Abstract
Wind energy has been integrated into power systems with the hope that it can improve energy efficiency and decrease greenhouse gas emissions. However, several studies from around the world have implied that this integration has had an opposite effect, mainly because of the negative correlation between wind availability and load. Under this dynamic situation, coal power plants are forced to cycle, which is not within their designed mode of operation. To prevent this unwanted result, a unit commitment decision should include the fuel usage and emission rates during the ramp up/down process. This paper proposes a new unit commitment decision process to accommodate the economic and environmental costs associated with the ramping process. These costs are generally not convex, because there is a positive cost if a generator output changes significantly (regardless of direction). As a result, the problem might be nonconvex. A piece-wise linear cost curve is introduced to model the impact of ramping processes. With this curve, convex linear programming is formulated and the impact of governmental policy is discussed.