"Northern European power system balancing under large scale wind integration"
I. INTRODUCTION
The intermittent production on all time scales is one of the major challenges when it comes to wind power integration. In a liberalised market wind power production (WPP), based on forecast scenarios, can be traded in the day-ahead market. However, short term deviations result in system imbalances. For WPP simulations the whole balancing area has to be considered, as smoothing effects in large geographical areas reduce the requirement for regulating reserves [1]. The system imbalances need to be compensated by the activation of regulating reserves, available to the power system.
InEurope, the procurement and possible subsequent activation of these regulating reserves is done within regulating power markets. In order to study the effects of WPP on system balancing the reserve procurement and system balancing in the northern European area is simulated and the according costs are estimated. This is done for national regulating power markets as well as an integrated northern European market, to estimate possible benefits of exchanging regulating reserves as well as energy.
II. MODELLING
The real time production is based on wind speed measurements including more than 200 measuring stations [2]. To avoid scaling errors the power production for each wind power facility is calculated under consideration of roughness length and topography. Wind speeds are taken from the numerical weather prediction tool COSMO EU which offers a point to point resolution of 7 km [3].
Even though the numerical weather prediction models have reached a high level of accuracy, the mean 24h forecast error in the used data set is about 25.3%, while the 3h error reduces to only 14.5%. For the following analysis the 24h forecast error is used.
The market model used in this analysis consists of three stages. It simulates an integrated northern European regulating power market, which is based on a common day-ahead market, including the Nordic countries the continental European countriesGermanyand theNetherlandsin the state of 2008.
The model structure consists of two general parts, represented by two different models, which are EMPS and the IRiE respectively. The EMPS model is a long- and mid-term optimisation [6], whereas IRiE has a short-term horizon [5].
III. CASE STUDIES
In order to study the effects of large amounts of WPP on the system operation, the WPP cases 2008, 2015 and 2020 are defined, where the later two each include a low and high wind scenario, taken from the TradeWind project [4]. In addition to increasing levels of WPP, the integration of Northern European regulating power markets is assessed, including the cases no and full market integration. Regulating power market integration implies the exchange of reserve capacity as well as balancing energy across country borders in the case of free transmission capacity.
The case studies show, that there is a significant increase of reserve activation (five times as high) from 2008 to 2020 due to increased system imbalances. Thus, costs for the procurement of reserves and for the balancing of the system rise as well. In the case of national regulating power markets (no market integration), the maximum cost increase is estimated to about 2 billion EUR per annum (2020 high wind), what is a triplication of the costs in 2008.
With an integration of regulating power market, i.e. an exchange of balancing services among Northern European countries, this development can be counteracted. In this case a share of about 15% of the required reserve capacity is procured across borders, while the activation of the reserve capacity is reduced by about 25%
This results in a significant cost reduction, down to about 60%. The main reasons for the cost reduction are the procurement of cheaper reserve capacity, which is situated in the Nordic area and the system imbalance netting among several countries.
IV. REFERENCES
[1] H. Holttinnen, “The impact of large scale wind power production on the Nordic electricity system“, VTT Publications 554, VTT Processes, Espoo., 2004. 82 p.+ app 111 p.
[2] T. Aigner, T. Gjengedal ”Detailed Wind Power Production in northern Europe”, Renewable Energy Conference 2010, Yokohoma, July, 2010
[3] Deutscher Wetter Dienst (DWD), www.dwd.de
[4] M. Korpås, L. Warland, J.O.G. Tande, K. Uhlen, K. Purchala, S. Wagemans, “Further Developing Europe’s Power Market for Large Scale Integration of Wind Power- Grid modelling and power system data”, Tradewind Report, 2008, http://www.trade-wind.eu/
[5] S. Jaehnert, G. Doorman, “Modelling an integrated northern European regulating power market based on a common day-ahead market”, Proc. of IAEE International Conference, Rio de Janeiro, Juni 2010.
[6] O. Wolfgang, A. Haugstad, B. Mo, A. Gjelsvik, I. Wangensteen, G. Doorman, “Hydro reservoir handling before and after deregulation”, Energy, Vol. 34, pp. 1642-1651, 2009.
