Adequacy Analysis of Overhead Line Model for Harmonic Stability Analysis of Grid-Connected Voltage-Source Converters

This paper investigates the harmonic stability of a STATCOM connected to the power grid over a 400 km double circuit overhead line. The impedance-based modelling approach is used for the harmonic stability analysis comparing the results from the frequency dependent (FD)-model and the π-model of the 400 km overhead line. It demonstrates that the the π-model approach produces pessimistic phase margin predictions leading to a conservative harmonic stability evaluation. The impedance model of the STATCOM is built in the αβ-frame, where the impacts of the inductive and capacitive operation modes are analysed. It reveals that the STATCOM introduces a negative resistance in the inductive operation mode, which may negatively interacts with the resonance frequencies of the grid. Time domain simulations using EMTDC™/PSCAD™ validate the critical stability point found by the impedance-based stability analysis.