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Saarinen, Linn
Publications (10 of 11) Show all publications
Saarinen, L., Norrlund, P., Yang, W. & Lundin, U. (2018). Allocation of Frequency Control Reserves and its Impact on Wear and Tear on a Hydropower Fleet. IEEE Transactions on Power Systems, 33(1), 430-439
Open this publication in new window or tab >>Allocation of Frequency Control Reserves and its Impact on Wear and Tear on a Hydropower Fleet
2018 (English)In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 33, no 1, p. 430-439Article in journal (Refereed) Published
Abstract [en]

Power systems are making a transition from purely technical, centrally planned systems to market based, decentralized systems. The need for balancing power and frequency control reserves are increasing, partially due to variable renewable production, which gives an opportunity for new incomes but also a challenge in terms of changed modes of operation with risk for reduced lifetime for controllable power plants. This paper investigates how the allocation of a sold volume of frequency control reserves within a large hydropower production fleet can affect the costs of providing primary and secondary reserves, in terms of its impact on wear and fatigue, production losses, and the quality of the delivered frequency control. The results show that for primary control, low static gain in the governors results in poor quality and a large amount of load cycles of the units. High static gain, on the other hand, increases the production losses. The control work of the fleet can be reduced by using a proper balance of primary and secondary control gain on each unit, although the intuitive results from linear models exaggerate this effect. Automatic secondary control improves the system frequency quality but also increases the wear.

Keywords
hydropower, frequency control, primary control, reserve allocation, wear and tear
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-308437 (URN)10.1109/TPWRS.2017.2702280 (DOI)000418776400038 ()
Note

Title of this article in dissertation reference lists: Allocation of Frequency Control Reserves and its Impact on Wear on a Hydropower Fleet

Available from: 2016-11-25 Created: 2016-11-25 Last updated: 2018-02-07Bibliographically approved
Yang, W., Sundqvist, P., Saarinen, L., Witt, A., Smith, B., Yang, J. & Lundin, U. (2018). Burden on hydropower units for short-term balancing of renewable power systems. Nature Communications, 9, Article ID 2633.
Open this publication in new window or tab >>Burden on hydropower units for short-term balancing of renewable power systems
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2018 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 2633Article in journal (Refereed) Published
Abstract [en]

There is a general need to change hydropower operational regimes to balance the growing contribution of variable renewable energy sources in power systems. Quantifying the burden on generation equipment is increasingly uncertain and difficult. Here, we propose a framework combining technical and economic indicators to analyze primary frequency control (PFC) on a timescale of seconds. We develop a model integrating hydraulic, mechanical, and electrical subsystems to characterize efficiency loss, wear and fatigue, regulation mileage, and frequency quality. We evaluate burden relief strategies under three idealized remuneration schemes for PFC, inspired by those used in Sweden, the USA, and China, respectively. We show how burden and compensation vary under future scenarios of renewable power systems. Our framework can be used by producers to develop favorable operation strategies that reduce burden and increase economic value, and by transmission system operators to provide insights on the relation between incentive structures and regulating performance.

National Category
Water Engineering
Identifiers
urn:nbn:se:uu:diva-361534 (URN)10.1038/s41467-018-05060-4 (DOI)000437677800010 ()29980673 (PubMedID)
Available from: 2018-09-25 Created: 2018-09-25 Last updated: 2018-09-25Bibliographically approved
Yang, W., Norrlund, P., Saarinen, L., Yang, J., Zeng, W. & Lundin, U. (2017). Wear reduction for hydro power turbines considering frequency quality of power systems: a study on controller filters. IEEE Transactions on Power Systems, 32(2), 1191-1201
Open this publication in new window or tab >>Wear reduction for hydro power turbines considering frequency quality of power systems: a study on controller filters
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2017 (English)In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 32, no 2, p. 1191-1201Article in journal (Refereed) Published
Abstract [en]

Nowadays, the wear and tear of hydropower turbines is increasing, due to more regulation movements caused by the increasing integration of intermittent renewable energy sources. In this paper, a controller filter is proposed as a solution to the tradeoff between reducing the wear of turbines and maintaining the regulation performance and thereby the frequency quality of the power systems. The widely used dead zone is compared with a floating dead zone and a linear filter, by time-domain simulation and frequency-domain analysis. Simulink models are built and compared with onsite measurement. Then, the time-domain simulation is used to investigate the guide vane movement, the load disturbance and the power system frequency, based on a one-day grid frequency datameasured in this study. In the theoretical analysis, the describing functions method and the Nyquist criterion are adopted to examine the stability of the system with different filters. The results show that the floating dead zone, especially the one after the controller, has a better performance than the dead zone on both the wear reduction and frequency quality. The linear filter has a relatively weak impact on both guide vane movements and the frequency quality. Other related conclusion and understandings are also obtained.

National Category
Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-262748 (URN)10.1109/TPWRS.2016.2590504 (DOI)000395865900033 ()
Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2017-04-27Bibliographically approved
Saarinen, L., Norrlund, P., Lundin, U., Agneholm, E. & Westberg, A. (2016). Full-scale test and modelling of the frequency control dynamics of the Nordic power system. In: 2016 IEEE POWER AND ENERGY SOCIETY GENERAL MEETING (PESGM): . Paper presented at IEEE-Power-and-Energy-Society General Meeting (PESGM), JUL 17-21, 2016, Boston, MA. New York: IEEE
Open this publication in new window or tab >>Full-scale test and modelling of the frequency control dynamics of the Nordic power system
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2016 (English)In: 2016 IEEE POWER AND ENERGY SOCIETY GENERAL MEETING (PESGM), New York: IEEE, 2016Conference paper, Published paper (Refereed)
Abstract [en]

The grid frequency quality in the Nordic power system has been deteriorating during the last decade. To improve the situation, a better understanding of the system is needed. In this paper, a model of the Nordic power system dynamics with respect to normal operation frequency control is set up and compared with full-scale measurements on the system. The "60 s oscillation" of the grid frequency is measured and explained by the system model.

Place, publisher, year, edition, pages
New York: IEEE, 2016
Series
IEEE Power and Energy Society General Meeting PESGM, ISSN 1944-9925
National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-332914 (URN)10.1109/PESGM.2016.7741711 (DOI)000399937902105 ()978-1-5090-4168-8 (ISBN)
Conference
IEEE-Power-and-Energy-Society General Meeting (PESGM), JUL 17-21, 2016, Boston, MA
Available from: 2017-11-03 Created: 2017-11-03 Last updated: 2017-11-03Bibliographically approved
Bladh, J., Wallin, M., Saarinen, L. & Lundin, U. (2016). Standstill Frequency Response Test on a Synchronous Machine Extended With Damper Bar Measurements. IEEE transactions on energy conversion, 31(1), 46-56
Open this publication in new window or tab >>Standstill Frequency Response Test on a Synchronous Machine Extended With Damper Bar Measurements
2016 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 31, no 1, p. 46-56Article in journal (Refereed) Published
Abstract [en]

Standstill Frequency Response (SSFR) test data from a salient-pole synchronous machine with reconfigurable damper winding is presented. In addition to the regular measurements, the damper bar currents are measured and used to obtain the stator-to-damper transfer functions. The test is performed three times with physically different damper winding configurations. An extension to the standard SSFR test analysis scheme is suggested where the stator-to-damper transfer functions are included. The validity of the identified models is substantiated by comparison of the simulated and measured machine response to a drive torque step disturbance. It is found that the damper winding measurements can be incorporated in the analysis scheme to isolate the effect of the damper circuits. However, for a machine of the type studied, also the standard SSFR test produce yields models that are accurate enough for power system studies.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-182155 (URN)10.1109/TEC.2015.2450994 (DOI)000372024100005 ()
External cooperation:
Available from: 2012-10-04 Created: 2012-10-04 Last updated: 2017-12-07Bibliographically approved
Yang, W., Norrlund, P., Saarinen, L., Yang, J., Guo, W. & Zeng, W. (2016). Wear and tear on hydro power turbines: influence from primary frequency control. Renewable energy, 87, 88-95
Open this publication in new window or tab >>Wear and tear on hydro power turbines: influence from primary frequency control
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2016 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 87, p. 88-95Article in journal (Refereed) Published
Abstract [en]

Nowadays the importance and need of primary frequency control of hydro power units are significantly increasing, because of the greater proportion of intermittent renewable energy sources and more complex structure of power systems. It brings a problem of increasing wear and tear of turbines. This paper studies this problem by applying numerical simulation and concise theoretical derivation, from the point view of regulation and control. Governor models under opening and power feedback mode are built and validated by measurement data. The core index, guide vane movement, is analyzed based on ideal sinusoidal frequency input and real frequency records. The results show the influences on wear and tear of different factors, e.g. governor parameters, power feedback mode and nonlinear governor factors.

National Category
Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-262747 (URN)10.1016/j.renene.2015.10.009 (DOI)000367759500008 ()
Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2017-12-04Bibliographically approved
Yang, W., Yang, J., Guo, W., Zeng, W., Wang, C., Saarinen, L. & Norrlund, P. (2015). A Mathematical Model and Its Application for Hydro Power Units under Different Operating Conditions. Energies, 8(9), 10260-10275
Open this publication in new window or tab >>A Mathematical Model and Its Application for Hydro Power Units under Different Operating Conditions
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2015 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 9, p. 10260-10275Article in journal (Refereed) Published
Abstract [en]

This paper presents a mathematical model of hydro power units, especially the governor system model for different operating conditions, based on the basic version of the software TOPSYS. The mathematical model consists of eight turbine equations, one generator equation, and one governor equation, which are solved for ten unknown variables. The generator and governor equations, which are different under various operating conditions, are presented and discussed in detail. All the essential non-linear factors in the governor system (dead-zone, saturation, rate limiting, and backlash) are also considered. Case studies are conducted based on one Swedish hydro power plant (HPP) and three Chinese plants. The simulation and on-site measurements are compared for start-up, no-load operation, normal operation, and load rejection in different control modes (frequency, opening, and power feedback). The main error in each simulation is also discussed in detail. As a result, the model application is proved trustworthy for simulating different physical quantities of the unit (e.g., guide vane opening, active power, rotation speed, and pressures at volute and draft tube). The model has already been applied effectively in consultant analyses and scientific studies.

National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-262746 (URN)10.3390/en80910260 (DOI)000362553000064 ()
Note

Correction in: Energies 9(6) Article number: 477 DOI: 10.3390/en9060477

Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2017-12-05Bibliographically approved
Saarinen, L., Norrlund, P. & Lundin, U. (2015). Field Measurements and System Identification of Three Frequency Controlling Hydropower Plants. IEEE transactions on energy conversion, 30(3), 1061-1068
Open this publication in new window or tab >>Field Measurements and System Identification of Three Frequency Controlling Hydropower Plants
2015 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 30, no 3, p. 1061-1068Article in journal (Refereed) Published
Abstract [en]

The dynamic behaviour of hydropower plants participating in primary frequency control is investigated in this paper through frequency response, step response and setpoint change tests on three Swedish hydropower plants. Grey-box system identification is used to estimate the parameters of simple linear models suitable for power system analysis and the major shortcomings of the linear models are discussed. It is found that frequency response tests with sinusoidal input signals give more reliable information about the dynamics of the plants than step response tests. It is also shown that backlash in the runner and guide vane regulating mechanisms are of great importance for the dynamic behaviour of the plants, and that the incremental gain from guide vane opening to power varies considerably with the operation point.

Keywords
hydropower, system identification, frequency control, field measurements
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-237793 (URN)10.1109/TEC.2015.2425915 (DOI)000360439300026 ()
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2017-12-05Bibliographically approved
Saarinen, L., Dahlbäck, N. & Lundin, U. (2015). Power system flexibility need induced by wind and solar power intermittency on time scales of 1-14 days. Renewable energy, 83, 339-344
Open this publication in new window or tab >>Power system flexibility need induced by wind and solar power intermittency on time scales of 1-14 days
2015 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 83, p. 339-344Article 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.

Keywords
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:nbn:se:uu:diva-237789 (URN)10.1016/j.renene.2015.04.048 (DOI)000358455100031 ()
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2017-12-05
Saarinen, L. (2014). A hydropower perspective on flexibility demand and grid frequency control. (Licentiate dissertation). Uppsala: Uppsala universitet
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. p. 57
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 339-14L
Keywords
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
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