The Research On Voltage Flicker Envelope Parameters Extraction And Flicker Value Calculation Method In Complex Environment

Voltage flicker is a major power-quality(PQ) disturbance in power system. Flicker analysis is an importance issue since its presence affects the safety and efficiency of electric power systems. With widely used of the non-linear load and impact load, power system gets great pollution, voltage fluctuation and flicker are generated, the unstable factors of power grid are increasing, and serious influence is affecting the industrial production and social life. The rapid and accurate measurement of voltage fluctuation and flicker can provide a reliable scientific basis for the flicker roots and the supression and elimination of the voltage fluctuation and flicker influence.Firstly, the social and economic values of the flicker measurement are expounded, the basic concepts and evaluation indicators of voltage fluctuation and flicker are introduced. Then the sources and influence of flicker are pointed out and the advantages and disadvantages of the existing testing methods are analyzed.Aiming at the existiong problem of the rapid and accurate estimation of voltage flicker envelope parameters, the real-time errors of complex voltage flicker envelope extraction based on Teager energy operator(TEO) are analyzed, the flicker envelope demodulation process by TEO is deduced and simplified, and the error correction factor of improved Teager energy operator(ITEO) is established in this thesis. Five-term Rife-Vincent(I) window is adopted to perform weighted correction on the results extracted with ITEO, then the corrected results are analyzed and corrected with improved Chirp-Z transform, and the applicated correction formulas for the amplitudes and frequencies extracted from the voltage flicker envelope are deduced. The algorithms for voltage flicker envelope parameters estimation with ITEO and improved Chirp-Z transform are proposed and established. Compared with the Teager energy operator, the flicker envelope components are accurately extracted with the ITEO with no root operation, which not only reduces the computation but also overcomes the interferences of harmonic and interharmonic. The Five-term Rife-Vincent(I) based improved Chirp-Z transform can avoid the spectral leakage and picket-fence effect. The amplitudes of the voltage fluctuaion component can be estimated accurately by the error correction factor of ITEO. The simulation analysis show that this approach has the high accuracy of measurement and can effectively overcome the influencys of the harmonic & inter-harmonic, grid fundamental frequency fluctuation and white noise on flicker measurement results.With the voltage flicker envelope extraction method with ITEO, the algorithm for voltage flicker envelope parameters extraction based on Nuttall window spectral correction is proposed. The accuracy of improved Chirp-Z transform and improved FFT based on ITEO for parameter estimation of voltage flicker is analyzed. The voltage flicker measurement process recommended in the IEC standard is simplified. The algorithms for voltage flicker envelope real time extraction and flicker value calculation using improved Teager energy operator based on Nuttall window spectral correction are proposed and established. The simulation analysis and experiment result show that this approach can achieve the accurate measurement of complex voltage flicker envelope parameters extraction and flicker value.To verify the real time and effectiveness of the proposed method with ITEO based on Nuttall window spectral correction, a flicker online measurement platform based on ADC+DSP+ARM is builded. The signal sampling circuit, the data acquisition circuit with the core of ADS8556 and the data processing circuit with the core of TMS320C6745 are introduced in detail. Then the software flow of flicker measurement unit modules is presented. The error sources of flicker measurement is analyzed. The voltage flicker online detect platform is builded. The experiment results show that the proposed method can achieve the online and precise measurement of the voltage flicker envelope parameters and flicker value, and meet the real time and accuracy of voltage flicker parameters in embedded system.