电压不平衡度的加窗FFT快速测量方法

电压不平衡度是电能质量的重要参数之一,其准确测量一方面依赖于三相电压基波相量(幅值和相位)的精确估计,另一方面需要快速求取相序分量。但是,频谱泄漏和栅栏效应会严重影响电压幅值和相位的估计精度,而相序分量计算过程中的开方运算又降低了不平衡度测量的实时性。提出电压不平衡度加窗快速傅里叶变换(FFT)测量方法。首先采用加窗FFT实现三相电压相量的准确计算,然后根据几何原理将方均根计算简化为多项式计算,从而实现相序分量及电压不平衡度的快速测量。仿真结果表明,所提方法可以达到与GB/T 15543—2008推荐方法相同的精度等级。实际测量实验进一步验证了所提算法的有效性及可行性。

Fast Measurement Method of Voltage Unbalance Factor Based on Windowed FFT

The voltage unbalance factor (VUF) is one of the most important parameters of power quality. The measurement of VUF depends on both the precise estimation of voltage phasors and the fast calculation of the magnitude of the zero, positive, and negative sequences. However, the accuracy of voltage phasors estimation is affected by the spectrum leakage and picket fence effect, and the measurement speed of VUF is limited because of the square root operation in the calculation of phase sequences. In this paper, a fast measurement method of voltage unbalance factor based on windowed interpolation fast Fourier transform (FFT) was presented. Firstly, windowed interpolation FFT was applied to calculate the voltage phasors. Then, the square root operation in the calculation of phase sequences was transformed into polynomial operation based on the geometric partitions. The simulation results show that the proposed method could achieve the same level of accuracy with the method recommended by GB/T 15543—2008. The measured results from the experiments of VUF verify the effective and practicability of the proposed method in further.