Research On Interharmonic Flicker Parameters Detection And Flicker Value Calculation Method Based On DMD

With the rapid development of power electronics and new energy technologies,a large number of shock and nonlinear devices have been put into use,re sulting in increasingly voltage fluctuation and flicker phenomenon.Flicker detection has become an important link to ensure power quality.In the existing flicker measurement studies,IEC61000-4-15 recommended by the International Electrotechnical Commission(IEC)is generally used as the basis.However,the standard is aimed at the flicker effect caused by amplitude modulation waves in the incandescent lamps.Due to the development of technology,on the one hand,all kind of new lighting equipment is used more and more widely,incandescent lamp has been gradually phased out;On the other hand,in addition to periodic load fl icker sources,interharmonics generated by various power electronic devices are injected into the power grid,causing flicker.Because flicker mechanism and research object are changing,how to accurately detect and evaluate flicker caused by interharmonics in power network environment has become an urgent problem to be solved.In this thesis,the background and significance of the research on interharmonic flicker are discribed firstly,and then the research status of flicker effect caused by interharmonic and the interharmonic flicker detection methods at home and abroad is explained.Combining with the principle of interharmonic flicker,the mathematical model of interharmonic flicker is constructed.The fluctuation frequency and envelopment characteristics of the voltage signal which contains interharmonic are analyzed,then the effects of single inter-harmonic,a pair of interharmonics and multiple interharmonics on the effective value and peak value are analyzed one by one.On the premise that interharmonic can lead to voltage peak value and voltage effective value fluctuation,which can cause flicker,from the perspective of signal modulation theory,the interharmonic parameters caused by voltage fluctuation and the voltage fluctuation parameters caused by interharmonic are deduced.By studying the quantitative relationship between interharmonic and flicker,the relationship between them is revealed.To solve the problem that it is difficult to accurately detect the relevant parameters by the existing traditional methods of interharmonic flicker parameter evaluation,a method of interharmonic flicker parameter detection based on dynamic mode decomposition is proposed.Hankel matrix is constructed for discrete interharmonic flicker voltage data.The principle of dimensionality reduction of data by eigendecomposition decomposition and singular decomposition is studied,and then using the singular value decomposition to calculate voltage data collection mapping matrix between the matrix of optimum low-dimensional approximation of A matrix.As for the choice of the number of singular values K,the singular value truncation method based on the frequency component of interharmonic flicker signal is determined.After the optimal low-dimensional approximation matrix is obtained,the optimal low-dimensional approximation matrix is eigendecomposed to obtain different DMD modes,so as to calculate the amplitude and frequency of different components in the interharmonic flicker signal,at the same time,the specific flow chart of parameter detection is given.The simulation results show that the proposed method has good detection accuracy on the conditions that the voltage singles coatain single interharmonic flicker component,multiple interharmonic flicker components,dense interharmonic flicker components,fundamental frequency offset and noise pollution.In the comparison experiment with the other commonly used detection methods,it reflects the superiority of the method in this thesis in terms of accuracy,which lays the foundation for the improvement of the subsequent IEC flicker detection method.By introducing the IEC flicker detection method,its limitations in detecting interharmonic flicker are analyzed.Aiming at the characteristics of non-incandescent lamps that are sensitive to peak fluctuati on,combined with dynamic mode decomposition interharmonic flicker parameter detection method,an improved flicker detection method is proposed on the basis of IEC,and the interharmonic fl icker value calculation method is further derived,what’s more,a preliminary study on the sensitivity of different non-incandescent lamp to interharmonic is conducted.Simulation results show that compared with the IEC method,this method can evaluate the flicker severity caused by high frequency interharmonic in non-incandescent lamps without affecting amplitude modulation flicker detection.Finally,based on the dynamic mode decomposition interharmonic flicker parameter detection and flicker value calcula tion method,an interharmonic flicker parameter detection and flicker value calculation system based on PXI+Lab VIEW is built to realize system login,data acquisition,interharmonic flicker parameter detection,flicker value calculation,report printing and other functions.The software solutions of different functional modules are elaborated.Through the experimental analysis on the platform,the feasibility of th e method is verified.