Research On Detection Algorithm Of Power Harmonics And Inter-harmonics Based On Windowed Interpolation ApFFT

With the development of power system to the direction of complexity and intelligence,as well as the impact of the increasing depletion of traditional fossil energy and the deterioration of environmental problems,together with the increasing proportion of new and complex loads such as new energy generation,impact load and electric vehicle connected to the power grid,a large number of nonlinear loads and power electronic equipment are applied to the power system.After these nonlinear loads and power electronic equipment are connected to the power grid,a large number of harmonics and inter-harmonics are generated in the system,which will not only pollute the entire electrical environment,but also cause the distortion of voltage and current waveforms,and then reduce the power quality.In serious cases,it will cause the misoperation of relay protection devices and control equipment,which is not conducive to the stable operation of the power system.Therefore,in order to ensure the safe,economic and efficient operation of the power system,it is of great practical significance to effectively detect harmonics and inter-harmonics for the treatment of power quality harmonics and inter-harmonics.In the treatment of power quality problems caused by harmonics and inter-harmonics,the primary goal is to detect the harmonic and inter-harmonics components in voltage or current distortion signals,specifically to detect the frequency,amplitude and initial phase of the harmonic and inter-harmonics components.This paper will combine the theory of apFFT spectrum analysis and single spectral line interpolation method of the traditional FFT to analyze and detect the harmonic and inter-harmonic signals,and provide some ideas and methods for improving power quality and controlling harmonic and inter-harmonic.Accurate detection of harmonic and inter-harmonic components in power distortion signal is the key to effectively control harmonic and inter-harmonic and improve power quality.Thus,based on the comparison of several typical window functions(such as Hanning window,Blackman window,Nuttall window and five-term Rife-Vincent I window),in view of ideal sidelobe characteristics and the progressive attenuation rate of the sidelobe of the five-term Rife-Vincent I window,a spectrum correction method based on the single peak spectral lines interpolation of five-term Rife-Vincent I convolution window apFFT is proposed,which is used in the detection of power harmonics andinter-harmonics.In the case of asynchronous sampling,the proposed method utilizes the main spectral line near the theoretical frequency point of each component in the measured signal to correct the frequency spectrum,so as to estimate the frequency value of the fundamental,harmonic and inter-harmonic components in the measured signal.At the same time,according to the phase invariability of the apFFT phase spectrum,the initial phase estimation can directly take the phase value of the main spectral line.Finally,combining the derived frequency correction and the amplitude spectrum of five-term Rife-Vincent ? convolution window apFFT,the amplitude of each component in the measured signal is inversely derived.Through a large number of simulation verification and comparative analysis with the existing methods proposed in some literatures,the proposed method can detect more accurate parameters of power harmonics and inter-harmonics,and the algorithm also has higher detection accuracy under strong white noise interference.The proposed method provides a practical and effective method for accurate detection of power system harmonics and inter-harmonics parameters.