As an efficient solution for medium to long-distance offshore wind power integration and large-scale onshore renewable energy base aggregation

flexible low-frequency transmission systems (FLFTS) demonstrate significant advantages in enhancing transmission capacity and reducing power losses. However

influenced by the fault ride-through control strategy of modular multilevel matrix converters (M3C)

phase-to-phase short-circuit faults in power-frequency lines pose substantial risks of protection failure (failure to operate/maloperation) for phase-comparison distance protection. This paper reveals the influence mechanism of M3C control strategies on the performance of distance protection. Building upon this analysis

a coordinated fault ride-through control strategy for M3C based on reactive current optimization injection is proposed. The strategy comprehensively considers multiple critical factors including protection performance enhancement

converter overcurrent limitations

and submodule capacitor overvoltage constraints

thereby formulating a complete control framework incorporating reclosing control and fault recovery mechanisms. The simulation results demonstrate that the proposed reactive current injection coordination strategy can significantly enhance the performance of distance protection

ensuring reliable operation within the protection zone and secure non-operation outside the zone

without adversely affecting system/converter overvoltage or overcurrent.