Optimal allocation of generation margin to cope with the expected line overloads

Allocation of sufficient regulating margin on each generator just before transmission line overloads enables the power system to obey quickly the security corrective actions. The rate at which the line flows can be reduced depends upon the generator operating point and its ramp limits. The time allowed to remove an overload depends upon the line rating and the magnitude of such an overload. If an overload is predicted by an emergency mode detector, the time required to alleviate this overload consists of two components: the time required to decide the suitable security corrective actions and the time required to perform these actions.In recent work by Farghal and others, a fast technique has been developed to alleviate the line overloads using sensitivity parameters evaluated from the base case before overloads, and so the few seconds needed for recalculation are saved. However, the second component of time with an order of a few minutes has still not been considered. In this paper, an attempt is made to minimize this time by proper allocation of system regulating margin just before an emergency.This paper proposes a method for the optimal allocation of system regulating margin employing Bender's decomposition principle coupled with a successive linearization technique. This method utilizes the existing package for economic dispatch as a master program and modifies the operating point of each generator output to allocate the suitable regulating margin according to the expected emergency in another subprogram with minimum cost increase. Thus, the method acts as a partial alternative to the expensive emergency start-up procedures.