Probabilistic Operation of Electric Power Systems Considering Environmental Constraint (Part 8)* -A Consideratioin for Thermal Unit Security-

An optimum operation scheduling method is reported regarding a fault of the thermal units as probabilistic. 0ptimum operation is considered as which the reliability limit and the NO_x emission constraint can be economically satisfied. The reliability limit is satisfied by increasing kinds of the power supply states. The power supply is considered as possible only when every line’s capacity is satisfied. A strict method and an approximate method are introduced to estimate the change of thermal output power after a unit fault. The strict method is a simple application of the economic load dispatch. The approximate method is an economical dispatch of the output power of a faulty unit using the demand supply balance. From model system simulations where the number of thermal units is 5, the estimating speed of the approximate method is shown to be 15 times faster than the strict one. Estimating error of the approximate results is also shown to be small. Line capacity is satisfied by modifying the economical power flow. The changed value of the thermal output power is estimated to satisfy the line capacity by using an exceeding flow value from the capacity. Many simulated results are shown applying the proposed method to a model system. It is concretely shown that the proposed method can estimate the optimum operation to satisfy the various reliability limits and the various emission constraints