The Research Of Power Harmonic Analysis Method

In recent years,with the continuous development of power electronics technology,more and more nonlinear electronic devices have been widely used in power system,and the resulting power harmonic problem is becoming more and more serious.The existence of a large number of power harmonics will seriously affect the power quality,generate additional power loss,and even cause the safety accident of the power system.Therefore,power harmonics must be controlled,and accurate analysis of power harmonics is the premise of harmonic control.The traditional power harmonic analysis methods are mainly divided into analog circuit analysis and digital signal processing analysis.In this paper,the two methods are studied respectively.Combined with the principle of frequency selection amplification,the principle and application range of common analog filters for power harmonic analysis are analyzed,and the frequency selection amplifier circuit composed of the most widely used double T circuit is studied.The cascaded network is introduced to realize the transfer function and improve the selectivity of active power filter,and the circuit simulation is used to verify it.The shortcomings of the analog circuit in the process of power harmonic analysis are pointed out.At the same time,Fourier principle is analyzed from the orthogonal function system.Taking FFT as the representative,the digital signal processing and analysis of power harmonics are studied,and the problems and shortcomings of FFT are analyzed theoretically and proved by simulation.In this method,a fast response zero-crossing detection circuit is introduced into the sampling process and the sampling starts from the zero crossing of the power sine wave.The principle of measuring frequency with timing method and counting method is studied respectively.The timer of STM32 is used to measure the fundamental wave period,and the sampling time interval is obtained by combining sampling points.The adaptive synchronous sampling is realized by combining with zero-crossing detection circuit,and then the relevant information of harmonic signal is obtained by FFT.The method overcomes the nonsynchronous sampling error caused by frequency fluctuation of power system by precisely controlling sampling interval.It solves the problems of large volume,high cost and low precision of traditional analog circuit analysis method,and the problem of non-synchronous sampling in the process of digital signal processing and analysis.According to the actual situation of power harmonics,the corresponding power harmonics signal is designed artificially,and the simulation experiment is carried out by using adaptive synchronous sampling method,traditional FFT and traditional analog circuit analysis method respectively,and the corresponding analysis data is obtained.Through the combination of theoretical analysis and simulation,it is proved that the accuracy of the adaptive synchronous sampling method proposed in this paper is obviously better than the traditional method in the process of power harmonic analysis.