利用Blackman窗函数对工频信号进行加窗FFT后校正计算出基波和谐波的幅值、频率和初始相角。-Blackman window function using frequency signal windowed FFT is calculated after the correction of fundamental and harmonic amplitude, frequency and initial phase angle.

跟prony算法一样，ESPRIT（Estimation of Signal Parameters Via Rotational Invariance Techniques）也是一种参数法，它是一种基于旋转不变技术参数估计的信号处理方法，此方法可以高精度地辨识电力系统中任意组合的衰减/非衰减正弦信号的频率，相位及其幅值等信息。它不需要对信号进行同步采样。此方法把信号空间分解为信号子空间和噪声子空间，能够在较短的信号长度内准确的检测出信号中各个谐波和间谐波成分。-ESPRIT

输入谐波幅值越大，会使输出幅值与输入幅值偏差增大，但不影响相位。频率越大，输出与输入相位偏差越大。 -The larger the input harmonic amplitude, causes the output amplitude input amplitude deviation increases, but does not affect phase. The frequency, the greater the output and input phase deviation.

采用幅值恒等原则建立的三相到两相静止坐标系和两相静止坐标系到三相坐标系的变换-Constant amplitude using the principles established by the three-phase to two-phase stationary coordinate system and the two-phase stationary coordinate system to transform the three-phase coordinate system

求取谐波频率，记算出各次谐波的幅值，有效值(The harmonic frequency is calculated, and the amplitude and effective value of each harmonic are calculated)