B.C. Ummels

Impacts of Wind Power on Thermal Generation Unit Commitment and Dispatch

This paper proposes a new simulation method that can fully assess the impacts of large-scale wind power on system operations from cost, reliability, and environmental perspectives. The method uses a time series of observed and predicted 15-min average wind speeds at foreseen onshore- and offshore-wind farm locations. A Unit Commitment and Economic Dispatch (UC-ED) tool is adapted to allow for frequent revisions of conventional generation unit schedules, using information on current wind energy output and forecasts for the next 36 h. This is deemed the most faithful way of simulating actual operations and short-term planning activities for a system with large wind power penetration. The problem formulation includes ramp-rate constraints for generation schedules and for reserve activation, and minimum up-time and down-time of conventional units. Results are shown for a realistic future scenario of the Dutch power system. It is shown that problems such as insufficient regulating and reserve power-which are typically associated with the variability and limited predictability of wind power-can only be assessed in conjunction with the specifics of the conventional generation system that wind power is integrated into. For the thermal system with a large share of combined heat and power (CHP) investigated here, wind power forecasting does not provide significant benefits for optimal unit commitment and dispatch. Minimum load problems do occur, which result in wasted wind in amounts increasing with the wind power installed

Statistical Wind Speed Interpolation for Simulating Aggregated Wind Energy Production under System Studies

In this paper we present a statistical interpolation method to generate a time series of system-aggregated wind power production values that can be used as an input to system operations planning tools such as unit commitment (UC) and economic dispatch (ED). We use historical wind speed data measured at several locations, in order to estimate average wind patterns and express the covariance between locations as a function of their distance. Then, for a new set of locations where wind parks are planned, we create wind time series for the study period such that the spatial correlation between the sites is taken into account. Depending on the system under study, this may be of specific importance due to the concentration of areas with favorable wind conditions, resulting in strong correlations between wind park outputs. These cross-correlations are essential when evaluating system adequacy and security in planning mode, in the presence of large-scale wind power. The resulting aggregated wind power time series are finally fed into the UC-ED module to help evaluate the amount of total system reserve required to maintain an adequate level of reliability. The method is applied to a simplified version of the Dutch power system

System integration of large-scale wind power in the Netherlands

This paper presents the results of a simulation of system operation in the Netherlands in the presence of future large-scale wind energy production. The study is aimed at identifying bottlenecks in system planning and operation due to wind integration, in particular base-load and ramp rate problems. These may constraint the amount of wind that can be accommodated given a projected production park of dispatchable units and yearly load profile by 2012. Wind data from 2004-2005, interpolated to existing locations for onshore and planned locations for offshore wind parks, were used to create a realistic yearly wind energy output profile. The unit commitment and economic dispatch formulation includes ramp rate constraints for generation schedules and reserve activation as well as minimum up- and down times. Of particular interest in this study are the combined heat & power (CHP) units, which impose additional constraints coupling their heat and energy production. Since no insight was available into the aggregated predictability of wind generation, both a 0-MW prediction, where conventional units are scheduled to meet the total load, and a perfect prediction have been investigated. No forms of electrical or heat storage were considered. The results show no ramp rate problems in the Dutch system by 2012, however base-load problems may arise at high wind penetration levels, only to be prevented by wasting available wind resources

Implementation of wind power in the Dutch power system

We present the current status of wind power in the Netherlands and its future prospects, in particular for the development of offshore wind. An overview is given of the performance of the wind power on land. We briefly discuss the experience with OWEZ, the first offshore wind park commissioned April 2007, and the expectations for Q7, to be completed March 2008. The organization of the energy and imbalance markets in the Netherlands is described. Balancing requirements due to variability and limited predictability of wind energy are estimated, at system and market participant level. Next, we present the results of a wind power integration study performed in order to estimate the amount of wind curtailment due to the technical limitations of the conventional units in the Netherlands. It is found that due to must-run constraints on the combined heat and power units, which constitute over 50% of the Dutch production park, sufficient reserve is available to cover wind fluctuations and prediction errors for up to 8000 MW installed wind power. The only limiting factor is the minimum output of the conventional units, which may result in increasing curtailed wind starting around 4000 MW installed capacity. Changes in system operating costs, curtailed wind and total emissions due to the application of various large-scale storage technologies are described in the final section of the paper.

Flexible international exchanges: A possible solution for large — Scale wind power integration

A production cost simulation model for the NorthWestern part of the UCTE system is developed in this paper. Information from various sources was gathered and combined to produce an integrated representative model of the areas under study. Specifically, the technical and economical limits of wind power integration within the power system are highlighted, by means of observing and analyzing various unit commitment schedules under different scenarios. The main question refers to which level of wind penetration the power system can operate in a safe and reliable fashion, while the incoming wind power is completely integrated and correlations between system variables in adjacent areas are taken into account. By answering this question, the system planner will have the flexibility to arrange in the future the power system operation accordingly so as to decrease the operation costs to a minimum and increase the efficiency of the total system to maximum. An investigation of this problem statement can only be executed with global models, which take into account both technical and economic constraints and further optimize the operation of the power system.

Transmission and System Integration of Wind Power in the Netherlands

In this paper, an overview of wind power transmission and system integration aspects is presented for the Netherlands. Particular aspects regarding the Netherlands, such as the market organisation with respect to wind power, the technical characteristics of conventional generation units and grid connection of offshore wind power, are discussed in detail. Power system integration of wind power typically comprises local impacts (distribution level), grid connection aspects (perephery of the network), system wide impacts (power balancing), grid codes and market designs.