ACS

Economic Dispatch

Design Features

The PRISM Economic Dispatch Calculation (EDC) subsystem is a program that dispatches the available generation of an electric power system (one control area) to supply a given load in the most economic manner in real–time operation.

The following characteristics apply to EDC:

  • Consideration of incremental transmission losses is considered indirectly by imposing penalty factors on the dispatchable units
  • Calculation of optimal economic megawatt base points and economic participation factors for all the generating units under economic dispatch in the system
  • Calculation of optimal economic megawatt base points for all dispatcher selected generating units
  • Real–time and study mode operation

 

The dispatch is based on the principle of operating all dispatchable generating units at the same incremental cost of generation. Incremental transmission losses are considered indirectly by imposing penalty factors on the dispatchable units.  Penalty factors are defined as manual points in the real–time data base and initialized with unity value, which can be updated manually or by other programs in real–time operation to represent the effects of incremental transmission losses.

 

The EDC program calculates the optimal economic megawatt base points and economic participation factors for all the generating units under economic dispatch in the system. The resulting dispatch is a system–wide optimum on the basis of individual generating units.

 

The EDC program also calculates the optimal economic megawatt base points for all dispatcher selected generating units in a study mode. The resulting dispatch provides recommendations to the dispatcher of the optimal megawatt levels of base points for all the selected units in AGC mode (1,2,3,4,5).

 

EDC is a slave program of Automatic Genration Control.  It can only be scheduled by AGC or an operator only in real–time operation.  In normal operation, AGC schedules EDC once every two minutes.  It may be scheduled more frequently when a unit changes its AGC control mode or when the Base Load Deviation (BLD) exceeds a pre–specified threshold.