Selection of UPFC suitable locations for system security improvement under normal and network contingencies
TENCON 2003. Conference on Convergent Technologies for Asia-Pacific Region
Electric power systems are exposed to various contingencies. Network contingencies often contribute to over-loading of network branches, unsatisfactory voltages and also leading to problems of stability/voltage collapse. To maintain security of the systems, it is desirable to estimate the effect of contingencies and plan suitable measures to improve system security/stability. This paper presents an approach for selection of UPFC suitable locations considering normal and network contingencies
... rk contingencies after evaluating the degree of severity of the contingencies. The ranking is evaluated using composite criteria based fuzzy logic for eliminating masking effect. The selection of UPFC suitable locations uses the criteria on the basis of improved system security/stability. The proposed approach for selection of UPFC suitable locations has been tested under simulated conditions on a few sample power systems and the results for a real life 36-node equivalent EHV power network are presented for illustration purposes. Contingency screening and ranking is one of the important components of on-line system security assessment. Most of the contingency ranking methods, generally, ranks the contingencies in an approximate order of severity with respect to a scalar performance index (PI), which quantifies the system stress -  . It has been pointed out that two separate ranking lists are required for real power flow problems and voltage profile problems, respectively, since the contingencies causing line overloads do not necessarily cause bus voltage violations and vice versa. Thus, two performance indices, which give measures for line overloads and for bus voltage violations respectively, are needed for real power and voltage contingency rankings  . The common disadvantage of several PI-based ranking methods is the masking phenomenon. With increased loading of existing power transmission systems, the problem of voltage stability and voltage collapse, has also become a major concern in power system planning and operation. It has been observed that voltage magnitudes do not give a good indicator of proximity to a voltage stability limit and voltage collapse [6, 7] . Therefore, in the network contingency ranking, it is necessary to consider voltage stability indices at all the load buses as the post-contingent quantities, in addition to real power loadings and bus voltage violations for estimating the actual system stress under a contingency. Then suitable measures/preventive control actions can be planned to improve system security/stability.