Dynamic Harmonic Analysis Method Based On Quasi-synchronous Sampling Algorithm

Harmonic analysis occupies an important role and key position in harmonic pollution, which is also the basis for the identification of metering and power quality analysis, diagnosis of high voltage insulation, compensation and suppression of power harmonic problem in the power system. Since the nonlinear interferences lead to harmonics with dynamic characteristics, it has low accuracy and poor noise immunity when adopting windowed interpolation fast Fourier transform (WIFFT) algorithm. Hence, it is of great practical and theoretic importance to study and implement a new dynamic harmonic analysis algorithm with higher accuracy and better noise immunity.This dissertation proposes a new dynamic harmonic analysis algorithm based on quasi-synchronous sampling algorithm (QSSA). Firstly, various dynamic harmonic analysis algorithms and the basic principles of QSSA are introduced. The QSSA can obtain the interested spectrum of each sampled sequence by a simple iteration procedure based on the time domain integration, and it can reduce the effect of synchronization error during the measurement by appropriately increasing the sampling period and the number of iterations.Secondly, dynamic harmonic analysis method based on QSSA is proposed according to the numerical integration in the QSSA. The workflows of dynamic harmonic analysis method based on QSSA are proposed. And comparisons of computation burden between the WIFFT and dynamic harmonic measurement method based on QSSA are presented. Variance of frequency based on the QSSA is theoretical performed. It shows that the time complexity is commonly estimated by counting the number of elementary operations performed by QSSA. And the computation burden of harmonic estimation obtained by the dynamic harmonic analysis method based on QSSA is not lower than that of WIFFT when the same sampling frequency and the same numbers of samples are used, but dynamic harmonic analysis algorithms based on QSSA greatly improved accuracy of harmonic analysis. Moreover, the variances of frequency measurement provided by proposed dynamic harmonic measurement method based on QSSA are less than that of WIFFT based on the four-item and third-order of Nuttall window (NW 4-?).Thirdly, many simulations are performed to illustrate the accuracy and noise immunity of the proposed dynamic harmonic analysis method based on QSSA with comparisons to the WIFFT based on NW 4-?, Hanning window and Hamming window. The influence of fundamental frequency fluctuations and white noise on harmonic parameters are evaluated. Compared with WIFFT based on NW 4-III, Hanning window and Hamming window, the simulation results show that the accuracy of proposed dynamic harmonic analysis method based on QSSA is higher, and the proposed method in this paper has better noise immunity.Finally, in this paper, LabVIEW virtual instrument platform achieve the proposed dynamic harmonic analysis algorithm based on QSSA. The calibration scheme for the harmonics of power system is proposed according to the national standards, i.e., GB/T 19862-2005, DL/T 1028-2006 and GB/T 15945-2008. By many calibration measurement experiments of the frequency, amplitude and phase, comparative analysis of the measurement bias before and after correction, and the measurement uncertainty of the harmonic results. The experiment results show that the proposed method can achieve the same level of accuracy as the method recommended in the national standards. Thus both simulation and experimental results have verified the effectiveness and accuracy of the dynamic harmonic analysis algorithm based on QSSA in the power system.