电磁兼容用测量仪器高频传递函数的建模方法

【作者】 赵坤；

【导师】 李庆民；

【作者基本信息】 山东大学 ， 高电压与绝缘技术， 2006， 硕士

【摘要】 变电站的柔性交流输电(FACTS)设备在运行过程中，因大功率器件的频繁开关过程将产生很陡的瞬态脉冲，经近场耦合和远场辐射形成较严重的高频传导和辐射干扰，影响周围的电磁环境并且威胁附近敏感性二次电子设备的正常工作。 理论分析和仿真计算固然重要，但对于最后的成功验证，也许没有任何其他领域像电磁兼容那样强烈地依赖于实际测量，特别是当所研究的电磁干扰的时域和频域特性都很复杂时。电磁兼容的研究与分析一般都是建立在实测数据的基础上，因此，测试手段及其准确度显得十分重要。 受各种设计因素限制，实际的测量传感器(如高频电流探头)和电磁场天线的频率特性(增益曲线)并不平坦，而FACTS设备的高频干扰一般具有多频率成分，频带在5kHz—20MHz之间，属于多频率分量信号，这就使得由测试仪器的输出来恢复实际的被测信号时产生困难。因此，必须校正传感器和天线的频率特性，否则测量误差较大。本文的研究目的，就是根据传感器和电磁天线的(厂家提供并由计量部门校准)典型增益曲线，建立其频域的等效传递函数，籍此在时域内对所测数据序列进行离散化处理，实现对传感器和天线频率特性的数字化补偿，以提高其测量准确度。 变电站中使用的PT和CT一般为工频50Hz设计，要建立其精确的基于物理参数的模型相当困难，关键是一些杂散参数难以确定，为此可利用数学方法构建其等效传递函数。论文提出了一种连乘式的高频传递函数模型，便于实现测量仪器测试误差的数字化校正；在进行频谱处理时，综合考虑幅频与相频信息，并采用寻优方法获取模型的各个参数，有效提高了频域等效模型的准确度。研究结果为进一步实现电磁干扰预测提供了一般分析方法。更多还原

【Abstract】 Steep transients will be caused by FACTS equipments operational within substations due to frequent switching of power electronic devices, which thereby results in serious high-frequency conducted and radiated interference through near-field coupling and far-field radiation. This affects the surrounding electromagnetic environment and poses potential threats to normal operation of the sensitive secondary electronic equipments positioned nearby.Theoretic analysis and digital simulation is important, however, measurements and experiments, normally as the last ditch for validation, render even more significance in EMC investigation, especially when the time- and frequency-domain characteristics of the electromagnetic interference being studied are complicated. So methodology with instrumentation and measurement in EMC are extremely emphasized.In fact, the frequency characteristics of a sensor or an antenna does not present a flat line, which poses difficulty in recovering the input signal from a sensor’s output, especially when the original signal possesses multi-frequency components. Therefore the frequency characteristics of a sensor or an antenna must be rectified, otherwise big error will be caused. Based on the available frequency response characteristics of a measurement transducer, an equivalent frequency-domain transfer function can be established and digital compensation can be realized to the measured data series in the time domain, which can effectively improve the measurement accuracy.PT and CT are normally designed specifically for applications at SOHz, thus physical modelling is quite difficult due to lack of the model parameters at high frequency. The practical way is to establish their equivalent models with mathematical methodology based on frequency response. A equivalent model of high frequency transfer function was proposed, in order to realized the digital compensation of measurement equipment’s error. The information of amplitude and phase is considered in the frequency domain, at the same time, optimization algorithm is used to get the parameter of the model, in order to improve the accuracy of model in the更多还原