| As the infrastructure of power system,electric energy metering device is the basis of energy transaction between power supplies and users.The 10 kV integrated energy metering device has the advantages of small volume and light weight relative to the traditional metering device,which is the trend of the future metering device.In recent years,the problem of harmonic distortion is becoming more and more serious due to the increase of nonlinear load in the power grid.Therefore,it is necessary to study the harmonic transfer characteristics of the 10 kV integrated power metering device.The 10 kV integrated energy metering device designed in this paper consists of three parts: voltage,current mutual inductance and measuring terminal.The metering terminal adopts the ADE7878,a professional energy metering chip produced by ADI company,as the voltage and current acquisition and data processing part.The ADE7878 chip is embedded a fixed-function digital signal processor and the processed data is stored in the chip internal register.The chip can simultaneously measure the fundamental and total electric energy.The total electric energy is the sum of fundamental and harmonic energy.The harmonic energy data can be obtained by measuring the total electric energy and subtracting the fundamental electric energy.The simultaneous measurement of the fundamental wave energy and the harmonic energy increases the adaptability of the metering device.The harmonic transmission characteristics of the current and voltage channels of the 10 kV integrated metering device are modeled and simulated respectively.The PSCAD simulation software is used to establish the J-A simulation model of LPCT,and the frequency characteristics of LPCT and the current preprocessing circuit of the metering terminal are studied.Based on the simulation results,the current preprocessing circuit is improved.The influence of stray capacitance and temperature coefficient of resistance on the resistor-divider transformer is simulated and analyzed.The results show that the frequency response of the resistor-divider transformer satisfies the requirement of harmonic measurement.The frequency characteristics of the voltage channel preprocessing circuit are simulated by frequency response method.Based on the analysis results,some improvements are proposed for the design of the voltage channel circuit.Based on the simulation analysis,the laboratory test of the transmission characteristics of 10 kV integrated electric energy metering device was carried out.The frequency characteristic of the metering terminal part is tested.Combined with the simulation analysis,the software phase compensation method is proposed to improve the harmonic propagation characteristics of the device.The total power and the fundamental power of the measuring device were calibrated respectively.The test results show that the accuracy of active power for this device is 0.5S level under the fundamental condition,which meets the requirements design.It proves that the method of software phase compensation improved harmonic transfer characteristics of the device without affecting the accuracy of the fundamental measurement. |
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