本项目瞄准舰船中压直流电力推进等场合对于高压大容量高可靠性的变频调速装置的重大需求，针对模块化多电平变换器MMC在交流传动领域应用的关键问题展开深入研究，探索并研究基于MMC的变频调速装置全频率范围内的安全裕度与输出转矩提升方法以及子模块故障情况下的多级容错运行方法等关键科学问题。研究MMC变频调速装置运行在高速区的桥臂电压、电流应力以及损耗等多个目标综合优化控制策略和低速区的电容电压波动抑制策略，进而提出全频率范围内的综合优化控制策略，提高变流器的安全裕度和最大输出转矩能力；进一步分析不同故障深度的桥臂环流与电容电压波动特性，提出一种多级故障容错运行方法，最大程度地实现MMC变频调速装置的不停机可靠运行。最终目标是提升MMC变频调速装置的安全运行裕度和韧性，突破并掌握MMC变频调速系统安全、可靠、优化运行的关键核心技术。

In order to satisfy the important requirements of ship electrical propulsion with medium voltage DC integrated power system for the high-voltage high-power high-reliable frequency inverters, this proposal is focused on the key technology of modular multilevel converters (MMC) applied in electric drive applications, including the enhancement of safety margin and output torque during the whole frequency range and fault tolerance operations of sub-modules multiple level faults. Study the multi-objective optimization strategy of MMC on high speed range and capacitor voltage fluctuation suppression method on low speed range. Then propose an integrated optimization strategy to enhance the safety operation margin and output torque ability. Further study the characteristics of bridge circulating currents and capacitor voltage ripples on different fault situations and propose a multiple level fault tolerance operation method to ensure MMC continuous reliable operating. The ultimate goal is to enhance the safety operation margin and flexibility of MMC, break through the core technology of safe, reliable and optimal operation of modular multilevel converters.