Dynamic long-term expansion planning of generation resources and electric transmission network in multi-carrier energy systems

In this paper, a new framework is proposed for long-term generation and transmission expansion planning in multi-carrier energy systems (MCES). The MCES considered here consists of combined heat and power (CHP), gas furnace, power generation unit and transmission lines associated to natural gas and electrical networks. In the proposed framework, by minimizing the total investment and operation costs, optimal capacity, location and time of installing of new heat and electrical generation resources and also electric transmission lines are determined in a multi-year horizon. A linearized AC load flow equations is used for modeling effects of electric transmission network and is compared with DC load flow model. Also, a linearized model of accurate gas flow equations in natural gas transmission pipelines is used and is compared with a simple model. By using linear models for energy transmission network, the expansion problem is converted to a mixed integer linear programming (MILP) problem. By solving the MILP model by GAMS in which mathematical algorithm is used, optimal operation and expansion strategies on heat and power generation resources as well as electric transmission lines are obtained over the planning horizon. Performance of the proposed model is evaluated through two system tests, where transmission losses, overall system efficiency, reliability of supply and emissions are considered as metrics. Simulation results show importance of energy transmission network modeling in investment and operation of MCES in the long-term.