The flexible low-frequency transmission technology based on modular multilevel matrix converter (M3C) has technical and economic advantages in intermediate-distance offshore wind power transmission scenarios. However

the negative sequence component under asymmetric faults can lead to voltage imbalance in the M3C bridge arm capacitor and affects the safe operation of low-frequency transmission systems. In light of this issue

asymmetric fault control strategy of M3C based on linear active disturbance rejection control (L-ADRC) is proposed. Firstly

the third-order extended state observer model of M3C is derived

and the L-ADRC is used for inner loop current tracking. The mutual coupling between dq axes is treated as internal disturbance

thus achieving complete decoupling control and improving system robustness. Secondly

by adjusting the low-frequency and power-frequency circulating current components between the bridge arms with L-ADRC

the capacitor voltage balance control between the sub-converters and between the bridge arms is achieved. Finally

the theoretical analysis is verified with simulations. The results show that the improved inner loop current controller based on L-ADRC has a faster dynamic response speed

and the fluctuation of active and reactive power is smaller under the negative sequence current suppression target. At the same time

the proposed energy balance strategy can be adopted to ensure the balance of capacitor voltage at all levels

and to greatly improve the asymmetric fault ride-through ability of M3C.