本文针对高压直流输电(high-voltage direct current,HVDC)工程中交流滤波电容器桥差保护电流表测量值异常偏大的问题展开研究。理论分析与现场实测表明,因电流表测量导线与电容器塔、导线与地面以及导线之间存在杂散电容,且导线对地布...本文针对高压直流输电(high-voltage direct current,HVDC)工程中交流滤波电容器桥差保护电流表测量值异常偏大的问题展开研究。理论分析与现场实测表明,因电流表测量导线与电容器塔、导线与地面以及导线之间存在杂散电容,且导线对地布线存在物理不对称,引起差模干扰,导致不平衡电流测量值大于真实值。研究建立了杂散电容的等效电路模型,推导了测量误差的计算公式,并分析了杂散电容对测量结果的影响程度。为精确量化杂散电容参数,基于COMSOL Multiphysics软件构建了电容器塔与测量导线的高保真三维静电场模型,为误差分析提供了关键输入。最后结合新疆哈密某±800 kV特高压直流工程实例,通过现场试验验证了理论分析的正确性,并提出以采集电压替代电流的方案,实现不平衡电流的等效测量。展开更多
This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike...This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.展开更多
文摘本文针对高压直流输电(high-voltage direct current,HVDC)工程中交流滤波电容器桥差保护电流表测量值异常偏大的问题展开研究。理论分析与现场实测表明,因电流表测量导线与电容器塔、导线与地面以及导线之间存在杂散电容,且导线对地布线存在物理不对称,引起差模干扰,导致不平衡电流测量值大于真实值。研究建立了杂散电容的等效电路模型,推导了测量误差的计算公式,并分析了杂散电容对测量结果的影响程度。为精确量化杂散电容参数,基于COMSOL Multiphysics软件构建了电容器塔与测量导线的高保真三维静电场模型,为误差分析提供了关键输入。最后结合新疆哈密某±800 kV特高压直流工程实例,通过现场试验验证了理论分析的正确性,并提出以采集电压替代电流的方案,实现不平衡电流的等效测量。
基金supported in part by the National Key Research and Development Program of China under Grant 2022YFB3207301Shandong Provincial Natural Science Foundation under Grant No.ZR2024ZD08.
文摘This paper proposes a differential mode measurement and control system(DMCS)for differential MEMS resonant accelerometer(DMRA),which operates the differential resonators of the DMRA at different vibration modes.Unlike traditional DMRA,the first resonator of the differential resonator operates in the first-order mode(R1M1),and the second resonator operates in the second-order mode(R2M2).Within the measurement range of DMRA,the frequencies of the two resonators will not cross,so there will be no mutual interference.This ensures the structural symmetry of the DMRA while avoiding the measurement dead zone phenomenon caused by the coupling of the differential vibration beam at similar resonant frequencies.The structural symmetry of the differential resonator ensures good temperature consistency of the differential vibration beam,and the consistency of the temperature frequency coefficient matches well,which enables the differential resonator to strongly suppress the temperatureinduced common-mode effects.During the temperature cycling process between-20℃ and 80℃,the equivalent acceleration drift of R1M1 and R2M2 were 341.6 mg and 414.6 mg,respectively.After using the differential temperature compensation algorithm,the equivalent acceleration drift was reduced to 1.19 mg.The minimum Allan variance measured statically at room temperature decreased from 1.42μg@0.85 s for R1M1 and 1.52μg@0.85 s for R2M2 to 0.23μg@7.15 s,indicating a significant improvement in the long-term stability of DMRA.In addition,the differential measuring method also eliminated common mode ambient noise in low frequency range,ultimately achieving a noise level of 220 ng=ffiffiffiffiffi Hz p@(0.2–0.8 Hz)for a prototype device with a measurement range exceeding±5 g.
