Performance evaluation of voltage stability index to assess steady state voltage collapse

The paper presents performance analysis of a comprehensive index to foresee voltage collapse at the weak load buses in the power system. A different approach for the assessment of voltage stability margins based on the P-Q-V curve technique and Thevenin´s equivalent is proposed. A P-Q-V curve shows the periphery of the maximum real/reactive power and the minimum voltage magnitude in a three-dimensional diagram. Voltage stability region is the set of all feasible point below this curve. Thus the area of this region is an indicator of closeness to the voltage stability limit. As the index provides quantitative measurement in terms of the real and reactive power margins of a specified bus, it is more significant to identify weak nodes. Results on IEEE-14 bus system and IEEE-30 bus system are presented to illustrate the nature of the index AVSR and its effectiveness to predict voltage collapse.