Research On Integrated Measurement Method Of AC-DC Mixed Field Based On Pockels Effect

With the development of smart grid,parallel AC and DC lines or erected on the same tower are becoming more and more common,and it is difficult for traditional voltage transformers to meet the requirements of integrated AC and DC electric field measurement.Optical electric field sensing system has the advantages of high electric field isolation,high sensitivity,small size,non-contact and wide frequency band,so the development of optical electric field sensor has a wide range of prospects.Therefore,this paper synthesizes the advantages and problems of optical electric field sensors,explores the hybrid field integration measurement method,improves the electric field distribution around the electro-optical crystal of the optical sensor,and proposes a processing algorithm for non-smooth signals.Firstly,based on Pockels effect,the sensing model of rotating optical electric field is established by using Jones calculation method of polarized light system.Based on the sensing model,the measurement methods of rotating optical DC electric field,AC electric field and AC-DC mixed field are analyzed and obtained.Based on the theoretical model,the finite element simulation module was established to verify the validity of the sensing model and measurement method.Secondly,to address the problem that the electric field inhomogeneity affects the measurement accuracy,an electric field distribution model around the BGO crystal is established,an evaluation index to characterize the electric field homogeneity is proposed,the factors influencing the electric field distribution homogeneity of the BGO crystal are analyzed,and an optimized structure of the electro-optical crystal of the optical sensor is proposed,and the feasibility of the proposed optimized structure is verified by simulating and calculating the change of electric field homogeneity before and after its optimization.Then,to solve the problem of high-frequency noise interference,an optical electric field signal filtering algorithm based on extended Kalman filter is proposed.On the basis of filtering out the interference wave,in order to accurately obtain the output signal amplitude at different frequencies,the Hilbert spectrum of the original output signal of electric field measurement is analyzed based on the Hilbert-Huang empirical mode decomposition,and the measurement scheme at different frequencies is given.Finally,an experimental platform for the integrated measurement of optical AC-DC mixed field is built.The AC field and DC field calibration experiments are carried out separately,and the AC-DC mixed field is simulated in the actual environment for measurement,and the correctness of the theoretical derivation and structural optimization is verified by the AC-DC integrated measurement experiments.