Design And Realization Of Three Phase Unbalance Monitoring Device For Low Voltage Distribution Network

At present,low voltage distribution network almost uses10kV/0.4kVtransformers to supply power for consumers in our country. Single phase loadand three phase load are included in the network. Because of load’sinhomogeneous distributinon, three phase unbalance is long existence in lowvoltage distribution network.And due to the distribution automation level is nothigh, this problem is unable to get timely improvement. If distribution networkruns under the situation of three phase unbalance for long time, power supplyand consumption would get adverse effect.So it is required to develop a threephase unbalance monitoring device to help power supply department adoptreasonable control measure. The main of this paper’s research contents are asfollows:(1) The current three phase unbalance status in low voltage distributionnetwork in our country is introduced. The necessity of the development of threephase umbalance monitoring device is pointed out. At the same time the currentresearch about the algorithm of three phase unbalance and the monitoring deviceof three phase unbalance is introduced; (2) The basic theory of three phase unbalance is discussed, and lays thetheoretical foundation for the development. The overall design of three phaseunbalance monitoring device is proposed, and the various core hardwaremodules are analysed, and the programming idea about software is determined;(3) This paper introduces the mixed radix FFT algorithm in detail,including the calculation process of the algorithm and its implementation in DSP.At the same time, the method is successfully applied in the three phaseunbalance monitoring device, which expands the scope of application of thetraditional FFT algorithm.(4) Three phase unbalance monitoring device’s hardware mainly includessignal conditioning module, analog-to-digital conversion module ADS8364, dataprocessing module TMS320F2812and GPRS wireless communication moduleEM310.The working principle of each module, caveats, and the hardware circuitdesign are introduced in detail.(5) Three phase unbalance monitoring device software design is introducedin detail in accordance with the modular programming idea, software driverprogram is written for each hardware module. the DSP main programdesign,EM310module driver program design,ADS8364driver programdesign,data processing program design and the FLASH programming are mainlyincluded;(6)Three phase unbalance monitoring device is debugged and trailed underthe condition of laboratory to verify the accuracy and reliability of the device; Furthermore,the monitoring device is installed in the low voltage distributionnetwork to conduct the24-hour monitoring, and the data are transferredwirelessly to the data center through GPRS and analyzed in detail.Analysisresults show that the three phase unbalance monitoring device can accuratelyreflect the three phase unbalance the change of three phase voltage and threephase current in power distribution network.