模块化多电平换流器功率模块过压保护策略及优化

Overvoltage protection strategy and optimization of sub-modules in modular multilevel converter

阐述了模块化多电平换流器(MMC)功率模块IGBT不同封装方式及失效机理,分析了功率模块在故障前后及旁路开关闭合前后的工作原理。阐述了不同IGBT封装方式的MMC功率模块过压保护工作原理,针对焊接式IGBT功率模块过压保护策略存在电压测量过程中采样异常导致换流器跳闸的风险,对功率模块过压保护策略提出优化设计。优化策略在功率模块控制板卡中实现,程序资源占用量小且易于实现,有效避免了高层级控制设备误判误动作的风险。此外,提出了过电压判据以避免系统过压时误旁路功率模块。通过仿真验证了文中所提优化策略的有效性和可行性,所提出的优化策略已在某一实际工程中应用。

Different IGBT packaging methods and failure mechanisms of the modular multilevel converter (MMC) are described in this paper. The working principle of sub-modules before and after the fault and the closing of the bypass switch are analyzed. The working principle of overvoltage protection for sub-modules in different IGBT packaging modes is introduced. The overvoltage protection strategy of bond wired IGBT modules has the risk of converter tripping due to the abnormal voltage sampling. To this end, the optimized design of overvoltage protection strategy for sub-modules is presented. The optimized strategy is implemented in sub-module control board, which is easy to be implemented with less program resources and effective to avoid the risk of misjudgment and malfunction of the high level control equipment. The system overvoltage criterion is proposed to avoid bypassing the sub-module in the case of system overvoltage. The effectiveness and feasibility of the optimization strategy proposed in this paper are verified by simulation, and the proposed optimized strategy has been applied in a practical project.