Frequency domain methods for stability assessment of grid-connected converters - An overview

Power electronic converters are today an essential part of the electrical power systems, employed to improve the system performance and enhance its stability. At the same time, the introduction of power converters might negatively affect the overall dynamic behaviour of the power system. System stability can be investigated from different perspectives, e.g. time-domain observation, eigenvalue analysis, or frequency-domain analysis. The aim of this paper is to provide an in-depth overview on two of the most popular frequency-domain methods for stability assessment of systems comprising grid-connected converters: the passivity approach and the net-damping criterion. The importance of proper system modelling is highlighted while advantages and pitfalls of the two methods are investigated. The considered frequency-domain methods are applied to a two-terminal high voltage direct current (HVDC) system, to investigate its stability both from the ac and dc side.