The Research On Harmonic Detection Algorithm Of Active Power Filter

As one of the most widely used power, the quality of electric energy and stability of power system has became an important symbol of a country’s social and economic stability and rapid development. Nowadays, a large number of non-linear equipment is applied to many industries, which is the main reason for the harmonic generation of electric current distortion. With the development of science and technology, the high precision load and the new equipment of high technology are also requesting to improve the quality of power network. In this paper, the harmonic detection algorithm based on active power filter is studied. The application of active power filter is an effective way to improve the power quality of the power grid. In this paper, the active power filter in points under the way of compensation, harmonic detection algorithm is studied and compared, and aims at the problems existing in the traditional method, to be improved.First, this paper mainly introduces the reasons and harms of the harmonic and the commonly used detection methods, including Fourier transform method, Goertzel Fourier transform, synchronous rotating coordinate system, Fourier transform combined with the wavelet transform method and Hopfield neural network,which analyzes the advantages and disadvantages of these methods.Secondly, when the Fourier transform harmonic detection algorithm sampling frequency is stable, and the current frequency changes, it is easy to increase the frequency leakage and make the steady-state error, and it Lead to large amount of calculation too. so the goertzel Fourier transform method is proposed based on a modified RDFT method of harmonic detection method. Verifing the method’s effectiveness by computer simulation.Thirdly, analysising the basic principle of synchronous rotating coordinate system method of harmonic detection.Get the multi module harmonics detection model based on the single module. In order to solve the problems of interaction between the single modules, an improved harmonic detection algorithm is proposed after changing the structure of algorithm. It is filtering out the effect of the fundamental and lowing order harmonic on the results, and improving the detection accuracy. Verifing the method’s effectiveness by computer simulation.Last, harmonic detection algorithms of multiple modules in parallel for three phase system are simulated under the condition of stable load current stability, the mutation of load current’s amplitude, the mutation of load current’s frequency. For improved harmonic detection method based on Fourier transform method,when the current frequency does not change, it has the highest steady-state accuracy, when the frequency is changed, it will appear the steady-state error in a certain frequency interval.For the improved synchronous rotating coordinate system, it can be used in the three kinds of load current conditions in this paper, and the dynamic response speed is fast.