Design Of Field Calibration System For Multifunctional Watt-hour Meter

At present,the field of smart grid is in a period of rapid development.Electric energy occupies a very important position in people’s daily life,and smart watt hour meter is an important part of the development of smart grid.China has a large number of electric energy meters and has a clustered distribution mode.The traditional centralized calibration cost of returning to the factory is high,and the phenomenon of false inspection and missed inspection will occur when the meter calibrators use the on-site calibration method.Many calibration systems fail to meet the requirements of calculation accuracy and real-time performance,and the cost is high.At the same time,the calibration data of electric energy meters are huge,recording data manually will cause the problem of copying wrong data.Therefore,it is very necessary to design an on-site calibration system of electric energy meter which can accurately detect the electric energy meter has high precision,has the functions of GPS positioning,bar code identification and data remote transmission.The on-site calibration system of electric energy meter designed in this thesis takes STM32F407ZGT6 as the processing core,converts the large voltage and current signal in the power grid into small signal through the front-end signal sampling and conditioning module,filters and amplifies it,and then converts the processed signal to analog-to-digital through the signal sampling module,and transmits it to STM32F407ZGT6 core processor for data analysis and processing.Aiming at the shortcomings of the traditional fast Fourier transform algorithm（FFT）,the windowed interpolation FFT algorithm is used to further improve the measurement accuracy of electrical parameters.The power is converted into pulses by the power frequency conversion module,and the error of the calibrated watt hour meter is calculated by the pulse comparison method.In order to avoid missed detection of electric energy meter,GPS positioning module is added to the system to obtain various information of meter calibration place and time,and the verification results and positioning information are fused and uploaded to the cloud service platform based on Nb-IOT wireless communication technology.The cloud service platform realizes data transmission with the mobile phones of on-site staff and the PC of the remote management system.At the same time,the bar code recognition function is added to the Android application end to record the ID of the calibrated energy meter and upload it to the server.The PC side of the remote management system stores the verification information through the cloud platform server and My SQL database.Users can log in to the management system through the web page and query the verification data of electric energy meter.After the completion of the system,the measurement accuracy of various electrical parameters is tested for the system,and then the calibration function of the electric energy meter is tested and analyzed.From the test results,it can be seen that the accuracy of the corrected multi-functional electric energy meter on-site calibration system has reached level 0.1,which meets the expected requirements,and fully proves the feasibility of the multi-functional electric energy meter on-site calibration system.It is suitable for on-site calibration of household electric energy meters and some industrial instruments.