Self-Sustained Oscillation Analysis of Grid-Interfaced Converters by Frequency-Domain Method Considering Harmonic Balance Principle

This letter presents a frequency-domain framework for the synchronization stability research of grid-following (GFL) converters in the case of disturbances such as phase-jumps and voltage-sags. It is revealed that a closed orbit around the stable equilibrium point, namely limit cycle (LC), may be emerged due to the operating conditions of GFL converters, which determines the stable boundary. A practical guideline, which covers model construction and stability criterion formulation within the developed framework, is detailed. It can be utilized for identification of LC parameters and system stability margins. The theoretical findings are corroborated by numerical and experimental tests.