说明：  用DFT 函数计算电压u, 电流i的基波(f1=50 Hz)的有效值和相位; 用FFT函数分别计算电压u和电流i 所包含的直流,基波和谐波的有效值和初相角; 可计算基波(f1=50 Hz)和各次谐波的功率p和功率因数con?.
(The effective value and phase of fundamental wave (f1 = 50 Hz) of voltage U and current I are calculated by DFT function. The effective values and initial phase angles of DC, fundamental and harmonic waves contained in voltage U and current I are calculated by FFT function, respectively. The power P and power factor con of fundamental wave (f1 = 50 Hz) and harmonics can be calculated.)