| 1. |
- Chatzigiannakou, Maria Angeliki, et al.
(författare)
-
Offshore deployments of wave energy converters by Uppsala University, Sweden
- 2019
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Ingår i: Marine Systems and Ocean Technology. - : Springer Science and Business Media LLC. - 1679-396X .- 2199-4749. ; 14:2-3, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- Ocean can provide an inexhaustible amount of energy. Many marine energy converters have been developed but most of them have not surpassed the experimental phase due to the high costs in installation, operation, and maintenance. Since 2002 Uppsala University has developed and deployed several units of wave energy converters of various designs. The Uppsala University wave energy converter concept consists of a linear generator directly connected to a point absorber buoy that is mounted on a concrete gravity foundation. Uppsala University deployments have been carried out using different deployment vessels and methods. Three main methods were utilized for these deployments that are discussed in terms of cost, manpower, and time efficiency. Depending on the desired outcome—multiple- or single-device deployment, low budget, etc.—one of the proposed methods can be used for the optimal outcome.
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| 2. |
- 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
-
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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| 3. |
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| 4. |
- Canales, Fausto A., et al.
(författare)
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Temporal dynamics and extreme events in solar, wind, and wave energy complementarity : Insights from the Polish Exclusive Economic Zone
- 2024
-
Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 305
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Tidskriftsartikel (refereegranskat)abstract
- The Polish Exclusive Economic Zone (EEZ) in the Baltic Sea is an area of increasing strategic importance for Poland 's pursuit of renewable energy, especially offshore wind. This research investigates the complementarity among solar, wind, and wave energy resources within the Polish EEZ to examine these energy sources ' temporal dynamics, correlations, and extremes. The primary data source corresponds to a 31-year hourly time series dataset from the ERA5 reanalysis, whose reliability was evaluated through performance metrics. The results from complementarity metrics indicate varying levels of association among the three variable renewable energy resources (VRES) in the EEZ, spanning from weak similarity to weak complementarity. The findings of this research indicate that blackouts are most probable at offshore locations during winter and autumn for renewable power systems integrating wind and solar energy, with over 70 % of occurrences within these seasons. The investigation of extreme events highlights critical elements when evaluating VRES and their complementarity. This understanding aids in effectively planning and managing renewable energy systems, ensuring resilience and reliability under challenging weather conditions. Furthermore, while the complementarity may be consistent throughout the entire Polish EEZ, the feasibility and cost of implementing hybrid power systems can significantly vary between locations.
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| 5. |
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| 6. |
- Chatzigiannakou, Maria Angeliki, et al.
(författare)
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Numerical analysis of an Uppsala University WEC deployment by a barge for different sea states
- 2020
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- Wave energy converters (WECs) have been deployed onshore, nearshore, and offshore to convert ocean wave movement into electricity. The exploitation of renewable energy sources has restrictions; in the case of wave energy, high installation, maintenance, and decommissioning costs have limited their commercial use. Moreover, these offshore operations can be compromised by safety issues. This paper draws attention to offshore operation safety of a WEC developed by Uppsala University. Specifically, this paper investigates what sea states are suitable for the safe deployment of a WEC from a barge. This study follows recommendations in DNV-RP-H103 for analysis of offshore operations, namely lifting through the wave zone. ANSYS Aqwa is used to find hydrodynamic forces acting on a typical barge, using frequency domain analysis. Based on these hydrodynamic simulation results and methodology given in DNV-RP-H103, tables are created to show the sea states that would allow for the safe installation of a WEC using a typical barge. Considered sea states have significant wave heights varying between 0 m and 3 m and the wave zero crossing periods varying between 3 s and 13 s. The WEC submersions are considered between 0 m and 7 m, i.e. when the WEC is in the air until it is fully submerged. © 2020 Elsevier Ltd
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| 7. |
- Chatzigiannakou, Maria Angeliki
(författare)
-
Offshore deployments of marine energy converters
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The depletion warning of non-renewable resources, such as gas, coal and oil, and the imminent effects of climate change turned the attention to clean and fossil fuel-free generated electricity. University research groups worldwide are studying solar, wind, geothermal, biomass and ocean energy harvesting. The focus of this thesis is the wave and marine current energy researched at the division of Electricity at Uppsala University (UU). The main drawbacks that hinder the commercialization of marine energy converter devices is a high installation, operation, maintenance and decommissioning cost. Furthermore, these processes are highly weather dependent and thus, can be time consuming beyond planning. In this thesis, an evaluation of the cost, time and safety efficiency of the devices’ offshore deployment (both wave and marine current), and a comparative evaluation regarding the safety in the use of divers and remotely operated vehicles (ROVs) are conducted. Moreover, a risk analysis study for a common deployment barge while installing an UU wave energy converter (WEC) is presented with the aim to investigate the failure of the crane hoisting system.The UU wave energy project have been initiated in 2001, and since then 14 WECs of various designs have been developed and deployed offshore, at the Lysekil research site (LRS), on the Swedish west coast and in Åland, Finland. The UU device is a point absorber with a linear generator power take off. It is secured on the seabed by a concrete gravity foundation. The absorbed wave energy is transmitted to shore through the marine substation (MS) where all the generators are interconnected. In 2008 an UU spin-off company, Seabased AB (SAB), was established and so far has developed and installed several WECs and two MSs, after the UU devices main principle. SAB deployments were conducted in Sotenäs, Sweden, at the Maren test site (MTS) in Norway; and in Ada Foah, Ghana. The active participation and the thorough study of the above deployments led to a cost, time and safety evaluation of the methods followed. Four main methods were identified and the most suitable one can be chosen depending on the deployment type, for example, for single or mass device deployment.The first UU full scale marine current energy converter (MCEC) was constructed in 2007 at the Ångström Laboratory and deployed at Söderfors, in the river Dalälven in March 2013. The UU turbine is of a vertical axis type and is connected to a directly driven permanent magnet synchronous generator of a low-speed. With this deployment as an example, four MCEC installation methods were proposed and evaluated in terms of cost and time efficiency.A comparative study on the use of divers and ROVs for the deployment and maintenance of WECs at the LRS has been carried out, showing the potential time and costs saved when using ROVs instead of divers in underwater operations. The main restrictions when using divers and ROVs were presented. Most importantly, the modelling introduced is generalized for most types of wave energy technologies, since it does not depend on the structure size or type.Finally, a table of safe launch operation of a WEC is presented. In this table the safe, restrictive and prohibitive sea states are found for a single WEC deployment, using a barge and a crane placed on it. The table can be utilized as a guidance for offshore operations safety and can be extended for a variety of device types and vessels.
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| 8. |
- Fjellstedt, Christoffer, et al.
(författare)
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A Review of AC and DC Collection Grids for Offshore Renewable Energy with a Qualitative Evaluation for Marine Energy Resources
- 2022
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:16
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Tidskriftsartikel (refereegranskat)abstract
- Marine energy resources could be crucial in meeting the increased demand for clean electricity. To enable the use of marine energy resources, developing efficient and durable offshore electrical systems is vital. Currently, there are no large-scale commercial projects with marine energy resources, and the question of how to design such electrical systems is still not settled. A natural starting point in investigating this is to draw on experiences and research from offshore wind power. This article reviews different collection grid topologies and key components for AC and DC grid structures. The review covers aspects such as the type of components, operation and estimated costs of commercially available components. A DC collection grid can be especially suitable for offshore marine energy resources, since the transmission losses are expected to be lower, and the electrical components could possibly be made smaller. Therefore, five DC collection grid topologies are proposed and qualitatively evaluated for marine energy resources using submerged and non-submerged marine energy converters. The properties, advantages and disadvantages of the proposed topologies are discussed, and it is concluded that a suitable electrical system for a marine energy farm will most surely be based on a site-specific techno-economic analysis.
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| 9. |
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| 10. |
- Frost, Anna E., 1988-
(författare)
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In the Air Gap of Linear Generators for Wave Power
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wave power conversion is one type of renewable electricity generation. Within wave power, there are many different concepts, whereof some utilizes linear generators for converting the energy in the ocean waves into electricity. A linear generator consists of a translator, which is moving and have magnets of alternating polarity, and a stator, which have conductors sur-rounded by laminated steel. Between the translator and stator is an air gap, which is only a few millimeters wide. All linear generators for wave power, to the author’s knowledge, are permanent-magnet synchronous generators. This thesis looks into the forces and power flow in the air gap of linear generators for wave power, with the purpose of improving their future performance. The studies have focused on permanent magnet synchronous generators for wave power, but several of the results should also be applicable for other applications of linear elec-trical machines.Depending on the design of the linear generators, the translator can move so long that it only partially overlap the stator. This is common among several different wave power concepts with linear generators. When the stator is only partially overlapped by the stator it is denoted as partial stator overlap. It is studied how partial stator overlap affects the generated electric-ity, the absorbed energy, and the tangential and normal force in the air gap. The generated electricity and absorbed energy of a linear generator are quadratically dependent on the partial stator-translator overlap is shown through Faraday’s law and simulations. Experimental data showed that the absorbed energy is both linearly and quadratic depending on partial stator over-lap, where the linear dependence is at least partially due to frictional losses. Simulated results confirm that voltage is linearly dependent on partial stator overlap, which means quadratic de-pendence between generated electric and partial stator overlap. The simulated forces showed a linear dependence.Decades ago, the Poynting vector was used to derive an expression for the power flow in the air gap of rotating electrical machines. In this thesis the equivalent expressions for both flat and tubular linear electrical machines were derived. The analytical results were also compared with results from simulations. Both the analytical expressions and simulations showed that tubular and flat linear electrical machines have slightly different behavior.
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| 11. |
- Frost, Anna E., 1988-, et al.
(författare)
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Power flow in the air gap of linear electrical machines by utilization of the Poynting vector : Part 1 - Analytical expressions
- 2022
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Ingår i: The Journal of Engineering. - : Institution of Engineering and Technology (IET). - 2051-3305. ; 2022:4, s. 377-388
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Tidskriftsartikel (refereegranskat)abstract
- Analytical solutions and estimations for the power flow in the air gap of linear electrical machines of different geometries are derived from Poynting's theorem. The different geometries considered are flat one-sided, multi-sided, and tubular linear electrical machines. The radial power flow for all considered geometries is dependent on the area of the air gap, the electric field, the magnetic field, and the load angle. The tangential power flow for both flat one-sided and tubular linear electrical machines is dependent of the area of the air gap, number of poles, the electric field, the magnetic field, and the load angle. The number of poles could be increased to decrease the tangential power flow in flat linear electrical machines. The expression for the tangential flow in tubular linear electrical machines is so complicated that it is difficult to draw conclusions from it.
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| 12. |
- Giannini, Gianmaria, et al.
(författare)
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Wave Energy Converter Power Take-Off System Scaling and Physical Modelling
- 2020
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Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Absorbing wave power from oceans for producing a usable form of energy represents an attractive challenge, which for the most part concerns the development and integration, in a wave energy device, of a reliable, efficient and cost-effective power take-off mechanism. During the various stages of progress, for assessing a wave energy device, it is convenient to carry out experimental testing that, opportunely, takes into account the realistic behaviour of the power take-off mechanism at a small scale. To successfully replicate and assess the power take-off, good practices need to be implemented aiming to correctly scale and evaluate the power take-off mechanism and its behaviour. The present paper aims to explore and propose solutions that can be applied for reproducing and assessing the power take-off element during experimental studies, namely experimental set-ups enhancements, calibration practices, and error estimation methods. A series of recommendations on how to practically organize and carry out experiments were identified and three case studies are briefly covered. It was found that, despite specific options that can be strictly technology-dependent, various recommendations could be universally applicable.
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| 13. |
- Hong, Yue, et al.
(författare)
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Damping Studies on PMLG-Based Wave Energy Converter under Oceanic Wave Climates
- 2021
-
Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:4
-
Tidskriftsartikel (refereegranskat)abstract
- Wave energy converters (WECs), which are designed to harvest ocean wave energy, have recently been improved by the installation of numerous conversion mechanisms; however, it is still difficult to find an appropriate method that can compromise between strong environmental impact and robust performance by transforming irregular wave energy into stable electrical power. To solve this problem, an investigation into the impact of varied wave conditions on the dynamics of WECs and to determine an optimal factor for WECs to comply with long-term impacts was performed. In this work, we researched the performance of WECs influenced by wave climates. We used a permanent magnet linear generator (PMLG)-based WEC that was invented at Uppsala University. The damping effect was first studied with a PMLG-type WEC. Then, a group of sea states was selected to investigate their impact on the power production of the WEC. Two research sites were chosen to investigate the WEC's annual energy production as well as a study on the optimal damping coefficient impact. In addition, we compared the WEC's energy production between optimal damping and constant damping under a full range of sea states at both sites. Our results show that there is an optimal damping coefficient that can achieve the WEC's maximum power output. For the chosen research sites, only a few optimal damping coefficients were able to contribute over 90% of the WEC's annual energy production. In light of the comparison between optimal and constant damping, we conclude that, for specific regions, constant damping might be a better choice for WECs to optimize long-term energy production.
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| 14. |
- Jonasson, Erik, et al.
(författare)
-
Design Of Wind-Solar Hybrid Power Plant By Minimizing Need For Energy Storage
- 2023
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An important aspect in designing co-located wind and solar photovoltaic hybrid power plants is the sizing of the energy converters to achieve as efficient power smoothening as possible. In this study, the ratio of wind- and photovoltaic energy converters in a hybrid power plant is determined by minimizing the overall stored energy that is needed to facilitate constant power output. Using Fourier transform the variability is isolated at predefined time scales that are relevant for grid integration. For the investigated time scales, energy and power ratings for energy storages are determined to counteract the variability. The resulting configuration is the one that is able to achieve constant power output with minimum stored energy. It is shown that co-locating wind- and photovoltaic energy converters smoothen seasonal energy generation, and reduce the energy storage need in both the diurnal and seasonal time scales. A case study for south-eastern Sweden is presented where the wind- \& solar hybrid plant configuration that minimizes the energy storage need and therefore most closely resembles constant output power is determined. It is found that a ratio of approximately 40-45\% wind power in the hybrid power plant yields the lowest need for energy storage. The presented method is valid for any number of co-located energy sources, and can also be extended to sizing of hybrid power systems.
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| 15. |
- Jonasson, Erik, et al.
(författare)
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Discussion of "Assessing temporal complementarity between three variable energy sources through correlation and compromise programming" FA Canales et al. Energy 192 (2020) 116637
- 2023
-
Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 269
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper discusses the article "Assessing temporal complementarity between three variable energy sources through correlation and compromise programming." The discussed paper proposes a novel method of assessing comple-mentarity between three energy sources using correlation, compromise programming, and normalization. The method is then used to calculate a complementarity index which is applied to a case study in Poland. However, upon inspection, the normalization of the index overestimates the complementarity potential. This issue is dis-cussed in detail in this paper, and an alternative way of calculating the index is proposed, eliminating the issue of overestimating complementarity.
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| 16. |
- Jonasson, Erik, et al.
(författare)
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Grid Impact of Co-located Offshore Renewable Energy Sources
- 2024
-
Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- As the share of renewable energy sources in the energy mix increases, weather-dependent variations in several time scales will have a significant impact on the power system. One way of mitigating these variations is to co-locate complementary energy sources at the same location. In this study, the complementarity between offshore floating photovoltaics, wave, and wind power is analyzed and the grid impact of such co-located energy sources is addressed using capacity credit. Additionally, the possibility of installing supplementary generation capacity within existing offshore wind power farms is investigated. It is found that co-locating wave power with offshore wind results in increased capacity credit compared to stand-alone wind power farms and that in all analyzed cases, the capacity credit of the co-located energy sources exceeds the capacity credit contribution of the separate energy sources. Co-locating photovoltaics with offshore wind brings little benefit to the capacity credit, but shows potential in increasing the utilization of the transmission cable.
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| 17. |
- Jonasson, Erik, et al.
(författare)
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Grid value of co-located offshore renewable energy
- 2023
-
Ingår i: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023. - : European Wave and Tidal Energy Conference.
-
Konferensbidrag (refereegranskat)abstract
- Co-locating renewable energy sources such aswave power, solar photovoltaic and wind power, forminga hybrid power plant, may reduce the overall variability,increase the utilization of the transmission system, and reduce the needed physical area. An important topic to address regarding the formation of hybrid power plants is which energy sources to co-locate, and to what proportions these energy sources should be included in the hybrid power plant. In this study, offshore hybrid power plants are analyzed in the North Sea region. By minimizing the plant variability the proportions of each energy source are found, forming the plant with minimal need for energy storage for constant power output operation. The added grid value of such plants is analyzed in terms of electrical infrastructure utilization and power production ramping. It is found that in conditions suitable for the wave energy converter used in the study, a plant configuration of 23% wave power, 22% wind power and 55% solar minimizes the need for energy storage. It is shown that the inclusion of wave power in a hybrid power plant lowers ramping of power generation, increases the capacity factor and provides an overall higher grid value compared to stand-alone installations.
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| 18. |
- Jonasson, Erik
(författare)
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Modeling and analysis of offshore hybrid power parks
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the past decade, the global share of fossil-based electricity generation has decreased from 67% to 61% in favor of renewable alternatives. To achieve global goals, a continued extensive expansion of electricity generation from renewable energy sources is necessary. Offshore wind power is expected to constitute a significant portion of this additional generation capability. However, intermittent energy generation like wind or solar power has negative impacts on the electricity grid due to its inherently variable and non-dispatchable nature. Furthermore, energy generation from renewable energy sources is characterized by low utilization and requirement of large geographical areas.One way to mitigate several of these negative aspects is by co-locating energy sources with complementary characteristics. Combining different types of complementary renewable energy sources can reduce overall variability, increase transmission system utilization, and decrease land use. This thesis addresses several aspects of grid integration of offshore co-located energy sources, primarily, offshore wind power, floating solar power, and wave power. One question analyzed in several of the included studies is the optimal combination of energy sources for co-location to achieve the lowest variability.Another aspect investigated is the capacity credit for a hybrid park consisting of co-located energy generation compared to the capacity credit for a wind farm. In a case study for the Netherlands, the capacity credit for combined wave and wind power is higher than for wind power alone. Additionally, the complementarity of renewable energy sources is analyzed and explained.
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| 19. |
- Leijon, Jennifer, et al.
(författare)
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Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power
- 2018
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- The wave energy converter (WEC) studied and developed at Uppsala University in Sweden is a point absorbing buoy connected to a linear generator (LG) on the seabed. Previous studies have improved the sustainability of the generator, changing its magnets from Nd2Fe14B-magnets to ferrites. In this paper, the magnetic circuit of the linear generator is further studied. Ferrite magnets of two different types (Y30 and Y40) are studied along with different shapes of pole shoes for the system. The finite element method (FEM) simulations in a program called Ace are performed. The results show that a linear generator including both Y30 and Y40 magnets and shortened T-shaped pole shoes can generate a similar magnetic energy in the airgap as a linear generator only containing Y40 magnets and rectangular pole shoes. This shows that the magnetic circuit can be altered, opening up sizes and strengths of magnets for different retailers, and thereby possibly lowering magnet cost and transportation. This work was previously presented as a conference at the European Wave and Tidal Energy Conference (EWTEC) 2017 in Cork, Ireland; this manuscript has been carefully revised and some discussions, on magnet costs for example, have been added to this paper.
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| 20. |
- Leijon, Jennifer, 1990-
(författare)
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Wave Power for Desalination
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis presents work related to wave powered desalination. Wave power for desalination could be an interesting alternative for islands or coastal regions facing freshwater shortage, and several systems have been proposed in literature. However, desalination is a process which demands a lot of energy. Studies presented in the thesis indicate that the wave energy converter designed at Uppsala University in Sweden could be used for desalination. This wave energy converter includes a floating buoy connected via a wire to a linear generator. The linear generator has magnets mounted on its movable part (the translator). Small-scale experiments have been included, indicating that intermittent renewable energy sources, such as wave power, could be used for reverse osmosis desalination. Moreover, hybrid systems, including several different renewable energy sources, could be investigated for desalination. There may be interesting minerals in the desalination brine. The thesis also includes investigations on the magnetic material inside the linear generator, as well as on control strategies for wave energy converters. An opportunity of including different types of ferrites in the linear generator has been analyzed. The thesis also presents pedagogic development projects for the electro engineering education at Uppsala University, suggesting that including a greater variability and more student-centered learning approaches could be beneficial.
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| 21. |
- Leijon, Jennifer
(författare)
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Wave Powered Desalination
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this licentiate thesis is to investigate opportunities to produce fresh-water and electricity using marine renewable energy sources, such as wave power and marine current power, for water scarce areas. It summarizes the ongoing work within the field and suggests some possibilities of future re-search. Specifically, the desalination process reverse osmosis has been dis-cussed in combination with the wave energy concept designed at Uppsala Uni-versity for a site by the Kenyan coast. A review on wave powered desalination systems was presented, and the wave climate of the Kenyan coast was reana-lyzed and discussed with respect to the wave power and desalination applica-tion. Also, the magnetic circuit of the linear generator was investigated, as well as the control of the system, to enhance its sustainability. Moreover, the marine current energy converter designed at Uppsala University was investi-gated for desalination purposes. Only literature studies and simulations were performed, and the research would benefit from experimental work.
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| 22. |
- Parwal, Arvind, et al.
(författare)
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A Comparative Analysis of Linear and Nonlinear Control of Wave Energy Converter for a Force Control Application
- 2024
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Ingår i: International Marine Energy Journal. - Southampton, UK : International Marine Energy Journal. - 2631-5548.
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Tidskriftsartikel (refereegranskat)abstract
- The aim of wave energy converters (WECs) is to harvest the energy from the ocean waves and convert into electricity. Optimizing the generator output is a vital point of research. A WEC behaves as a nonlinear system in real ocean waves and a control that approximates the behaviour of the system is required. In order to predict the behaviour of WEC, a controller is implemented with an aim to track the referenced trajectory for a force control application of the WEC. A neural model is implemented for the system identification and control of the nonlinear process with a neural nonlinear autoregressive moving average exogenous (NARMAX) model. The neural model updates the weights to reduce the error by using the Levenberg-Marquardt back-propagation algorithm for a single-input-single-output (SISO) nonlinear system. The performance of the system under the proposed scheme is compared to the same system under a PI-controller scheme, where the PI gains have been tuned accordingly, to verify the control capacity of the proposed controller. The results show a good tracking of dq (direct-quadrature) axes currents by regulating the stator currents, and hence a force control is achieved at different positions of the translator. The dynamic performance of the control is verified in a time domain analysis for the displacement of the translator.
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| 23. |
- Parwal, Arvind, et al.
(författare)
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Energy management for a grid-connected wave energy park through a hybrid energy storage system
- 2018
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 231, s. 399-411
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Tidskriftsartikel (refereegranskat)abstract
- The concern for climate change and energy consumption has increased the demand for renewable energy production considerably. Marine energy sources attract attention because of their high energy density. Wave energy is an attractive renewable energy source with large potential. Due to the nature of the ocean waves, a linear wave energy converter generates intermittent power. It is therefore crucial to regularize the power before connecting to the grid. Energy storage systems present effective ways to minimize the power fluctuations and deliver a steady power to the grid. In this paper, we present an energy management control system with a dynamic rate limiter. The method is applied to control a hybrid energy storage system, combining battery and supercapacitor, with a fully active topology controlled by the power converters. The results show that the method is able to control the charging and discharging states of the battery and the supercapacitor, and minimize the power fluctuation to the grid. The algorithm ensures low losses by shifting the required power and the stored power smoothly over the energy storage system.
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| 24. |
- Parwal, Arvind, et al.
(författare)
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Experimental Test of Grid Connected VSC to Improve the Power Quality in a Wave Power System
- 2018
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Ingår i: 2018 5th International Conference on Electric Power and Energy Conversion Systems, EPECS 2018. - 9781538664575
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Konferensbidrag (refereegranskat)abstract
- This paper provides an overview of electric power conversion system installed at the Lysekil research site, located at the west coast of Sweden. The electric power conversion system consists of rectifiers, rectifying the power from the wave energy converters, a DC-link and a grid-tied inverter. The paper focuses on the performance of the inverter and the filter and presents experimental results obtained during the grid integration.
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| 25. |
- 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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| 26. |
- Parwal, Arvind, et al.
(författare)
-
Virtual Synchronous Generator Based Current Synchronous Detection Scheme for a Virtual Inertia Emulation in SmartGrids
- 2019
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Ingår i: Energy and Power Engineering. - : Scientific Research Publishing. - 1949-243X .- 1947-3818. ; 11:3, s. 99-131
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Tidskriftsartikel (refereegranskat)abstract
- Renewable energy sources, such as photovoltaicwind turbines, and wave power converters, use power converters to connect to the grid which causes a loss in rotational inertia. The attempt to meet the increasing energy demand means that the interest for the integration of renewable energy sources in the existing power system is growing, but such integration poses challenges to the operating stability. Power converters play a major role in the evolution of power system towards SmartGrids, by regulating as virtual synchronous ge-nerators. The concept of virtual synchronous generators requires an energy storage system with power converters to emulate virtual inertia similar to the dynamics of traditional synchronous generators. In this paper, a dynamic droop control for the estimation of fundamental reference sources is imple-mented in the control loop of the converter, including active and reactive power components acting as a mechanical input to the virtual synchronous generator and the virtual excitation controller. An inertia coefficient and a droop coefficient are implemented in the control loop. The proposed con-troller uses a current synchronous detection scheme to emulate a virtual iner-tia from the virtual synchronous generators. In this study, a wave energy converter as the power source is used and a power management of virtual synchronous generators to control the frequency deviation and the terminal voltage is implemented. The dynamic control scheme based on a current synchronous detection scheme is presented in detail with a power manage-ment control. Finally, we carried out numerical simulations and verified the scheme through the experimental results in a microgrid structure.
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| 27. |
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| 28. |
- Potapenko, Tatiana
(författare)
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Modelling of Ocean Wave Energy Conversion for Increased Power Absorption
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Earth is also called the blue planet, because more than 70 % of its surface is covered by water, mainly in oceans and seas. Wind blowing over the oceans is creating water waves, which can travel thousands of kilometers with just a small energy loss. Despite the abundant potential for the green energy market, wave energy is not yet exploited to the extent of wind and solar energies.There have been numerous attempts to convert wave energy into electricity. The wave energy converter, developed at Uppsala University, Sweden is of a point absorber type. The principal idea lies in utilizing a novel linear generator. The translator is a moving part inside the sub-merged linear generator and it is connected to a buoy, floating on the water surface. The buoy moves with the waves and the translator is dragged up and down relative to the stator. This reciprocal motion induces a voltage in the stator windings.The up-to-date stage of development for wave energy converters poses various issues. Still open challenges hold the technology away from commercial energy production. One of the main goals in wave energy research is to enhance the absorbed power for a single device, as well as for a wave power park of multiple wave energy converters. The power harvest can be increased in different ways, for example by optimizing the buoy, the generator or by implementing control on the operation of the device.This thesis focuses on studying wave energy converters in different wave climates by their power absorption. The main criteria influencing absorbed power are buoy size, weight on the system, damping force and available wave energy potential at the location of interest. The damping force can be computed by different approaches: constant optimal damping, resistive load (replicating passive control of currents in the stator windings) and RC-load (modeling a grid connected linear generator with an active rectification, such as phase angle compensation).Waves have a random nature. Therefore, the grid connection of the linear generator requires special solution. Power fluctuations of converted wave energy by the direct drive linear genera-tor may affect the integration into existing electrical grids. To study the connection of a single wave energy converter, as well as the wave park of three and ten devices, power hardware in the loop experiments have been carried out. The power quality analysis has been performed.Wave power has high potential and it can be integrated into the existing wind and solar energy production towards fully renewable microgrids. Yet, there is a chance of at least one quiet night during the year, when there are no wind and no waves. Estimation of frequency occurrence of absorbed power gives an insight into the regularity of such events. A case study in Hvide Sande, Denmark is presented. A mix of renewable energies (wind, solar and wave) is beneficial, as it gives a more stable energy supply with less variation in power production than when taken individually. Based on 30 years of historical data it is concluded, that the required battery size is sufficiently reduced for the renewable energy mix. The mix of wind, solar and wave has been shown to secure the lowest frequency of zero occurrences in power production and therefore is the most favorable choice for the future.
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| 29. |
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| 30. |
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| 31. |
- Potapenko, Tatiana, et al.
(författare)
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Renewable Energy Potential for Micro-Grid at Hvide Sande
- 2023
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Decarbonization of ports is a major goal to reduce their global carbon footprint. The port of Hvide Sande is located on the coast of the North Sea in Denmark and it has the potential to utilize various renewable energy sources. Wind and solar thermal parks are already installed there. Wave energy is an alternative to solar and wind energies and its advantage is the spatial concentration, predictability, and persistence. Heat to the town is provided by Hvide Sande Fjernvarme. In this work, it is investigated if the heat demand could be fully covered by renewable energies. Power profiles for each renewable energy resource were calculated using 30 years of re-analysis environmental data. Long, mid, and short term time series of power supply has been statistically and quantitatively examined. Considering the heat demand of Hvide Sande, the lowest frequency of zero occurrence in power generation can be ensured by the combination of wind, solar energy and wave. The article also estimated the capacity for Lithium-ion batteries. The optimal size of the battery is found by the bisection method. Finally, different combinations of renewable energy and demand as well as batteries are evaluated. The lowest zero occurrences in power production is met by the mix of three renewable energies. Also, the mix of three renewable energies significantly reduces the value of energy, required from the battery.
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| 32. |
- Potapenko, Tatiana
(författare)
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Wave energy converter: hydrodynamics and control
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Waves, just like wind and solar radiation, is a widely available renewable energy source. Waves are created when winds move across the sea surface. The estimated potential of wave energy is abundant, but the commercial harvesting technologies are still in their infancy. There are different wave energy converter designs, one of which is developed at Uppsala University and is based on a permanent magnet linear generator. A semi-submerged buoy on the water surface absorbs the energy of the wave and converts the mechanical energy into electricity with a direct drive linear generator.One of the main goals in wave energy research is to enhance the absorbed power for a single device and multiple devices in wave energy parks. The energy harvest can be increased in different ways: by optimizing the buoy, the generator, and/or by implementing control strategies. To assess the best optimization strategies numerical modeling is an inexpensive tool, aimed to predict the complex behavior of the system. This licentiate thesis focuses on the study of wave energy converters in irregular waves for testing sites, such as in Lysekil (Sweden) and Wave Hub (UK). The numerical model is used to analyze the wave energy conversion power performance. The hydrodynamic model involves radiation force approximation for a state-space model. It has been shown that a higher order of approximation can be achieved by vector fitting than by the transfer function fitting in the frequency domain, especially for the interaction of several bodies with the incident wave. Wave energy converter concepts are evaluated in terms of absorbed power for the resistive load connection, representing the passive control of the currents in the generator windings. Additionally, RC-load intends to model a grid-connected generator with active rectification, such that phase angle is compensated. Finally, a power-hardware-in-the-loop study of a grid-connected wave energy converter is presented. The current and voltage profiles of a grid-connected wave energy converter are shown with a suggestion on the implementation of RLC filter for power smoothing.
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| 33. |
- Potapenko, Tatiana, et al.
(författare)
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Wave energy converter’s slack and stiff connection : study of absorbed power in irregular waves
- 2021
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:23
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Tidskriftsartikel (refereegranskat)abstract
- Two different concepts of wave energy converter coupled to the novel C-GEN linear generator have been studied numerically, including the evaluation of different buoy sizes. The first concept has a slack connection between the buoy and the generator on the seabed. Another concept is based on a stiff connection between the buoy and the generator placed on an offshore platform. Three different approaches to calculate the damping force have been utilized within this study: the optimal damping coefficient, R-load, and RC-load. R-load is a model for the load applied to a grid-connected generator with passive rectification. RC-load is a model for a phase angle compensation applied to a system with active rectification. The radiation forces originating from the oscillatory motion of the buoy have been approximated using the transfer function in the frequency domain and the vector fitting algorithm. A comparison of the approximation methods is presented, and their accuracy has been evaluated. The advantage of the vector fitting method has been shown, especially for higher approximation orders which fit the transfer function with high accuracy. The study’s final results are shown in terms of the absorbed power for the sea states of March 2018 at Wave Hub, UK.
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| 34. |
- Remouit, Flore, 1988-, et al.
(författare)
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Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site : A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
- 2018
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous.
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| 35. |
- Rojas-Delgado, Brenda, et al.
(författare)
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GA-Based Permutation Logic for Grid Integration of Offshore Multi-Source Renewable Parks
- 2022
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Ingår i: Machines. - : MDPI. - 2075-1702. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes and analyzes a genetic algorithm based permutation control logic applied to the aggregator of an offshore multi-source park. The energy losses at the common coupling point are accounted for in the feedback. This paper focuses on offshore distributed energy resources, such as floating photovoltaic (PV), wind, and wave power. The main contributions of this research are the development of a control system that is capable of tracking the set-point imposed by the demand curve for each source individually, the introduction of a capacity factor for combined offshore floating PV/wind/wave power farms, and the unveiling of pure offshore renewable sources as potential storage-less flexibility service providers. The results of a case study for a site near San Francisco showed that energy losses and capacity factors are positively influenced by implementing the proposed approach.
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| 36. |
- Santos Döhler, Jéssica
(författare)
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Microgrid Power Control Strategies: Enabling Distributed Energy Resources in Power Systems
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As the world continues to deal with the effects of climate change, the need for carbon neu-trality becomes increasingly urgent. To achieve this goal, many countries are exploring the potential of distributed energy resources to reduce their dependence on fossil fuels and transition to renewable sources of energy. A microgrid is a small, independent energy system that can operate on its own or in connection with the main power grid. It integrates different energy sources like solar panels and batteries. Inverters are crucial in microgrids as they facilitate the seamless integration of various energy sources and contribute to grid stability. These inverters can be categorized into three distinct groups: grid-feeding, grid-supporting, and grid-forming. Each category serves a unique purpose, from synchronizing power with the main grid to providing support during grid disturbances and even enabling autonomous grid operation. These varying inverter functionalities contribute to the adaptability and resilience of microgrids, ensuring they can meet diverse energy needs and operate effectively in a range of scenarios. The thesis provides a comprehensive background of critical aspects of power systems and distributed energy resources, specifically focusing on microgrids and their significance in the evolving energy landscape. A particular emphasis is placed on the crucial functions served by inverters within microgrid architectures. Additionally, the thesis delves into fault analysis and mitigation strategies to ensure system resilience. Furthermore, the study highlights the importance of hybrid energy storage systems in enhancing the power quality of wave energy converters, achieved through the mitigation of power fluctuations. The outcomes and results of this thesis were developed and simulated using two platforms: MATLAB/Simulink and PSCAD. It delves into five distinct scenarios, each examining microgrid inverters from different perspectives in terms of circuit topology and control structures. The first one, shows the integration of a hybrid energy storage system as a key factor in elevating system efficiency, mitigating power fluctuations, and optimizing battery performance within the context of a wave energy system. In the second scenario, the thesis shifts its attention to grid-feeding and grid-forming inverters connected to a three-phase four-wire power system. The results showed the effectiveness of the suggested control strategy with smooth synchronization where the grid-forming inverter was able to form a network with an unbalanced factor lower than 2%, sinusoidal voltage, and frequency within standard limits. The third scenario places its emphasis on grid-supporting inverter, showcasing adaptability, and robust response to fault conditions by injecting or absorbing power, helping to mitigate voltage dips and fluctuations. The fourth, grid-forming inverter successfully formed a network with an unbalanced degree lower than standard regulations, maintaining sinusoidal voltage and frequency within standard limits. The fifth scenario explores the potential benefits and challenges of combining grid-feeding, grid-supporting, and grid-forming inverters as multi-functional inverters in the context of grid integration of wave energy converters. The multifunctional inverter configuration offers increased operational flexibility and resilience, effectively addressing a wider range of grid and microgrid possibilities.
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| 37. |
- Savin, Andrej, et al.
(författare)
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Statistical analysis of power output from a single heaving buoy WEC for different sea states
- 2018
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Ingår i: Marine Systems & Ocean Technology. - : Springer. - 1679-396X .- 2199-4749. ; 2-4, s. 103-110
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Tidskriftsartikel (refereegranskat)abstract
- Output power fluctuations from a wave energy converter (WEC) utilizing the principle of an oscillating body are unavoidable due to the reciprocating movement of the translator inside the generator. Moreover, the wave energy flux largely varies with time and propagates with the wave group velocity. Making use of the oscillating output power is a challenge for many wave energy conversion concepts. Therefore, estimation of the output power from a WEC solely by the mean power does not fully reflect the process of energy conversion, especially, by a direct drive linear generator. In the present paper, the output power from the WEC with a linear generator power take-off (PTO) is considered as a stochastic process, and the WEC performance is evaluated from the statistical point of view and related to the linear generator’s (LG) stroke length. Statistics as mean, standard deviation, relative standard deviation, maximum, and mode are found for different sea states. All statistics have shown an expected overall tendency with a rising significant wave height of incoming waves. As the significant wave height increases, statistics of the power output such as mean, standard deviation, maximum, and quantile are increasing, and the mode is decreasing beside the mode for the sea state C. It has been noted that for a significant wave height equal to the LG’s stroke length, the mode is greater than the same values for sea states of other significant wave heights. The results are based on a full-scale offshore experiment and may be used for the design of energy conversion systems based on a linear generator PTO.
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| 38. |
- Šljivac, Damir, et al.
(författare)
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Integration of Wave Power Farms into Power Systems of the Adriatic Islands : Technical Possibilities and Cross-Cutting Aspects
- 2021
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Ingår i: Water. - BASEL SWITZERLAND : MDPI. - 2073-4441. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Wave energy is of interest for regions with high wave power potential, as well as for regions with modest wave power potential such as the Adriatic/Mediterranean coastlines and islands. In the present paper, the possibility of integrating a wave power farm with the power system of an island in the Adriatic Sea, combining the wave power with a battery energy storage system (BESS) and solar photovoltaics (PVs) is explored and its impact on the local weak low voltage grid is investigated. The load profile is typical of the demand (consumption) of an Adriatic island, in which the demand substantially increases during summer (the tourist season). The wave power technology is a point-absorbing wave energy converter (WEC) with a direct drive linear permanent-magnet synchronous generator power take-off device. Wave power farms (WPFs) consist of two to ten WECs. In this study, we show that the integration of a WPF consisting of two WECs into the grid is optimal and helps to reach zero grid exchange, and a BESS reduces the intermittency of the power flow into the grid. Since a potential wave power farm is to be installed in a populated recreational area, the technical study is complemented by discussion on cross-cutting aspects such as its environmental and social impact.
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| 39. |
- Temiz, Irina, 1981-, et al.
(författare)
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Economic aspects of latching control for a wave energy converter with a direct drive linear generator power take-off
- 2018
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 128:Part A, s. 57-67
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Tidskriftsartikel (refereegranskat)abstract
- A wave energy converter (WEC) should be controlled in order to increase the average output power. In this paper, economic aspects of latching applied to a point absorbing WEC with a linear generator power take-off (PTO) are discussed. The capacity utilisation factor (CUF) is suggested to be used along with average absorbed power for control optimisation. Optimum and suboptimum latching controls are assessed for the WEC and compared with a constant damping PTO force control. The WEC performance is simulated using monochromatic waves for the wave conditions of the Wave Hub test site, UK. The linear wave theory is used in a hydro-mechanical two-body simulation model. It is shown that the latching controls possess considerable practical challenges significantly increasing the return of investment time periods.
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| 40. |
- Temiz, Irina, 1981-, et al.
(författare)
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Farms of Wave Energy Converters and Grid Integration
- 2024
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Ingår i: Reference Module in Earth Systems and Environmental Sciences. - : Elsevier. - 9780124095489 ; , s. 1-22
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This article presents the state-of-the-art and challenges related to the optimization and grid integration of farms of wave energy converters (WECs). Various physical and electrical circuit layouts have been proposed to interconnect WECs. The grid impact of wave power farms (WPFs) is associated with energy variability in ocean waves. Although fluctuations in the WPF output power might be reduced due to the farm aggregation effect, it remains highly variable, changing from minimum to maximum within several seconds. Parameters assessing the grid impact of farms of WECs are presented here, and various solutions to reduce the grid impact from WPFs are summarized.
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| 41. |
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| 42. |
- Temiz, Irina, 1981-, et al.
(författare)
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Wave absorber ballast optimization based on the analytical model for a pitching wave energy converter
- 2021
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Ingår i: Ocean Engineering. - : Elsevier. - 0029-8018 .- 1873-5258. ; 240
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Tidskriftsartikel (refereegranskat)abstract
- The present paper considers pitching wave energy converters (WECs) integrated in a floating platform, e.g., floating foundation for a wind turbine. Each WEC consists of a partially submerged wave absorber that rotates about the hinge located above the still water level under the influence of waves. Each wave absorber contains separated ballast tanks that are used to ensure the desired initial tilting angle of the absorber with respect to the floating foundation (called the rest angle). The same rest angle can be achieved by filling different ballast compartments that impacts the inertia moment about the hinge, response amplitude operator (RAO), resonance frequency of the absorber, and the power absorption performance. The exhaustive search for a suitable ballast configuration can quickly become a computationally expensive task depending on the number of ballast tanks. In this paper, the ballast optimization algorithm based on an analytical model is developed. The algorithm is applied to investigate the impact of the ballasts on the rest angle, RAO and resonance frequency of the wave absorber. It provides a base for ballast design and location for improved power absorption performance. The proposed algorithm can be adapted to the ballast optimization of other pitching WECs.
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| 43. |
- Temiz, Irina, 1981-, et al.
(författare)
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Wave energy resource assessment at Hvide Sande on the west coast of Denmark
- 2021
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Konferensbidrag (refereegranskat)abstract
- The wave power potential in the North Sea was studied in several publications for different locations. This paper estimates the wave power potential at a specific location, namely, near the town of Hvide Sande, located on the western coast of Denmark. To assess the wave energy resource at Hvide Sande, a hindcast model utilizing SWAN (Simulating WAves Nearshore) simulation tool is developed. The model is calibrated and validated with the 8-years data from a wave measurement buoy located close to Hvide Sande. Significant wave heights from simulations show a high correlation with the buoy data, and the mean wave periods are in good agreement with the measurements. Utilizing 30-years ERA5 reanalysis wind and wave data provided by the European Centre for Medium-range Weather Forecasts, the model was used to obtain the sea states at four sites. These sites are chosen to fulfil the placement requirements of two wave energy converter concepts: Seabased and ECO Wave Power. The average annual power density is found from 17.3 kW/m to 18.32 kW/m for offshore locations and 10.8 kW/m for the breakwater location. The obtained results on wave power potential and the time series of sea states during the 30-years period will be used for the (micro-) grid studies for the town of Hvide Sande.
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| 44. |
- Ullah, Md Imran, et al.
(författare)
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Analysis of a hybrid energy storage system in a grid-tied wave energy converter for varying power demand
- 2022
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Ingår i: 11th International Conference on Renewable Power Generation - Meeting net zero carbon (RPG 2022). - : Institution of Engineering and Technology. - 9781839537899 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- Wave energy is one of the emerging sustainable energy resources due to its high energy density and vast untapped areas. Nevertheless, the intermittency of wave resources is a significant challenge for the grid operator. Additionally, a varying grid demand is an added complexity to wave resources. Energy storage systems such as batteries and supercapacitors can be used to smoothen the power injection into the grid and match the available energy with the grid demand. Thus, this study compares battery energy storage with the hybrid energy storage system and proposes a control strategy to reduce the power fluctuations on the battery, allowing power delivery for varying grid demands. The study found that the hybrid system increases the system efficiency, in addition to the reduction in power fluctuations and enhancement of battery's performance, among other gains when the proposed control is implemented.
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| 45. |
- Ullah, Md Imran
(författare)
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Control strategies for various grid conditions in wave energy system
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The imperative goal of reducing carbon emissions and reaching net zero emissions in electricity generation has driven various renewable technologies, including wind energy, solar energy, and wave energy, among others. Even though wave energy is a recent addition to the already existing renewable energy technologies, it offers distinct advantages, such as a high power density and lower inter-annual variability compared to wind energy. In addition to supplying electric power to the grid, wave energy has the potential to supply power to other applications, such as remote islands or desalination plants. However, one of the primary challenges of wave energy lies in its inherent variability, which poses difficulties in terms of grid integration and can lead to increased current harmonics at its grid connection point. With advancements in power electronic converters and energy storage systems, it has now become feasible to control and manage these variabilities, thereby ensuring higher power quality for grid integration of wave energy. This thesis delves into different power electronic converter controls employed within the electrical network of wave energy converters. It explores the utilization of a hybrid energy storage system comprising a battery and supercapacitor integrated into the DC bus of the electrical network. The wave energy converter electrical network is simulated in MATLAB/Simulink. The results illustrate notable enhancements in power quality at the grid connection point and reduced stress on the battery. Additionally, the system effectively mitigates the intermittent nature of wave power, enabling the provision of constant power to the grid. Furthermore, the thesis delves into the design of grid forming control, specifically designed to electrify islanded loads utilizing a wave energy converter. A multimode converter control is developed for electrifying a remote island modelled as a 10 kW and 1 kVAR load using a wave power park with three wave energy converters. The inverter is controlled in three different modes: grid following, grid supporting and grid forming, which is modelled using MATLAB/Simulink. One of the main issues of using grid following control is the voltage dip at the island’s point of common coupling. A grid support control is implemented with the multimode converter to counteract the voltage dip and restore the voltage to its nominal value. The converter was able to follow the IEEE 519-2022 standard for voltage harmonics and IEEE std 1547 for current harmonics at PCC while supplying the load.
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| 46. |
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| 47. |
- Ullah, Md Imran, et al.
(författare)
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Multi-mode converter control for linear generator-based wave energy system
- 2024
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Ingår i: IET Renewable Power Generation. - : John Wiley & Sons. - 1752-1416 .- 1752-1424.
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Tidskriftsartikel (refereegranskat)abstract
- The electrification of remote islands has long been a subject of research interest, primarily because of their historical reliance on fossil fuels, leading to a significant carbon footprint. Recent advancements in wave energy converters offer a promising avenue to make these islands more self-sustainable while considerably reducing carbon emissions. However, the persistent issue of voltage dips due to weaker grids continues to pose a challenge. This study introduces a multi-mode converter control strategy with the goal of electrifying remote islands, employing a linear generator-based wave energy converter in a unified electrical model. Various scenarios, including voltage dips and mainland grid disconnection, are simulated using MATLAB/Simulink. The study demonstrates the converter's ability to transition swiftly and smoothly in response to these scenarios, ensuring an uninterrupted power supply. Furthermore, the analysis indicates that the power quality at the point of common coupling remains well within acceptable standards.
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| 48. |
- Ullah, Md Imran, et al.
(författare)
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Power quality assessment of a wave energy converter using energy storage
- 2023
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Ingår i: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023. - : European Wave and Tidal Energy Conference.
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Konferensbidrag (refereegranskat)abstract
- Wave energy has been an immense area of interest in research and industry in our move towards a sustainable energy production society due to its high energy density and surface area. However, the grid connection of wave energy converters is still one of the major challenges due to the complexity of varying wave resources (amplitude and frequency). Wave energy converter grid integration can lead to several potential challenges, such as voltage fluctuations, harmonics and flicker. Using an energy storage system can help mitigate a few challenges by balancing the grid demand with the wave energy converter power supply. Hence improving the power quality. This study assesses the power quality of wave energy converters equipped with energy storage against the scenario without any energy storage at different power levels. The power quality in this paper is investigated using total harmonic distortion (THD)of the grid current, dc-link voltage ripple and battery current ripple. The study shows that the addition of a hybrid energy storage system lowers the grid current THDat the point of common coupling (PCC), stabilizes the dc-link voltage ripple and reduces the stress of the battery.
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