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Introduction
Let's make large scale offshore wind power and offshore HVDC grids a reality
Current institution
Equinor
Current position
- Principal Engineer
Additional affiliations
August 2014 - May 2023
March 2004 - July 2007
January 2009 - November 2013
Education
January 2009 - November 2013
April 2005 - September 2008
October 2002 - March 2005
Publications
Publications (64)
![Figure 1: Bootstraps (Figure extracted from [3]).](profile/Til-Vrana/publication/281269291/figure/fig32/AS:669993268174856@1536750251479/Bootstraps-Figure-extracted-from-3_Q320.jpg)
![Fig. 1: New PV Installations in Germany, 2010 figures until October [1]](profile/Til-Vrana/publication/281269291/figure/fig38/AS:669993268162580@1536750251594/New-PV-Installations-in-Germany-2010-figures-until-October-1_Q320.jpg)
The construction of the North Sea Super Grid is the major step towards meeting the future demand for electric power transmission in northern Europe. This grid will likely also extend onshore towards the load centres, and eventually form the European Super Grid.
Large-scale electric power generation at remote locations will lead to significant long...
In a DC grid, contingencies such as converter outages give rise to a current imbalance that is reflected in the DC node voltages in the grid. This imbalance has to be accounted for by changing the currents flowing in and out of the DC system. These DC node voltages can be directly influenced by controlling the DC current of the HVDC converter at th...
The future electric grid development plan in Europe foresees the North Sea Super Grid (NSSG). This grid will need to integrate individually and independently planned projects, leading to a rather grown than optimised structure. This will offer a lot of technical challenges, since it is a clear pioneer project. Offshore cluster grids could be either...
Active power converters are flexible and highly dynamic. Many power converters, as battery charging devices, use only a small
part of their technical capabilities. This paper develops a new control method that combines the primary converter function
with grid frequency control. Doing this, the frequency stability can be influenced positively, using...
The share of wind power in power systems is increasing dramatically, and this is happening in parallel with increased penetration of solar photovoltaics, storage, other inverter-based technologies, and electrification of other sectors. Recognising the fundamental objective of power systems, maintaining supply–demand balance reliably at the lowest c...
![Mean wind speed at hub height [m s-1].](publication/384151630/figure/fig4/AS:11431281279042325@1726779174727/Mean-wind-speed-at-hub-height-ms-1_Q320.jpg)
Maps showing the mean wind speed only give an inaccurate indication of the quality of locations for future wind power developments. Calculating the capacity factor and plotting that on a map gives a better indication of the expected mean power output, but the outcome depends on the turbine choice. In this article, we introduce a general step-by-ste...
The share of wind power in power systems is increasing dramatically and this is happening in parallel with increased penetration of solar photovoltaics, storage, other inverter-based technologies, and electrification of other sectors. Integrating all these technologies in a cost-effective manner while maintaining (or improving) power system reliabi...
Maps showing the mean wind speed only give an inaccurate indication on the quality of locations for future wind power developments. Calculating the capacity factor (based on a weather time series and a wind turbine power curve) and plotting that on a map gives a better indication on the expected mean power output, but the outcome depends on the tur...
The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with...
The ongoing large-scale deployment of offshore wind parks creates the need for substantial investments in Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) transmission infrastructure. An investment cost model with a corresponding cost parameter set was established in 2018 to improve the accuracy of HVDC grid expansion plannin...
Various aspects of power system flexibility are evaluated within the multi-country study framework of IEA Wind Task 25. Grid components and actions which have been adopted for enhancing flexibility in different areas, countries, regions are addressed, as well as how Transmission System Operators, Independent System Operators, Utilities intend to ma...
This article introduces and describes the integrated energy system of the Low Emission Oil and Gas Open reference platform. It is a hypothetical case meant to represent a typical oil and gas installation in the North Sea. The aim of this detailed specification is to serve as an open reference case where all the information about it can be publicly...
This paper considers the operation of offshore oil and gas platform energy systems with energy supply from wind turbines to reduce CO2 emissions. The study is conducted through simulations of a case that reflects a “typical” oil and gas platform on the Norwegian Continental Shelf, with energy demand for gas lift and gas export compressors, separato...
This article introduces and describes the integrated energy system of a the Low Emission Oil&Gas Open (LEOGO) reference platform. It is a hypothetical case meant to represent a typical oil&gas installation in the North Sea. The aim of this detailed specification is to serve as an open reference case where all information about it can be publicly sh...
Concepts for control of wind farms (WFs) can be clustered into two distinct concepts, namely, wind power plant control (WPPC) and wind farm flow control (WFFC). WPPC is concerned with the connection to the power system, compliance with grid codes, and provision of power system services. This comprises the traditional way of operating a WF without c...
As the share of VRE (variable renewable energy) has grown rapidly, curtailment issues have arisen worldwide. This paper evaluates and compares curtailment situations in selected countries using an objective and quantitative evaluation tool named the “C-E map” (curtailment-energy share map). The C-E map is a correlation map between curtailment ratio...
This report summarises findings on wind integration from the 17 countries or
sponsors participating in the International Energy Agency Wind Technology
Collaboration Programme (IEA Wind TCP) Task 25 from 2006–2020. Both real
experience and studies are reported. Many wind integration studies incorporate
solar energy, and most of the results discussed...
The demand for low carbon energy calls for close to 100% renewable power systems, with decarbonization of other energy sectors adding to the anticipated paradigm shift. Rising levels of variable inverter-based renewable energy sources (VIBRES) are prompting questions about how such systems will be planned and operated when variable renewable genera...
The assessment of compliance with grid codes requirements can be challenging for researchers and (early stage) technology developers. To tackle this problem, a generic grid code is proposed in this article that defines certain requirements aimed for future scenarios with high shares of renewables. The proposed code is not linked to a particular gri...
Rapidly increasing levels of variable inverter‐based renewable energy sources (are quickly changing electric power systems and prompting questions about how the systems will be operated when renewable generation becomes the dominant technologies. In this article, we review the status of this shifting paradigm in power systems throughout the world....
Some grid data sets contain only electrical parameters, but not the individual transmission line lengths. The failure rates of transmission lines are often estimated based on aggregated statistics given in failure rate per unit length of transmission line. These failure rates are key input parameters to power system reliability assessments. When le...
This article reviews dc transmission technologies for future power grids. The article emphasises the attributes that each technology offers in terms of enhance controllability and stability, resiliency to ac and dc faults, and encourages increased exploitations of renewable energy resources (RERs) for electricity generation. Discussions of ac/dc an...
This study investigates the techno-economic potential of offshore power generation from natural gas with carbon capture and storage to reduce the climate impact of mainland electricity and the offshore oil and gas industry. This potential is assessed through techno-economic assessments over two relevant cases (“floating” and “shallow water” cases)...
This report summarises recent findings on wind integration from the 17 countries and Wind Europe participating in the International Energy Agency (IEA) Wind collaboration research Task 25 from 2015–2017. Both real experiences and studies are reported. Many wind integration studies incorporate solar energy, and most of the results discussed here are...
Several attempts have been made to produce a levelized "system integration cost" number to add to the levelized cost of electricity (LCOE) of variable renewable energy (VRE 1) to facilitate comparison with thermal power plants and other generators. However, capturing this "system integration cost" component is a challenge. By contrast, total system...
Many individual wind and solar integration studies have been conducted in the past. The integration studies have evolved towards looking at the integration of wind and solar at the same time. Integration studies typically simulate a future power system with wind and solar contributions (share or penetration) varying from 5% to more than 50% of annu...
Expansion of offshore wind power and the use of high voltage direct current (HVdc) technologies in power transmission are modifying the power system dynamics making them more sensitive to power disturbances. Thus, in order to ensure a power system secure and stable operation, transmission system operators require wind power and HVdc systems to prov...
In the increasingly interconnected and integrated European power system, transmission system operators need to consider new kinds of risk associated with the interconnection to neighbouring systems. For the Nordic power system, there is now more than 8 GW of HVDC interconnector capacity connecting the Nordic synchronous area to other synchronous ar...
Investment model cost parameters for VSC HVDC transmission infrastructure continue to be associated with high uncertainty and their validity remains a crucial challenge. Thus, it is the key objective of this analysis to identify a new cost parameter set providing better investment cost estimates than currently available cost parameter sets. This pa...
Grid codes are technical specifications that define the requirements for any facility connected to electricity grids. Wind power plants are increasingly facing system stability support requirements similar to conventional power stations, which is to some extent unavoidable, as the share of wind power in the generation mix is growing. The adaptation...
Present grid codes might not be a suitable reference for future-oriented research. The diversity of grid codes by different transmission system operators makes it challenging to get a clear and compact general overview on grid code requirements. ENTSO-E aims to develop a uniform grid code framework for Europe, which at present, however, still leave...
A significant number of wind and solar integration studies have been conducted in recent years, and methodologies have evolved steadily. Since power system characteristics and data availability vary significantly, the results and methodologies used in these studies have varied accordingly. This article presents findings from an international collab...
Cost parameters for VSC HVDC transmission infrastructure have been gathered from an extensive collection of techno-economic sources. These cost parameter sets have been converted to a common format, based on a linear investment cost model depending on the branch length and the power rating of cable systems and converter stations. In addition, an av...
This article presents preliminary results from ongoing work on establishing a simulation model for R&D activities on the impact of the increasing number of HVDC links in the Nordic power grid. The total HVDC power capacity will be 13100 MW (excluding some smaller systems) by 2021. This study addresses a future scenario with additional 7400 MW of HV...
An analytical approach towards the operation of very long HVAC cables has been developed. The main physical phenomena have been expressed with simplified analytical equations. A comparison with numerical simulations has shown acceptable accuracy. A set of long distance cable parameters has been introduced. The main conclusion is that beyond a certa...
The DC node voltage can be influenced by controlling the current/power of the high-voltage direct current (HVDC) converter at that node. This chapter classifies the different node voltage control methods, which have been proposed in the literature in recent years. It introduces three overall converter control strategies namely, constant voltage con...
A systematic terminology for the field of HVDC networks has been developed, closing the gap between the well-established terminologies from AC power systems and HVDC technology. The most relevant items, topologies and concepts have been given clear and unique defined names, and these have been classified in a systematic way. e motivation for this w...
Grid codes are technical specifications that define requirements for any facility connected to electricity grids in order to ensure safe, secure and economic operation of the electricity system. For a wind turbine or a wind power plant to be allowed connection to the electricity grid, it needs to prove that the grid codes for the relevant connectio...
A new method for controlling active power in HVDC grids has been tested on the meshed CIGRE B4 DC grid test system. The control strategy is based on the recently proposed undead-band droop control, which combines DC voltage and AC frequency droop. It provides sufficient room for optimisation for both normal and disturbed operation. Its main feature...
![Fig. 3. Offshore wind clusters (from [10])](profile/Til-Vrana/publication/261225033/figure/fig3/AS:296945944940550@1447808838754/Offshore-wind-clusters-from-10_Q320.jpg)
![Fig. 4. Optimised grid structure (from [10])](profile/Til-Vrana/publication/261225033/figure/fig4/AS:296945944940551@1447808838794/Optimised-grid-structure-from-10_Q320.jpg)
![Fig. 5. Meshed offshore grid (adapted from [10])](profile/Til-Vrana/publication/261225033/figure/fig5/AS:296945944940552@1447808838826/Meshed-offshore-grid-adapted-from-10_Q320.jpg)
The large remote offshore wind clusters that are planned in the North Sea will most likely be connected with a meshed HVDC grid. Power will mostly flow from the offshore wind clusters to shore, creating asymmetrical requirements for the HVDC links that will consist of several parallel HVDC systems. To realise an asymmetrical link, some of those sys...
The earlier developed control method using a piecewise linear droop curve, with different droop values for the different segments, has now been optimised for dynamic performance. Non-linearities at the junctions of two linear droop sections have been adressed. Also non-linearity of power based DC voltage control has been adressed. Dynamic instabili...
In Deutschland sind etwa 80% der installierten Photovoltaikleistung an das Niederspannungsnetz angeschlossen. Im Sommer 2011 wurden regelmäßig mehr als 12 GW tatsächlicher Einspeiseleistung beobachtet. Dies zeigt, dass Erzeugungsanlagen an der Niederspannung signifikante Systemrelevanz erreicht haben. Folglich müssen sie einen Beitrag zur Wahrung d...
Grid codes for distributed energy resources had to be improved when medium voltage and later low voltage feedings became system relevant. On the other side of the balance sheet, the self-regulation effect of loads is continuously shrinking. Plug-in vehicles (PiV) have the potential to form a large collective, distributed power source which is able...
Grid codes for distributed energy resources had to be improved when medium voltage and later low voltage feedings became system relevant. On the other side of the balance sheet, the self-regulation effect of loads is continuously shrinking. Plug-in vehicles (PiV) have the potential to form a large collective, distributed power source which is able...
A new control method for large meshed HVDC grids has been developed, which helps to keep the active power balance at the AC and the DC side. The method definition is kept wide, leaving the possibility for control parameter optimisation. Other known control methods can be seen as specific examples of the proposed method. It can serve as a framework...
![Figure 1: Bootstraps (Figure extracted from [3]).](profile/Til-Vrana/publication/281270015/figure/fig1/AS:284457358643200@1444831327033/Bootstraps-Figure-extracted-from-3_Q320.jpg)
Europe has a clear objective of obtaining a large share of wind power in the overall energy mix. A significant part of the installed wind power capacity will come from offshore wind farms. As an alternative to connecting every wind farm to the onshore grid separately, the 'supergrid' concept has been proposed. A supergrid would allow international...
![Fig. 1: New PV Installations in Germany, 2010 figures until October [1]](profile/Gunnar-Kaestle/publication/267727019/figure/fig1/AS:295642476892169@1447498067873/New-PV-Installations-in-Germany-2010-figures-until-October-1_Q320.jpg)
![Fig. 2: German PV feed-in on 2010-09-06 [2]](profile/Gunnar-Kaestle/publication/267727019/figure/fig2/AS:295642476892170@1447498067916/German-PV-feed-in-on-2010-09-06-2_Q320.jpg)
![Fig. 4: Active Power Frequency Response (over frequency), R5.9 [3]](profile/Gunnar-Kaestle/publication/267727019/figure/fig4/AS:669138909401095@1536546556210/Active-Power-Frequency-Response-over-frequency-R59-3_Q320.jpg)
![Fig. 8: Active Power Provision by Inertia, R7.10 [3]](profile/Gunnar-Kaestle/publication/267727019/figure/fig5/AS:669138909401097@1536546556231/Active-Power-Provision-by-Inertia-R710-3_Q320.jpg)
In Germany, about 80% of installed photovoltaic power is connected to the low voltage grid. During the summer of 2011, more than 10 GW actual feed-in is expected on a regular basis, indicating that low voltage power producers have gained significant system relevance. As a consequence they need to contribute to grid stabilisation, whereas former gui...
In Germany, about 80% of installed photovoltaic power is connected to the low voltage grid. During the summer of 2011, more than 10 GW actual feed-in is expected on a regular basis, indicating that low voltage power producers have gained significant system relevance. As a consequence they need to contribute to grid stabilisation, whereas former gui...
A wind farm (WF) connected by voltage source converter-based HVDC (VSC-HVDC) results in a completely 'inertia-less' in offshore AC grid . AC frequency is determined by control of the VSC-HVDC on the WF side, independently of the main grid frequency. Moreover, the rotational speed of a variable speed wind turbine is independent of the AC frequency o...
Reliable electric power supply is essential for modern society. The extensive use of electricity has led to a high susceptibility to power failures. In this way, reliability of supply has gained focus and it is considered increasingly important for electric power system planning and operation. In this paper, an overview is given of the state of the...
The North Sea Super Grid (NSSG) will include several independently planned projects, comprising a variety of different AC and DC technologies. The offshore clusters will most likely be AC based. Long distance transmission will be HVDC and nowadays Voltage Source Converter (VSC) technology is applied for offshore projects. However in the future, Lin...
Questions
Question (1)
I am looking for published sources with Cost/Price information regarding recent HVDC projects. Every contracted new HVDC project usually comes along with press releases, but they do not always contain information on the financial contract volume. If you have any information on the agreed price for recent HVDC projects (conveters, cable, total,...), I would be very happy
thank you in advance
