从Excel表中读取数据，然后分析其频谱、相谱和总谐波畸变率，并画出图（plot）。-Read data from an Excel table, and then analyze its spectrum, phase spectrum and total harmonic distortion rate, and draw the diagram (plot).

fft谐波分析的实例，并求出THD即谐波畸变率 -Examples fft harmonic analysis, and find THD

利用matlab编程对电能质量进行分析，包括电压有效值，频率，功率因数和谐波畸变率(The power quality is analyzed by MATLAB programming, including voltage effective value, frequency, power factor and harmonic distortion rate.)

首先读取csv文件（来自示波器或其他来源），csv是字符格式的文本文件。然后，对采样波形进行谐波分析，将输入信号分解成：A0直流分量，A1基频分量，A22次谐波，A33次谐波……N噪声。采用的是加hanning窗的FFT算法。最后，求取 总谐波失真率THD（%）(First read the CSV file, and CSV is a character format text file. Then, the input signal is decomposed into A0 DC comp