【作者】 迟长春；

【导师】 李奎；

【作者基本信息】 河北工业大学 ， 电机与电器， 2008， 博士

【摘要】 过载保护技术是低压电器智能化技术的重要组成部分,广泛应用于低压断路器、过载继电器等产品中,是保证电动机、配电线路安全运行的重要技术。因此深入研究过载对电动机、配电线路运行影响的内在规律,建立适用于不同对象的过载保护模型,研究过载保护的新型数字算法,对提高过载保护的有效性具有重要意义。本文根据热平衡方程建立了以温升为变量的动态过载保护数学模型,确定了被保护对象的负载电流变化时的温升变化过程。与常用反时限保护特性相比较,此保护模型更符合负载的实际运行规律及保护要求,并对测量误差关系进行了分析。同时根据对称分量法的基本原理,提出以等效电流作为电动机热积累计算的依据的算法。小波分析作为时频分析方法中一种新的信号处理技术,近年来取得了飞速的发展,并在各种实际工程领域中获得了广泛的应用。针对全周傅里叶算法不能滤除衰减直流分量与频率特性较差的问题,在深入研究各参数对给出的Morlet复小波幅值算法性能影响的基础上,提出减法滤波器加全周Morlet复小波幅值算法,计算配电线路的基波的幅值。它可有效滤除衰减直流分量并具有较好的频率特性与较高的计算精度。设计了以PIC18F458单片机为核心的过载保护器硬件系统和过载保护的软件模块化系统,并通过RS-485串行口以及通信软件的设计,实现了上位机与过载保护器之间的远程双向通信。更多还原

【Abstract】 The over-load protection technology is an indispensable constituent of the low voltage apparatus intellectualization and is widely used in the products, such as low-voltage circuit-breaker, overload relay and so on. Moreover, this technology is very important to ensure the electric motor and the distribution line safe operation. The study of inherent laws of over-load influence for the electric motor and the distribution line, building of over-load protection model for the different objects, and new digital algorithm of over-load protection is meaningful to improve the efficiency of the over-load protection validity.This paper establishes a mathematical model for the dynamic over-load protection, based on the heat balance differential equation, to determine how temperature increases with the change of the protection object’s current. Different from the common inverse time characteristic, this model conforms to the load actual operating law and the protection request, and takes the analysis of measurement error into consideration. And, the equivalent current algorithm for the electric motor heat accumulation is proposed based on the symmetrical component method.Wavelet analysis, as a new kind of time-frequency representation technique, has made great progress recently and been applied widely in different engineering practice. To solve the problem of the full-wave Fourier algorithm which is disable to filter decaying DC component and has worse frequency characteristic, it is presented a algorithm depending on the combination of subtraction filter and full-wave Morlet complex wavelet amplitude algorithm to get out the amplitude value of fundamental component of the current in the distribution line by studying each parameter’s influence on the performance of Morlet complex wavelet amplitude algorithm. It can filter efficiently decaying DC component, has clear frequency characteristic, and make calculation with high precision.The hardware and software modulation systems of the intelligent over-load protector are designed with the core of microprocessor PIC18F458. Moreover the remote bi-directional communication, between superior computer and over-load protector, is achieved by the RS-485 serial communication interface and software.更多还原