Browsing by Author "Milligan, Michael"
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- Design and operation of power systems with large amounts of wind power : Final report, Phase one 2006-08, IEA WIND Task 25Publication . Holttinen, Hannele; Meibom, Peter; Orths, Antje; Van Hulle, Frans; Lange, Bernhard; O'Malley, Mark; Smith, J. Charles; Estanqueiro, Ana; Ricardo, João; Ummels, Bart C.; Gomez, Emilio; Matos, M.; Soder, Lennart; Shakoor, Anser; Strbac, Goran; Tande, John O.; Pierik, Jan; Ela, Erik; Milligan, MichaelThere are already several power systems coping with large amounts of wind power. High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind power s variability and uncertainty on power system reliability and costs. The case studies summarized in this report are not easy to compare due to different methodology and data used, as well as different assumptions on the interconnection capacity available. Integration costs of wind power need to be compared to something, like the production costs or market value of wind power, or integration cost of other production forms. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and working electricity markets at less than day-ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits,electricity markets and larger balancing areas. From the investigated studies it follows that at wind penetrations of up to 20 % of gross demand (energy), system operating cost increases arising from wind variability and uncertainty amounted to about 1 4 /MWh. This is 10 % or less of the wholesale value of the wind energy.
- Design and operation of power systems with large amounts of wind power: State of the art reportPublication . Holttinen, Hannele; Lemstrom, Bettina; Meibom, Peter; Bindner, Henrik; Orths, Antje; Van Hulle, Frans; Ensslin, Cornel; Tiedemann, Albrecht; Hofmann, Lutz; Winter, Wilhelm; Tuohy, Aidan; O'Malley, Mark; Smith, Paul; Pierik, Jan; Tande, John O.; Estanqueiro, Ana; Ricardo, João; Gomez, Emilio; Soder, Lennart; Strbac, Goran; Shakoor, Anser; Smith, J. Charles; Parsons, Brian; Milligan, Michael; Wan, Yih H.High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind powers variability and uncertainty on power system reliability and costs. The case studies summarized in this report are not easy to compare due to different methodology and data used, as well as different assumptions on the interconnection capacity available. Integration costs of wind power need to be compared to something, like the production costs or market value of wind power, or integration cost of other production forms. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and working electricity markets at less than day-ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas. From the investigated studies it follows that at wind penetrations of up to 20% of gross demand (energy), system operating cost increases arising from wind variability and uncertainty amounted to about 14 /MWh. This is 10% or less of the wholesale value of the wind energy. With current technology, wind power plants can be designed to meet industry expectations such as riding through voltage dips, supplying reactive power to the system, controlling terminal voltage, and participating in system operation with output and ramp rate control. The cost of grid reinforcements due to wind power is very dependent on where the wind power plants are located relative to load and grid infrastructure. The grid reinforcement costs from studies in this report vary from 50 /kW to 160 /kW. The costs are not continuous; there can be single very high cost reinforcements, and there can also be differences in how the costs are allocated to wind power. Wind generation will also provide some additional load carrying capability to meet forecasted increases in system demand. This contribution can be up to 40% of installed capacity if wind power production at times of high load is high, and down to 5% in higher penetrations and if local wind characteristics correlate negatively with the system load profile. Aggregating larger areas benefits the capacity credit of wind power. State-of-the-art best practices so far include (i) capturing the smoothed out variability of wind power production time series for the geographic diversity assumed and utilising wind forecasting best practice for the uncertainty of wind power production (ii) examining wind variation in combination with load variations, coupled with actual historic utility load and load forecasts (iii) capturing system characteristics and response through operational simulations and modelling and (iv) examining actual costs independent of tariff design structure.
- Flexibility chart: Evaluation on diversity of flexibility in various areasPublication . Yasuda, Yoh; Ardal, Atle Rygg; Carlini, Enrico Maria; Estanqueiro, Ana; Flynn, Damian; Gomez-Lázaro, E.; Holttinen, Hannele; Kiviluoma, Juha; Van Hulle, Frans; Kondoh, Junji; Lange, Bernhard; Menemenlis, Nickie; Milligan, Michael; Orths, Antje; Smith, J. Charles; Soder, LennartThis paper evaluates various aspects of flexibility in power systems worldwide within the multi-country study framework of IEA Wind Task 25, including grid components and actions which have been favoured for enhancing flexibility in different areas/countries/regions, and how TSOs/ISOs/ utilities intend to manage variable generation in their operating strategies. One methodology to evaluate the diversity of flexibility sources is a "flexibility chart”, which can illustrate several flexibility parameters (e.g. hydro, CCGT, CHP, interconnection) in a polygonal radar (spider) chart.
- Summary of experiences and studies for wind integration: IEA Wind Task 25Publication . Holttinen, Hannele; Robitaille, André; Orths, Antje; Pineda, Ivan; Lange, Bernhard; Carlini, Enrico Maria; O’Malley, Mark; Dillon, Jody; Tande, John Olav; Estanqueiro, Ana; Gomez-Lázaro, E.; Soder, Lennart; Milligan, Michael; Smith, J. CharlesIEA WIND R&D Task 25 on “Design and Operation of Power Systems with Large Amounts of Wind Power” collects and shares information on wind generation impacts on power systems, with analyses and guidelines on methodologies. This paper summarizes the main results from the report published on January 2013 describing experience of wind integration as well as the most relevant wind power grid integration studies in the 15 participating countries. The studies build on the already significant experience in integrating wind power in power systems addressing concerns about the impact of wind power’s variability and uncertainty on power system security of supply and costs as well as grid reinforcement needs. The mitigation of wind power impacts includes more flexible operational methods, incentivising flexibility in other generating plants, increasing interconnection to neighbouring regions, and application of demand-side flexibility. Electricity storage is still not as cost effective in larger power systems as other means of flexibility, but is already seeing initial applications in places with limited transmission.
- Variability in large-scale wind power generationPublication . Kiviluoma, Juha; Holttinen, Hannele; Weir, David; Scharff, Richard; Söder, Lennart; Menemenlis, Nickie; Cutululis, Nicolaos Antonio; Lopez, Irene Danti; Lannoye, E.; Estanqueiro, Ana; Gomez-Lázaro, E.; Zhang, Qin; Bai, Jianhua; Yih-Huei, Wan; Milligan, MichaelThe paper demonstrates the characteristics of wind power variability and net load variability in multiple power systems based on real data from multiple years. Demonstrated characteristics include probability distribution for different ramp durations, seasonal and diurnal variability and low net load events. The comparison shows regions with low variability (Sweden, Spain and Germany), medium variability (Portugal, Ireland, Finland and Denmark) and regions with higher variability (Quebec, Bonneville Power Administration and Electric Reliability Council of Texas in North America; Gansu, Jilin and Liaoning in China; and Norway and offshore wind power in Denmark). For regions with low variability, the maximum 1?h wind ramps are below 10% of nominal capacity, and for regions with high variability, they may be close to 30%. Wind power variability is mainly explained by the extent of geographical spread, but also higher capacity factor causes higher variability. It was also shown how wind power ramps are autocorrelated and dependent on the operating output level. When wind power was concentrated in smaller area, there were outliers with high changes in wind output, which were not present in large areas with well-dispersed wind power.
- Variability of load and net load in case of large scale distributed wind powerPublication . Holttinen, Hannele; Kiviluoma, Juha; Estanqueiro, Ana; Gómez-Lázaro, E.; Raw, Barry; Dobschinski, Jan; Meibon, Peter; Lannoye, Eamonn; Aigner, Tobias; Wan, Yih H.; Milligan, MichaelLarge scale wind power production and its variability is one of the major inputs to wind integration studies. This paper analyses measured data from large scale wind power production. Comparisons of variability are made across several variables: time scale (10-60 minute ramp rates),number of wind farms, and simulated vs. modeled data. Ramp rates for Wind power production, Load (total system load) and Net load (load minus wind power production) demonstrate how wind power increases the net load variability. Wind power will also change the timing of daily ramps.
- Wind and solar curtailmentPublication . Lew, Debra; Bird, Lori; Milligan, Michael; Speer, Bethany; Wang, Xi; Carlini, Enrico Maria; Estanqueiro, Ana; Flynn, Damian; Gomez-Lázaro, E.; Holttinen, Hannele; Menemenlis, Nickie; Orths, Antje; Smith, J. Charles; Soder, Lennart; Sorensen, Poul; Altiparmakis, Argyrios; Yoh, YasudaHigh penetrations of wind and solar generation on power systems are resulting in increasing curtailment. Wind and solar integration studies predict increased curtailment as penetration levels grow. This paper examines experiences with curtailment on bulk power systems internationally. It discusses how much curtailment is occurring, how it is occurring, why it is occurring, and what is being done to reduce curtailment. This summary is produced as part of the International Energy Agency Wind Task 25 on Design and Operation of Power Systems with Large Amounts of Wind Power.
- Wind integration cost and cost-causationPublication . Milligan, Michael; Kirby, Brendan; Holttinen, Hannele; Kiviluoma, Juha; Estanqueiro, Ana; Martín-Martínez, Sergio; Gomez-Lázaro, E.; Pineda, Ivan; Smith, J. CharlesThe question of wind integration cost has received much attention in the past several years. The methodological challenges to calculating integration costs are discussed in this paper. There are other sources of integration cost unrelated to wind energy. A performance-based approach would be technology neutral, and would provide price signals for all technology types. However, it is difficult to correctly formulate such an approach. Determining what is and is not an integration cost is challenging. Another problem is the allocation of system costs to one source. Because of significant nonlinearities, this can prove to be impossible to determine in an accurate and objective way.