Interharmonics Detection Algorithm Based On Windowed Interpolation FFT And Atomic Decomposition

In recent years,inter-harmonic content in power system is bigger and bigger along with the use of power electronic devices and the increasing of the impact loads.Besides the integer harmonic harm,inter-harmonic can cause voltage flicker and problems such as zero drift,it has brought serious influence to the power quality and threatened the safe and economic operation of power system,so it's imminent to manage the inter-harmonic problem.,In order to suppress and govern inter-harmonic and improve the environment of power supply,ensure the normal working of power supply equipment,we must accurately detect the parameters of inter-harmonic and analysis it's signal.Theory and the basic form of Fourier transform are analyzed firstly in this article,FFT algorithm is the commonly used method of harmonics inter-harmonic detecting because the simple algorithm and small amount of calculation.But problems such as spectrum leakage and fence effect will appear because of the unsynchronized of samples which make FFT error of detection increase.To solve these problems,use add window interpolation algorithm is proposed by scholars to improve the detection accuracy.However,because of the limitation of the frequency resolution,add window interpolation is not applicable for the detection between similar frequency signals.Then,atomic decomposition algorithm of detecting harmonic and inter-harmonic signals is proposed in this paper.Two key problems of Atomic decomposition is how to build the library of atoms and find the best matching atoms,in view of the low matching degree between commonly used Gabor atoms and the signal characteristics of inter-harmonic in sparse decomposition,the method using sine atoms to build a complete library is put forward;because the larger amount of calculation by using matching pursuit algorithm to find the best atomic,discrete parameter is optimized in order to reduce amount of calculation.The atomic decomposition algorithm is well suitable for harmonic and inter-harmonic analysis and detection after being improved and optimized which laid a theoretical foundation for the algorithm.Hybrid algorithm was proposed finally after combining the advantages of window interpolation and atomic decomposition algorithm,and the steps of the algorithm implementation are also introduced in detail in this paper.Signals truncated by Hanning window is analyzed through FFT,amplitude of three spectrum lines near the real spectrum are obtained,and then judge whether existing line interference by the spectral interference criterion,finally chose the inter-harmonics detection algorithm according to the judgment.Simulation result shows that the algorithm can not only reduce the calculation of atomic decomposition algorithm,but also make up for the resolution deficiency of the add window interpolation,namely the algorithm can obtain between harmonic parameters when the frequency of harmonic and inter-harmonic is very close.