Frequency measurement with high accuracy and method for harmonics identification in polluted distribution power networks

As demands for high quality, reliability and usability of electrical power source are increasing and essential, many studies investigate algorithms of harmonic source detection. To evaluate the quality of electrical network, a method for fundamental frequency and harmonics characteristics with high accuracy is proposed. The interest of this work is to control the stability, safety and efficiency of an electrical network with fast and accurate estimation of the fundamental frequency and harmonic distorsion. In practical cases, the fundamental frequency is considered uncertain. Its deviation induces large perturbation on high range harmonics. To alleviate this drawback, we consider the fundamental frequency as an uncertain frequency and suggest a method to evaluate its value with high degree of accuracy. From this correct numerical value of the fundamental frequency, all magnitude and phase of harmonics are estimated with higher precision. Thus, this paper deals with the identification of fundamental frequency and selective harmonic identification. The method developed is derived with the Fourier series for fundamental frequency and on the Discrete Fourier Transform (DFT) for harmonics. Outset, we will focus just on the first coefficient of the Fourier series not to perform the magnitude and phase, but to explain a condition that allows to reach the real value of fundamental frequency. The algorithm is an iterative one. The result is presented in continuous case and in discrete case. After, the DFT method is applied to obtain magnitude and phase of fundamental and harmonics. The simulation and experimental results show the ability of the developed algorithm.