Stefan Jaehnert

The Effect of Large-Scale Wind Power on System Balancing in Northern Europe

Summary form only given. The on-going development in the electrical system and the transition from a mainly thermal dominated power system into a system, widely affected by renewable production resources, requires a revision of future balancing strategies facilitating the secure integration of renewable energy. Especially the increasing wind power penetration with its uncertain production on all time scales will largely affect the system operation, requiring a higher flexibility and thus more reserve capacity providing balancing energy.

Modelling of prices using the volume in the Norwegian regulating power market

A statistical model of the regulating market based on the regulating volume is proposed. The modelling process is divided into two steps; a long term and a short term study. The long term study is based on recorded data for 5 years. This analysis provides a statistical model of regulating prices and volumes for the whole market for the considered period. The combination of the long term model with expected regulating states and volumes is used in order to generate short term scenarios of the regulating market. The regulating state determination uses a Seasonal Auto Regressive Integrated Moving Average (SARIMA) process. The regulating volume scenarios are generated by using the statistical properties of the regulating volume based on recorded data. The proposed model is based on data from southern Norway and the result is a model estimating the regulating prices using the estimated regulating volumes. The resulting model makes it possible to estimate regulating market prices under changing conditions, like those occurring when different national markets are integrated.

Impact of large scale wind integration on power system balancing

With an increasing wind power penetration, more generation intermittency will be added to the power system, requiring higher flexibility and thus more regulating reserves. Based on high resolution numerical weather prediction models and wind speed measurements, the actual and the forecasted wind power production is simulated for five scenarios covering the years 2010, 2015 and 2020. These scenarios are taken as an input to an integrated northern European market model, analyzing the procurement of regulating reserves and their activation. Further on, the possible benefit of integrating the northern European regulating power markets for handling the intermittent production is investigated.

Benefits of cross-border reserve procurement based on pre-allocation of transmission capacity

Integration of national balancing markets is one of the tools needed to integrate large amounts of intermittent generation. Such integration affects both balancing and day-ahead markets in the involved countries and analyses to study the effects of such integration are required. This paper describes an approach where the bidding prices for reserve capacity of generation units are determined on the basis of their opportunity costs in the day-ahead for the period considered for the reserve procurement. The approach is described both for a single balancing area, and for a system with several balancing areas, in which case also the availability of transmission capacity is important. The approach is illustrated with a small example.

Bidding in the Frequency Restoration Reserves (FRR) market for a Hydropower Unit

In this work we present an approach to determine the Frequency Restoration Reserves (FRR) bidding price for hydropower units. The piecewise linear approximation of discharge to power output relationship of a hydropower unit is used for the price estimation. The bidding prices for reserve capacity of generation units are determined on the basis of their estimated opportunity costs in the day-ahead market for the period reserves are procured. The approach is illustrated with a numerical example. The bidding prices for both upward and downward FRR from a hydro unit are related to the difference between the daily average spot price forecasts and the water value at the given day.

Analysing the generation adequacy in power markets with renewable energy sources

With an integrated operation and investment optimisation model, the system adequacy for power markets with a large share of renewable energy sources (RES) is assessed. The analyses address the effect of increasing RES penetration and a potential implementation of a capacity mechanism to tackle the resulting lack of generation capacity. Moreover, sensitivity analyses for the price cap as well as the share of elastic demand are executed, pinpointing to further possibilities for resolving the system adequacy issue. The analyses show that an increasing RES penetration has a significant effect on the system adequacy. However, the implementation of a capacity mechanism or an increased price cap as well as more demand elasticity can solve the challenge.

Balancing energy market integration considering grid constraints

The increase in market integration and renewable penetration in European countries highlights the importance of balancing market integration. We use a DC optimal power flow (DCOPF) based balancing energy market formulation on a modified version of the IEEE 30-bus test system. The impact of cross-border exchange of balancing energy in relation to local balancing is assessed. By calculating the net transfer capacities (NTC) from the maximum transmission capacities, NTC based balancing market formulation is also considered for comparison. With a possibility of exchanging balancing energy between zones, a significant reduction in balancing costs and net imbalances is observed compared to local balancing. For both balancing market formulations, about half of the imbalances are netted when there is a possibility of balancing energy exchange. Results also show that with a possibility of inter-zonal balancing energy exchange, NTC based balancing is more expensive than the DCOPF approach. This is because the units committed for balancing and the flows paths taken are not identical for both arrangements.

Assessing the economic impacts for outages of HVDC-cables connecting the Nordic area and continental Europe

The Nordic and especially the Norwegian hydro-based power production is in a favourable position to provide parts of required generation back-up capacity for RES in continental Europe. In order to provide this capacity, sufficient transfer capacity needs to be available. For such HVDC-cables, it is observed that outages do occur occasionally and can remain for long periods. During these events, back-up capacity could not be provided. The aim of the analysis presented in this paper is to assess the impact of HVDC-cable outages on the value of providing back-up generation capacity to continental Europe. In addition, the effects of transmission outages are compared to outages of thermal generation capacity.

Sensitivity analysis of optimal transmission capacity reservation for cross-border exchange of reserve capacity in Northern Europe

This paper discusses the impact of Nordic hydro inflow and change in planning period on total costs, optimal transmission capacity reservation, and country wise reserve procurement. The model is intended for the Northern European system including the day-ahead and reserve markets. The main impact of the inflow variation in the Nordic system is on the total costs. The effect of inflow variation on optimal transmission capacity reservation is not significant. Similarly, the main impact of the distinct peak and off-peak period reserve procurement is the flexibility a generating unit gets with shorter planning periods which subsequently results in lower costs. For the case with peak and off-peak distinction, Optimal transmission capacity reservation values in a given day are different whereas the pattern does not change for the whole year. The volume of upward and downward reserves procured was consistent irrespective of the Nordic inflow variation or the shortening of the planning period for reserve procurement.

European regulating power market operation: Reserve requirement levels for wind power production

Large-scale integration of renewable energy sources in todays European hydro-thermal dominated power system will challenge its future operation. In Northern Europe wind power production is expected to contribute the main share to renewable energy sources. Wind forecasting and its inherent forecast error lead to increasing system imbalances. This will require higher production flexibility and more regulating reserves in the system, to ensure its secure and efficient operation. A model of the Northern European power market, including a 2010 and a 2020 scenario, is used to assess the impact of the wind forecast error and the level of reserves, which are required in the system. The analyses show an enormous increase of system imbalances up to 2020 and thus socio-economic costs, which occur in the regulating power market. Rather low requirement level turn out to be most cost effective. However, in 2010 as well as 2020 highest savings can be achieved by the integration of national regulating power markets, concurrently leading to an increased system security.