| 11. |
- Parwal, Arvind, et al.
(författare)
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Grid impact and power quality assessment of wave energy parks: Different layouts and power penetrations using energy storage
- 2021
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Ingår i: JOURNAL OF ENGINEERING-JOE. - : Institution of Engineering and Technology (IET). - 2051-3305. ; 2021:8, s. 415-428
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Tidskriftsartikel (refereegranskat)abstract
- Power fluctuations induced by wave energy converters (WECs) may reflect negative impact on the power quality of the power grid. Assessing their impact is an important step to ensure the grid compliance level of the energy park. The IEC 61000-4-15 standard classifies the allowable disturbances in the grid. This study analysed and assessed the grid impact in terms of flicker, harmonic distortion and voltage variations. The assessments were performed without energy storage and compared when using the energy storage. A single WEC is emulated as an irregular power output of a real WEC using a combined model of power take-off in the Simulink model. Time series based on data obtained in earlier offshore experiments, conducted at the Lysekil research site in Sweden, is used to emulate a wave energy park (WEP) power in a land-based test rig in real-time power hardware-in-the-loop simulations. A total of three and ten WECs are emulated by introducing a time delay in the time series to investigate the grid impact in each layout. Flicker emissions, voltage variations, individual and total harmonics of the voltage at the connection point in each layout are studied and compared with the limits to be grid compliant for layouts of the WEP. In addition, voltage and current harmonics for the single WEC and individual harmonics in each phase of the voltage are measured and analysed to assess the compliance level of the WEP.
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| 12. |
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| 13. |
- Parwal, Arvind, et al.
(författare)
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Grid integration and a power quality assessment of a wave-energy park
- 2019
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Ingår i: IET Smart Grid. - UK : Institution of Engineering and Technology (IET). - 2515-2947. ; 2:4, s. 625-634
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a step toward the grid connection of a wave-energy park through an electric power conversion system (EPCS) developed and installed for the wave-energy harvesting in Lysekil, Sweden. The EPCS comprises a rectifier, a DC bus, and an inverter followed by a harmonic filter (HF). The higher- and lower-order harmonics injected by the inverter in a power quality context are investigated. The lower-order voltage harmonics partially distort the voltage-source inverter output grid current. A phase-locked loop-based (PLL) grid-phase tracking is used to attenuate the lower-order harmonics by reflecting the grid harmonics in the inverter output. An expression for the grid-current harmonics as a function of the grid-voltage harmonics has been derived and implemented. A mathematical model is derived to obtain a transfer function for the PLL, and finally, proportional–integral gains are tuned for stable system operation. An HF for mitigating the higher-order harmonics has been implemented. The total harmonic distortion is evaluated experimentally, and the results fulfil the grid-code requirements at various frequencies and harmonic orders.
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| 14. |
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| 15. |
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| 17. |
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| 18. |
- Apelfrojd, Senad, et al.
(författare)
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A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter
- 2015
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:2, s. 808-820
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Tidskriftsartikel (refereegranskat)abstract
- The paper proposes a back-to-back 2L-3L grid connection topology for a marine current energy converter. A prototype marine current energy converter has been deployed by a research group at Uppsala University. The concept behind the prototype revolves around a fixed pitch vertical axis turbine directly connected to a permanent magnet synchronous generator (PMSG). The proposed grid connection system utilizes a well known and proven two level voltage source converter generator-side combined with a three-level cascaded H-bridge (CHB) multilevel converter grid-side. The multilevel converter brings benefits in terms of efficiency, power quality and DC-link utilization. The system is here presented for a single marine current energy converter but can easily be scaled up for clusters of marine current energy converters. Control schemes for both grid-side and generator-side voltage source converters are presented. The start-up, steady state and dynamic performance of the marine current energy converter are investigated and simulation results are presented in this paper.
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| 19. |
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| 20. |
- Apelfröjd, Senad, et al.
(författare)
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Experimental Verification of a Back-to-Back 2L-3L Grid Connection System for a Marine Current Energy Converter
- 2016
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Konferensbidrag (refereegranskat)abstract
- Rivers, tides and other ocean currents are renewable energy sources with great potential across the globe.A research group at Uppsala University is working on converting the power in rivers and ocean tidesusing a vertical axis turbine with a directly driven permanent magnet generator. The concept in focususes an omnidirectional, fixed pitch vertical axis turbine directly connected to a permanent magnetgenerator. Few moving parts and an overall low mechanical complexity is the main idea behind theconcept. A first full prototype was deployed in 2013 in the river Dalälven in the town of Söderfors. Thework presented here is a step towards grid connection of the marine current energy converter prototype.A back-to-back 2L-3L grid connection topology has been proposed. The system is adapted to the scaledprototype but is intended for larger turbines. The proposed grid connection system utilizes a three-levelcascaded H-Bridge voltage source converter (3L-CHBVSC) on the grid side together with a well knowtwo-level voltage source converter on the generator side. The use of a multilevel converter brings severaladvantages such as higher efficiency, more sinusoidal voltages and currents and smaller grid filtersamong other advantages. The proposed grid connection system has been constructed in the laboratory.The work presented here aims to evaluate the system in the laboratory. A synchronous generator with avery similar design to the on-site generator is used for the tests. The generator, driven by an inductionmotor, is connected to the system and power is successfully transferred to the grid. The conducted testsare used to verify the functionality of the system before installation at the research site.
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