| Under the requirement of digital substation information digitalization,digital energy metering system has been widely deployed and constructed in substations.The error between laboratory test and actual operation of digitized electric energy metering equipment is quite different,and field faults occur frequently,In order to ensure the accuracy and reliability of digital energy metering system,this paper carries out research on laboratory detection technology and detection device of digital energy metering system.Firstly,the essential difference between digital energy metering system and traditional energy metering system is analyzed from two aspects: the composition difference between digital energy meter and traditional energy meter and the influence factors of communication link error.Packet dropping error and compensation method under point product sum algorithm are studied.Secondly,aiming at the single problem of existing laboratory testing items and testing methods for digital energy metering equipment,based on the existing standards,a multifunctional test platform for digital energy metering devices is proposed,which includes overall performance testing,analog real load testing and communication performance testing.Then,according to the three difficulties of the test platform software design,the corresponding research is carried out:(1)It is difficult to design the main frame of the test platform because of its multifunction,high coupling between test modules and complex parallel task flow,on the basis of LabVIEW multi-threading technology and synchronization technology,the main program framework based on queue-user interface events is designed,which improves the flexibility and efficiency of program flow control.(2)LabVIEW's timing control can only reach ms level,which is difficult to satisfy the us level requirement for the unpacking program to judge the loss of packets and compensate for the loss of packets.For this difficulty,LabVIEW's cross-language programming technology is studied.DLL(dynamic link library)and winpcap's underlying packet capture technology are used to realize the precise timing control of the unpacking program.(3)Aiming at the difficulty of fault location analysis and self-healing in debugging complex software,the LabVIEW error handling mechanism is studied and a special error handling subroutine is written to achieve the expected goal of error handling and reporting.After,according to the specific requirements of the software data preservation and detection algorithm of the test platform,three key points of LabVIEW database technology,FFT interpolation algorithm and real load electric energy algorithm are studied.Four thirdorder Nutall window and bispectrum interpolation FFT interpolation algorithm are adopted to ensure the accuracy of signal eigenvalue extraction,and the combination of cubic spline interpolation and numerical integration is used to improve the transient performance.Under these conditions,the accuracy of standard electric energy calculation is achieved.Finally,LabVIEW2014,MySQL and VC6.0 were used to complete the programming of the host computer software on the test platform.The system software and hardware were tested online,and the problems and solutions encountered in the test were summarized.the upper computer software is optimized from two aspects of reducing memory occupation and complexity of program block diagram.The core signal testing device such as the standard signal conversion acquisition device,the digital power source and the standard electric energy meter of the electronic input transformer and the analog input merging unit in the test platform have passed the detection of the authoritative testing mechanism.The multi-function test platform is used to carry out related testing tests on the overall performance,simulated real-life test and network communication performance of the digital energy metering system.The test results verify that the platform performance meets the design requirements. |
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