Single-photon avalanche diodes(SPADs)are the most widespread commercial solution for single-photon counting in quantum key distribution applications.However,the secondary photon emission that arises from the avalanche...Single-photon avalanche diodes(SPADs)are the most widespread commercial solution for single-photon counting in quantum key distribution applications.However,the secondary photon emission that arises from the avalanche of charge carriers that occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the transmission key.In this paper,we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and temporal characterization for different detector models and different operating parameters.We qualitatively bound the maximum information leakage due to backflash light and propose solutions for preventing such leakage.展开更多
平均光强分布是自由空间激光通信(Free Space Optical Communication,FSOC)性能分析中的一个重要参数,非零均值不等方差的跟踪误差场景下平均光强分布理论的封闭表达式尚未得出。采用统计平均的方法对非零均值不等方差跟踪误差下的平均...平均光强分布是自由空间激光通信(Free Space Optical Communication,FSOC)性能分析中的一个重要参数,非零均值不等方差的跟踪误差场景下平均光强分布理论的封闭表达式尚未得出。采用统计平均的方法对非零均值不等方差跟踪误差下的平均光强分布进行建模并推导出其理论的封闭表达式,通过蒙特卡洛模拟对所推导的结果进行验证。在非零均值不等方差跟踪误差的影响下,高斯光束的平均光强分布廓线的形状和中心位置均发生变化。此外,采用相同面积的方形接收孔径代替圆形接收孔径,推导出非零均值不等方差跟踪误差下的平均接收功率。该工作能为非零均值不等方差跟踪误差下的自由空间激光通信系统性能分析和链路设计提供理论指导。展开更多
针对可再生能源通过电力电子设备并人电力系统,导致电网系统强度减弱,物理惯性降低的问题,文章提出一种适用于柔性直流输电(Modular Multilevel Converter Based High Voltage Direct Current,MMC-HVDC)连接弱交流系统MMC内部能量控制...针对可再生能源通过电力电子设备并人电力系统,导致电网系统强度减弱,物理惯性降低的问题,文章提出一种适用于柔性直流输电(Modular Multilevel Converter Based High Voltage Direct Current,MMC-HVDC)连接弱交流系统MMC内部能量控制的组网控制策略。在下重组网控制的基础上,加入惯性环节和PI控制环节,使得MMC能够自动跟踪负荷变化调整自身功率输出,实现对交流电压和频率的无差调节。针对组网控制的MMC内部能量波动较大的问题,设计了一种MMC内部能量补偿控制策略,该策略能够有效降低子模块电容电压波动。最后,基于PSCAD/EMTDC电磁暂态仿真平台建立MMC-HVDC系统,并选取交流系统负荷增加、负荷减少两种工况,验证了所提控制策略的可行性和有效性。展开更多
基金funding from the European Union’s Horizon 2020the EMPIR and EMRP Participating States in the contexts of the projects EXL02 SIQUTE and 14IND05 MIQC2,respectivelysupport from FIRB Project No.D11J11000450001 funded by MIUR and from the NATO SPS Project 984397.
文摘Single-photon avalanche diodes(SPADs)are the most widespread commercial solution for single-photon counting in quantum key distribution applications.However,the secondary photon emission that arises from the avalanche of charge carriers that occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the transmission key.In this paper,we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and temporal characterization for different detector models and different operating parameters.We qualitatively bound the maximum information leakage due to backflash light and propose solutions for preventing such leakage.
文摘平均光强分布是自由空间激光通信(Free Space Optical Communication,FSOC)性能分析中的一个重要参数,非零均值不等方差的跟踪误差场景下平均光强分布理论的封闭表达式尚未得出。采用统计平均的方法对非零均值不等方差跟踪误差下的平均光强分布进行建模并推导出其理论的封闭表达式,通过蒙特卡洛模拟对所推导的结果进行验证。在非零均值不等方差跟踪误差的影响下,高斯光束的平均光强分布廓线的形状和中心位置均发生变化。此外,采用相同面积的方形接收孔径代替圆形接收孔径,推导出非零均值不等方差跟踪误差下的平均接收功率。该工作能为非零均值不等方差跟踪误差下的自由空间激光通信系统性能分析和链路设计提供理论指导。
文摘针对可再生能源通过电力电子设备并人电力系统,导致电网系统强度减弱,物理惯性降低的问题,文章提出一种适用于柔性直流输电(Modular Multilevel Converter Based High Voltage Direct Current,MMC-HVDC)连接弱交流系统MMC内部能量控制的组网控制策略。在下重组网控制的基础上,加入惯性环节和PI控制环节,使得MMC能够自动跟踪负荷变化调整自身功率输出,实现对交流电压和频率的无差调节。针对组网控制的MMC内部能量波动较大的问题,设计了一种MMC内部能量补偿控制策略,该策略能够有效降低子模块电容电压波动。最后,基于PSCAD/EMTDC电磁暂态仿真平台建立MMC-HVDC系统,并选取交流系统负荷增加、负荷减少两种工况,验证了所提控制策略的可行性和有效性。
