Unified solution of security-constrained unit commitment problem using a linear programming methodology

With the advent of open markets trading of power as a commodity, secure operation is an enduring concern of the independent system operator. A comprehensive security-constrained unit commitment (SCUC) methodology to coordinate a secure and economic generation pattern for the day-ahead market is an urgent requirement. An ineffective coordination of electric power transfer over the transmission lines could result in congestion, and inadvertently an outage cause through line overloading. In the current practice, the SCUC is solved by decoupling the cost evaluation aspect from the network security aspect. The primary frequency regulation reserve deployable in a manner after a (n-1) contingency has not been fully utilised in the present approaches. A unified approach to the solution of the SCUC using a linear programming methodology with an extended DC network model embedded in the main algorithm is presented. The line-flow-based power flow equations are used to couple the economic dispatch (ED) and the network security process, and the proposed SCUC will include primary reserve as a part of the security constraint. Unlike the traditional SCUC programs that solve the ED first and then check it with the network for any violation, the proposed method solves the optimisation by fixing the line limits to solve the ED from the UC. A six-bus three generator and a modified IEEE 30-bus nine generator systems illustrate the implementation of the proposed SCUC formulation.