【目的】海上风电送出系统受端电网短路故障下构网型模块化多电平换流器（modular multilevel converter， MMC）运行特征不明，故障穿越与构网型主动支撑暂态交互机理不清，给海上风电柔性直流系统的可靠运行带来巨大威胁。并且传统故障穿越策略在和构网控制结合过程中存在故障前后策略切换下暂态冲击电流较大与无功支撑响应较慢的问题。【方法】文章基于此提出一种构网型MMC低电压故障内电势重构穿越控制策略，首先分析电网电压跌落时构网型模块化多电平换流器的短路电流特性，构造基于构网型模块化多电平换流器电压方程空间矢量下的故障穿越电流限幅边界，然后通过电流优化指令重构内电势，旨在挖掘不同电网电压跌落下构网控制主动型电压支撑能力。【结果】通过半实物实验平台对所提故障穿越策略进行验证，研究结果表明，该策略在不同程度故障下均可实现低电压穿越，随着电网电压跌落程度加深，所发无功随即增加，但并网电流会在较深的跌落程度下加以限制。与传统故障穿越策略相比，可以降低暂态冲击电流，同时能够快速提供无功支撑，改善并网点电压的恢复速率。【结论】分析揭示了构网型MMC主动电压支撑运行特性，并提供了基于矢量角度修正电流的思路。为深远海恶劣电压跌落工况模式下故障穿越技术的研究打下基础，促进大型海上风电基地安全可靠运行，有效推动能源产业革新。

[Objective] The operational characteristics of the grid-forming modular multilevel converter （MMC） in offshore wind power transmission systems under short-circuit faults in the receiving-end grid are unclear， and the interaction mechanism between fault ride-through and grid-forming active support is not well understood， which poses a significant threat to the reliable operation of offshore wind power flexible direct current systems. In addition， traditional fault ride-through strategies face the issues of large transient impact currents and slow reactive power support responses during the switching of strategies before and after faults， in conjunction with grid control. [Methods] This study proposes a low-voltage fault internal potential reconstruction ride-through control strategy for grid-forming MMCs. Specifically， it analyzes the short-circuit current characteristics of MMCs under grid voltage dips， constructs a fault ride-through current-limiting boundary based on the voltage equation space vector of the grid-forming MMC， and reconstructs the internal potential using current optimization commands. This study aimed to demonstrate the capability of active voltage support in grid control under different grid voltage dips. [Results] The proposed fault ride-through strategy was validated using a semi-physical experimental platform， and the results indicated that low-voltage ride-through could be achieved under varying degrees of faults. As the grid-voltage dip deepens， the reactive power generated increases accordingly； however， the grid-forming current is limited at deeper dip levels. Compared with traditional fault ride-through strategies， this approach can reduce transient impact currents while quickly providing reactive power support and improving the recovery rate of the grid connection point voltage. The analysis revealed the operational characteristics of active voltage support in a grid-forming MMC and provided insights based on the vector angle correction of currents. [Conclusions] This study lays the foundation for the study of fault ride-through technology under severe voltage drop conditions in deep-sea environments， promoting the safe and reliable operation of large offshore wind power bases and effectively advancing innovation in the energy industry.