Non Synchronous Sampling Reactive And Harmonic Algorithm Of The Power System Under Study

The design principle of the existing power meter is based on the sinusoid circuit theory, and this kind of power meter is only suitable for the measurement of linear load electric energy of which voltage and current waveform is orthoscopic. However, along with the swift growth of non-linear elements in the power system, the sinusoidal circuit power theory has gradually presented unsuitability. This paper studies the measurement algorithm of the reactive energy and Harmonic analysis by using the quasi-synchronization.The reactive energy measurement plays an important role in power system. Several prevalent methods such as digital phase shift method, integration method and Hilbert transform method for reactive power measurement are introduced in this paper. The measuring error and the methods of correcting the error are also analyzed. The feasibilities of the hardware and software based on these methods are discussed simply.The estimation of electrical harmonic parameters by using the quasi-synchronization and interpolated FFT are emphatically introduced in the harmonic measurement. The main factor of spectral leakage is conducted when the sampling is non-synchronous. The computing formulas for the harmonic parameters are given based on the features of Hanning Window and Blackman Window. The computing formulas are given based on the method of quasi-synchronization as well.The simulation results show that the four measurement methods of reactive power of sinusoidal circuit are more accurate when the harmonic content of voltage and current is small. Finally, the accuracy and reliability of the algorithm are analyzed, combining their frequency characteristics and phase characteristics.All the three measurement methods will reduce the spectrum leakage significantly. Some suggestion is proposed for the practical use of the algorithms, based on the accuracy, the error characteristics changing with frequency, and the practicability.Eventually, based on the low-voltage reactive power compensation projects, the hardware system of the harmonic and reactive energy measurement is emphasized on, and the real reactive and harmonic measurement is introduced as well.