Possibilistic–Probabilistic Security Constrained Unit Commitment using Z_number model

Authors

Faculty of Electrical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran

Abstract

Security constrained unit commitment (SCUC) is a difficult optimization problem by which the generators optimal output  are scheduled over the whole dispatch period. Here, different constraints such as demand and generation equality, generators limits and transmission flow limit should be considered. This paper presents a new structure for SCUC in the presence of wind and load uncertainties. Here, demand responsive loads are called for alleviating the aforementioned uncertainties as well as minimizing the operation cost. Wind speed uncertainty is modeled by Wiebull probability distribution function as a probabilistic variable. Moreover Z_number is applied to model the demand uncertainty as a possibilistic variable. Then, demand is converted form Z_number model to fuzzy one. Demand bidding programs are also implemented to reduce demand at peak hours. Load reduction payment is modeled by a quadratic function of the reduced power. In this paper, α-cut and monte carlo methods are mixed together to solve the SCUC problem considering the abovementioned uncertainties. In order to evaluate the proposed framework, numerical simulations has been conducted over the modified IEEE-24 bus system.

Keywords