For radar targets flying at low altitude, multiple pathways produce fade or enhancement relative to the level that would be expected in a free-space environment. In this paper, a new detec- tion method based on a wide...For radar targets flying at low altitude, multiple pathways produce fade or enhancement relative to the level that would be expected in a free-space environment. In this paper, a new detec- tion method based on a wide-ranging multi-frequency radar for low angle targets is proposed. Sequential transmitting multiple pulses with different frequencies are first applied to decorrelate the cohe- rence of the direct and reflected echoes. After receiving all echoes, the multi-frequency samples are arranged in a sort descending ac- cording to the amplitude. Some high amplitude echoes in the same range cell are accumulated to improve the signal-to-noise ratio and the optimal number of high amplitude echoes is analyzed and given by experiments. Finally, simulation results are presented to verify the effectiveness of the method.展开更多
强干扰区多类噪声时空叠加,对电磁勘探的影响严重且复杂.以往的人工源电磁(Controlled-Source Electromagnetic Method,CSEM)信号处理方法大多针对单道数据进行处理,并未考虑各道之间的相关性,从而产生非必要的误差.为此,在同步观测的...强干扰区多类噪声时空叠加,对电磁勘探的影响严重且复杂.以往的人工源电磁(Controlled-Source Electromagnetic Method,CSEM)信号处理方法大多针对单道数据进行处理,并未考虑各道之间的相关性,从而产生非必要的误差.为此,在同步观测的基础上,本文提出一种基于站间传递函数的CSEM有效信号提取方法.首先,从多域对同步观测的CSEM数据进行质量评价,优选出高信噪比的参考站;其次,基于参考站与测站之间的时域信号方差比(Ratio of variance,ROV)实现测站强干扰噪声的快速识别与定位,采用密度聚类方法(Density-based spatial clustering of applications with noise,DBSCAN)筛选出测站高信噪比数据段,并构建频率域站间传递函数;最后,考虑各道之间的相关性,利用参考站信号与站间传递函数对受强干扰时间段的观测数据进行处理,从而实现了强干扰环境下CSEM有效信号的高精度提取.通过对仿真信号与广域电磁法(Wide Field Electromagnetic Method,WFEM)实测数据的处理,验证了方法的有效性和实用性.结果表明,本文提出的基于站间传递函数的CSEM信噪分离方法不仅考虑了多道同步观测数据之间的相关性,还能在不增加野外工作量的基础上实现对有效信号的高精度提取,方法具有普适性,为CSEM同步阵列数据处理提供了一种快速、可行的解决方案.展开更多
双碳战略下,新能源电源渗透率的不断提升导致电力系统转动惯量降低,具备同步机的惯量和电压支撑能力成为并网变流器的重要运行需求。为此,首先提出了一种基于跟网型框架的功率控制型静止同步机控制策略。该策略通过参考功率点跟踪环和...双碳战略下,新能源电源渗透率的不断提升导致电力系统转动惯量降低,具备同步机的惯量和电压支撑能力成为并网变流器的重要运行需求。为此,首先提出了一种基于跟网型框架的功率控制型静止同步机控制策略。该策略通过参考功率点跟踪环和电压电流双闭环实现对同步机电压频率支撑特性的模拟。然后,建立了功率控制型静止同步机并网系统的状态空间模型,分析了控制参数对系统稳定性的影响,比较了所提控制与经典跟网型、构网型以及基于测量频率微分值(rate of change of frequency,RoCoF)的惯量控制的运行特性及适用场景。最后,基于PSCAD/EMTDC搭建的电磁暂态仿真模型验证了所提静止同步机控制策略的有效性。展开更多
基金supported by the National Natural Science Foundation of China(6137213661372134+2 种基金61172137)the Fundamental Research Funds for the Central Universities(K5051202005)the China Scholarship Council(CSC)
文摘For radar targets flying at low altitude, multiple pathways produce fade or enhancement relative to the level that would be expected in a free-space environment. In this paper, a new detec- tion method based on a wide-ranging multi-frequency radar for low angle targets is proposed. Sequential transmitting multiple pulses with different frequencies are first applied to decorrelate the cohe- rence of the direct and reflected echoes. After receiving all echoes, the multi-frequency samples are arranged in a sort descending ac- cording to the amplitude. Some high amplitude echoes in the same range cell are accumulated to improve the signal-to-noise ratio and the optimal number of high amplitude echoes is analyzed and given by experiments. Finally, simulation results are presented to verify the effectiveness of the method.
文摘强干扰区多类噪声时空叠加,对电磁勘探的影响严重且复杂.以往的人工源电磁(Controlled-Source Electromagnetic Method,CSEM)信号处理方法大多针对单道数据进行处理,并未考虑各道之间的相关性,从而产生非必要的误差.为此,在同步观测的基础上,本文提出一种基于站间传递函数的CSEM有效信号提取方法.首先,从多域对同步观测的CSEM数据进行质量评价,优选出高信噪比的参考站;其次,基于参考站与测站之间的时域信号方差比(Ratio of variance,ROV)实现测站强干扰噪声的快速识别与定位,采用密度聚类方法(Density-based spatial clustering of applications with noise,DBSCAN)筛选出测站高信噪比数据段,并构建频率域站间传递函数;最后,考虑各道之间的相关性,利用参考站信号与站间传递函数对受强干扰时间段的观测数据进行处理,从而实现了强干扰环境下CSEM有效信号的高精度提取.通过对仿真信号与广域电磁法(Wide Field Electromagnetic Method,WFEM)实测数据的处理,验证了方法的有效性和实用性.结果表明,本文提出的基于站间传递函数的CSEM信噪分离方法不仅考虑了多道同步观测数据之间的相关性,还能在不增加野外工作量的基础上实现对有效信号的高精度提取,方法具有普适性,为CSEM同步阵列数据处理提供了一种快速、可行的解决方案.
文摘双碳战略下,新能源电源渗透率的不断提升导致电力系统转动惯量降低,具备同步机的惯量和电压支撑能力成为并网变流器的重要运行需求。为此,首先提出了一种基于跟网型框架的功率控制型静止同步机控制策略。该策略通过参考功率点跟踪环和电压电流双闭环实现对同步机电压频率支撑特性的模拟。然后,建立了功率控制型静止同步机并网系统的状态空间模型,分析了控制参数对系统稳定性的影响,比较了所提控制与经典跟网型、构网型以及基于测量频率微分值(rate of change of frequency,RoCoF)的惯量控制的运行特性及适用场景。最后,基于PSCAD/EMTDC搭建的电磁暂态仿真模型验证了所提静止同步机控制策略的有效性。
