23-02-2013, 02:35 PM
The Role of Wind Forecasting in Grid Operations & Reliability
The Role of Wind.pdf (Size: 332.19 KB / Downloads: 48)
Abstract
Wind energy is increasingly viewed as a desirable energy source, but it must be integrated into power grids and electric utility systems that are understandably oriented around issues of power, capacity and reliability. It is important to know the actual impact costs of significant wind penetration levels, and the paper first describes a study approach and the results of a specific wind integration study in North America. Once the impact costs are understood, it is then possible to design tools and operating practices to minimize these impact costs. Wind forecasting tools are a critical element in minimizing the impact costs and ensuring reliability with larger amounts of wind energy on the grid, and the approaches and reasonable expectations for state-of-the-art wind forecasting methods are described. The value of wind energy is increased, and larger amounts of wind energy can be used, if it can be scheduled using wind forecasting methods.
INTRODUCTION
A significant obstacle to the development of wind generation stems from the fact that utility systems are necessarily biased toward resource capacity – the rate of energy transfer to the grid, not just the total amount delivered over a longer period of time - to insure the adequacy, reliability, and security of the electric supply.
Integrating large amounts of wind energy into the larger portfolio of electric generation resources requires some special considerations on the part of those charged with operating the electric system. Substantial amounts of wind generation in a utility system can increase the demand for various actions and services. The ability of the control area to provide the required level of these services for successful integration, and their additional cost of doing so, depends on the makeup of its generating fleet, agreements with neighboring control areas, or the existence of competitive markets for such services.
WIND FORECASTING IN GRID OPERATIONS & RELIABILITY
Background on Utility Impacts of Wind
The nature of its “fuel” supply distinguishes wind generation from more traditional means for producing electric energy. The electric power output of a wind turbine depends on the speed of the wind passing over its blades. This moving air stream exhibits variability on a wide range of time scales – from seconds to hours, days, and seasons. Local and regional weather patterns, seasonal variations, terrain and other nearby turbines are just a few of the factors that can influence the electrical output variability of a wind turbine generator.
From the perspective of the power system, the aggregate performance of a large number of turbines rather than an individual turbine is generally more important. Wind turbines are usually spread out over a significant geographical area within the wind plant, and multiple wind plants are distributed over a much larger area within the control area. This spatial diversity has the beneficial effect of smoothing some variations in electrical output.
Xcel Study Results
The high-fidelity data from the meteorological simulations provided a very solid basis for various analysis of how the operation of the Xcel control area in Minnesota would be affected by the proposed wind generation. Specific impacts that were analyzed included:
• How much additional regulation capability would be required due to the addition of wind generation? Regulation is generating capacity allocated to follow the fastest fluctuations in control area demand. Units on regulation respond to automatic commands over tens of seconds to a few minutes. 560 km (350 miles)
• How does fluctuating wind generation affect the amount of controllable generation required to follow slower changes – tens of minutes to hours – of the control area demand as it proceeds through a daily pattern?
• How does the uncertainty associated with wind generation forecasts affect the commitment and scheduling of generation for the next day or days, and what are the economic consequences?
Summary & Conclusions
High-resolution wind speed data from meteorological simulations combined with historical utility system data provides a realistic foundation for assessing wind generation impacts on electric system operations. A similar approach can be extended to studies of transmission and power
issues. This is a powerful technique for determining the impact costs and operating impacts of additional wind generation.