Effects of security constraints on unit commitment with wind generators

Wind electric generators (WEGs) are increasingly integrated into power systems. Impetus for their integration in North America overlaps in time with deregulation of the monopolistic business of bulk energy delivery through electric power systems. Their growth is restricted, in part by the available transmission capacity and ability of scheduling algorithms to allow their seamless integration while satisfying norms set out by regional reliability council. This paper studies the effects of capacity limit of lines connecting WEGs on the optimal unit commitment (UC) schedule. Stochastic characteristic of the WEGs is captured in this work. It is used to compute expected energy not served (EENS), a measure which quantifies the amount of output that may not become online from WEGs at any given hour. It is parameterized and added to the spinning reserve constraint to counter the risk introduced through the inclusion of WEGs. This inclusion is analogous to N-1 reliability criteria. The UC formulation minimizes the total operating cost while satisfying all operational constraints considering both conventional and renewable energy generators. An analysis of the effect of line flow limit on operating costs, reserve costs, EENS and marginal clearing prices are studied and reported.