Network equivalent-based VQ Curve method and its application in a novel real-time voltage stability assessment methodology.

• Network Equivalent-based VQ Curve is used in real-time voltage stability assessment. • Voltage stability margin is derived from PV to VQ curves through network equivalent. • Network equivalent and power flow methods used to identify voltage stability limit. • Operation tasks encourage to explore the complementarity between PV and VQ curves. • Voltage and reactive power margins improve real-time voltage stability assessment. The PV and VQ curves have been widely accepted tools for monitoring voltage stability. Although these curves have been used in offline studies, their online applications are not trivial, involving specific issues and complexities concerning real-time environment. The literature presents some approaches to determine quantities related to voltage stability limit in real-time analysis of the PV curve. However, it does not occur with the corresponding quantities for the VQ curve, making it difficult to analyze these curves jointly. This work presents two significant innovative contributions, based on the use of real-time network equivalents estimated through measurement data. The first is a technique suitable for real-time applications to calculate the complete VQ curve, called Network Equivalent-based VQ Curve. The second is a methodology for determining voltage stability margins using information from both PV and VQ curves. Simulations were carried out in RVS Test System, and 9, 14, 30 and 118 Bus Test Cases available in MATPOWER. The results of Network Equivalent-based VQ Curve application were validated by power flow solution. The voltage stability assessment methodology proposed in this paper represents a significant advance, going beyond the traditional approaches. [ABSTRACT FROM AUTHOR]