The Research Of Harmonic Active Power Measurement Based On Non-integer Period Sampling

The electrical energy is the main source of energy both to national economic and the lives of the people. Electrical energy measurement datas affect economic benefits of power generations, power supplies and power consumers. Large-scale of applications of non-linear loads in power system such as power electronic devices have brought a great deal of power system harmonics, which lead voltage and current waveforms to deviate from the sine wave to distortion. As grid frequency fluctuating, electrical energy measurement equipments can not be achieved strictly interger-period sampling, therefore the study for harmonic active power measurement with non-integer period sampling gets a growing concern.The main study of the dissertation is harmonic active power measurement with non-integer period sampling signals to seek the rational method of measurement as base frequency is not ideal 50Hz. Above all, the dissertation discusses the importance of electrical energy measurement in economic trade, describes the common existence of harmonics and their serious harms, and then analyses the harmonic impact on energy measurement. Through the research to active power measurement of linear load users and nonlinear load users in harmonic environment including background harmonic source and nonlinear load, the dissertation analyzes the error source of active power measurement and the influence on active power measurement.Secondly, influence to harmonic active power measurement caused by non-integer period sampling signals has been discussed. Conventional calculation formulas of active power is only suit to be used in interger-period sampling signals. The effect caused by the same frequency and different frequency voltage and current harmonic singals due to frequency windage of non-interger-period sampling signals to active power measurement is studied. Beginning with the basic definitions of active power, calculation formulas of the active power and it's error in time domain for various harmonic signals is developed. To measure fundamental frequency power and harmonic power separately and exactly, develop calculation formulas of the active power in frequency domain for various harmonic signals, and it's a feasible and effective method for harmonic active power measurement. The calculation formulas have been testified by Matlab simulation using example simulation.Finally, to meet the requirements of accuate measurement of harmonic active power with non-integer period sampling signals, interpolation of parabolic in time domain FFT, ,interpolation of Hanning windows FFT, interpolation of Blackman windows FFT, interpolation of Rife-Vincent(Ш) windows FFT have been used in this dissertation. Measurement of harmonic frequency, amplitude and initial phase are the basis for the calculation of harmonic active power, the harmonic parameters measurement technology has affected the development of harmonic active power measurement. The algorithm of interpolation of hanning windows FFT reduce the spectral leakage error and the interference between harmonics. The algorithms have been tested by simulation soft, simulation results show that signal amplitude and phase calculation achieve higher accuracy using the algorithms of interpolation windows FFT, and the algorithms can reduce errors of spectral leakage caused by non-integer period sampling. They are feasible and effective methods both for harmonic analysis and harmonic active power measurement. Interpolation of Blackman windows FFT, interpolation of Rife-Vincent(Ш) windows FFT have been used in this dissertation to meet the requirements of high accuate measurement.