Day-Ahead Scheduling of Combined Natural Gas and Electricity System with Mid-and Long-Term Electricity Contract Decomposition

In the background of further electricity market reforms and rapidly increasing penetration of gas-fired units in China, it is of economic and environmental importance to construct combined natural gas and electricity system with mid-and long-term electricity contract decomposition. The traditional scheduling model of combined natural gas and electricity system does not account for the problem of contract decomposition, and its scheduling plan formulation deviates from the actual application requirements. In this paper, the nested optimization of mid-and long-term electricity contract decomposition is considered in the scheduling model. For the case that the decomposition results may be non-executable in the scheduling plan, a method based on Lagrange multiplier is proposed for the first time to find the infeasible factor. And a coordinated optimization method is proposed to eliminate the infeasible power quantities, accounting for the effectiveness of medium and long-term transactions. In addition, the second-order cone relaxation method is adopted to linearize the nonlinear boundary of natural gas flow. Case study results verify the rationality and efficiency of the proposed method.