Method Of Current Measurement And Electric Energy Measurement Based On Exponential Time Domain Function

In DC distribution system,solar energy and energy storage are connected to the system through DC/DC.Voltage ripple and current waveform are often expressed as piecewise exponential functions formed by pulse width modulation.Accurate measurement of current and voltage is beneficial to protection measurement and control system and electric quantity measurement.With the improvement of IGBT’s performance,the switching frequency becomes higher and higher,and the wider modulation period is shorter.Under the limited sampling rate,the sampling points in one cycle are sparse,which brings difficulties to digital measurement equipment.In DC distribution system,when output is steady,the user side current is periodic,and when fault occurs,the transient current on the grid line is non-periodic.When measuring electric energy,the former is often taken into account,while the accurate measurement of the latter is often taken into account in relay protection.Firstly,this paper summarizes the working principle and types of DC/DC converter,analyses its output current and voltage characteristics,analyses the time-domain function and spectrum of DC/DC output and the error caused by frequency-domain calculation method,designs a calculation method based on time-domain exponential function,and puts forward the identification method of sampling points in segments,realizes the power consumption under sparse sampling.The calculation of current and voltage with high accuracy provides a reference scheme for DC system energy metering.Then,taking Buck DC/DC output energy metering as an example,the accuracy of the measurement methods based on time domain and frequency domain is compared and analyzed.In view of the large error when the duty cycle is near the extreme value.this paper proposes a method based on the holding circuit for energy meterinh and short-circuit current calculation,computing time domain parameters by peak or valley.The accuracy of the time domain calculation method before or after peak or valley is compared and analyzed.Finally.taking the Buck DC/DC circuit as an example,the value of the circuit parameters is investigated when applied to the calculation of short-circuit current.The above analysis conclusions were verified on the Matlab/Simulink simulation platfonn.