Coordinated fault ride-through strategy for parallel multi-terminal UHV flexible DC grids

To address faults in flexible DC grids with photovoltaics (PV) and hydropower turbines, this paper proposes a coordinated fault ride-through strategy. PV-side converter stations adopt a negative voltage blocking-power isolation strategy to attenuate fault current and dissipate excess power via negative voltage modulation. Hydropower turbine-side converter stations use active current-limiting coordinated control, setting a voltage lower limit to block reverse current and maintain rated current transmission. Receiving-end converter stations with fixed DC voltage adopt zero-current control for rapid fault isolation and sub-module overvoltage protection. Fixed-power converter stations use a phased coordinated control, balancing fault control and receiving-end power supply with active current limiting. Verified via a four-terminal grid model in PSCAD, the strategy effectively controls fault current, shortens fault clearing time, and maintains voltage stability and power transmission.