Starting from the basic equations of hydrodynamics, the maximum power- type variational principle of the hydrodynamics of viscous fluids was established by Weizang CHIEN in 1984. Through long-term research, it is clar...Starting from the basic equations of hydrodynamics, the maximum power- type variational principle of the hydrodynamics of viscous fluids was established by Weizang CHIEN in 1984. Through long-term research, it is clarified that the maximum power-type variational principle coincides with the Jourdian principle, which is one of the common principles for analytical mechanics. In the paper, the power-type variational principle is extended to rigid-body dynamics, elasto-dynamics, and rigid-elastic：liquid coupling dynamics. The governing equations of the rigid-elastic-liquid coupling dynamics in the liquid-filled system are obtained by deriving the stationary value conditions. The results show that, with the power-type variational principles studied directly in the state space, some transformations in the time domain space may be omitted in the establishing process, and the rigid-elastic-liqUid coupling dynamics can be easily numerically modeled. Moreover, the analysis of the coupling dynamics in the liquid-filled system in this paper agrees well with the numerical analyses of the coupling dynamics in the liquid-filled system offered in the literatures.展开更多
In the article,we prove that the inequalities H_(p)(K(r);E(r))>π/2;L_(q)(K(r);E(r))>π/2 hold for all r 2(0;1)if and only if p≥3=4 and q≥3=4,where Hp(a;b)and Lq(a;b)are respectively the p-th power-type Heroni...In the article,we prove that the inequalities H_(p)(K(r);E(r))>π/2;L_(q)(K(r);E(r))>π/2 hold for all r 2(0;1)if and only if p≥3=4 and q≥3=4,where Hp(a;b)and Lq(a;b)are respectively the p-th power-type Heronian mean and q-th Lehmer mean of a and b,and K(r)and E(r)are respectively the complete elliptic integrals of the first and second kinds.展开更多
This paper deals with blowing up of solutions to the Cauchy problem for a class of general- ized Zakharov system with combined power-type nonlinearities in two and three space dimensions. On the one hand, for co = ＋o...This paper deals with blowing up of solutions to the Cauchy problem for a class of general- ized Zakharov system with combined power-type nonlinearities in two and three space dimensions. On the one hand, for co = ＋oo we obtain two finite time blow-up results of solutions to the aforementioned 4 ≤ p 〈 N＋2/N-2 4 system. One is obtained under the condition a ≥ 0 and 1 ＋ 4/N or a 〈 0 and 1 〈 p 〈 1 ＋ （N = 2,3）; the other is established under the condition N = 3, 1 〈 p 〈 N=2/N-2 and α（p - 3） 〉 0. On the other hand, for co 〈 ＋∞ and α（p - 3） 〉 0, we prove a blow-up result for solutions with negative energy to the Zakharov system under study.展开更多
加快建设沙戈荒源网荷储一体化基地有力推动了电力系统低碳转型,但基地内缺乏常规电源,呈现出电网弱、低惯量、弱阻尼等特征。高压大功率变流器是主力电源型新能源场站的关键电气装备,起到自主构建电压/频率,提供阻尼和惯量支撑等作用...加快建设沙戈荒源网荷储一体化基地有力推动了电力系统低碳转型,但基地内缺乏常规电源,呈现出电网弱、低惯量、弱阻尼等特征。高压大功率变流器是主力电源型新能源场站的关键电气装备,起到自主构建电压/频率,提供阻尼和惯量支撑等作用。在此背景下,首先介绍了源网荷储一体化基地变流拓扑及汇集方式,对“多机并联-多级升压”汇集拓扑所引发的宽频振荡、协同构网控制困难以及过载能力弱等问题进行了分析。其次,分别对光伏发电系统、蓄电池储能系统(battery energy storage system,BESS)以及光储一体化系统的高压大功率变流拓扑特点进行了梳理和分析。最后,探索了高压大功率变流器亟待解决的关键问题。展开更多
随着“双碳”目标建设和大型城市旧城改造的推进,传统发电设施逐渐迁移,导致“电源空心化”问题凸显,系统惯量下降,电网安全稳定运行面临挑战。以成都电网为例,其作为四川电网的负荷中心,受电主要依赖外部通道,南部重负荷片区暂态电压...随着“双碳”目标建设和大型城市旧城改造的推进,传统发电设施逐渐迁移,导致“电源空心化”问题凸显,系统惯量下降,电网安全稳定运行面临挑战。以成都电网为例,其作为四川电网的负荷中心,受电主要依赖外部通道,南部重负荷片区暂态电压支撑不足,因此有必要开展新型动态无功补偿技术的研究。首先分析了成都电网的动态无功需求,研究了跟网型静止无功发生器(static var generator,SVG)、调相机、构网型SVG等动态无功补偿装置的技术特点。通过比选,提出并研发了单体具备稳态无功60Mvar、暂态无功450Mvar能力的构网型SVG成套设备。该设备通过500kV人工短路试验验证了其大电流、快响应的暂态性能,有效解决了成都电网的动态无功不足问题,实现了德宝直流提升100万kW送电能力。相关研究为治理新型电力系统电网电压稳定问题提供了典型案例示范,为构网型产品成套设计和工程应用提供了理论依据。展开更多
基金supported by the National Natural Science Foundation of China(No.10272034)the Fundamental Research Funds for the Central Universities of China(No.HEUCF130205)
文摘Starting from the basic equations of hydrodynamics, the maximum power- type variational principle of the hydrodynamics of viscous fluids was established by Weizang CHIEN in 1984. Through long-term research, it is clarified that the maximum power-type variational principle coincides with the Jourdian principle, which is one of the common principles for analytical mechanics. In the paper, the power-type variational principle is extended to rigid-body dynamics, elasto-dynamics, and rigid-elastic：liquid coupling dynamics. The governing equations of the rigid-elastic-liquid coupling dynamics in the liquid-filled system are obtained by deriving the stationary value conditions. The results show that, with the power-type variational principles studied directly in the state space, some transformations in the time domain space may be omitted in the establishing process, and the rigid-elastic-liqUid coupling dynamics can be easily numerically modeled. Moreover, the analysis of the coupling dynamics in the liquid-filled system in this paper agrees well with the numerical analyses of the coupling dynamics in the liquid-filled system offered in the literatures.
基金Supported by the National Natural Science Foundation of China(11971142)the Natural Science Foundation of Zhejiang Province(LY19A010012)。
文摘In the article,we prove that the inequalities H_(p)(K(r);E(r))>π/2;L_(q)(K(r);E(r))>π/2 hold for all r 2(0;1)if and only if p≥3=4 and q≥3=4,where Hp(a;b)and Lq(a;b)are respectively the p-th power-type Heronian mean and q-th Lehmer mean of a and b,and K(r)and E(r)are respectively the complete elliptic integrals of the first and second kinds.
基金supported by National Natural Science Foundation of China (Grant Nos. 11171241, 10801102,11071177)Sichuan Youth Science and Technology Foundation (Grant No. 07ZQ026-009)China Postdoctoral Science Foundation Funded Project
文摘This paper deals with blowing up of solutions to the Cauchy problem for a class of general- ized Zakharov system with combined power-type nonlinearities in two and three space dimensions. On the one hand, for co = ＋oo we obtain two finite time blow-up results of solutions to the aforementioned 4 ≤ p 〈 N＋2/N-2 4 system. One is obtained under the condition a ≥ 0 and 1 ＋ 4/N or a 〈 0 and 1 〈 p 〈 1 ＋ （N = 2,3）; the other is established under the condition N = 3, 1 〈 p 〈 N=2/N-2 and α（p - 3） 〉 0. On the other hand, for co 〈 ＋∞ and α（p - 3） 〉 0, we prove a blow-up result for solutions with negative energy to the Zakharov system under study.
文摘加快建设沙戈荒源网荷储一体化基地有力推动了电力系统低碳转型,但基地内缺乏常规电源,呈现出电网弱、低惯量、弱阻尼等特征。高压大功率变流器是主力电源型新能源场站的关键电气装备,起到自主构建电压/频率,提供阻尼和惯量支撑等作用。在此背景下,首先介绍了源网荷储一体化基地变流拓扑及汇集方式,对“多机并联-多级升压”汇集拓扑所引发的宽频振荡、协同构网控制困难以及过载能力弱等问题进行了分析。其次,分别对光伏发电系统、蓄电池储能系统(battery energy storage system,BESS)以及光储一体化系统的高压大功率变流拓扑特点进行了梳理和分析。最后,探索了高压大功率变流器亟待解决的关键问题。
文摘随着“双碳”目标建设和大型城市旧城改造的推进,传统发电设施逐渐迁移,导致“电源空心化”问题凸显,系统惯量下降,电网安全稳定运行面临挑战。以成都电网为例,其作为四川电网的负荷中心,受电主要依赖外部通道,南部重负荷片区暂态电压支撑不足,因此有必要开展新型动态无功补偿技术的研究。首先分析了成都电网的动态无功需求,研究了跟网型静止无功发生器(static var generator,SVG)、调相机、构网型SVG等动态无功补偿装置的技术特点。通过比选,提出并研发了单体具备稳态无功60Mvar、暂态无功450Mvar能力的构网型SVG成套设备。该设备通过500kV人工短路试验验证了其大电流、快响应的暂态性能,有效解决了成都电网的动态无功不足问题,实现了德宝直流提升100万kW送电能力。相关研究为治理新型电力系统电网电压稳定问题提供了典型案例示范,为构网型产品成套设计和工程应用提供了理论依据。
