Unit Commitment Considering Generation Flexibility and Environmental Constraints

This paper proposes a new framework for the power system unit commitment process, incorporating generation flexibility requirements and environmental constraints into the existing unit commitment algorithm. The generation flexibility requirements are to address the uncertainty and variability associated with large amounts of intermittent resources as well as with load, which cause real-time balancing requirements to be variable and less predictable. The proposed flexibility requirements include capacity, ramp-rate and energy (or ramp duration) for both upward and downward balancing reserves. The environmental constraints include emission limits for fossil fuel-fired generators and ecological regulations for hydro power plants. The calculation of emission rates is formulated. Unit commitment under this new framework will be critical to the economic and reliable operation of the power grid and the minimization of its negative environmental impacts, especially when high penetration levels of intermittent resources are being approached, as required by the renewable portfolio standards in many states.