 ; , s. 2970-2976
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Konferensbidrag (refereegranskat)abstract
- A sound maintenance planning is of crucial importance for wind power farms, and especially for offshore locations. There is a large potential in cost savings by maintenance optimization to make the projects more cost-efficient. This paper presents an opportunistic maintenance optimization model for offshore wind power system. The model takes advantage of wind forecasts and corrective maintenance activities in order to perform preventive maintenance tasks at low costs. The approach is illustrated with an example to demonstrate the value of the optimization. In this example 43% of the cost to perform preventive maintenance could be saved using the proposed method.
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| 2. |
- Bollen, Math, et al.
(författare)
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Controlled island operation of part of the 50-kV grid in Southern Sweden
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech Proceedings. - Piscataway, NJ : : IEEE Communications Society. - 9781424422357 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- This paper is based on measurements obtained during a test of controlled islanding of part of the 50-kV grid in Southern Sweden. The purpose of the test was to verify operation of generator controls during islanding. The variations in voltage magnitude and frequency are shown as well as flicker severity and very-short variations. A number of performance indices have been calculated and compared with limits. Voltage magnitude and frequency have been studied in some detail around the disconnection and reconnection instants. The frequency varies much more during the island operation than during grid-connected operation. Voltage magnitude variations and flicker remain within their normal range. However the variations in the time range between 3 seconds and 10 minute appear to be higher than normal.
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| 3. |
- Bollen, Math, et al.
(författare)
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Performance indicators for microgrids during grid-connected and island operation
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech Proceedings. - Piscataway, NJ : IEEE Communications Society. - 9781424422357
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Konferensbidrag (refereegranskat)abstract
- This paper discusses methods for quantifying the performance of microgrids during island operation. Such methods are essential for comparing different designs and different control algorithms. Performance indicators and objectives are proposed for voltage-quality variations, for individual dips and interruptions, and for the reliability during island operation.
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| 4. |
- Hassan, F., et al.
(författare)
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Active islanding of a current-controlled converter-interfaced DG
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech. - Piscataway, NJ : IEEE Communications Society. - 9781424422357
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Konferensbidrag (refereegranskat)abstract
- Islanding of a voltage source converter (VSC) equipped DG unit is considered in this paper. Some internal controller signals are implemented in the islanding detection method in order to provide a robust operation. Particularly, the estimated frequency of the grid voltage along with a point of common coupling (PCC) voltage regulator and a dynamic reference-current limiter are proposed for islanding detection algorithm. Using a PCC-voltage regulator adds the active, or dynamic, property for the detection algorithm and increases its reliability. Moreover, implementing a dynamic current limiter, a robust operation is achieved. Through the proper design of the current limiter, the DG unit can have the ability to ride-through voltage dips with magnitudes above a certain limit, which can be set according to the grid codes, and detect islanding if the voltage decreases beyond that limit. The algorithm has also been verified for the case of island motor loads, which is considered as the worst case since dynamic loads affect the grid states in the case of islanding.
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| 5. |
- Istardi, Didi, et al.
(författare)
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Understanding Power System Voltage Collapses Using ARISTO: Effects of Protection
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech: Innovative Ideas Toward the Electrical Grid of the Future; Bucharest; Romania; 28 June 2009 through 2 July 2009. - 9781424422357
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Konferensbidrag (refereegranskat)abstract
- This paper is based on a project work of the course "Power Engineering Design Project" given by the Division of Electric Power Engineering, Chalmers University of Technology in Sweden in Fall semester, 2008. The project has focused on simulating power system voltage collapse scenarios using Advanced Real-Time Interactive Simulator for Training and Operation (ARISTO) software. The simulated voltage collapse scenario was successfully implemented. To understand the effects of protection on voltage collapses, the study also focused on different "blackout mitigation" schemes to prevent the complete system blackout such as modification of settings of distance relays and blockings of critical circuit breakers on the transmission systems. The simulation results have shown that with these measures, substantial part of the system can be prevented from blackout. The Nordic 32-bus system is used in the study.
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| 6. |
- Larsson, Anders, et al.
(författare)
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Emission and immunity of equipment in the frequency range 2 to 150 kHz
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech Proceedings. - Piscataway, N.J. : IEEE Communications Society. - 9781424422357 ; , s. 2325-2329
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Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of emission and immunity standards in the frequency range from 2 to 150 kHz. Based on existing standardization a complete set of limits is proposed by the authors. A distinction is thereby made between narrowband emission, broadband emission and recurrent oscillations. The measuring technique is vital to the results. In this frequency range, there are two different sets of standards covering measurement equipment. Due to fact of development of time-domain based instrument we propose to only use this type of instruments for the whole frequency range.
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| 7. |
- Nilsson, Julia, et al.
(författare)
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An Opportunistic Maintenance Optimization Model for Shaft Seals in Feed-Water Pump Systems in Nuclear Power Plants
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech. - New York : IEEE. - 9781424422340 ; , s. 2962-2969
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Konferensbidrag (refereegranskat)abstract
- Nuclear power is one of the main electricity production sources in Sweden today. Maintenance management is one tool for reducing the costs for operation of a power plant. Driving forces for cost-efficiency has pushed the development of new methods for maintenance planning and optimization forward. Reliability Centered Asset Management (RCAM) is one of these new approaches, and maintenance optimization is one way to perform quantitative analysis which is a feature of RCAM. This paper proposes a model for opportunistic maintenance optimization where replacement schedules for shaft seals in feed-water pump systems in nuclear power plants are constructed. The feed-water pump system is important for the availability of the entire nuclear power plant. Results show that the optimization model is dependent on e.g. the discount interest and a limit for when the optimal solution goes from non-opportunistic to opportunistic is calculated. The circumstances for which opportunistic maintenance could be used have been investigated given different values of discount rates and remaining life at start of the planning period.
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| 8. |
- Rönnberg, Sarah, et al.
(författare)
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Interaction between equipment and power line communication : 9-95 kHz
- 2009
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Ingår i: 2009 IEEE Bucharest PowerTech Proceedings. - : IEEE Communications Society. - 9781424422357
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Konferensbidrag (refereegranskat)abstract
- This paper presents detailed measurements of currents flowing between modern electronic devices in a domestic environment. The results shown in this paper cover the frequency range 9 to 95 kHz, being the frequency band dedicated to power-line communication by network operators. Large differences exist between different devices, even when they are of the same type. It is also shown that the voltage waveform and the emission by other equipment have a significant impact on the current flowing between a device and the grid. An important conclusion from the measurements is that the high-frequency currents mainly flow between neighbouring devices.
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