Optimal Operation of Compressors in an Integrated Gas and Electricity System—An Enhanced MISOCP Method

Abstract

The optimal operation of gas-driven compressors (GDCs) and electric-driven compressors (EDCs) was investigated to minimise the cost of operating a gas network. The operational optimisation model of the gas network with relatively detailed representation of gas compressors was formulated as a Mixed-Integer Second Order Cone Programming (MISOCP) problem. A bound-tightening algorithm was used to improve the quality of the solution from the relaxed MISOCP formulation. Using this model, the operation of the high-pressure gas transmission network in South Wales and Southwest of England was optimised considering day-ahead gas and electricity prices. The results show that, compared to the case in which only gas-driven compressors are available, nearly 63% of the operating cost of the gas network can be reduced through coordinated operation of gas-driven and electric-driven compressors, while it produces only 36% of carbon dioxide emissions compared of case that only gas-driven compressors are allowed to work. Although, these specific figures for cost and emission reductions depend on electricity and gas prices, as well as emission intensity of the power grid, the results demonstrate the potential for using the inherent flexibility of the high pressure gas network to reduce its operating cost and emission, and to support the operation of power systems. The within-pipe storage capability (i.e., linepack) of the high-pressure gas network is a key enabler that allows electric-driven compressors to shift their operation schedule in time to benefit from low electricity prices.INDEX TERMS Bound-tightening algorithm, electric-driven gas compressors, integrated electricity and gas network, MISOCP, optimal operation. NOMENCLATURE A. SETS