金属化膜电容器交流和直流电压劣化特性分析

AC and DC voltage degradation characteristics of metallized film capacitors

金属化膜电容器是模块化多电平换流器(MMC)的关键设备,在长期的电热应力作用下其状态不断劣化,给换流器和柔性直流输电系统的安全运行带来隐患。文中分别搭建了交、直流加速劣化试验平台,得到了不同电压作用形式和不同状态劣化程度的样品。进而利用共聚焦显微镜和扫描电子显微镜对解剖样品进行表面观测,结合能谱扫描的元素分析结果,掌握金属化膜电容器在不同电压形式下的状态劣化特性。结果表明,电容器由于在不同电压下的劣化机理不同,电容值下降规律和劣化点形貌有明显不同;通过加速老化试验,得到了电容器在交、直流电压下劣化点的典型形貌特征,从而可以进一步分析金属化膜电容器劣化机理,具有实用价值。

As a key component of modular multi-level converter(MMC),metallized film capacitor has the advantages of good reliability,high energy storage density and high working field strength.The failure of capacitors will affect the safe operation of the converter and even the even VSC-HVDC transmission systems.AC and DC accelerated aging test platforms are set up,and get aging samples through accelerated aging test.The aging characteristics of metallized film capacitors under different electrical stress are obtained by scanning electron microscope and confocal microscope.The results show that due to the different degradation mechanism of capacitors under different kind of voltages,the rule of capacitance value′s ruducing and the morphology of degradation point are obviously different.Through accelerated aging test,the typical morphology characteristics of the degradation point of capacitors under AC and DC voltage are obtained,which can further analyze the degradation mechanism of metallized film capacitors.The research has practical value.