一种新型MMC并联双端口子模块及其三阶段故障电流阻断机理

为使模块化多电平换流器(modular multilevel converter,?MMC)具备直流故障自清除能力和电容电压均衡能力，提出了一种新型并联双端口子模块：钳位双全桥子模块(clamp double full bridge submodule,?CD-FBSM)。该子模块器件成本和运行损耗较低，正常工作时相邻子模块之间具有多种协同运行模式，通过特有的并联模式可提高电容电压均衡度。故障闭锁时，模块内部电容并联、模块之间电容串联且反向接入电路，能够可靠阻断故障电流并均衡电容电压，有利于系统快速重启。此外，提出了三阶段故障电流阻断机理分析方法，对CD-FBSM的故障电流阻断过程进行了研究。通过Matlab/Simulink的仿真结果表明，所提子模块电容电压均衡度较高，可快速阻断故障电流，且故障电流阻断过程与理论分析一致。

Static information, K-neighbor, and self-attention aggregated scheme: a transient stability prediction model with enhanced interpretability

To equip a modular multilevel converter (MMC) with DC fault self-clearing and capacitor voltage balancing capability, a novel parallel dual-port submodule named clamp double full bridge submodule (CD-FBSM) is proposed. Both device cost and operating loss of CD-FBSM are low, and during a normal working state, there are multiple coordinated operation modes between adjacent submodules, and the balance degree of the capacitor voltage can be enhanced by the unique parallel mode. When CD-FBSMs are blocked because of a fault, capacitors inside submodules are parallel while capacitors between submodules are serial, and all capacitors are reversely connected into a circuit. The fault current can be reliably blocked and the voltage of capacitors is balanced. This is conducive to a quick system restart. In addition, a three-stage analyzing method for the fault current blocking mechanism is proposed, and the fault current blocking procedure of CD-FBSM is researched. Simulation results based on Matlab/Simulink show that the proposed submodule has high balance degree of capacitor voltage, and the fault current can be quickly blocked while the blocking procedure is consistent with the theoretical analysis. This work is supported by the National Natural Science Foundation of China (No. 52077079).