非稳态下电力谐波分析的改进FFT方法

频率偏差以及间谐波等的存在制约了非稳态下电力谐波分析的准确度,而传统FFT算法容易受到频谱泄漏和栅栏效应的影响.分析了余弦函数窗频谱特性,并提出基于余弦偶次幂窗改进FFT的非稳态谐波分析方法.在改进的FFT方法中运用最小二乘拟合法推导信号基波与各次谐波的频率、幅值和相位计算修正公式.仿真结果表明:提出的方法能有效减小基波频率波动以及间谐波的影响、提高谐波参数的计算准确度,适合于非稳态条件下的谐波分析.嵌入式系统应用验证了算法的正确性.

Power System Harmonic Analysis Under Nonstationary Situations and Its Application Based on Improved FFT Method

The accuracy of power system harmonic analysis under nonstationary situations is constrained by frequency deviation and interharmonic while the traditional FFT algorithm is susceptible to spectral leakage and picket fence effect. This paper analyzes the spectral characteristics of the cosine window, and proposes an improved FFT method for harmonic analysis based on the even order cosine window (EOCW). In the improved FFT method, the rectification formulae of the frequency, amplitude and phase of the fundamental and harmonics are obtained by using the least squares fitting method. Simulation results indicate that the calculation precision of the harmonic parameters can be highly improved by the proposed algorithm, no matter with the fundamental frequency varies and the presence of interharmonics, and thus the proposed algorithm is suitable for harmonic analysis under nonstationary situations. The correctness of the algorithm is verified by its application to an embedded system.