为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决...为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决定分解模态数和带宽,结合最小二乘-旋转不变技术(total least square-estimating signal parameter via rotational invariance techniques,TLS-ESPRIT)对分解出的振荡分量进行参数辨识,无需另外使用降噪算法。通过复合信号测试法、PSCAD/EMTDC电磁暂态仿真法验证了所提方法的有效性。最后,将所提方法与改进Prony算法、MCEEMD法在不同噪声水平和振荡频率下进行对比,结果表明,所提方法能够有效地抑制原始信号的噪声干扰,对耦合的次/超同步振荡信号分解更加准确,参数辨识结果可靠性较高,对风电系统振荡溯源、改善系统阻尼具有一定的参考意义。展开更多
The cubic pyrochlore Tl_(2)Ru_(2)O_(7) undergoes concurrently a metal–insulator transition (MIT) and a first-order structural transition at T_(MIT)≈120 K,below which the system was found to form one-dimensional spin...The cubic pyrochlore Tl_(2)Ru_(2)O_(7) undergoes concurrently a metal–insulator transition (MIT) and a first-order structural transition at T_(MIT)≈120 K,below which the system was found to form one-dimensional spin-one Haldane chains associated with an orbital ordering of Ru-4d electrons.With an aim to tune and access distinct ground states with strong entanglements of multiple degrees of freedom,i.e.,spin,orbital,charge,and lattice,we utilize a high-pressure approach to regulate the MIT of this system.Our detailed resistivityρ(T) measurements on the polycrystalline Tl_(2)Ru_(2)O_(7) samples under various hydrostatic pressures indeed reveal an unusual evolution of the electronic ground states.At first,the MIT is suppressed monotonically from 120 K at ambient to about 70 K at 1.5 GPa and then vanishes suddenly at about 1.8 GPa without achieving a metallic ground state.Meanwhile,the system evolves into a semiconducting ground state with magnitude ofρ(T) in the entire temperature range enhanced gradually by further increasing pressure.Prior to the abrupt disappearance of MIT,a new electronic order manifested as a kink-like anomaly inρ(T) emerges at T_(0)>T_(MIT) at 1.2 GPa and it continues to increase with pressure,producing a tricritical-point-like behavior in the T–P phase diagram of Tl_(2)Ru_(2)O_(7).The presence of two successive transitions at T_(0 )and T_(MIT )in the pressure range 1.2–1.5 GPa indicates an inhomogeneous electronic state nearby the tricritical point.At P≥3 GPa,another broad anomaly emerges inρ(T) at T_(1)>T_(0),and T_(1)continuously increases with pressure,dividing the semiconductingρ(T) into distinct thermally activated regions.These rich phenomena in the pressurized Tl_(2)Ru_(2)O_(7) should originate from the complex interplay of strongly entangled multiple quantum degrees of freedom in the system near the localized-to-itinerant crossover regime.展开更多
文摘为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决定分解模态数和带宽,结合最小二乘-旋转不变技术(total least square-estimating signal parameter via rotational invariance techniques,TLS-ESPRIT)对分解出的振荡分量进行参数辨识,无需另外使用降噪算法。通过复合信号测试法、PSCAD/EMTDC电磁暂态仿真法验证了所提方法的有效性。最后,将所提方法与改进Prony算法、MCEEMD法在不同噪声水平和振荡频率下进行对比,结果表明,所提方法能够有效地抑制原始信号的噪声干扰,对耦合的次/超同步振荡信号分解更加准确,参数辨识结果可靠性较高,对风电系统振荡溯源、改善系统阻尼具有一定的参考意义。
基金supported by the National Key Research and Development Program of China (Grant Nos. 2023YFA1406100 and 2021YFA1400200)the National Natural Science Foundation of China (Grant Nos. 12025408 and 12174424)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Scineces (Grant No. 2023007)support from the National Natural Science Foundation of China (Grant No. 11904272)the Open Fund of Hubei Provincial Key Laboratory of Metallurgical Industry Process Systems Science (Grant No. Z202202)。
文摘The cubic pyrochlore Tl_(2)Ru_(2)O_(7) undergoes concurrently a metal–insulator transition (MIT) and a first-order structural transition at T_(MIT)≈120 K,below which the system was found to form one-dimensional spin-one Haldane chains associated with an orbital ordering of Ru-4d electrons.With an aim to tune and access distinct ground states with strong entanglements of multiple degrees of freedom,i.e.,spin,orbital,charge,and lattice,we utilize a high-pressure approach to regulate the MIT of this system.Our detailed resistivityρ(T) measurements on the polycrystalline Tl_(2)Ru_(2)O_(7) samples under various hydrostatic pressures indeed reveal an unusual evolution of the electronic ground states.At first,the MIT is suppressed monotonically from 120 K at ambient to about 70 K at 1.5 GPa and then vanishes suddenly at about 1.8 GPa without achieving a metallic ground state.Meanwhile,the system evolves into a semiconducting ground state with magnitude ofρ(T) in the entire temperature range enhanced gradually by further increasing pressure.Prior to the abrupt disappearance of MIT,a new electronic order manifested as a kink-like anomaly inρ(T) emerges at T_(0)>T_(MIT) at 1.2 GPa and it continues to increase with pressure,producing a tricritical-point-like behavior in the T–P phase diagram of Tl_(2)Ru_(2)O_(7).The presence of two successive transitions at T_(0 )and T_(MIT )in the pressure range 1.2–1.5 GPa indicates an inhomogeneous electronic state nearby the tricritical point.At P≥3 GPa,another broad anomaly emerges inρ(T) at T_(1)>T_(0),and T_(1)continuously increases with pressure,dividing the semiconductingρ(T) into distinct thermally activated regions.These rich phenomena in the pressurized Tl_(2)Ru_(2)O_(7) should originate from the complex interplay of strongly entangled multiple quantum degrees of freedom in the system near the localized-to-itinerant crossover regime.
