轴承绝缘对双馈异步发电机高频轴电压和轴电流抑制效果研究  

Analysis of High Frequency Bearing Voltage and Bearing Current Suppression of Doubly Fed Induction Generators Based on Bearings Insulation

作　　者：刘瑞芳[1] 陈嘉垚 朱健 任雪娇 Liu Ruifang;Chen Jiayao;Zhu Jian;Ren Xuejiao(School of Electrical Engineering Beijing Jiaotong University,Beijing,100044,China)

机构地区：[1]北京交通大学电气工程学院

出　　处：《电工技术学报》2020年第S01期212-219,共8页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金资助项目（51777008）

摘　　要：双馈异步发电机具有变流器容量小、体积小、成本低等优点,成为风力发电系统中广泛使用的机型之一。由于双馈异步发电机采用变频器转子侧供电,变频器产生的高频共模电压经电机杂散电容耦合在转轴上感应出轴电压,其引起的轴电流会带来轴承早期失效。针对该问题,目前主要采用轴承部位绝缘同时转轴经电刷接地的方案来抑制轴电压和轴电流,而不同绝缘方案的抑制效果有待从机理上进行分析。该文首先建立了双馈异步电机变频器系统轴电流模型,分析了绝缘层电容对轴承分压比的灵敏度影响,然后针对绝缘轴承座、绝缘端盖以及绝缘轴承三种方案的轴电压和轴电流的抑制效果,对绝缘层所处的位置、绝缘层的厚度和材料对轴承分压比影响进行了计算。分析表明,混合陶瓷轴承可有效抑制轴电流。采用较厚的绝缘层时,绝缘端盖和绝缘轴承座抑制轴电压效果较明显,但需要配合电刷才能抑制轴电流。由于喷涂绝缘轴承的涂层一般较薄,因此,采用喷涂绝缘轴承并不能有效降低高频轴电压,也不能有效抑制高频轴电流。Doubly fed induction generator(DFIG)is one of the most widely used forms of wind power generation systems.It has the advantages of small capacity,small volume and low cost.Due to the power supply form,the common mode voltage of the converter induces the bearing currents which cause the bearing premature failure.The brush grounding and insulating bearing are the two often adopted methods in the industry on suppressing bearing currents.However the effect of different bearing insulation methods such as insulating the bearing housing,insulating the end cover,spraying bearings and hybrid bearings should be compared and analyzed theoretically.In this paper,the equivalent circuit for analyzing the bearing currents was set up.The sensitivity analyzing of insulation layer on the suppression method was carried out.Then the influence of the position,thickness and material of the insulation layer were studied.The analysis shows that the hybrid ceramic bearing is the most effective method to suppress the bearing current.The insulated bearing housing or end cover is useful to decrease the bearing voltage while the insulation layer is thick enough,but the brush is still needed to suppress the bearing current.The sprayed insulated bearing cannot effectively suppress the high frequency bearing voltage and current because of the thinner coating.

关 键 词：双馈异步发电机 轴电流 轴承分压比 杂散电容 轴承绝缘 

分 类 号：TM315[电气工程—电机]