engleski

Implementation of the Benders Decomposition in Hydro Generating Units Maintenance Scheduling

Before the liberalization of the power sector, the generating units maintenance had one single constraint – the maintenance of associated transmission lines. Since the transmission lines and generating utility were both controlled by national electric utility, there were no confronted entities with different goals. The great advantage of centrally planned scheduling for each electric facility was optimizing the system reliability and reducing the maintenance cost of the entire system. After restructuring of electric utilities, the maintenance of generating utility can not be planned nor done independently. Owners of generating facilities will want to deliver electricity when its price is high, and will want to perform maintenance when the price is low. Maximization of the profit is the prime goal of all generating companies in restructured power systems. If excluded that shareholders and economists will want to keep running their generators only with inevitable maintenance in order to maximize profit, each generating company will want to perform maintenance when the market clearing price is low or when it is unable to deliver electricity. But regularly this will not be approved by the ISO, the entity which ensures the instantaneous balance of the power system. If ISO would approve all desired maintenance schedules of all generating companies, the power grid reliability standards could not be met. Another object ISO has to meet is to keep the transmission lines under the congestion level. All this can be introduced as the constraint to the objective, i.e. maximizing the profit by performing the maintenance according to desired schedule. The system reliability requirement from the ISO is not the only constraint the generating companies have to obey. There is also a problem with the number of specialized maintenance crews. These crews can not perform the specific maintenance in more generating companies simultaneously, so the availability of maintenance crew is also a constraint to generating companies. The availability of spare parts also has to be taken into account when deciding to undertake a maintenance procedure. Another common constraint is the sequence of maintaining of the parts of generating facility, i.e. a specific part of the facility can be maintained only after the maintenance of another part is over. In addition, all signed treaties for delivering electricity must be taken into account or rigorous penalties will have to be paid.

Benders Decomposition; Maintenance Scheduling; Generating Units

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