中文摘要：

提出了基于动态直流泄能电阻的模块化多电平柔性输电直流方案，以提高基于感应双馈电机风电场的低电压穿越能力。基于矢量控制及无源电压跟随控制分别设计了系统侧、风场侧柔性直流换流器在风电场稳态运行时的控制策略。当交流系统故障导致电压跌落时，详细分析了动态直流泄能电阻的工作原理、动作判据及导通持续时间，以实现风电场低电压穿越；同时研究了其与系统侧模块化多电平换流器在故障清除后电压恢复期的协调控制，以快速恢复风电场有功输出能力。仿真结果表明：当交流系统故障时，含动态直流泄能电阻的柔性直流输电系统能够维持直流电压且不改变风电场输出电压电流；当故障清除后，风电场输出功率恢复速率远大于电力系统行业标准相关技术指标。

英文摘要：

A modular multilevel voltage sourced converter-based HVDC （MMC-HVDC） power transmission scheme based on dynamic chopper controlled breaking resistor （DCCBR） is proposed to improve the low-voltage ride through （LVRT） capability of wind farm composed of doubly fed induction generators （DFIG）. Based on vector control and network voltage tracing control the control strategies for grid side modular multilevel converter （GSMMC） and wind farm side modular multilevel converter （WFMMC） under steady state operation of wind farm are designed respectively. Under voltage sag caused by fault in AC power grid, the working principle, operating criterion and turn-on duration time of DCCBR are analyzed in depth to realize LVRT of wind farm;meanwhile, to recover the active power output capability of wind farm rapidly the coordinated control for DCCBR and GSMMC during the voltage recovery after clearing of the fault is researched. Simulation results show that during the fault in AC power grid the flexible HVDC transmission system containing DCCBR can maintain the DC voltage of HVDC system while the voltage and current output by wind farm are not changed; after the clearing of the fault, the recovery velocity of wind farm power output is much faster than relevant technical index specified in domestic power industry standards.