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Uncertainty in Electricity System Planning

Kamran Tehranchi, MS '23, Civil & Environmental Engineering
Graduate Fellow
California ISO

(Photo credit: Kamran Tehranchi)

Since coming to the California Independent System Operator (ISO) I have learned so much about the importance of incorporating uncertainties in electricity system planning models. With increasing levels of renewable energy in the electricity grid, the costs and reliability of the system has become increasingly dependent on the natural variations of weather. In system models that plan ten to twenty years in the future, using only one input assumption for solar, wind, and load grossly underestimates the range of possible system conditions we may experience in a given year. Enter, stochastic simulation. Stochastic simulations utilize multiple input assumptions to represent a range of possible system conditions and thus costs. These input assumptions span a probability distribution of possible wind, solar, and load years to represent the system uncertainty. My project this summer focused on developing a tool that the ISO will use to generate these stochastic load, wind, and solar profiles for the annual CAISO Transmission Planning Process.

My first goal was to understand the differences between the different methods used at different CA agencies to develop stochastic variables in system planning models.  I read through papers describing various neural network, regression, and stochastic process based approaches to develop stochastic variables. I read through research papers comparing the impacts these approaches have on the quality of simulation results. These topics in stochastic modeling and uncertainty analysis of production cost and capacity expansion modeling piqued my interest. Prior to joining the ISO for this fellowship I had a surface-level understanding of uncertainty analysis and production cost modeling used in reliability assessments, transmission and resource planning. Through the fellowship I had the opportunity to dive into the modeling assumptions and inputs used resource and transmission planning, and I am now planning to dive deeper into this area as I advance my career.

As my summer comes to a close, I am working to finish and package the stochastic profile generation tool for the ISO to use in the coming transmission planning process. I will be running a simulation of the WECC transmission system to gain hands-on experience with the end-product of my work. This simulation will take over five days to run- so hopefully I get my results to analyze before it is time to leave. The summer has flown by!