Corrective Control Computations for Large Power Systems

This paper presents a novel methodology for optimal corrective and/or emergency controls computations. It is based on a model reduction procedure, and linearization leading to a linear program which is solved via a dual simplex algorithm with upper bounds developed specifically for this problem. The methodology computes optimal adjustments of generation schedules, VAR source allocations, transformer tap settings and if necessary load shedding. In case of problem infeasibility, it computes the best possible adjustments which will move the operating state of the system closer to a secure state. In addition an analysis of the impact of each individual control action on the emergency conditions of the system is generated. Capacitors and reactors are switched in/out in discrete steps. Such discrete controls are handled with an efficient suboptimal procedure based on a partial enumeration of linear programming relaxations. A computer program has been developed. The software are sparsity coded. Efficiency evaluation of the various components of the program is given. The methodology is illustrated with sample results from two test systems: (a) the IEEE 30 bus system, and (b) the Georgia Power Company´s 500 kV/230 kV/115 kV system, which is a 981 bus system. The second test system demonstrates the applicability of the method to practical large scale systems.