A Solution for Unit Commitment Problem Considering LNG Fuel Constaraints

Abstract

In this paper, an algorithm is proposed to find a quasi-optimal schedule for the short-term thermal unit commitment problem considering LNG fuel constraints.
In recent years, LNG fuel is used increasingly. As a result, LNG fuel constraints should be considered in making a unit commitment schedule. Generally, unit commitment is a non-linear combinatorial problem including discrete variables. Adding LNG fuel constraints extensively increases the complexity of the problem. To solve the problem, a two-step algorithm is developed using mathematical programming methods. First a Linear Porgramming problem is solved to determine the amount of LNG fuel to be consumed by each LNG unit, then a Lagrangian Relaxation approach is used to obtain a unit commitment schedule. This two-step algorithm simplifies the problem and thus has good characteristics in convergence.
To test the effectiveness of the proposed algorithm, a numerical simulation is carried out on a 46-unit thermal system over a 24-hour period. The result is obtained with the dual-gap of 0.00546.