一种递推改进的DFT同步相量测量方法的特性分析

Analysing on characteristics of an improved recursive synchronized phasor measurement method of discrete Fourier transform

针对传统离散傅里叶变换(DFT)测量算法提出改进方案,以减小电网频率波动时不同步采样造成的测量计算误差。运用采样点函数的递推关系构建特征值方程,选择数据点数可变的采样数据窗,削弱因系统频率偏移造成的周期截断误差,推导出了递推改进的同步相量计算公式。在基频额定值偏移量分别为定值、正弦量、线性函数值、随机数等情况下进行测试,相比传统DFT算法,改进算法的相角和幅值测量精度均有显著提升。在此基础上研究了采样频率和采样策略对算法性能的影响,以及算法对含有谐波信号的应用效果。试验结果表明,改进的DFT算法的计算精度和实时性均明显提高。

In order to reduce the measurement and calculation errors that were caused by asynchronous sampling due to grid frequency fluctuation,this paper proposed an improved scheme of traditional discrete Fourier transform( DFT) measuring algorithm. In this improved scheme,an eigenvalue equation was constructed using the recurrence relation of sampling point function,a sampling data window with variable data number was chosen,the period truncation error due to system frequency deviation was reduced,and an improved recursive synchronized phasor measurement method was derived. Compared with the traditional DFT algorithm,the phase angle and amplitude measurement accuracies of the improved algorithm were significantly increased,which were tested under the conditions of fundamental frequency rating offsets were set as constant value,sinusoidal quantity,linear function value and random number,etc. And on this basis,this paper studied the impacts of sampling frequency and sampling strategy on algorithm performance,and the application effect of algorithm on the signal contains harmonic. The test results show that the calculation accuracy and real-time performance of the improved DFT algorithm were significantly increased.