【作者】 李怀龙；

【导师】 孟志强；

【作者基本信息】 湖南大学 ， 测试计量技术与仪器， 2006， 硕士

【摘要】 随着电力事业的迅速发展,对电力系统运行可靠性要求将越来越高,电气设备绝缘检测技术的发展更加受到重视。充油设备在电力系统中占有相当大的比例,而绝缘油介质损耗因数是反映其绝缘状况的重要参数。因此,研究绝缘油介质损耗因数的测量方法具有十分重要的实际意义。论文介绍了电力绝缘材料在电场作用下产生介质损耗的机理,指出影响绝缘油介质损耗因数的主要因素和测量绝缘油介质损耗的意义。阐述了过零鉴相法、过零点电压比较法、同步正交分离法和自由矢量法测量介质损耗的原理,同时指出这些测量方法的优缺点。由于电网中存在大量的谐波干扰,导致测量系统中取样信号也含有很大的谐波,为了消除谐波对测量结果的影响,论文深入研究了傅立叶变换谐波分析法的测量原理,分析了测量中频谱泄漏和栅栏效应形成的原因,提出了采用锁相环倍频技术实现信号的整周期同步采样,消除频谱泄漏和栅栏效应对测量结果的影响,并对锁相环倍频技术的理论进行了深入研究,给出锁相环倍频技术的实现方法。针对介质损耗测量中存在的随机干扰,阐述了基于小波变换的硬阈值消噪理论在测量系统中的应用。同时,论文分析了常用加热绝缘油方法的不足,在研究传统PID控制和模糊控制原理基础上,综合两种控制算法的优点,在绝缘油介损测量系统中,提出采用模糊+PID控制算法对绝缘油温度进行控制,并实现了模糊+PID控制器的设计。通过MATLAB仿真,验证了小波硬阈值消噪能有效降低随机干扰对测量结果的影响,利用PID控制算法、模糊控制算法和模糊+PID控制算法对选定的被控对象进行仿真,由仿真结果可知模糊+PID控制算法能满足测量绝缘油介质损耗的温度要求。论文最后设计了一个基于DSP TMS320LF2407的绝缘油介质损耗数字测量系统,给出了系统总体结构框图和系统的工作原理,对信号取样电路、信号硬件预处理电路、基于锁相环倍频技术的整周期同步采样电路以及温度测量和绝缘油加热控制电路进行了详细地设计和分析,给出了软件部分的主程序和主要功能子程序流程图。更多还原

【Abstract】 With the rapid development of electric power enterprise,the demand on the reliability of electric power system is further more,and the development of insulation monitoring technique has been paid more attention.Oil-filled equipment plays a very important role in power system,and the dielectric loss factor(tgδ) is an important parameter to reflect the insulation condition.Therefore,studying the tgδof insulating oil is of important practical meaning.The paper introduces electric power insulation material’s dielectric loss mechanism under the action of electric field, points out the major factors which influence insulating oil dielectric loss and important significance of measuring dielectric loss. expatiates on measurement principium of crossing-zero phase demodulation method、crossing-zero voltage comparison method、orthogonal synchronous separation method and freedom vector method,and points out advantages and disadvantages of these methods. Because massive harmonic interference in the electrical network, it causes signal-sampling to include the very big harmonic in the measurement system , for eliminating measurement result influence by harmonic,the paper has an in-depth study of Fourier transformation harmonics analysis measurement principle, analysis the forming reasons of frequency spectrum leakage and railing effect during measurement,achieves phase locked loop and frequency multiplier technique to realize integer-period synchronous sampling and eliminate impact of frequency spectrum leakage and railing effect in the result of measurement, and investigates in depth theory on phase locked loop and frequency multiplier technique, gives the method of realizing phase locked loop and frequency multiplier technique. for eliminating random disturbance in the measurement system of dielectric loss ,elaborates application on the theory of hard threshold value de-noise based on the wavelet transformation in the measurement system. Meanwhile, the paper analysis shortage of the methods commonly used heating insulating oil,investigate principles of traditional PID control and fuzzy control, integrats the advantage of two control algorithms, makes use of fuzzy+PID control algorithm to control insulating oil temperature, and has designed fuzzy+PID controller.Through MATLAB simulation, validates that wavelet hard threshold vale de-noise method can effectively reduce the impact of random disturbance. carries on the simulation to the controlled object更多还原