Power Quality Monitor And Analysis System

With the development of science and technology, power quality has become the most concerned issue of the world especially the developed countries. For one thing, the increasing factors which affect the power quality, for example, the distorted wave of voltages and currents caused by the extensive application of power electronic apparatus and nonlinear equipment and the frequently turning on and off of the large electricity-consumption facilities, has worsened the power quality. For another, the populsarity of the complicated, exactitude and power quality-sensitive electricity appliances, such as home appliances, office facilities, experimental facilities and auto-control facilities in the consecutive and precision production process, has made people focus on the quality and reliability of the power. The traditional monitoring technology based on the virtual value theory cannot precisely describe the power quality problem due to the much-long time window, so a new monitoring technology are wanted to meet the high-level needs.The disturbing factors (like harmonics, transient voltage fluctuation, and etc) often come up at the same time, however, the current power quality monitor, analyzing the power quality cannot give a reliable analysis of the power quality because quite a few real-time data are lost during the stops of the sampling. In order to maintain the high speed and consecutiveness of power quality monitoring, we choose DSP, CPLD and FIFO to make sampling and data analyzing work simultaneously to monitor the power quality without intervals. This paper introduces the hardware structure and software design of this power quality monitoring system,especially the process of the simultaneously data sampling and data analyzing. The periodic signal analysis this paper adopts to analyze the power quality can process and analyze most of the parameters of power quality standards as well as handle the power quality problems in a short time and long time. This paper also lists out the 2 important algorithms in the signal processing system(FFT and Digital filter). Also this paper show the process of FFT and digital filter flow and programming and points out the key part thats should be pay attention to and the most common mistakes in the programming.This paper puts forward a flicker signal measuring algorithm based on wavelet measuring for the problems existing in the flicker disturb signal monitoring. The algorithm, making use of the partial characteristics of the time-domain and frequency-domain during the wavelet well-performed period, can precisely monitor the characteristics of the transient disturbing signals. Wavelet change is considered the measurement of the starts and stops of the flicker disturbs to locate the flicker signals and then the long FFT processing of those signals with flicker component will be started. The amplitudes and frequencies with precision frequency points of the flicker disturbing signals measured by FFT will help better calculate the PCT and PLT. This paper forwards a DWT algorithm based on FFT, which is to calculate the scattered wavelet change by the core process of FFT and give out the frequency domain representing the process of high-pass and low-pass filters in the multi-resolution analysis, The result of simulation proves the reliability of the algorithm and the practical value in the current power quality monitoring system.