Abstract
This paper develops a small-signal impedance model of modular multilevel converters (MMCs) using harmonic state-space (HSS) method and studies the stability in a multiple converter scenario. In order to simplify analysis on the coupling characteristics between different frequencies in MMCs, the proposed model is developed in the positive-negative-zero (PN0) sequence-frame, where the zero-sequence current in three-phase three-wire system is directly set to zero without introducing complicated method. A simple 2 by 2 admittance matrix in PN0-frame is extracted from the MMC small-signal model for ease of system stability analysis. Using the developed impedance model, the multi-infeed interaction factor (MIIF) measure is adopted to analyze the most significant interactions for multi-infeed converter systems to be prioritized. Different outer-loop controllers are adopted and compared in the analysis to illustrate the effect of different control modes on converter impedance and system stability. Analytical studies and time-domain simulation results are provided to validate the proposed model and stability analysis.
| Original language | English |
|---|---|
| Number of pages | 12 |
| Journal | IEEE Journal of Emerging and Selected Topics in Power Electronics |
| Early online date | 16 Oct 2020 |
| DOIs | |
| Publication status | E-pub ahead of print - 16 Oct 2020 |
Keywords
- impedance
- stability analysis
- harmonic analysis
- modular multilevel converter