Power network partitioning and its applications to security control

It is well known to power system engineers that most disturbances affect only a small portion of a large power network, leaving the operating state of the rest of the system almost unchanged. The computational speed of many power system application programs is proportional to the dimension of the system. Thus, the use of smaller sub-networks of a large power system is likely to improve the computational efficiency of these application programs.;Due to the electrical proximity of the busses of the same cluster, steady-state power system studies can be performed, semi-independently, within each sub-network of the system. Unused portions of the large system are represented by their external equivalents. For many application programs, however, the applied sub-networks can only be determined on-line. Consequently, off-line external equivalent methods cannot be employed. This thesis also describes an on-line external equivalent technique. Each unused sub-network is reduced to one equivalent voltage controlled bus. The computation of the complex voltages and net power injections at the equivalenced busses are based on the REI external equivalent method. Fictitious branches connecting the equivalenced busses to the retained sub-networks are determined on-line without the use of Gaussian elimination.;The applications of the network partitioning and on-line external equivalent techniques have been tested on a steady-state security control program because fast solutions are required to avoid damages to the power equipments and service interruption. A sensitivity-based technique to perform the steady-state corrective control has been developed. It brings the system from an emergency state of operations, at which electrical circuits are overloaded and/or nodal voltage magnitudes are violated, to a normal state. Real and reactive power generator outputs, generator voltage outputs, switchable shunt devices, tap position of voltage transformers and switchable transmission elements are the possible control variables.;The corrective control strategy is applied to three different power systems: the IEEE 24-bus reliability test system, the IEEE 118-bus test system and the Mexican interconnected 256-bus system. Several emergency situations have been simulated in these three systems. Corrective strategies obtained for the partitioned and equivalenced systems are compared with those found using the unreduced systems regarding accuracy of the solution and computational speed.;This thesis describes a power network partitioning technique that clusters the system's busses according to their electrical interdependence. The method is based on the concept of electrical distances among nodes. The clusters of busses define sub-networks of the larger system such that the electrical distances among busses of the same cluster are short, and electrically distant busses are assigned to different sub-networks.