Large-signal stability analysis for offshore wind power fractional frequency transmission system with modular multilevel matrix converter

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Aiming to achieve zero carbon emission, the rapid development of offshore wind power transmission system faces stability challenge. The fractional frequency transmission system (FFTS) with modular multilevel matrix converter (M3C) holds considerable promise among the solutions for large-scale and long-distance offshore wind power transmission. Currently, numerous demonstration projects involving FFTS are being conducted worldwide, necessitating urgent attention to system stability analysis for practical engineering applications. Notably, conventional approaches focusing on small-signal stability are inadequate when confronted with large-signal disturbances. In this study, the Takagi–Sugeno fuzzy model of FFTS is proposed considering the complex control strategy of M3C and the system strong nonlinearity. Subsequently, the Lyapunov function and the large-signal stability domain of attraction (LS-DOA) are constructed expeditiously based on the proposed fuzzy model. When analyzing the system larger-signal stability, the novel stability strength and optimal optimization factor are further introduced to develop a quantitative and efficient methodology for parameter optimization guidance compared with the conventional method. Thus, the FFTS different-frequency interaction features are elucidated from normal and different characteristics parameters mathematically and comprehensively. The effectiveness of proposed methods is verified by the simulation-based study.