Research On Characteristics Of Low Voltage Power Line Communication Channel

Power line communication (PLC) is a way of communication that using power lineas a medium for voice and data transmission. The technology has been widely used byelectric power company in the automatic management in electric network. However,affected by factors in power line environment such as high noise, impedance mismatch,transmission loss and time-varying characteristics, the data transfer rate of power linecarrier-current communication is restricted. Because of lack of sufficient research, therestill have some problems which have effected on the protocol development andtechnology selection. This dissertation aims to study the characteristics of low voltagePLC channel. Setting up the time-varying model of noise channel and dispersivechannel based on the parameters which getting from the typical grid environment andelectrical equipment. Providing efficient tools for the study of channel characteristicsand evaluating performance of systems.Firstly the dissertation analyzes the key influence factors of channel transmissioncharacteristic based on the transmission theory. The line attenuation, multipath effectand the typical multipath model of power line channel are researched. Then the specificmeasurement schemes for different channel parameters are proposed, the test circuitsand program are carried out. The noise, signal attenuation and input impedance weremeasured. According to the analysis of these data, some conclusions were given that thenoise amplitude of same sampling instant obeys the normal distribution in AC cycle andthe distributions of narrowband decline seem to be the same without considering lineimpedance. Based on the analysis of the collected data and theoretical derivation, themodeling method of power line noise and fading channel are researched in depth. Thepower line noise are classified into three categories and the model are established whichrestore the cyclic stationary characteristics of noise. According to the characteristics thatchannel attenuation is affected by varying impedance, the time-varying impedancemodels are established. A periodic time-varying channel model is put forward based ontwo-network theory. Finally, the thesis analyzes the influence of different power gridenvironment on transmission characteristic and capacity of channel after the model is testified. A communication simulation experiment is carried out, the performance ofsystem are also analyzed.The dissertation researched the modeling methods of the cyclic stationary noiseand periodic time-varying fading channel based on the measurement and analysis oftime-varying characteristic of power line channel. The channel model is presentedwhich can simulate the periodic time-varying of power line channel. The thesis providesa reference and tool for further research of power line channel and communicationtechnology.