谐波阻抗扫描是高压直流输电(HVDC)中谐波谐振分析、交流或直流滤波器设计等工作的重要手段。采用电路叠加定理说明了适用于HVDC谐波阻抗扫描的测试信号法。基于测试信号法基本原理及其在HVDC应用研究中的进展,提出测试信号法应用于HVD...谐波阻抗扫描是高压直流输电(HVDC)中谐波谐振分析、交流或直流滤波器设计等工作的重要手段。采用电路叠加定理说明了适用于HVDC谐波阻抗扫描的测试信号法。基于测试信号法基本原理及其在HVDC应用研究中的进展,提出测试信号法应用于HVDC谐波阻抗扫描的谐波源幅值选择方法和用于减小谐波源初相位影响的改进扫描方法。最后,以CIGRE First Benchmark模型为例,在PSCAD/EMTDC仿真平台上定量分析了谐波源幅值、谐波源初相位对谐波阻抗扫描的影响,以验证所提出的方法可用于进一步提高HVDC谐波阻抗扫描结果的可靠性,为实际直流输电工程设计提供参考。展开更多
The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group＇s s...The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group＇s sweep to terminate. The cycle time can be reduced drastically and hence the production efficiency can be increased significantly but harmonic distortion of one sweep will leak into the record of the other sweep. In this paper, we propose an anti-correlation method for removing harmonic distortion in vibroseis data. This method is based on decomposition of the ground force signal into fundamental and harmonic components. Then the corresponding anti-correlation operator can be computed to estimate the energy of each harmonic after correlating the vibroseis data with the corresponding harmonic component. Finally, the vibroseis harmonic noise to be removed can be obtained by subtracting the extracted harmonic noise from the traces of the previous group＇s sweep. The advantage of the proposed method is that it can process both uncorrelated and correlated vibroseis seismic data. Moreover, the algorithm is simple, stable, and computationally fast. Especially, the significant contribution of this method is a considerable reduction in the harmonic without any alteration of the desired signals. The method was tested on both synthetic and field data sets to validate the good harmonic noise suppression results.展开更多
We recently proposed a new class of wavelength-swept lasers for swept-source optical coherence tomography （SS-OCT）. It uses the same gain medium with the conventional swept lasers, but does not require any tunable f...We recently proposed a new class of wavelength-swept lasers for swept-source optical coherence tomography （SS-OCT）. It uses the same gain medium with the conventional swept lasers, but does not require any tunable filters. It is based on a principle called ＂dispersion tuning＂, in which a highly dispersive medium is inserted in the laser cavity, and loss/gain modulation is applied to mode-lock the laser. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent work on the application to the SS-OCT system.展开更多
文摘谐波阻抗扫描是高压直流输电(HVDC)中谐波谐振分析、交流或直流滤波器设计等工作的重要手段。采用电路叠加定理说明了适用于HVDC谐波阻抗扫描的测试信号法。基于测试信号法基本原理及其在HVDC应用研究中的进展,提出测试信号法应用于HVDC谐波阻抗扫描的谐波源幅值选择方法和用于减小谐波源初相位影响的改进扫描方法。最后,以CIGRE First Benchmark模型为例,在PSCAD/EMTDC仿真平台上定量分析了谐波源幅值、谐波源初相位对谐波阻抗扫描的影响,以验证所提出的方法可用于进一步提高HVDC谐波阻抗扫描结果的可靠性,为实际直流输电工程设计提供参考。
基金supported by the Sinopec Service Company and China National Petroleum Corporation
文摘The slip-sweep technique is one of the high-efficiency, high-fidelity, and environmental vibroseis seismic prospecting techniques which consists of a vibrator group sweeping without waiting for the previous group＇s sweep to terminate. The cycle time can be reduced drastically and hence the production efficiency can be increased significantly but harmonic distortion of one sweep will leak into the record of the other sweep. In this paper, we propose an anti-correlation method for removing harmonic distortion in vibroseis data. This method is based on decomposition of the ground force signal into fundamental and harmonic components. Then the corresponding anti-correlation operator can be computed to estimate the energy of each harmonic after correlating the vibroseis data with the corresponding harmonic component. Finally, the vibroseis harmonic noise to be removed can be obtained by subtracting the extracted harmonic noise from the traces of the previous group＇s sweep. The advantage of the proposed method is that it can process both uncorrelated and correlated vibroseis seismic data. Moreover, the algorithm is simple, stable, and computationally fast. Especially, the significant contribution of this method is a considerable reduction in the harmonic without any alteration of the desired signals. The method was tested on both synthetic and field data sets to validate the good harmonic noise suppression results.
文摘We recently proposed a new class of wavelength-swept lasers for swept-source optical coherence tomography （SS-OCT）. It uses the same gain medium with the conventional swept lasers, but does not require any tunable filters. It is based on a principle called ＂dispersion tuning＂, in which a highly dispersive medium is inserted in the laser cavity, and loss/gain modulation is applied to mode-lock the laser. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent work on the application to the SS-OCT system.
