A Sliding Window Technique for Calculating System LOLH Contributions of Wind Power Plants

As electricity markets undergo restructuring, it is becoming apparent that the responsibility for providing power and the ancillary services associated with power generation is being allocated to different entities. Former electric utilities enter spot markets and sign power-delivery contracts, and generating companies bid or otherwise offer electricity for sale. Operating units, such as Regional Transmission Organizations often take on a system-wide perspective that includes assessing reliability and securing related ancillary services. As the complexity of power contracting increases, reliability will almost certainly decline as the grid becomes stretched and the number of transactions increases. At the same time, the electricity produced by wind power plants is increasing in the United States and around the world. Given these developments, the ability to accurately measure intermittent power generators may become more important as we move towards the future. Conventional generation reliability models do not typically recognize the probabilistic nature of the power variations from wind plants. Most models allow for an accurate hourly representation of wind power output, but do not incorporate any probabilistic assessment of whether the given level of wind power will vary from its expected value. The technique presented in this paper uses this variation to calculate an effective forced-outage rate for wind power plants (EFORW). Depending on the type of wind regime undergoing evaluation, the length and diurnal characteristics of a sliding time window can be adjusted so that the EFORW is based on an appropriate time scale. The algorithm allows us to calculate the loss-of-load probability (LOLP) on an hourly basis, fully incorporating the variability of the wind resource into the calculation. This makes it possible obtain a more accurate assessment of reliability of systems that include wind generation when system reliability is a concern.