Essays on Unit Commitment and Interregional Cooperation in Transmission Planning

One of the most challenging problems in the power industry is deciding which transmission lines to build. The process of answering this question leads to some very interesting and complex optimization problems. Answers to subsidiary questions about the detail of generator operations to simulate, generator siting, environmental regulations, political boundaries, and the ways in which these factors interact with each other, together inform the decision of building transmission lines. For example, carbon taxes may favor transmission expansion to areas with high levels of renewable energy, and consequently, fast ramp-rate generation may be desired to balance the variable nature of renewable energy sources. Transmission investment decisions can have far-reaching consequences for investors and a host of other entities connected to the electric grid. In addition to being expensive and time-consuming to build, these lines influence other transmission and generation investments, operations, and electricity prices. This work presents a series of essays on the transmission planning problem. There are two main themes: the effects of short-term operations, and the effects of political boundaries, on long-term transmission plans. Contributions of these essays include the following: 1. An alternative formulation of the Unit Commitment (UC) problem that solves faster than the standard UC formulation, and UC approximations that improve computational performance while maintaining high fidelity in the quality of the solution (reduction of binary variables and tightening of constraints). 2. Demonstrating how to bridge the gap between short-term (hours) operational models and long-term (years) transmission and generation co-optimization models, using an application of the U.S. Western Interconnection. 3. Demonstrating that short-term operational constraints have the potential to affect long-term transmission and generator investments. As an example, we find that, when operational constraints such as ramp-rates and minimum-run capacities are considered, transmission investment can sometimes act as a substitute to generation investments. 4. A novel formulation of the noncooperative regional transmission planning problem that shows how regional transmission operators acting in their own self-interest can negatively impact transmission investments. 5. Demonstrating that adjoining transmission operators can both benefit from cooperating with each other in the transmission planning process. Interestingly, we find that it is not enough to focus on seam lines connecting two regions. There are lines internal to each region that have interregional benefits and are identified only though a cooperative planning process. 6. Approximations of the non-cooperative transmission planning model that aid scale-up of this framework to large data-sets, further improving computational performance. Limitations of these models, practical issues involved, and future research directions are discussed in the concluding chapter. Together, these essays illuminate the effects of operational constraints and political boundaries on transmission planning, and encourage decision makers to consider them in their planning processes