Research And Design Of Electric Energy Measurement System Based On The Pulse Current Charge For Electric Cars

Pulsed charging is one of the main ways to achieve efficient and safe charging,which has gradually been favored by people.But its application promotion has been greatly limited because of the low metering accuracy on pulsed charging energy.The main reasons for the large energy measurement error are the following: First,the rectifier equipment generates a large number of higher harmonics;Second,common transformers do not adapt to changes in pulse current amplitude and frequency,which result in large errors in pulse current measurement.In this situation,This article through theoretical research and simulation analysis of pulsed charging current characteristics of electric vehicles,master the characteristics of pulsed charging current and its influence on measurement results,designing Rogowski Coil Sensors for Pulsed Charging Current Measurement and Electric Energy Metering System.The main research contents and conclusions are as follows:First of all,the change curve of pulsed charge current was analyzed,which starting from the best charging curve and rectifying equipment for common power batteries,Summarizes the characteristics of pulsed charging current amplitude and frequency,and its effect on current measurement;Further,analysis the high-order harmonic changes in the pulsed charging process and its effect on energy metering by establishing a pulsed charging rectifier simulation model.A method of pulsed charging energy metering scheme for electric vehicles is proposed to design different harmonic power calculation methods for the two different conditions of steady state and unsteady state of the measured current waveform.Then,the equivalent circuit model of Rogowski coil is established,which based on the principle of mutual inductance.Simulated and analyzed the influence of Rogowski coil's own parameter changes on its own amplitude frequency and phase frequency characteristics with used MATLAB software.At the same time,according to the design flow,the size of the cross-section of the Rogowski coil,the coil capacitance and inductance parameters,the number of turns of the coil,and the termination resistance are designed and improved.Third,the electric energy metering system suitable for pulsed charging piles has been designed,which based on an improved Rogowski coil.The hardware part mainly includes Rogowski coil current transformer,voltage sensor,signal processing circuit,high frequency AD conversion and sampling circuit,as well as power metering modules based on the embedded TMS320F2812 chip,etc.The Rogowski coil current transformer accurately reflects the pulsed charging current amplitude and frequency;The software part mainly includes metrology system main program,data reading module,and electric energy measurement module,etc.Among them,AD high-frequency sampling module can quickly obtain charging current and harmonic current.The energy metering module mainly measures the active energy and the harmonic energy respectively,eliminating the influence of harmonic power on the overall energy metering,thereby improving the accuracy of energy metering.Finally,the measurement and test system of current transformer were designed and built.It found that Rogowski coil current transformer performance measurement can reach 0.2S level indicators through the analysis of experimental results.This shows that the designed current transformer can adapt to pulse current amplitude and frequency variation.Further,through the Error Analysis and Synthesis,the calculation results show that the accuracy of the energy metering system can reach 0.5,which can be used for pulsed charging piles for energy metering.