Large-Signal Stability Analysis and Enhancement of Modular Multilevel Matrix Converter Under Power Fluctuation Based on T-S Fuzzy Model Theory
Ziyue Duan, Yongqing Meng, Yunkang Duan, Haitao Zhang, Xiuli Wang, Xifan Wang
Abstract
As one of the converter family based on modular multilevel converters technology, the modular multilevel matrix converter (M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C) is a promising grid-connected converter topology for large-scale renewable energy transmission in low-frequency ac/ac system and upgrading power transmission capacity of urban network. But the existing methods of small-signal stability of M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C are inapplicable for analysis under large-signal power fluctuation conditions. Consequently, this study comprehensively performs a large-signal stability analysis of M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C under power fluctuation, considering the sophisticated inner and outer loop decoupling control strategy, subconverter voltage balancing approach, and different-frequency interaction factor. Based on Takagi–Sugeno fuzzy model theory, the Lyapunov function is constructed and the corresponding large-signal stability domain of attraction (LS-DOA) is obtained efficiently. Furthermore, the stability strength by synthesizing the minimum energy boundaries and rotating angles of LS-DOA is proposed as a quantitative index to improve the traditional qualitative observation method. By taking into account the different-frequency interaction factor, it further proposes the enhancement methods for the large-signal stability from two aspects: topology structural parameters optimization and control strategy improvement. Ultimately, the effectiveness of the proposed method is verified through simulation and experimental results.