Research On Electric Power Quality Monitoring System And Algorithm

Power quality technology is an interdisciplinary and pioneering subject. With the development of power system and the progress of science and technology, some power quality problems are from bad to worse. Researches about power quality monitoring are more and more attached importance to overseas and domestic experts, scholars, and electric power personnels. Based on the the thoughts of networking and computerization, this thesis studies and develop the electric power quality montoring in lower computer(based on double dsp data capture and compression Communications System) and upper computer(center administration host computer). The detailed researches are as follows:1. Research on the need for power quality monitoring, introduced the study device status and the concept and classification of power quality. Describes the algorithm for power quality monitoring, comparising of the continuous Fourier transform, discrete Fourier transform and fast Fourier transform. Describes the definition and characteristics of the dynamic, pointed out the dynamic can deconstruct the signal based on structural features, to find out the distortion point and identify power quality transient disturbances.2. Proposed Ethernet-based power quality monitoring system architecture model. The system uses two DSP as its core, Realized the real time data acquisition and transmission, as well as flash memory storage. In the part of data acquisition,using anti-aliasing filter circuits and phase-locked frequency circuit to make sure correctness and completeness; in the part of data transmission, using CAN bus transfer to relize data transmission with high speed based on Ethernet and TCP/IP protocol, in the part of flash memory storage, record real-time field data completely, realize data storage offline. The upper computer is designed for data reception, power quality data analysis, database storage and man-machine interface.3. Prepared the algorithm of power quality monitoring system. Write FFT program codes, to analyze the real-time voltage and current signal, painted the figure of harmonic component contains rate distribution, completed the unbalanced three-phase degree program; Write the algorithm of Dyn codes, to analyze the real-time voltage signal, paint the figure of Dyn, completed the sag and frequency deviation program; write RMS program codes, to analyze the real-time voltage signal, completed the voltage deviation and fluctuation program.4. Introduced the upper computer functions of the power quality monitoring system. Write a communications part program, using serial port and network Ethernet communications technologies, to realize data classification transmission According to the practice; design the database and write the connection program, to realize data mass storage and classification; design man-machine interface, make staff for easy operation system and management data.5. Introduces the minimum and slope point Dyn measure in the application of power quality perturbation analysis. A method for disturbance parameter estimation was presented based on the Dynamics of minimum point and the slope of distortion point. A novel algorithm to detect Dynamics and three characteristic quantities were derived. The three quantities can be used in parameter estimation of disturbances with lower computational load and real-time computing. Simulation results show this monitoring method is feasible by using the parameters estimation of single disturbance or mixed disturbance of voltage sags, oscillatory transients and the notches. It also shows the effectiveness of the method.