| 1. |
- Hou, Yining, 1984-, et al.
(författare)
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Impact on voltage rise of PV generation in future swedish urban areas with high PV penetration
- 2014
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Ingår i: ENERGYCON 2014 - IEEE International Energy Conference. - : IEEE Computer Society. - 9781479924493 ; , s. 904-911
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Konferensbidrag (refereegranskat)abstract
- There have been a large amount of statements from different countries, claiming that the integration of photovoltaic generation in the distribution grids can eventually impact the power quality and pose challenges for the distribution system operator. In Sweden, the level of penetration of small scale distributed generation is still low and no such problems have been observed. This study is conducted to investigate the voltage levels in an urban distribution grid when the level of photovoltaic generation is increased. The study is done by modeling the Swedish urban area by PSCAD. The aspects of the model include network design of a real distribution grid, everyday load, photovoltaic generation based on real data, photovoltaic penetrations at different levels and considers the current regulations in Sweden. The results indicate that there are no problems with overvoltages even with a high penetration of photovoltaic generation. Instead the risk of over-current through the installed cables seems to be a greater limitation. The loading of the distribution transformers is decreased due to the mix of commercial and domestic loads in the local grid.
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| 2. |
- Bissal, Ara, 1986-, et al.
(författare)
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Comparison of two Ultra-fast actuator concepts
- 2012
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Ingår i: IEEE transactions on magnetics. - : IEEE Press. - 0018-9464 .- 1941-0069. ; 48:11, s. 3315-3318
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, two different types of ultra-fast electromechanical actuators are compared using a multi-physical finite element simulation model that has been experimentally validated. They are equipped with a single-sided Thomson coil (TC) and a double-sided drive coil (DSC), respectively. The former consists of a spirally-wound flat coil with a copper armature on top, while the latter consists of two mirrored spiral coils that are connected in series. Initially, the geometry and construction of each of the actuating schemes are discussed. Subsequently, the theory behind the two force generation principles are described. Furthermore, the current, magnetic flux densities, accelerations, and induced stresses are analyzed. Moreover, mechanical loadability simulations are performed to study the impact on the requirements of the charging unit, the sensitivity of the parameters, and evaluate the degree of influence on the performance of both drives. Finally, it is confirmed that although the DSC is mechanically more complex, it has a greater efficiency than that of the TC.
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| 3. |
- Bissal, Ara, 1986-, et al.
(författare)
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Loadability and scaling aspects of Thomson based ultra-fast actuators
- 2012
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Ingår i: Actuator 2012.
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Konferensbidrag (refereegranskat)abstract
- In this paper, an ultra-fast single-sided Thomson based actuator is studied. The actuator is comprised of a flat spiral-shaped coil with a conductive armature in its proximity. This armature is mechanically loaded with a uniform mass distribution over its cross section. The energizing source consists of a capacitor bank that is discharged through the actuator coil resulting in a high magnetic pressure within fractions of a millisecond. The coil is dimensioned to withstand the temperature rise.An experimentally validated multi-physical finite element model is used to perform simulations by varying the mechanical load to explore the performance of the actuator topology. The obtained currents, induced forces, stresses, and accelerations of the armature are then analyzed in an attempt to develop scaling techniques that can predict for example velocity and efficiency. Finally, the results of the scaling techniques are presented and compared to each other.
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| 4. |
- Bissal, Ara, et al.
(författare)
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Optimal Energizing Source Design for Ultra-Fast Actuators
- 2013
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Konferensbidrag (refereegranskat)abstract
- One of the key enabling technologies for multi-terminal HVDCgrids is the existence of a breaker that can operate withina few milliseconds. A lot of research has been done to builddifferent ultra-fast drives to actuate the electric contacts ofthese breakers. What they all have in common is an operationalefficiency of at best 5 %. Capacitor banks are discharged throughspirally shaped flat coils to generate ultra-fast repulsive forces. Tooptimize the efficiency of the drive, the design of the energizingcircuit is crucial. The aim of this paper is to optimize theenergizing source and provide a deep explanation of the effectof the chosen capacitance and charging voltage for two actuatorconcepts, the Thomson coil (TC) and the double sided coil (DSC)for different stroke requirements. An experimentally validatedmulti-physics finite element method (FEM) simulation model is applied.
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| 5. |
- Magnusson, Jesper, 1984-, et al.
(författare)
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Design Aspects of a Medium Voltage Hybrid DC Breaker
- 2014
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Ingår i: 5th IEEE/PES Innovative Smart Grid Technologies Europe (ISGT EUROPE) 2014.
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Konferensbidrag (refereegranskat)abstract
- With increased demands on energy efficiency and stability, the use of direct current (DC) will have a natural place in the future smart grid. Today DC is mostly used in high voltage, high power transmission over large distances and in low voltage systems where the demands on reliability are high, e.g. data centres. New applications as wind farm collection grids and a desire to replace over-head lines with cables opens possibilities for DC distribution grids in medium voltage.The use of DC grids will require the development of DC breakers to handle fault in the grid. This paper presents the design aspects of a hybrid DC breaker for a medium voltage application. Since the hybrid topology consists of a mechanical switch as well as semiconductor components and metal oxide varistors, the design must handle trade-offs in performance and cost both for each part and also between the different components.
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| 6. |
- Magnusson, Jesper, 1984-, et al.
(författare)
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On the Use of Metal Oxide Varistors as a Snubber Circuit in Solid-State Breakers
- 2013
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Ingår i: 2013 4th IEEE/PES Innovative Smart Grid Technologies Europe, ISGT Europe 2013. - : IEEE. - 9781479929849 ; , s. 6695454-
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Konferensbidrag (refereegranskat)abstract
- When solid-state switches are used in DC-breaker topologies, the turn-off operation can cause transient over-voltages that might harm the semiconductor itself. The over-voltage is caused by the combination of the very rapid current decrease of a solid-state switch and an undesired stray inductance in the parallel MOV-branch. The authors have proposed a possible solution where a smaller MOV is connected close to the solid-state switch to limit the over-voltage. This way, the over-voltage protection can be separated from the energy absorption task of the MOV. A small scale test set-up has been used to show that the peak voltage across the breaker is fully determined by the inner MOV. It is also shown that the performance can be increased by changing the U-I-characteristics of the outer MOV by adding several components in parallel.
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| 7. |
- Magnusson, Jesper, 1984-, et al.
(författare)
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Optimal design of a medium voltage hybrid fault current limiter
- 2014
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Ingår i: 2014 IEEE International Energy Conference, ENERGYCON. - : IEEE Computer Society. - 9781479924493 ; , s. 431-438
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Konferensbidrag (refereegranskat)abstract
- The connection of distributed generation increases the short circuit power which in turn might exceed the ratings of the installed circuit breakers. A solution is to limit the available short circuit power by increasing the grid impedance, but since there is a constant strive for lower losses and higher power transfer capabilities, this is not desired. The application of a fault current limiter (FCL) that can limit the current before the first peak enables a power system with high short circuit power and low short circuit current. This can increase the stability of the grid and reduce the requirements of other equipment. This work presents a simulation model to be used as an aid in the design of a hybrid FCL for a 12 kV AC system. The proposed model combines a transient analysis circuit model with an optimization module to obtain multiple sets of possible design parameters. The design is not straight forward since there is a trade-off between several of the design parameters.
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