一种基于广义逆的电流互感器励磁特性分析方法

A method to analyze the excitation characteristics of current transformer based on Moore-Penrose inverse algorithm

电流互感器出厂时提供的伏安曲线大多只覆盖5～200mA这段低励磁电流区间,难以据此评估大倍数一次电流时的电流传变特性。采取简单指数函数拟合伏安数据,提出用Moore-Penrose逆方法对指数函数进行参数辨识。针对直接辨识产生的较大拟合误差,将数据取值间隔规律化并用线性或样条插值填充数据的方法对原始数据进行预处理,可降低辨识过程中非线性因素的影响,改善拟合精度。以饱和起始点的励磁电压作为参考,通过归一化处理能降低所需辨识的参数空间的维数,从而简化计算。根据辨识得到的拟合函数可方便地求出满足10%误差要求的电流互感器二次负载的允许上限值曲线,该曲线可用于检验电流互感器的二次负载是否与其励磁特性相匹配。

Because of the voltage-ampere curve offered by manufacturer,mostly covering the low excitation current area ranging from 5 to 200 mA,it is difficult to assess the working performance of current transformer when its primary current reaches high times of the rated value.This paper takes a simple exponent function to approach the original excitation curve and recognizes the parameters of the exponent function by pseudo-inverse algorithm.But,without data pretreatment,the parameters recognized by Moore-Penrose method will produce a big fitting error.Through regularizing the sampling interval of argument and filling few of dependent variables by linear or spline interpolation to pretreat the raw data,the influence of the nonlinear factor in recognition process is depressed and the fitting accuracy is improved.Then using the starting saturation point of excitation voltage as the reference,the dimension of parameter space which needs to be recognized can be reduced by normalized operation,and the calculation is correspondingly simplified.On the basis of fitting function gotten by recognitian,it is easy to draw the limitation curve of secondary load of current transformer under the 10% error desire.The curve is helpful to judge whether the given current transformer＇s secondary load matches its excitation characteristics.