Evaluation of PV and QV based Voltage Stability Analyses in Converter Dominated Power Systems

Abstract

PV and QV analyses have been widely used in industry. It has already been proven that these steady state methods can be used to assess power system's load ability from voltage stability perspective and that their use in terms of accuracy is justified when compared to time domain simulations. However, this prior validation was carried out for conventional synchronous generator dominated power systems. With increasing levels of power electronics interfaced generation (PEIG) being integrated in power systems, the accuracy of the PV and QV methods for these 'green' power systems can be challenged. This paper investigates to what extend the use of these methods is justified when the power system faces a displacement of conventional generation with PEIG. To this end, assessments with the IEEE 9 bus system and full converter wind turbine generators have been performed in this study. It is shown that, when compared to time domain simulations, the traditional PV and QV analyses do not always accurately predict the saddlenode bifurcation point. Steady state PV analyses show inaccuracies between 1.8% and 16.8% (when compared to time domain simulations) in identification of the instability point. The mismatch between steady state and time domain QV analyses is between 6.1% and 22.9%. Based on the achieved results, QV analysis is shown to be typically less accurate than PV analysis for PEIG rich systems.

Comprehensive Review of Short-Term Voltage Stability Evaluation Methods in Modern Power Systems

“…Sources of reactive power used in regulating the voltage are not as centralized as before, limiting the practical feasibility of Q-margin monitoring. A related issue has been addressed in [28], where it was shown that related PV and QV curves, widely used in industry for maximum loadability and voltage stability, are becoming increasingly inaccurate in modern power systems.…”

Análisis de Estabilidad de Voltaje en un Sistema de Subtransmisión, Mediante Curvas QV – PV y Análisis Modal

“…Con las 10 cargas anteriormente nombradas se obtienen las curvas pv por medio del software DigSilent. Cada barra tiene diferentes tipos de cargas, por lo que sus ángulos, voltajes y potencia va a variar, se obtuvo una curva por cada barra para analizar e identificar el punto de colapso en el bus más crítico del sistema de estudio [25].…”

QV Analysis for the Identification of Vulnerable Zones to Voltage Collapse: A Study Case

“…It is a fast method compared to dynamic studies, and unlike PV curves, it has fewer problems when it comes to convergence [11]. Also, it is a widely used tool: Recent studies have reported using simulation software such as PSSE [12], DigSilent [13], PowerWorld [14], NEPLAN [15], Matlab [16], and Python [17] to develop QV curves in real and test circuits. The analysis of these curves, and if possible, complemented with other voltage stability criteria such as modal or sensitivity analysis, helps to study the reactive power margins, determine the most suitable areas to install reactive compensation, and make planning decisions in the long and medium term.…”