Independent Channel Design Approach for Stability Analysis of Grid-Connected Converters,

Artikel i vetenskaplig tidskrift, 2020

The independent channel design approach proposes that the stability of a multiple-input multiple output system can be studied through the analysis of single-input single-output (SISO) systems. In the case of the grid-connected converters (GCCs) studied in this paper, two SISO systems are defined as positive and negative sequence channels, PSC and NSC, respectively. Further simplifications for the SISO systems are proposed so that the simplified PSC and NSC are decoupled. The advantage of studying decoupled SISO systems is that the identified instabilities can be given a physical interpretation. For example, it is found that instabilities related to ac-grid resonances are due to the fact that the GCC acts as a negative conductance in the PSC. Instability is less likely to occur in the NSC since resonances take place at a higher resonance frequency where the GCC acts as a positive conductance. It is also argued that the proposed simplification is able to reproduce fairly close instabilities related to ac-grid resonances, while for instabilities of other nature, complete expressions need to be used.