Modeling Techniques and Stability Analysis Tools for Grid-Connected Converters

Large-scale integration of renewable generation interfaced to the network through power electronic converters has led to drastic changes in power system dynamics. In islanded microgrids or weak grids, different control concepts for the synchronization of converters have been proposed to provide virtual inertia and improve their resilience against transient events, ensuring safe operation without heavy redundant design. The complexity of these power-related control algorithms and their interaction with the inner control loops causes problems in frequency components above the range of traditional studies which calls on modeling techniques with a wider bandwidth. This work aims to provide an outline of modeling methods for grid-connected converter dynamics from subsynchronous to switching sideband frequency range and relevant analyzing tools. The major contributions of this work are: 1. Theoretical foundations and the derivation processes are discussed for each of the modeling methods within the time domain, frequency domain and harmonic domain. 2. Similarities and differences between these methods are highlighted and recommendations are given regarding different grid situations. 3. A case study with an active front end converter is shown and the analysis results are validated by simulation and Hardware-in-the-Loop (HiL) test, illustrating the effectiveness of these methods.