The Research And Realization Of Power System Harmonic Monitoring And Analysis System Based On Internet

Power quality is an increasing concern for utilities and their commercial and industrial electrical power users. One of the most common power quality problems of today is due to power systems harmonics. With the development of modern electronic technology and the wide use of nonlinear loads such as television receives, personal computers and thristors for controlling electric motors, lamps and heaters in recent year, the problem concerning harmonic in power supply system becomes serious. Therefore, to cancel the harmfulness of harmonics and handle harmonic pollution, it is greatly necessary to real-time monitor and analyze harmonics, and determine clearly each order of harmonics.A usual method of harmonic monitoring and analysis from distorted waves is the FFT algorithm. However, this method has the limitation that it requires more than two cycles of samples, so harmonic monitoring is delayed and it is impossible to real-time determine the harmonics.Now artificial neural network (ANN) has got special attention to the researchers because of its simplicity, learning and generalization ability and it has been successfully applied in the fields of engineering, business and economy. Among the different neural network algorithms, Back Propagation (BP) neural network is the most widely used supervised learning algorithm, which is well known for its learn ability and high speed recognition, This paper applies BP neural network to monitor each harmonic from distorted waves. Neural network approach is used the partial association of neural network. By providing the sequentially samples of distorted wave to neural network, the components of each order harmonic will be monitored to each corresponding unit in output layer. In order to demonstrate the effectiveness of neural network, the magnitude and phase of 3rd and 5rd harmonic components are monitored by means of Matlab simulation. Form the simulation results it is seen that ANN is a more effective, efficient, reliable and simple method, compared with FFT algorithm.In this paper, an equipment of harmonic monitor and analysis based on internet technology is designed. This equipment, which has a high efficient CPU board, an intelligent sampling card based on DSP and GPS interface, is designed based on Windows9X operational system by applying VC++. It can provide two main functions, namely, daily and special harmonic monitoring and analysis. It can perform harmonic monitoring, analysis and statistic on line in real time and out ofline, and also realize harmonic concentrated monitoring, supervision and synthetic handling at different places in the same power supply system or in the different power supply system by using internet communication technology base on Client/Server.Finally, the simulation experiment is made by Real-Time Digital Simulation (RTDS). The results show that the measuring system has high accuracy and reliability. It can satisfy the general and real time needs of power systems harmonic monitoring.