Error Analysis For Digital Energy Metering System Based On IEC 61850

With the strategic objective of developing "strong smart grid",our country comprehensively promote smart grid construction.Based on the characteristics of high accuracy and strong anti-jamming capability,digital energy metering system has been large-scale application.In practical application,semi-digital energy metering system widely used in intelligent substation,it is consist of traditional transformer,analog signal input merging unit and digital watt-hour meter.At present,the results of digital energy metering is still rarely used for gateway settlement.As digital power metering belongs to new technology,there are some controversy in the theory of traceability,detection technology and error source.This paper will study the analog signal input merging unit and digital watt-hour meter in electric energy metering system,and analyse error sources of the new digital measuring instrument.First,briefly introduce communication standards between the substation automation equipment.Describe the ASCI model of sampling value transmission and the mapping of IEC 61850-9-2(LE)in digital energy metering.Analyse the influence of sampling value transfer process to digital energy metering.Analysis of the Error Source for analog signal input merging unit.The influence of an typical 16 bits ADC to proportional error is researched via SNR.The chip satisfy the accuracy requirement of 0.2S level.A/D Chipset with more than 16 bits and higher SNR is recommended.Analyse Dc offset error in merging unit,find that the measurement is affected when the load is low or the power factor is small.Dc offset error should be eliminated.The quantization error introduced by IEC 61850-9-2LE protocol is researched.The relative uncertainty formula of RMS and active power is derived,we find that the quantization error of IEC 61850-9-2LE is only relative to the quantity of primary current and voltage.It can be ignored for the current/voltage level in actual substations.Manufacturer should standardize the output signal of merging unit,testing agency should standardize testing process of digital watt-hour meter.Analysis of the Error Source for digital watt-hour meter.The measurement performance of the numerical integration algorithm is analyzed,Simpson integral algorithm is compared to dot product and algorithm.It is found that Simpson integral algorithm has higher measuring accuracy than dot product algorithm in the condition of dynamic distortion waveform.Research harmonics measurement accuracy,the dot product the algorithm can accurately measure the harmonics,when harmonics can sample 3 points and above in each cycle.Research on sampling value missing error and compare of commonly used handling method,it is found that Newton three times forward interpolation is the optimistic method between performance and simplicity.To build digital watt-hour meter error test platform,carry out harmonic error test and sampling value missing test,which proves the correctness of theoretical derivation and simulation analysis.