不对称电压暂降下最大功率输出的MMC协调控制策略

针对柔性直流输电系统交流侧不对称电压暂降下，模块化多电平换流器（modular multilevel converter，MMC）运行时出现的功率波动、三相电流不平衡等问题，提出了不对称电压暂降下最大功率输出的MMC协调控制策略。该策略根据不对称电压暂降下MMC系统运行特性随调节参数的变化规律，以抑制有功功率波动与输出三相平衡电流的协调控制为目标，构建了线性加权解析式确定调节参数，在保证MMC输出电流峰值在最大限制范围内时，输出最大有功功率。该策略既拓展了有功功率输出能力，又提升了系统的整体控制保护性能。仿真和实验结果验证了所提方法的有效性。

MMC Coordinated Control Strategy for Maximum Power Output Under Asymmetric Voltage Sag

Aiming at the problems of asymmetric voltage sag on the AC side of flexible DC transmission system, such as the power fluctuation and three-phase current imbalance during the operation of modular multilevel converter (MMC), a MMC coordinated control strategy for maximum power output under asymmetric voltage sag is proposed in this paper. Taking the coordinated control of suppressing the fluctuation of active power and outputting the three-phase balance current as objective, a linear weighted analytical formula is constructed to determine the regulation parameters according to the variation law of the operation characteristics of MMC system with the regulation parameters under asymmetric voltage sag, and then the maximum active power is outputted while ensuring that the outputted peak current of MMC system is within the maximum allowable working range; The proposed strategy not only expands the active power output capacity, but also improves the overall control and protection performance of the system. Finally, the effectiveness of the proposed method is verified through simulation and experiment.