To address the high cost of fault isolation in multi-terminal direct current (MTDC) systems integrating offshore wind power via diode rectifier units (DRUs)

a fault handling scheme based on a receiving-end diode-type modular multilevel converter (DMMC) is proposed. First

for bipolar short-circuit faults in DC submarine cables

the passive blocking of the receiving-end diodes and the coordinated isolation mechanism at the offshore end are clarified; for monopole-to-ground faults

the adaptive fault ride-through mechanism in a pseudo-bipolar configuration is analyzed. Then

the coupling process between diode natural turn-off and transient traveling waves in submarine cables is investigated. An equivalent short-circuit discharge circuit model is established

and an analytical expression for the maximum reverse overvoltage across the diode is derived based on the quarter-wavelength resonator theory. Finally

a ±500 kV/6 GW four-terminal DC collection electromagnetic transient model is built in PSCAD/EMTDC to validate the proposed scheme. The results show that

under a bipolar short-circuit fault

the series-connected diodes can achieve rapid current zero-crossing and passive blocking within 50 μs

while the DC bus voltage remains above 0.9 pu during the fault transient. Under a monopole-to-ground fault

uninterrupted system ride-through can be realized.