Research On Synchronous Control Method For Combined Verification Power Supply Base On Ultra-High Voltage Current Transformer

With the development of UHV power grid in China,in order to ensure accurate measurement and protection design,more and more attention has been paid to the calibration system of UHV gas insulated enclosed(GIS)current transformer.In order to make the current transformer calibration system of GIS maintain high accuracy in wide voltage range,this paper presents a combined calibration power supply scheme with the advantages of digitalization,large capacity,wide voltage and high precision.This scheme adopts a combined power supply structure in series between power electronic power supply and electrical power supply,in which power electronic power supply adopts single-phase full-bridge inverter structure.With the power frequency power supply,the structure can complete the functions of coarse and fine tuning,which can meet the requirements of UHV current transformer calibration for power supply voltage regulation accuracy and voltage regulation.In order to make the electrical power supply work normally under the condition of voltage distortion,this paper studies the phase-locked method when the frequency of power grid fluctuates.It can lock the phase of positive sequence fundamental voltage quickly and accurately.An improved second-order generalized integrator phase-locked loop is adopted and simulated.It is concluded that the phase-locked loop can track the phase of power grid accurately under the condition of voltage distortion.In view of the control strategy of combined power supply,a control strategy based on PR controller is proposed.Because of the fluctuation of(±0.5Hz)in the grid frequency,a frequency adaptive PR controller is added to the control strategy.Finally,the experimental verification is carried out on a 200 kVA combined power supply calibration prototype.The experimental results show that the frequency adaptive PR controller can make the power electronic power supply output high-precision voltage waveform and keep the frequency and phase synchronization with the electrical power supply at all times.The output voltage of the combined power supply is stable and reliable,and can be used as the calibration power supply of UHV GIS current transformer.