| With the promotion of the construction of smart grid and new power system by the state,the proportion of large-scale access to power grid of clean energy and new loads will show a rapid growth trend.As a result,a large number of new power quality problems,such as voltage fluctuation and flicker,are generated,which brings new challenges to the existing IEC flicker detection.New power system is developing towards high proportion of new energy and high proportion of power electronic equipment.The random load fluctuation of the power grid signal on the generation side and the power consumption side becomes larger,and the interaction between diversified power electronic equipment and the power grid will make more broadband and high-frequency harmonics/interharmonics in the power grid signal,and most of them are unstable.Voltage fluctuations and flicker in complex power grid environments have undergone obvious changes in terms of participants,fluctuation forms and flicker effect mechanisms,which make the analysis and detection of voltage fluctuations and flicker effects more complex,and bring major tests to the balance regulation and flexible operation of power systems.The inapplicability of IEC recommended flicker meters,voltage flicker parameter detection under sine wave and rectangular wave modulation,interharmonic flicker detection and unsteady voltage flicker parameter detection methods are studied in this paper,so as to meet the needs of voltage flicker parameter signal detection in complex power grid environments.An embedded online test platform for complex voltage flicker parameters based on synchronous ADC+high-speed DSP+ARM structure and a virtualized complex voltage and voltage flicker parameter system based on PXI bus and virtual instrumentation are developed.The main research contents is as follows:(1)In order to improve the measurement process and scope of IEC flicker,the possible limitations of flicker parameter detection and flicker value calculation are discussed from the aspects of the inapplicability of IEC flicker to interharmonic flicker,the unapplicability of detection under different lamps and the imapplicability of IEC flicker to rapid voltage change,aiming at the application of IEC flicker detection principle in new power system.The characteristics of voltage fluctuations caused by interharmonics were explored from the fluctuation of rms value and peak voltage fluctuation caused by interharmonics.The influence of rapid voltage change amplitude,fluctuation slope and fluctuation time on flicker is analyzed,and the non-applicability of IEC flicker standard is studied..(2)Aiming at the problems of spectrum leakage and low detection frequency resolution of flicker envelope signal in spectrum analysis under asynchronous sampling,an accurate estimation method of sinusoidal modulation voltage flicker envelope parameters based on analytical mode decomposition(AMD)and windowed three-point interpolated Chirp-Z transform(WICZT)is proposed.A high resolution inter-harmonic flicker detection algorithm based on double windowed three point interpolated Chirp-Z transform(DWICZT)is proposed.Firstly,the filtering link in square detection method is improved by using analytical mode decomposition,and the flicker envelope extraction model based on analytical mode decomposition is constructed to effectively avoid spectrum aliasing.Then,based on the improved Chirp-Z transform of six term maximum sidelobe attenuation window,the extracted flicker envelope is estimated by tri spectral line interpolation spectrum,and the required frequency resolution is adaptively adjusted to improve the detection accuracy of sinusoidal modulation voltage flicker signal.In order to meet the requirements of high precision and high resolution detection of interharmonic flicker parameters,a high resolution interharmonic flicker detection algorithm based on DWICZT is constructed on the basis of sinusoidal flicker envelope analysis algorithm.Through simulation and analysis of flicker signals in complex environments and comparison with traditional flicker detection algorithms,the results show that the algorithm proposed in this chapter can effectively suppress the influence of various interferences,improve the accuracy of flicker parameter analysis,and suppress the measurement error caused by asynchronous sampling deviation and flicker waveform parameter changes,which is better than traditional detection methods,and is suitable for high accuracy and high resolution flicker analysis.(3)According to the characteristics of multi-turn of rectangular flicker envelope and flicker parameter detection under rectangular modulation,a flicker parameter detection method based on new central difference improved Teagle energy operator(CD＿ITEO)and K-SMSD cross-convolution window with three spectral lines interpolation FFT is proposed.The improved new symmetric differential energy operator can improve the accuracy of voltage flicker wave component extraction under rectangular wave modulation effectively.A new K-SMSD cross-convolution window function is constructed.Based on the improved FFT of three spectral lines,the flicker parameters are detected and the calculation formulas of amplitude and frequency of flicker envelope components are derived.The detection process of voltage flicker parameters under rectangular modulation model is proposed in this paper.Through simulation experiment analysis,the flicker parameter measurement method under rectangular wave modulation proposed in this paper has high accuracy under single frequency and multi frequency rectangular wave modulation,and can effectively overcome the influence of fundamental frequency variation and various harmonics and noise interference.Compared with some traditional flicker detection algorithms,the algorithm proposed in this paper is easy to implement,with high real-time detection accuracy and strong anti-interference,meeting the requirements of accurate detection and analysis of rectangular modulation flicker parameters in complex power grid environment.(4)Aiming at the problem that the time-varying amplitude and frequency of unsteady flicker components make it hard to accurately detect parameters,an unsteady flicker envelope extraction model based on analytical mode decomposition is established.It is proposed to construct the energy difference ratio method by reconstructing the relationship between signal energy and original signal energy,and combine the loss coefficient to obtain the number of decompositions,decompose the unsteady amplitude modulation wave flicker envelope signal into multiple submode components containing only a single frequency,and finally find the instantaneous amplitude and frequency curve and instantaneous curve of the submodal component by Hilbert transform,and establish Analytic-Adaptive based on analytic mode decomposition and adaptive variational mode decomposition Variational Mode Decomposition(AAVMD)is a time-frequency analysis method for unsteady voltage flicker parameters.Simulation and comparison experiments show that the proposed method can not only accurately extract the flicker parameters of unsteady amplitude modulation wave,but also reflect the time-frequency characteristics of the signal,have strong anti-interference ability,and timevarying voltage flicker can be realized effectively.(5)An embedded complex voltage flicker parameter online detection experimental platform based on synchronous ADC + high-speed DSP + ARM structure and a virtualized complex voltage and voltage flicker parameter system based on PXI bus and virtual instrumentation are developed,and the basic principle,overall framework,hardware design and software design and workflow of the two experimental platforms were introduced in detail,and the test experiments of the two detection platforms were completed.The measurement results and error analysis show that the measurement accuracy of the flicker-related parameters of the designed platform meets the predetermined requirements,and can effectively realize the high-precision measurement of various voltage flickers in complex power grid environments. |
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