Research On Flicker Envelope Parameters Extraction And Interharmonic Flicker Detection Method Based On K-RV Mutual Convolution Window

With the advancement and development of science and technology,the nonlinearity,impact load and asymmetrical load of the power system are increasing,which leads to increasingly serious power quality problems such as harmonic,voltage fluctuation and flicker in the power grid.With the rapid development of smart grid construction and energy internet,continuous access to new energy sources and loads,the causes and changes of voltage flicker waveforms in complex grid environments are more complex.How to accurately detect and analyze flicker parameters in complex grid environments has gradually become a hot topic at home and abroad.The significance of the detection of voltage flicker parameters in complex grid environment is described in this thesis.And the existing methods of voltage flicker detection at home and abroad are analyzed,and the development status of the flicker meter is introduced.Combining with the characteristics of different modulation waveform of voltage flicker signal,the mathematical models of voltage flicker under sine wave and square wave modulation are constructed.The basic principle and advantages and disadvantages of several common detection algorithms are compared.By analyzing the basic principle of mathematical morphology and selecting the appropriate structure elements,a combinatorial mathematical morphology filter is constructed to filter the voltage flicker signal that contains the noises,and it is verified through simulation that the mathematical morphology filter has a good de-noising effect.On the basis of mathematical morphology filter,the voltage flicker detection method based on improved energy operator is proposed,and the calculation formula of the flicker envelope signal is deduced.This method is simple in calculation and the anti-noise performance is improved.Through the simulation and comparison experiment,the effectiveness of amplitude modulation flicker envelope extraction based on improved energy operator is verified,which provides a precondition for the accurate extraction of the parameters of the futher flicker envelope signal.Through in-depth study of the flicker detection process recommended by IEC,a flicker parameter simplification calculation procedure based on spectrum analysis is deduced.By analyzing the spectrum characteristics of various common window functions,a new K-RV mutual convolutional window function based on Kaiser window and Rife-Vincent window is constructed.The detection method of amplitude modulation voltage flicker parameters using three line interpolation FFT is proposed,which is based on the improved energy operator and new K-RV mutual convolution window.The calculation of amplitude and frequency parameters of amplitude modulation flicker envelope is derived,and the parameters detection process of amplitude modulation voltage flicker is proposed.Through the simulation experiment analysis,it is shown that the algorithm of flicker parameters measurement under the sine wave and square wave modulation has a high accuracy,which is under the circumstances of a single flicker fluctuation components,multiple frequency fluctuation components,the change of base wave frequency,and various harmonic and noise interference.Compared with common flicker detection method,this method has a higher accuracy and better adaptability,which can be used for the detection and analysis of the flicker envelope parameters generated by the amplitude modulation wave.Through the in-depth analysis of the voltage flicker effect caused by interharmonics,the model of interharmonic voltage flicker is constructed,and the influence of interharmonic component on change of voltage RMS and peak fluctuation values is analyzed,and the relationship of fluctuation frequency and fluctuation values is obtained.Through the detection error analysis of voltage flicker caused by interharmonics based on the method recommended by IEC standard,an interharmonic flicker parameter detection algorithm based on K-RV convolution window complex modulation refinement spectrum analysis is proposed.The results of simulation experiments analysis show that the proposed algorithm expands the range of flicker frequency detection caused by interharmonics compared with the method recommended by the IEC standard.It has high measurement accuracy and effectively overcomes the effects of frequency deviation of grid fundamental wave and the interference of noise,and it has better applicability.Finally,based on K-RV mutual convolution window flicker envelope parameters extraction and interharmonic flicker detection method proposed in this thesis,the virtual voltage flicker parameter detection system based on PXI and LabVIEW platform is developed.The software design flow of each module in the software system is given,and the software designs of system initialization module,data acquisition module,main program module and flicker parameter measurement module are completed,and the testing experiment of the detection system is completed,which verifies the effectiveness of the method in this thesis.