本课题针对MMC-STATCOM桥臂电容电压的均衡问题，构建一种新型拓扑，拟通过串入优化限流电感的双向二极管钳位电路，对桥臂电容电压的均衡问题开展研究；针对MMC-STATCOM的动态性能问题，拟通过离散化方法获取上桥臂电流的离散数学模型，结合重复-无差拍控制，对状态观测器、通讯延迟以及死区等环节进行研究；针对MMC-STATCOM子模块电容电压波动的抑制问题，拟通过建立上、下桥臂的功率模型，推导流经桥臂的功率中的直流波动，优化二倍频环流的幅度比、电网电压初相角和功率波动中不同阶数的功率振幅之和三个参数之间的关系，实现波动抑制；针对MMC-STATCOM子模块故障问题，拟通过零序电压注入方法修正调制重构中的参考电压，计算故障与非故障相调制信号的区间表达式，实现系统的故障容错控制。本项目的研究成果将有效的提高电网的安全性、可靠性和经济性，为实现节能环保提供技术支持。

In this proposal, focusing on the problem of arm capacitor voltage balance, a novel topology is proposed. With the embedded diode clamped circuits with current limiting inductors, the voltage balance problem for arm capacitor will be explored. Furthermore, focusing on the dynamic operation of MMC-STATCOM, the discrete model of arm-current is derived and the corresponding analysis of state estimators, communication delay and dead-band compensation are conducted, along with repetitive and deadbeat control. For the mitigation of voltage ripples in each submodule, the power models of upper and lower bridges are derived to identify the DC components in arm power oscillations, and optimize the relationship among the amplitude of second-order circulating current, initial voltage angle of grid voltage and sum of power oscillations with different orders. To mitigate the impacts of faults at each submodule, zero-sequence voltage injection is proposed to adjust the reference voltage in modulation reconstruction. Hence, the phase modulation signals can be derived in both fault and normal operation modes. The deliverables of this project can effectively ensure grid security, reliability and economic operation, and also provide technical support for energy saving and environmental protection.