一种模块化多电平换流器电压均衡改进策略

模块化多电平换流器MMC(modular multilevel converter)是柔性直流输电系统的核心设备,其子模块的电容电压均衡问题直接影响系统的正常运行.针对此问题,首先介绍了一种现有的基于固定轮换的均压方法,指出其优缺点;再进一步提出一种改进的均压策略,能够在达到几乎相同的均压效果的基础上,减少模块的轮换;...

Improved Voltage Balancing Strategy for Modular Multilevel Converter

The modular multilevel converter(MMC) is the core equipment in a flexible DC transmission system, and the capacitor voltage balancing of its submodule directly affects the normal operation of the system. To solve this problem, the existing voltage balancing method based on fixed alternation is introduced at first, and its advantages and disadvantages are pointed out. Then, an improved voltage balancing strategy is proposed, which can reduce the submodule alternation on the basis of achieving almost the same voltage balancing effect. Finally, an MMC system was built on an RTDS hardware-in-the-loop test platform to verify the effectiveness of the proposed strategy. Experimental results show that this strategy can greatly reduce the switching frequency and improve the operating efficiency of the MMC without affecting its safe and stable operation.