Static Voltage Security Assessment Of Power Systems

Traditionally, we use two kinds of security analysis to ensure the security of power system. One is static security assessment (SSA), the other is dynamic security assessment (DSA), and voltage security assessment (VSA) was included in SSA and DSA. Because several accidents of voltage collapse took place from the 1980's, voltage security has become more concerned. So VSA was independent from the two assessments gradually. There are several aspects of VSA; this paper proposes the determination of voltage security criteria and the method of interface margin of voltage security analysis.The traditional criteria of voltage security relied on ensuring that pre-contingency and post-contingency voltage level is acceptable for the system states. Power systems may keep the safety voltage level even near its limit, but that is very danger since maybe it is near the voltage collapse point. From this paper, we can conclude that power system should have enough voltage security margins whether in pre-contingency or post-contingency state.To maintain security of power system, loads of several transmission lines between different regions are constrained by the thermal limit, voltage limit, and stability limit. This paper increases active power flow of key transmission line by shifting generation from the study region to others, and this paper traces interface Flow-voltage curve by apply a continuation power flow method. From the Flow-voltage curve, interface flow margin can be obtained, which is useful to determine secure flow limit of specified interface.