提高工频电流电压基波计算精度的Fourier均值算法

Fourier averaging algorithm for improving accuracy of basic wave voltages and currents calculations on industrial frequencies

准确、快速地采集和计算出电力系统实时电压和电流的基波分量的有效值 (或幅值 )和相位对于保证电力系统的稳定、安全和经济运行十分重要。其精度和速度也是各种微机继电保护和自动控制装置的重要性能指标。然而 ,当电力系统频率偏离 5 0 Hz时 ,在定采样间隔条件下 ,利用快速Fourier变换 (FFT)计算电压和电流的基波 ,会产生较大的误差。该文提出一种简单实用的基于 FFT的均值算法 ,它可以明显地提高基波电压和电流向量的计算准确度 ;利用该算法 ,可使电力系统频率在偏离额定频率± 2 Hz时 ,基波幅值计算结果的误差 <0 .5 % ,相角误差也明显减少。

Accurately and quickly acquisition of effective values (or amplitudes) and phases of real time basic wave currents and voltages is needed to guarantee the stability, security and economics of power systems. Accuracy and speed are also important performance indices of different micro -processor relay protection devices and automatic control equipment. However, when the frequency of the power system is not 50 Hz, the use of fixed sampling intervals with fast Fourier transforms (FFT) to calculate the basic wave current and voltage will cause significant error. This paper presents a realistic FFT based averaging algorithm which significantly improves the calculation accuracy of the basic wave current and voltage vectors. With this algorithm, when the power system frequency has a bias of ±2 Hz from the normal frequency, the calculational error for the basic wave amplitude is limited to less than 0.5%, and the phase error is reduced significantly as well.