In this paper, we propose a new unit commitment model that captures the sub-hourly variability of wind power. Scenarios are included in the stochastic unit commitment formulation to represent the uncertainty and intermittency of wind power output. A modified Benders decomposition method is used to improve the convergence of the algorithm. The numerical results show that the proposed model based on finer granularity outperforms the conventional model of hourly resolution. (C) 2013 Elsevier Ltd. All rights reserved.