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Power system flexibility need induced by wind and solar power intermittency on time scales of 1-14 days
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Vattenfall AB, Älvkarlebylaboratoriet, Älvkarleby, Sweden. (Hydropower)
Vattenfall AB, Älvkarlebylaboratoriet, Älvkarleby, Sweden. (Hydropower)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Hydropower)
2015 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 83, 339-344 p.Article in journal (Refereed) Published
Abstract [en]

This article describes a method to assess the needed production flexibility to adapt the power system to the production from variable renewable energy sources such as wind power and photovoltaics over time horizons of 1-14 days. Load and production data from the German power system is used to quantify the flexibility need in terms of power and energy storage requirement due to higher shares of renewable energy (20-80%). It is found that with an 80% variable renewable energy share in the German system, the average power need from flexible sources decreases by 31 GW (59%) while the peak power need only decreases by 3 GW (4%). In terms of energy, the storage need over a two week horizon increases by 2.6 TWh, which is 14% of the average load per day. If the European plans for 100 GW wind power in the North Sea region are realised, this would mean an increase of the energy storage need in the region with 2.2 TWh over a two week horizon.

Place, publisher, year, edition, pages
2015. Vol. 83, 339-344 p.
Keyword [en]
Energy storage, wind power, solar power, dispatching, balancing
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-237789DOI: 10.1016/j.renene.2015.04.048ISI: 000358455100031OAI: oai:DiVA.org:uu-237789DiVA: diva2:768915
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2017-12-05
In thesis
1. A hydropower perspective on flexibility demand and grid frequency control
Open this publication in new window or tab >>A hydropower perspective on flexibility demand and grid frequency control
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The production and consumption of electricity on the power grid has to balance at all times. Slow balancing, over days and weeks, is governed by the electricity market and carried out through production planning.  Fast balancing, within the operational hour, is carried out by hydropower plants operating in frequency control mode. The need of balancing power is expected to increase as more varying renewable energy production is connected to the grid, and the deregulated electricity market presents a challenge to the frequency control of the grid.

The first part of this thesis suggests a method to quantify the need for balancing or energy storage induced by varying renewable energy sources. It is found that for high shares of wind and solar power in the system, the energy storage need over a two-week horizon is almost 20% of the production.

The second and third part of the thesis focus on frequency control. In the second part, measurements from three Swedish hydropower plants are compared with the behaviour expected from commonly used power system analysis hydropower models. It is found that backlash in the guide vane and runner regulating mechanisms has a large impact on the frequency control performance of the plants.

In the third part of the thesis, the parameters of the primary frequency control in the Nordic grid are optimised with respect to performance, robustness and actuator work. It is found that retuning of the controller parameters can improve the performance and robustness, with a reasonable increase of the actuator work. A floating deadband in the controller is also discussed as a means to improve performance without increasing the actuator work.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2014. 57 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 339-14L
Keyword
hydropower, frequency control, balancing
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-237798 (URN)
Presentation
2014-12-01, ITC1211, Uppsala, 14:00 (English)
Opponent
Supervisors
Available from: 2014-12-11 Created: 2014-12-05 Last updated: 2015-10-08Bibliographically approved
2. The Frequency of the Frequency: On Hydropower and Grid Frequency Control
Open this publication in new window or tab >>The Frequency of the Frequency: On Hydropower and Grid Frequency Control
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Variations in the electricity consumption and production connected to the power system have to be balanced by active control. Hydropower is the most important balancing resource in the Nordic system, and will become even more important as the share of variable renewable energy sources increases. This thesis concerns balancing of active power, especially the real-time balancing called frequency control. The thesis starts in a description of the situation today, setting up models for the behaviour of hydropower units and the power system relevant to frequency control, and comparing the models with experiments on several hydropower units and on the response of the Nordic grid. It is found that backlash in the regulating mechanisms in hydropower units have a strong impact on the quality of the delivered frequency control. Then, an analysis of what can be done right now to improve frequency control and decrease its costs is made, discussing governor tuning, filters and strategies for allocation of frequency control reserves. The results show that grid frequency quality could be improved considerably by retuning of hydropower governors. However, clear technical requirements and incentives for good frequency control performance are needed. The last part of the thesis concerns the impact from increased electricity production from variable renewable energy sources. The induced balancing need in terms of energy storage volume and balancing power is quantified, and it is found that with large shares of wind power in the system, the energy storage need over the intra-week time horizon is drastically increased. Reduced system inertia due to higher shares of inverter connected production is identified as a problem for the frequency control of the system. A new, linear synthetic inertia concept is suggested to replace the lost inertia and damping. It is shown that continuously active, linear synthetic inertia can improve the frequency quality in normal operation and decrease wear and tear of hydropower units delivering frequency control.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 105 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1460
Keyword
hydropower, frequency control, governors, power system stability, inertia, primary control
National Category
Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-308441 (URN)978-91-554-9769-9 (ISBN)
Public defence
2017-02-07, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2017-01-13 Created: 2016-11-25 Last updated: 2017-01-17

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Saarinen, LinnDahlbäck, NiklasLundin, Urban

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