2009 Scenario Reliability Assessment - NERC

Scenario Reliability Self-Assessmentsmaturing. It is anticipated that the VGS would serve as the central point of facilitation for studyof renewable issues in the Western Interconnection.In addition to study activity in the Western Interconnection, there have been a number of pilotprograms and operational changes to facilitate the integration of variable generation. Theseinclude balancing cooperation agreements between BAs, ancillary service agreements, andchanges to transmission tariffs. Two examples of these are described below.The ACE Diversity Interchange (ADI) is an example of BA cooperation to reduce the impacts ofvariable generation. It provides a mechanism for BAs to share their variability, which reduces thelevel of generation changes required by each entity. There are currently 16 BAs in the WesternInterconnection participating in this activity. For the entities involved, participation has beenshown to reduce balancing costs and improve NERC Control Performance Standard (CPS2)scores.The Joint Initiative is a voluntary joint project sponsored by ColumbiaGrid, Northern TierTransmission Group, and WestConnect. Collectively, these three Regional planning groupscover most of the two non-ISO areas of the Western Interconnection. In addition, the project hasmany participants among WECC member utilities, merchants, and stakeholders. The goal of theJoint Initiative is to tap into the existing flexibility that exists within the WesternInterconnection. The Joint Initiative is recommending changes to Transmission Service Providerbusiness practices to: Facilitate within-hour transmission purchase and scheduling.Develop tools to facilitate within-hour bilateral transactions.Develop a dynamic scheduling system consisting of standard protocols andcommunication infrastructure that would allow access to resources across multiple BA’s,subject only to transmission constraints.Operational issues vary significantly depending on the size of the BA, the mix of generation,penetration of wind, geographic dispersion of wind, market structure, and performance of windplants. There are many and varied methods to mitigate the reliability and operational impacts ofvariable generation. However, these methods all focus on reducing the uncertainty of variablegeneration and accessing flexibility in the existing generation. This can be accomplishedthrough: Larger balancing areas (actual or virtual) Better wind forecasting Geographically dispersing wind generation over a larger area Increasing the amount of flexible generation (ramping capability) Ability to access flexible generation, including bi-lateral agreements between utilities ormarkets Rules and technology that allow for operational flexibility in near real-time throughdynamic scheduling, intra-hour re-dispatch, and ancillary service markets2009 Scenario Reliability Assessment Page 157