基于容性参数等效的功率变换器系统电磁辐射预估方法及抑制措施

Method of Electromagnetic Radiation Prediction and Suppression Based on Capacitance Parameter Equivalence in Power Converter System

电磁辐射在空间通过电磁波的形式干扰其他电气电子设备,是电磁兼容研究领域中的热点问题之一。鉴于功率变换器系统(PCS)远场辐射机理的复杂性,该文以Boost变换器为研究对象,探索得到功率变换器中的共模(CM)电流是PCS的主要辐射噪声源,并通过输入线缆与地平面之间的寄生电容传递,由此建立功率变换器的共模电流通路(CCP)模型。通过适当的简化,CCP进一步等效为等效辐射预测模型(EMR);采用有限元法(FEM)提取变换器系统的寄生电容,进而迭代设计确定EMR结构,利用信号发生器给EMR馈电模拟变换器的电磁辐射。在电波暗室中分别对PCS和EMR测试比较,两种模型的辐射场强很好地吻合,从而验证了该方法的可行性。最后,该文提出基于散射参数的方法对电磁噪声抑制效果进行评估;在此基础上,选择铁氧体磁环改变线缆系统的散射参数矩阵,从而可对电磁辐射进行抑制;给出了磁环的推荐安装方式,使得PCS通过GB 9254 ClassB测试标准。

Electromagnetic radiation interferes with electrical and electronic equipment in the form of electromagnetic wave in space,which is one of the key issues in research area of EMC.In view of the complexity of far-field radiation of power converter system(PCS),this paper takes the common-mode(CM)current as the main noise source,and transmits through parasitic capacitance between input cables and ground,thus CM current path model(CCP)is established.Moreover,CCP is formed as equivalent prediction model of radiation(EMR)by appropriate simplification.The parasitic capacitance of EMR and PCS is extracted by finite element method(FEM),and then geometric parameter of EMR is obtained by iterative design.The EMR is fed by signal generator to simulate radiation emission of PCS.Furthermore,PCS and EMR are tested in the anechoic chamber,and the radiation emission of two models is in good agreement,thereby verifying the feasibility of the method.At last,the scattering parameters are used to evaluate the effect of electromagnetic noise suppression.On this basis,the ferrite magnetic ring is selected to change scattering parameter matrix,and electromagnetic radiation can be suppressed.The recommended installation of magnetic ring is given that makes converter pass the GB 9254 ClassB test standard.