Considering three two-level atoms initially in the GHZ state, then one atom of them is put into an initially empty cavity and made resonant interaction. It is shown that the emission properties of the atom inside the ...Considering three two-level atoms initially in the GHZ state, then one atom of them is put into an initially empty cavity and made resonant interaction. It is shown that the emission properties of the atom inside the cavity can be affected only when both of the atoms outside the cavity have been manipulated. This conclusion can also be generalized to n two-level atoms.展开更多
We analyze the connection between quantum operations and accessible information. And we find that the accessible information decreases under quantum operations. We show that it is impossible to perfectly manipulate an...We analyze the connection between quantum operations and accessible information. And we find that the accessible information decreases under quantum operations. We show that it is impossible to perfectly manipulate an unknown state in an open quantum system. That the accessible information decreases under quantum operations gives a fundamental limitation in the microscopic world.展开更多
风电机组参与调频可提高风电并网系统的频率稳定性,但现有下垂控制难以兼顾频率响应特性和风机自身运行状态。为此,文中提出一种计及频率变化率(rate of change of frequency,ROCOF)与转子动能的自适应下垂控制策略,充分利用转子动能参...风电机组参与调频可提高风电并网系统的频率稳定性,但现有下垂控制难以兼顾频率响应特性和风机自身运行状态。为此,文中提出一种计及频率变化率(rate of change of frequency,ROCOF)与转子动能的自适应下垂控制策略,充分利用转子动能参与调频,确保风机稳定运行。首先,根据系统频率情况,将ROCOF划分区间,通过分段函数构建下垂系数与ROCOF的耦合函数,确保风电机组在扰动初期释放更多能量,提高风机对频率的支撑能力,减缓频率跌落速度。然后,引入转速影响因子,根据风机自身运行状态调整下垂系数,防止风机转子失速,避免频率二次跌落。最后,在MATLAB/Simulink平台上搭建风火联合系统仿真模型验证了所提控制策略有效性。仿真结果表明所提策略在保证风机转速稳定的同时,能有效利用风机转子动能改善系统频率响应特性。展开更多
极端灾害将导致电力系统与通信系统同时发生大面积瘫痪,基于“保电救灾、通信先行”原则,优先恢复故障通信是支撑保障电力系统安全运行的关键。该文针对灾后电力通信高效恢复问题,提出了一种计及电力侧状态感知需求与运行调控能力保障...极端灾害将导致电力系统与通信系统同时发生大面积瘫痪,基于“保电救灾、通信先行”原则,优先恢复故障通信是支撑保障电力系统安全运行的关键。该文针对灾后电力通信高效恢复问题,提出了一种计及电力侧状态感知需求与运行调控能力保障的增广路径最大流电力通信网络恢复算法。首先考虑到电力通信系统与电力物理系统的紧耦合特性,设计了计及电力侧影响的状态感知与运行调控能力量化指标,辨识关键信息节点。然后,通过图论最大流理论,搜寻关键信息节点的增广路径集。在此基础上,引入恢复贡献度,从增广路径集中选择具有大容量、低延时以及少故障链路的通信路径进行优先重建,为灾后电力系统快速恢复过程提供可达、可靠的通信支撑。最后,以IEEE39标准系统作为仿真算例,验证了所提恢复策略下的通信系统具有更高的通信服务质量(quality of service,QoS),避免了在恢复过程中由于带宽容量不足而发生业务频繁掉线风险。展开更多
文摘Considering three two-level atoms initially in the GHZ state, then one atom of them is put into an initially empty cavity and made resonant interaction. It is shown that the emission properties of the atom inside the cavity can be affected only when both of the atoms outside the cavity have been manipulated. This conclusion can also be generalized to n two-level atoms.
文摘We analyze the connection between quantum operations and accessible information. And we find that the accessible information decreases under quantum operations. We show that it is impossible to perfectly manipulate an unknown state in an open quantum system. That the accessible information decreases under quantum operations gives a fundamental limitation in the microscopic world.
文摘风电机组参与调频可提高风电并网系统的频率稳定性,但现有下垂控制难以兼顾频率响应特性和风机自身运行状态。为此,文中提出一种计及频率变化率(rate of change of frequency,ROCOF)与转子动能的自适应下垂控制策略,充分利用转子动能参与调频,确保风机稳定运行。首先,根据系统频率情况,将ROCOF划分区间,通过分段函数构建下垂系数与ROCOF的耦合函数,确保风电机组在扰动初期释放更多能量,提高风机对频率的支撑能力,减缓频率跌落速度。然后,引入转速影响因子,根据风机自身运行状态调整下垂系数,防止风机转子失速,避免频率二次跌落。最后,在MATLAB/Simulink平台上搭建风火联合系统仿真模型验证了所提控制策略有效性。仿真结果表明所提策略在保证风机转速稳定的同时,能有效利用风机转子动能改善系统频率响应特性。
文摘极端灾害将导致电力系统与通信系统同时发生大面积瘫痪,基于“保电救灾、通信先行”原则,优先恢复故障通信是支撑保障电力系统安全运行的关键。该文针对灾后电力通信高效恢复问题,提出了一种计及电力侧状态感知需求与运行调控能力保障的增广路径最大流电力通信网络恢复算法。首先考虑到电力通信系统与电力物理系统的紧耦合特性,设计了计及电力侧影响的状态感知与运行调控能力量化指标,辨识关键信息节点。然后,通过图论最大流理论,搜寻关键信息节点的增广路径集。在此基础上,引入恢复贡献度,从增广路径集中选择具有大容量、低延时以及少故障链路的通信路径进行优先重建,为灾后电力系统快速恢复过程提供可达、可靠的通信支撑。最后,以IEEE39标准系统作为仿真算例,验证了所提恢复策略下的通信系统具有更高的通信服务质量(quality of service,QoS),避免了在恢复过程中由于带宽容量不足而发生业务频繁掉线风险。