Extensive Unit Commitment Function including Fuel Allocation and Security Area Constraints

Abstract

This paper describes the new enhancements and their respective solution approaches for the existing Florida Power & Light's Unit Commitment program in service in its System Control Center in Miami, Florida since 1979. The main part of the enhancements covers two areas, gas allocation and security area constraints for which solution approaches are described in the paper. In addition to that, other problem areas like unit power sales agreements, Florida Energy Broker System, combined cycle units, sliding pressure operation and gas turbine banks are functionally defined in the paper. The gas allocation problem is solved by using a two-step approach. In the first step the daily gas schedule is broken down into hourly schedules. In the second step units are committed by a dynamic programmming approach taking into account the amounts of gas made available for each particular hour. The gas will be allocated to the units while recognizing gas constraints in the combination processor and in the economic dispatch calculations. In addition, security limits on tie-line flows between three FPL areas and several external companies have to be satisfied. In both steps security area constraints are taken into account by using a DC power flow model of the system. By doing this, gas allocation and security area constraints will determine which units should be on-line and what the loading of the units should be.