Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we use...Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we used a coincident-loop and central loop type of configuration, where the coil plane l） vertical to and 2） parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudes. The result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled. When the excavator is 6 m from the observatory, the interference of tunneling machine can be ignored.展开更多
The denoising and detection of transient disturbances are two important subjects for power quality monitoring and analysis. To effectively denoise and detect transient disturbances under noisy conditions, an improved ...The denoising and detection of transient disturbances are two important subjects for power quality monitoring and analysis. To effectively denoise and detect transient disturbances under noisy conditions, an improved iterative adaptive kernel regression method is proposed in this paper. The proposed method has advantages that itdoes not need to estimate the noise variance or a filter threshold, and has both denoising and detection capabilities for transient disturbances. Simulation results demonstrate that the proposed method provides excellent denoising effects, which can not only suppress noise effectively but also preserve disturbance features of sudden change points well. Additionally, it provides good detection and location performance for single and combined transient disturbances, even under strong noise conditions. Finally, the effectiveness of the proposed method is further verified by using real disturbance data.展开更多
由于无法辨析并网点(point of common coupling,PCC)电压跌落的本质原因,光伏电站低压穿越(low voltage ride through,LVRT)控制与现有的孤岛保护在同时满足动作条件时缺乏选择性,影响系统的安全稳定。为研究与光伏LVRT相互协调的孤岛...由于无法辨析并网点(point of common coupling,PCC)电压跌落的本质原因,光伏电站低压穿越(low voltage ride through,LVRT)控制与现有的孤岛保护在同时满足动作条件时缺乏选择性,影响系统的安全稳定。为研究与光伏LVRT相互协调的孤岛检测方法,根据孤岛现象和电压暂态扰动现象发生时PCC谐波电压的差异,提出一种基于光伏并网点谐波电压突变的无功功率扰动孤岛检测方法。该方法在检测到PCC处的谐波电压突变后,经40 ms延时,对光伏逆变器输出的无功电流采用基于PCC频率变化量函数进行扰动,使PCC频率超出正常范围,实现孤岛检测功能。仿真结果表明:方法在保证与LVRT协调配合的前提下能在较短时间内完成对光伏电站孤岛状态的检测;此外在故障特征量较小的工况下方法依然可靠适用,消除了传统孤岛检测方法盲区的同时保证了孤岛检测的准确性。展开更多
The ability to evaluate the testability of digital circuits before they are actually implemented is critical for designing highly reliable systems. This feature enables designers to verify the fault detection capabili...The ability to evaluate the testability of digital circuits before they are actually implemented is critical for designing highly reliable systems. This feature enables designers to verify the fault detection capability of online as well as offline testable digital circuits for both permanent and transient faults, during the design stage of the circuits. This paper presents a technique for transient and permanent fault injection at the VHDL level description of both combinational and sequential digital circuits. Access to all VHDL blocks a system is straight forward using a specially designed single fault injection block. This capability of inserting transient and permanent faults should help in evaluating the testability of a digital system before it is actually implemented.展开更多
基金support received from the National Basic Research Program of China (No2007CB209400)the National Natural Science Foundation of China (No50774085)the Young Scientists Fund of the School Science Foundation of CUMT (No2008A046)
文摘Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we used a coincident-loop and central loop type of configuration, where the coil plane l） vertical to and 2） parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudes. The result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled. When the excavator is 6 m from the observatory, the interference of tunneling machine can be ignored.
基金supported in part by the NationalKey R&D Program of China (No. 2016YFB1200401, No. 2017YFB1201103)in part by the Program for Application of Cophase Power Supply Technology (No. 2018002)
文摘The denoising and detection of transient disturbances are two important subjects for power quality monitoring and analysis. To effectively denoise and detect transient disturbances under noisy conditions, an improved iterative adaptive kernel regression method is proposed in this paper. The proposed method has advantages that itdoes not need to estimate the noise variance or a filter threshold, and has both denoising and detection capabilities for transient disturbances. Simulation results demonstrate that the proposed method provides excellent denoising effects, which can not only suppress noise effectively but also preserve disturbance features of sudden change points well. Additionally, it provides good detection and location performance for single and combined transient disturbances, even under strong noise conditions. Finally, the effectiveness of the proposed method is further verified by using real disturbance data.
文摘由于无法辨析并网点(point of common coupling,PCC)电压跌落的本质原因,光伏电站低压穿越(low voltage ride through,LVRT)控制与现有的孤岛保护在同时满足动作条件时缺乏选择性,影响系统的安全稳定。为研究与光伏LVRT相互协调的孤岛检测方法,根据孤岛现象和电压暂态扰动现象发生时PCC谐波电压的差异,提出一种基于光伏并网点谐波电压突变的无功功率扰动孤岛检测方法。该方法在检测到PCC处的谐波电压突变后,经40 ms延时,对光伏逆变器输出的无功电流采用基于PCC频率变化量函数进行扰动,使PCC频率超出正常范围,实现孤岛检测功能。仿真结果表明:方法在保证与LVRT协调配合的前提下能在较短时间内完成对光伏电站孤岛状态的检测;此外在故障特征量较小的工况下方法依然可靠适用,消除了传统孤岛检测方法盲区的同时保证了孤岛检测的准确性。
文摘The ability to evaluate the testability of digital circuits before they are actually implemented is critical for designing highly reliable systems. This feature enables designers to verify the fault detection capability of online as well as offline testable digital circuits for both permanent and transient faults, during the design stage of the circuits. This paper presents a technique for transient and permanent fault injection at the VHDL level description of both combinational and sequential digital circuits. Access to all VHDL blocks a system is straight forward using a specially designed single fault injection block. This capability of inserting transient and permanent faults should help in evaluating the testability of a digital system before it is actually implemented.
