Optimal Power Flow procedure for real-time security and economic re-dispatching in a market structure

This paper investigates the possibility of utilizing Optimal Active Power Flow (OAPF) and Optimal Reactive Power Flow (ORPF) algorithms for on-line safety and economic re-dispatching in an Ancillary Services Market (MSD) structure. It is described a procedure that the Italian Transmission System Operator (TERNA) has implemented recently for real-time operation. Starting from a real-time snapshot, the procedure ranks all the possible contingencies and re-dispatches the active (through OAPF) and reactive (through ORPF) power productions in order to prevent the effects of the most dangerous ones. The re-dispatching is achieved by minimizing the economic effort, according to the offer/bids on the MSD. The fulfilled constraints are: nodal balance, maximum flow limit for the transmission lines (under N and N-1 security conditions), nodal voltage limits, minimum and maximum power offered in the MSD, gradient limitations. Examples are provided about the application of the procedure to the Italian main transmission system (1700 buses).