Modular multilevel converter based high voltage direct current (MMC-HVDC) transmission is the prospective technology for large-scale wind farms integration. In this paper, a comprehensive coordinated control strategy for DC fault ride-through (FRT) of wind farms connected to the grid through bipolar MMC-HVDC transmission is proposed. To reduce the requirement of breaking speed and capacity of DC breakers, an active current-limiting control method is proposed to limit the rise rate of DC fault current, and the principle of parameter selection is designed. After DC breakers isolate fault, the control mode switching methods of bipolar MMC are designed to make the fault pole MMC operate as a STATCOM to support the AC grid and improve the active power transmission capability of the healthy pole MMC, which can reduce the impact range of unbalanced power between wind farms and converter station. In addition, a coordinated control strategy for wind farms load-shedding considering speed constraints is designed to realize the optimal distribution of load-shedding power among wind turbines, which can regulate unbalanced power together with the healthy pole MMC to realize DC FRT. Finally, the effectiveness and feasibility of the proposed control methods are verified by simulation results.

中文翻译：

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通过双极 MMC-HVDC 传输连接到电网的风电场的一种新型直流故障穿越方法

基于模块化多电平转换器的高压直流（MMC-HVDC）传输是大规模风电场集成的前瞻性技术。在本文中，提出了一种通过双极 MMC-HVDC 传输连接到电网的风电场直流故障穿越 (FRT) 的综合协调控制策略。为降低对直流断路器分断速度和容量的要求，提出了一种有源限流控制方法来限制直流故障电流的上升速度，并设计了参数选择原则。直流断路器隔离故障后，设计了双极MMC的控制模式切换方法，使故障极MMC作为STATCOM运行，支持交流电网，提高健康极MMC的有功传输能力，可减小风电场与换流站之间不平衡功率的影响范围。此外，设计了一种考虑速度约束的风电场切负荷协调控制策略，实现风力机间切负荷功率的优化分配，与健康极MMC一起调节不平衡功率，实现直流FRT。最后，通过仿真结果验证了所提出的控制方法的有效性和可行性。