Researches On The Frequency Characteristic Of MV Electronic Voltage Transformer Based On The Principle Of Capacitive Voltage Divider

The existence of non-linear loads in traditional power system,the use of the new power semiconductor devices and the parallel operation of the distributed energy source,inject a large number of harmonics into the power grid,which has great influence on the power quality of the power grid.At present,the substation mainly uses the traditional electromagnetic voltage transformer and the capacitive voltage transformer to measure the bus voltage directly,but its response bandwidth can not cover the harmonic frequency range in the power grid.In this paper,a capacitive voltage type electronic voltage transformer(ECVT)based on coaxial capacitance structure is studied to realize the measurement of the harmonic voltage in the bandwidth of the required frequency.The capacitive voltage divider of the coaxial capacitor has the ideal response bandwidth,and the mathematical model of the voltage sensor is established by designing the capacitive voltage divider of the coaxial capacitance divider structure which satisfies the medium voltage voltage class insulation requirement.In the low-voltage arm capacitor on the parallel resistance,the sensor transfer function that the output voltage is measured once the voltage differential,through the integrated circuit to restore the measured voltage.According to the structure and theoretical model of the measurement system,the influence of the structural parameters,the parallel resistance and the integral circuit parameters on the system bandwidth is analyzed,and the parameter design to meet the requirements of the frequency band is obtained.The electric field distribution of the sensor and the influence of the adjacent phase are analyzed by ANSYS simulation platform,which shows that the sensor has strong anti-interference ability.The experimental results show that the ECVT based on the coaxial capacitance structure satisfies the expected target in the harmonic bandwidth of 5 kHz,in addition to satisfying the fundamental linearity requirement.