Analysis of Modular Multilevel Matrix Converter Considering Coupling of Electrical Variables Under Grid-side Asymmetric Faults

The flexible low-frequency AC transmission system (LFAC) is a novel transmission scheme oriented to the efficient consumption of new energy resources. However, the safety operation of LFAC will be threatened under grid-side asymmetric faults. This paper focuses on the analysis of internal dynamic coupling characteristics among electrical variables in M3C under grid-side asymmetric faults with the integration of closed-loop analysis method and the 2-D phasor method. This method can effectively realize the modeling of each electrical variables under asymmetric faults, clearly describe the internal coupling modes, and further reveals the coupling mechanism of internal and external characteristics in M3C. Firstly, the cyclic coupling relationship of electrical variables in M3C based on closed-loop analysis method is introduced; Then, the generation mechanism and coupling characteristics of secondary ripple voltage components and triple harmonic current components is further analyzed. Finally, the correctness of analysis method is verified by Matlab/simulink.