Subtransmission System Expansion Planning with DGs Considering Natural Gas Transmission Constraints

Network expansion planning is a complex, nonconvex and combinatorial problem. This paper proposes a method for subtransmission system expansion planning with sizing of gas-fired distributed generation units, considering natural gas transmission constraints. The proposed model allocates distributed generation units over subtransmission network and determines the capacity of them. Furthermore, the power transmission lines and substations that should be expanded are addressed. To obtain more accurate results, in addition to the natural gas pipelines, compressors and storage facilities are also considered. The objective function of the optimization problem is the total construction and operation costs, and a metaheuristic method, combined by PSO and backward algorithms, is utilized to solve the optimization problem. The Newton-Raphson method is also employed to determine the gas system load flow. Zanjan in Iran subtransmission system is used to evaluate the implementation of the proposed approach.