Research On The On-line Power Quality Monitoring System

With the vigorous development of the national economy and constantinnovation of science and technology, some nonliner, impact application equipmentwith rich harmonic begin to pour into power systems, enterprises and users arepaying more and more attention to the power quality problems caused by this. At thesame time, their requirments to power quality are also increasing. Therefore, in orderto achieve long-term, real-time online monitoring of power system under high-pressure environment, a set of power quality monitoring system with features ofhigh-speed acquisition, multi-index analysis, high-precision monitoring and strongcomputing and processing capabilities is needed to be developed.In this paper, power quality monitoring system consists of data acquisitionmodule, the data transmission module and the host computer’s LabVIEW datacalculation section, among these, data acquisition module and data transmissionmodule belong to the hardware design section of the monitoring system. Thehardware part take the sensor, A/D conversion chip, FPGA EP3C25master chip aswell as high-pressure-resistant fiber optic transceivers as the core, power qualitythree-phase voltage, current data acquisition and digital signal5B6B encoding anddecoding uploading are achieved. The software part is designed based on theLabVIEW platform, it adopted parallel processing method against multi-channel dataand completed the processing of basic power quality parameters, steady-stateparameters and transient parameters.In the high-voltage power supply system, there is a need to implement theisolated transmission of the signal between the high-voltage main circuit and control,measurement systems, fibre isolated transmission can not only meet the electricalrequirements of high voltage insulation, but also has a strong anti-electromagneticinterference capability. On the characteristics of the fiber itself, this paper uses5B6B encoding and decoding method to solve the digital signal’s transmission problems infiber-optical. Firstly, the software calculating part calculated the signal phase voltage,line current, power and other parameters according to the basic parameters’measurement principle. Secondly, according to the requirements of the steady stateparameters, software analyzed and processed the voltage deviation, frequencydeviation, phase unbalance, voltage fluctuations and flicker, and implementedvoltage harmonic’ analysis and monitoring by FFT; In order to eliminate noise andrealize accurate positioning of the starting and ending time of the disturbance signal,the signal denoising is completed by wavelet scale space algorithm and realizeddenoised signal’s disturbance positioning by means of wavelet modulus maxima.The system is capable of real-time monitoring of power quality problems in thepower grid under the environment of high-pressure, and has faster processing speed,higher monitoring precision, and provides scientific and accurate data support toimprove power quality problems, it has good and practical application prospect.