Long-term optimal operation of hydrothermal power systems.

摘要

When new construction projects are postponed or cancelled because of socio-economic concerns, greater emphasis is placed on enhanced operational planning---to get the most at the least cost, from the existing projects.;Of the approaches that made significant improvement in the operation of energy production systems is the co-ordination between hydro and thermal power plants. In this research, the problem of "Long-term Optimal Operation of Hydro-Thermal Power Systems" is addressed. Considering the uncertainty in reservoir inflows, the problem is defined as a "two-stage stochastic linear network programming with recourse". To avoid dimensionality problem generally associated with the employment of dynamic programming in large scale applications, Benders' decomposition approach is employed as the solution algorithm basis for the defined problem. Using the "General Algebraic Modelling System", a modelling code, the "Hydro-Thermal Co-ordinating Model (HTCOM)" is developed. In HTCOM, each sequence of hydrologic inflows generates a subproblem which is solved deterministically. The solutions of all subproblems are next co-ordinated by a master problem to determine a single feasible optimal policy for the original problem. This policy includes optimal reservoirs releases as well as allocation of energy generation at different power plants in the subsequent time period. The objective minimizes the expected total cost of meeting the energy demands while satisfying the system constraints over the long-term horizon of one to three years.;To demonstrate the applicability of HTCOM, a real world case study named the "Khozestan Water and Power Authority (KWPA)" in Iran is employed as a system of two multipurpose reservoirs with five hydro-thermal power plants and transactions of energy. The KWPA system components and operating policies are simulated as the network flow model and an integrated solution procedure is planned to determine the optimal operation policies. This procedure included the development of three specialized models: (1) HTCOM-I: to investigate the potential improvements of the current system; (2) HTCOM-II: to provide the required confidence in using the model in future simulations by evaluating the actual savings; and (3) HTCOM-III: to simulate the system operation under uncertainty, and determining the optimal operation policies for the next month. The results of employing all three codes in the KWPA system conclude that the selected approach for formulating the problem, the adopted algorithm based on Benders' decomposition technique, and the models (developed in the GAMS environment) are suitable, capable to handle stochasticity of inflows, and considerably cost-efficient.