CONJUNCTIVE OPERATION OF HYDROELECTRIC AND THERMAL POWER-PLANTS

An integrated approach combining deterministic dynamic programming and simulation models has been developed and applied to determine the opt imal operation policy and performance of a mixed hydro-thermal power s ystem consisting of a reservoir, and several run-of-the-river hydroele ctric and thermal power plants. The objective of the optimization mode l is to maximize annual firm energy generation while treating the outp uts of the run-of-the-river and thermal power plants as parameters. Si mulation of the combined system is based on a standard operating rule, imposing an additional constraint of target demand derived from the d ynamic programming model. Stochastic behavior of the system is conside red implicitly by introducing synthetic flows. Comparison of combined and separate operations of the reservoir with the run-of-the-river and thermal power plants shows that combined operation is advantageous. F or the investigated system in Nepal, combined operation improves the o utput by 26%. The target demand of 1,226.7 GWh is satisfied with a mea n overall reliability of 98.8%, a dry season reliability of 97.2%, max imum deficit of 5.6%, and average maximum number of consecutive failur e months of 4.2.