| Electric energy is the most widely used energy in modern society.The vigorous development of high-precision industries and the increasingly sophisticated power equipment undoubtedly put forward higher requirements for the stability and reliability of power quality.Therefore,it is of great research significance to accurately calculate the power parameters and accurately analyze the power quality,so as to provide a reference for the management of the power system.Empirical wavelet transform,as an emerging branch of current power parameter time-frequency detection,has achieved many achievements in engineering signal analysis due to its excellent adaptability and low computational complexity,which provides power quality detection new ideas.In conclusion,based on the background of the power analyzer project,this thesis studies the calculation method of electric energy parameters based on the theoretical basis of Improved Empirical Wavelet（IEWT）and Hilbert transform（HT）.（1）For the defects of empirical wavelet and Hilbert transform: the number of sampling points is limited by the integer power of 2,the high-order harmonics are seriously polluted by noise,the detection of similar frequency components has modal aliasing,and the jitter phenomenon of Hilbert spectrum.To improve the above defects,in this thesis propose an IEWT-HT algorithm.By using Cooley-Tukey mixed-base FFT algorithm,spectrum boundary continuation,transition boundary parameter optimization and Hilbert spectral line smoothing.Experiments show that the IEWT-HT algorithm is closer to the actual needs of the power analyzer,has higher accuracy,and also has significant improvements in anti-noise and anti-aliasing;（2）In view of the defect that the traditional Fourier detection method cannot provide the time-frequency characteristics of the signal,and the traditional threshold method disturbance detection cannot extract the components of the signal,this thesis applies IEWT-HT to the disturbance signal detection.The IEWT is used to decompose the modal components of the signal adaptively,and HT is used to solve the instantaneous amplitude and frequency of each component of the signal.Therefore,the spectrum leakage defect of the traditional detection method can be effectively avoided.At the same tine,the IEWT-HT can also accurately detect each component of the signal.At the same time,based on the definition of electrical energy parameters in IEC standard,this thesis proposes to apply IEWT-HT to the calculation of electrical energy parameters.According to the instantaneous amplitude and frequency of each frequency component of the signal detected by IEWT-HT,this thesis realizes the calculation and detection of various instantaneous power parameters such as active power and power factor;（3）Finally,tihis thesis build a experimental platform,formulate the power analyzer architecture of FPGA+DSP+PC,design the corresponding transmission and storage calculation scheme based on the project development goals.Lastly,the verification experiment is carried out on the experimental platform of power analyzer.The results show that the detection accuracy of the IEWT-HT algorithm proposed in this thesis is as follows: the detection error of harmonic/interharmonic is within 2%;the detection error of flicker factor and flicker frequency is within 1.5%;stationary or nonstationary electrical energy The detection errors of the parameters are all within 1%.To sum up,it can be proved that the IEWT-HT electric energy parameter calculation method has has high accuracy and good adaptability.And IEWT-HT proposed in this thesis meets the requirements of project development and industry standards. |
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