| The High-Power Testing Center at the Institute of Plasma Physics of the Chinese Academy of Sciences is the largest direct current test platform in China,which is mainly responsible for test of various kinds of power supply equipment for the international cooperation project ITER(International Thermonuclear Experimental Reactor).Based on the operation and current output characteristics of ITER electrical test platform,this paper studies the large direct current long pulse digital Rogowski sensor.The main contents and innovation points of this paper are as follows:Aiming the application of ITER electrical test platform,corresponding model structure is established by analyzing the structure parameters and circuit parameters of the Rogowski coil,and the influence of different coil cross-section parameters on mutual inductance error is discussed.The error caused by the return structure is analyzed,and the formula of minimum return structure error is given to reduce the vertical magnetic field interference of the test platform.According to the coil circuit model,the influence of load resistance on the measurement of direct current long pulse is discussed.The research contents provide theoretical guidance for the design of Rogowski coil.In viewing difficulty of measuring large direct current long pulse current,the structure characteristics of analog and digital Rogowski integrator are compared and analyzed.The drift characteristics of integrator under long working time are emphatically studied,and the formula for calculating drift error of integrator is given.The corresponding error solving measures are put forward from two aspects of structure and integral algorithm.At the same time,based on the developed digital Rogowski sensor,a dual-channel sampling sensor structure is proposed to solve the problem of large direct current long pulse current drift.The analysis results show that the structure can eliminate the direct current bias in the sensor and overcome the integral drift caused by the change of the device parameters in the long time work,and the problem that common Rogowski sensor cannot measure the large direct current long pulse current in the ITER electrical test platform is solved.Aiming at the strong interference problem of ITER electrical test platform,the source and transmission path of interference noise are studied from two angles of magnetic field interference and electric field interference,and the noise conduction model is proposed.According to the model,calculation and simulation are carried out,which provides a theoretical reference for the design of anti-interference sensor.Furthermore,according to the polarity characteristics of interference noise,the structure scheme of bipolar composite coil is proposed.The results show that the structure can effectively reduce the amplitude of interference noise and solve the problem that Rogowski sensor cannot be used in the test platform.The noise characteristics and differential signal are studied in detail,aiming the problem that the measurement accuracy of sensor is decreased due to interference noise.According to frequency distribution difference between the noise and the differential signal,a composite filter structure of comb notch filter combined with high and low pass filter is proposed.The experimental results show the proposed scheme is effectively filter the noise,smooth the output current waveform,and improve the measurement accuracy.According to the application requirement of ITER electrical test platform,a large direct current long pulse digital Rogowski sensor is developed.Finally,experimental results show that the digital sensor has high sampling accuracy,good repeatability and small drift error for measuring large direct current long pulse current.The maximum current can satisfy 130kA,the maximum precision is 0.2%and the longest direct current pulse measurement time is 1200s.Compared with the same type of Rogowski sensor,the measurement performance of large direct current pulse current is better than domestic level. |
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