Power Electronic Converters

16Impedance-Based Stability Assessment

16.1 Introduction

Grid-connected three-phase power electronic converters have been reported to suffer from power quality problems since the introduction of mercury-arc thyristor-based converters. In the work carried out by Ainsworth in 1967, abnormal harmonics were reported in a HVDC system that did not correspond to normal odd harmonics caused by normal operation of such converter [1]. The problems were reported to be most severe in a weak AC system. Moreover, the used control scheme had a significant impact on converter stability. Similar “harmonic instability” has been reported later, for example, in Ref. [2] related to a traction power system. The term “harmonic instability” or “harmonic resonance” ...