信号注入法测量电容电流的关键技术研究

发布时间：2018-01-19 11:39

本文关键词： 电容电流信号注入法等值模型频率范围容量大小数字相敏检波　出处：《西安科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着大规模的配电网改造及大量电缆线路投入运行,中压配电网电容电流越来越大。为减少电容电流的危害和提高配电网的运行可靠性,普遍采取在中压配电网中性点安装消弧线圈的措施。要合理配置消弧线圈的容量,就必须准确测量中压配电网的电容电流。目前测量电容电流的方法较多,但是随着电缆线路比例的增大,中压配电网对称度升高,依赖于不对称度的传统一次侧测量电容电流方法的测量精度降低甚至无法测量。此外,这些传统测量方法存在操作繁琐且不安全的弊端。为此,可采用在二次侧操作、且无需依靠不对称度保证测量精度的信号注入法测量中压配电网的电容电流。但是,在现场应用中,该方法的测量误差较大,产生误差的原因是信号注入法测量电容电流的一些关键技术仍存在不足,如中压配电网零序回路的等值模型不够精确、注入信号的频率范围和容量不合适,返回电压信号的检测算法不准确等。为了能够更精确的测量中压配电网的电容电流,文中在信号注入法测量电容电流原理的基础上,对信号注入法的几个关键技术进行深入研究。首先,对信号注入法中的三频法、分频法、扫频法的测量原理和误差进行深入分析和仿真验证,并对每种方法的特点及适用范围做出综合评价。其次,以三芯电缆零序参数频率特性为基础分析中压配电网零序阻抗频率特性,利用一端口串联等值网络的方法改进中压配电网零序回路等值模型,结合PT模型得到精确的信号注入法测量模型。将传统的测量模型与精确测量模型进行了比较分析,证明了传统测量模型的准确性,也说明信号注入法的测量原理并不存在方法误差。再次,对PT励磁特性和PT传变特性进行试验研究并分析试验数据,确定了注入电流信号的频率范围。考虑注入信号衰减和PT容量限制的因素确定了注入信号的容量大小。最后,用数字相敏检波技术(DPSD)来检测淹没在中压配电网中的低信噪比返回电压信号。设计检测算法并通过仿真验证,发现DPSD算法有效地抑制了中压配电网中谐波信号和强噪声,并准确地将返回电压信号提取出来。因此,信号注入法测量电容电流的关键技术研究成果对现场测量和测量仪器的研发均有指导性意义。
[Abstract]:With the large-scale transformation of the distribution network and a large number of cable lines put into operation, the capacitive current of the medium voltage distribution network is increasing. In order to reduce the harm of the capacitance current and improve the reliability of the distribution network. The measures of installing arc-suppression coil in neutral point of medium voltage distribution network are generally adopted. In order to reasonably configure the capacity of arc-suppression coil, it is necessary to accurately measure the capacitance current of medium voltage distribution network. At present, there are many methods to measure capacitance current. However, with the increase of the proportion of cable lines, the symmetry of medium voltage distribution network increases, and the accuracy of the traditional primary side capacitance current measurement method, which depends on the asymmetry, decreases or even cannot be measured. These traditional measurement methods have the disadvantages of cumbersome and unsafe operation. Therefore, the secondary side operation can be adopted. And the signal injection method which does not depend on asymmetry degree to ensure the measurement accuracy is used to measure the capacitance current of the medium voltage distribution network. However, in the field application, the measurement error of this method is large. The reason of the error is that some key techniques of measuring capacitance current by signal injection method are still insufficient, such as the equivalent model of zero sequence loop in medium voltage distribution network is not accurate enough, the frequency range and capacity of injection signal are not suitable. In order to measure capacitance current of medium voltage distribution network more accurately, the principle of capacitance current is measured by signal injection method. Several key technologies of the signal injection method are studied. Firstly, the measurement principle and error of the three frequency method, the frequency division method and the sweep method are analyzed and simulated. And make a comprehensive evaluation of the characteristics and applicable range of each method. Secondly, based on the frequency characteristics of zero-sequence parameters of three-core cable, the zero-sequence impedance frequency characteristics of medium-voltage distribution network are analyzed. The method of one-port series equivalent network is used to improve the zero-sequence circuit equivalent model of medium voltage distribution network. The accurate signal injection measurement model is obtained by combining the PT model. The accuracy of the traditional measurement model is proved by comparing the traditional measurement model with the accurate measurement model. It also shows that there is no error in the measurement principle of the signal injection method. Thirdly, the excitation characteristics of PT and the transmission characteristics of PT are studied and the test data are analyzed. The frequency range of the injection current signal is determined. The capacity of the injection signal is determined by considering the attenuation of the injection signal and the limit of the PT capacity. Digital phase sensitive detector (DPSD) is used to detect the low signal-to-noise ratio (SNR) return voltage signals submerged in the medium voltage distribution network. The detection algorithm is designed and verified by simulation. It is found that the DPSD algorithm can effectively suppress the harmonic signal and strong noise in the medium voltage distribution network and extract the return voltage signal accurately. The research results of the key technology of measuring capacitive current by signal injection are instructive to the research and development of field measurement and measuring instruments.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM933.1

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