【作者】 姜保军；

【导师】 梁维燕； 孙力；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2007， 博士

【摘要】 虽然PWM电机驱动系统因其具有良好的运行特性,而在工业系统和民用装置中得到了广泛地应用,但它所带来的EMI问题也日趋严重,这不但严重地威胁着系统自身的安全、稳定运行,而且还对周边其它电气系统构成了较大的威胁。其中的传导共模EMI,因其传播路径包含大地,而会增大系统辐射EMI发射强度,同时它还会以电流的形式注入其它电气系统形成干扰,并且这种干扰的发射强度正随着功率变换器开关频率和电压、电流变化率的提高而逐渐增强。为此本文就PWM电机驱动系统传导共模EMI的抑制技术、及相关等效电路的建立方法进行了深入研究,并在此基础提出了相应的解决方法。本文在详细研究PWM电机驱动系统感应电机侧共模电压形成机理、时域/频域特性,及该侧共模EMI电流形成机理的基础上,提出了一种感应电机传导干扰频段共模等效电路。该等效电路是依据感应电机高频共模特性及绕组对地、对中性点阻抗幅频特性测量值获取等效电路参数。此共模等效电路可以用于分析和预测PWM电机驱动系统传导共模EMI发射强度、感应电机侧共模EMI电流。等效电路仿真结果与实验结果的具有良好的一致性。针对系统功率变换器侧传导共模EMI发射强度难以得到有效抑制这一问题,本文在深入分析该EMI形成机理与传播特点的基础上,提出了一种用于降低系统功率变换器侧传导共模EMI发射强度的方法。该方法是通过提高散热器对地共模阻抗实现这一目的的。为了从理论上验证该方法正确,论文通过FEM-BEM耦合法对采用此抑制方法前/后散热器表面电场强度的变化情况进行了数值模拟。模拟结果和实验结果证明了该方法能够有效地抑制功率变换器侧传导共模EMI发射强度。鉴于PWM电机驱动系统感应电机侧普遍存在着共模电压、共模电流这一EMI问题,本文依据系统感应电机侧共模电压、共模电流的形成机理,提出了一种应用于功率变换器输出端的无源共模EMI滤波器结构。它由结构类似于只具有单边星接绕组变压器结构的电感,且每相绕组两端并联电容的共模电压检测单元和起电压补偿作用的四绕组共模变压器组成。该滤波器克服了传统功率变换器输出端无源共模EMI滤波器高低频特性难以兼顾,且体积过大的缺点。仿真结果和实验结果均验证了该无源滤波器可以有效地抑制感应电机侧共模电压、共模电流,实现有效降低整个系统传导共模EMI发射强度的目的。研究了有源EMI滤波器的插入损耗及设计与应用中的最佳匹配问题,并依据所得出的“电流检测电流补偿方式反馈型有源滤波器适用于共模电流噪声和漏电流的抑制”观点,提出了一种用于抑制系统共模EMI电流的有源EMI滤波器结构。该有源滤波器是以反向补偿电流直接注入系统的方法阻断系统电源侧共模电流流通路径,实现有效抑制系统传导共模EMI发射强度这一目的。与采用补偿电流注入大地方式的典型有源EMI滤波器相比,该有源EMI滤波器克服了补偿电流不足所带来的插入损耗变小的缺点。同时,在该滤波器的电源设计上还注重了共模EMI电流的抑制。仿真结果与实验结果均证明该有源滤波器可以有效地抑制系统传导共模EMI发射强度。更多还原

【Abstract】 PWM motor drive system is widely applied to industrial systems and civil devices because it has excellent operating characteristic; however, it also brings severe EMI problem. The EMI affects the safety and stabilization not only of the motor drive system itself but also of other surrounding electrical system. The conducted common-mode EMI has enhanced systematic radiated interference because its circulating path includes the earth. At the same time it also brings conducted interference to other electrical system in the form of interference current. Emission intensity will gradually strengthen with the rise of switching frequency, voltage and current ratio of power converter. So this dissertation investigates conducted common-mode EMI suppression techniques in the PWM motor drive system and the modeling method of related equivalent circuit. Taking this as a base, some methods to solve this problem are proposed.The common-mode equivalent circuit of induction motor in conducted interference frequency band is proposed based on deep research of the formation mechanism and the time/frequency domain characteristics of common-mode voltage and formation mechanism of common-mode current at induction motor side in PWM motor drive system. In this model, equivalent circuit parameters are obtained according to measurement values of high frequency common-mode characteristic of induction motor and measurement values of amplitude and frequency characteristic of impedances which are winding to the earth and to the neutral point. This equivalent circuit model can be used to analyze and predict common-mode EMI emission intensity and common-mode EMI current at motor side in PWM motor drive system. The consistency of simulation and experimental result is good.It is hard to reduce effectively conducted common-mode EMI emission at power convert side, in order to solve the problem this paper propose a common-mode EMI suppression method by analyzing the formation mechanism and propagation characteristic of common-mode EMI at this side. The suppression is implemented by increasing the common-mode impedance between heat sink and the earth. By adopting FEM-BEM coupling method, the paper simulates numerically the surface electric field of heat sink with and without the presented method separately. The simulation and experimental result validate that the presented method can effectively suppress common-mode EMI emission intensity at power convert side, eventually reducing the EMI emission intensity of the whole system.Whereas common-mode voltage and common-mode current problem exists commonly at induction motor side in PWM motor drive system, this paper proposed a novel structure of passive common-mode EMI filter placed at power converter output side according to the formation mechanism of common-mode voltage and common-mode current at induction motor side. This passive filter is composed of a common-mode voltage detecting element and a four-winding voltage compensation transformer. The common-mode voltage detecting element adopts inductors, the structure of which is similar to an unilateral transformer in Y connection, and capacitors, paralleled with each phase winding. The proposed filter overcomes the disadvantage of conventional filter which has either poor high frequency characteristic or poor low frequency characteristic and has too large bulk. Both simulation result and experimental result prove that the proposed passive filter can effectively suppress common-mode voltage and common-mode current at induction motor side, realizing effective suppression of emission intensity of conducted EMI of the whole system.Insert losses of active EMI filter and optimal match problem in the design and application are researched. And a novel structure of active EMI filter is proposed to restrain common-mode EMI current in the system according to the conclusion that current detection and compensation mode active EMI filter adapts to suppress common-mode current noise and leakage current. In the proposed active filter, compensation current is directly injected into system, thus, propagation path of common-mode EMI at source side of the system is blocked and the aim to effectively suppress common-mode conducted EMI is achieved. Compared to typical active filter, compensation current of which is directly injected into the earth, the proposed filter overcomes the shortcoming of small insert loss caused by deficiency of compensation current. In the source design of the proposed filter, much attention is paid to suppression of common-mode EMI current. Both simulation result and experimental result prove that the proposed filter can effectively reduce emission intensity of conducted EMI in system.更多还原