民用非线性负荷谐波模型及集合效应研究

发布时间：2018-06-23 06:15

本文选题：电能质量 + 非线性负荷　；参考：《山东大学》2017年硕士论文

【摘要】：近年来,在节能发展主题意识的驱动下,电力电子技术发展地异常迅速。在低压配电系统中,含电力电子整流环节的家用电器类谐波源占据了越来越大的比重。通常,该类谐波源的单台功率很小,但是其产生的谐波电流总畸变率都在100%上下,有时候甚至更严重。因此,该类谐波源负荷的大量使用势必会对整个电力系统造成谐波污染。传统谐波分析方法是把各谐波源看作恒流源,对谐波源的集合效应不给予考虑,这样往往容易造成对电网谐波发射水平的不准确评估。本文聚焦民用非线性负荷的谐波发射水平研究。一方面,通过分析典型家用电器的等值电路的运行机理,建立了一种精确的谐波耦合导纳矩阵数学模型,并提出了一种计算多谐波源总电流的理论;另一方面,利用建立的精确谐波耦合导纳矩阵数学模型以及所提出的计算多谐波源系统总电流的理论,从定量分析的角度对民用非线性负荷的谐波集合效应进行了研究。论文的主要内容及突出成果如下:(1)详细分析典型家用电器等值电路的运行机理,借助傅里叶变换在频域中建立了能准确反映典型家用电器等值电路谐波产生特性的精确谐波耦合导纳矩阵数学模型。整个建模过程中未涉及近似等效问题,克服了原模型由于对等值电路直流侧电压采取近似处理而导致模型存在不同程度误差的问题。此外,采用高斯-赛德尔法和牛顿-拉夫逊法配合使用的方法对等值电路对应的导通角和关断角进行精确计算,从而进一步提高所建立的谐波耦合导纳矩阵数学模型的准确度。模型计算和时域仿真的对比结果证明了论文所建模型的精确性。(2)提出一种计算民用多谐波源系统总电流的方法。利用该方法计算系统总电流的多个算例的编程计算结果和相应的时域仿真结果的对比证明了该方法具有较好的适用性。(3)基于所建立的典型家用电器等值电路的精确谐波耦合导纳矩阵数学模型以及所提出的计算民用多谐波源系统总电流的理论,从定量分析的角度分别对民用多谐波源系统的谐波衰减效应、分散效应以及集合效应进行了研究。研究结果表明:系统谐波阶数越高,谐波衰减现象越明显;负荷侧并联的负荷数量越多,系统各次谐波衰减的幅度越大,衰减因子AF可很好地衡量系统的谐波衰减程度;不同类型的负荷集各自对应的分散因子DF可以很好地表征不同类型负荷对系统总谐波分散效应的贡献程度;集合因子CF可直观地反映系统的谐波集合现象。(4)分析了线性负荷对民用多谐波源系统谐波集合效应的影响。研究发现,线性负荷的加入会使系统总电流的总谐波畸变率减少,并且阻值小的线性负荷更利于减少系统总电流的总谐波畸变率。
[Abstract]:In recent years, driven by the theme consciousness of energy conservation development, power electronics technology has developed very rapidly. In the low-voltage distribution system, the harmonic source of household appliances with power electronic rectifier is more and more important. Usually, the power of this kind of harmonic source is very small, but the total distortion rate of harmonic current is about 100%, sometimes even more serious. Therefore, the heavy use of this kind of harmonic source load will inevitably cause harmonic pollution to the whole power system. The traditional harmonic analysis method regards each harmonic source as a constant current source and does not consider the collective effect of the harmonic source, which often results in an inaccurate evaluation of the harmonic emission level of the power network. This paper focuses on the harmonic emission level of civil nonlinear load. On the one hand, by analyzing the operation mechanism of equivalent circuit of typical household appliances, a precise mathematical model of harmonic coupling admittance matrix is established, and a theory of calculating the total current of multiple harmonic sources is put forward. Based on the mathematical model of accurate harmonic coupling admittance matrix and the theory of calculating the total current of multi-harmonic source system, the harmonic set effect of civil nonlinear load is studied from the point of view of quantitative analysis. The main contents and outstanding results are as follows: (1) the operation mechanism of equivalent circuit of typical household appliances is analyzed in detail. By means of Fourier transform, a mathematical model of harmonic coupled admittance matrix is established in the frequency domain, which can accurately reflect the harmonic generation characteristics of typical equivalent circuit of household appliances. The problem of approximate equivalence is not involved in the whole modeling process, which overcomes the problem that the original model has different degree of error due to the approximate treatment of DC side voltage of equivalent circuit. In addition, the Gauss-Seadell method and Newton-Raphson method are used to calculate the conduction angle and turn-off angle of equivalent circuit accurately, so as to further improve the accuracy of the mathematical model of harmonic coupling admittance matrix. The results of model calculation and time domain simulation prove the accuracy of the model. (2) A method to calculate the total current of civil multi-harmonic source system is proposed. The comparison of the results of programming calculation and corresponding time domain simulation of the total current of the system shows that the method has good applicability. (3) based on the established equivalent circuit of typical household appliances, the method is proved to be accurate. The mathematical model of harmonic coupled admittance matrix and the theory proposed to calculate the total current of civil multi-harmonic source system are presented. From the point of view of quantitative analysis, the harmonic attenuation effect, dispersion effect and collective effect of civil multi-harmonic source system are studied respectively. The results show that the higher the harmonic order of the system, the more obvious the harmonic attenuation phenomenon is, and the larger the load number at the load side is, the larger the harmonic attenuation amplitude of the system is. The attenuation factor AF can well measure the harmonic attenuation degree of the system. The dispersion factor DF corresponding to different load sets can well characterize the contribution of different types of load to the total harmonic dispersion effect of the system. The set factor CF can directly reflect the harmonic set phenomenon of the system. (4) the influence of linear load on the harmonic set effect of civil multi-harmonic source system is analyzed. It is found that the total harmonic distortion rate of the total current of the system is reduced with the addition of linear load, and the linear load with small resistance value is more favorable to reduce the total harmonic distortion rate of the total current of the system.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM711

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