Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used la...Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.展开更多
Microgrid (MG) is a small entity of electrical network which comprises of various Distributed Generation (DG) sources, storage devices, and group of loads in various classes. MG provides reliable and secure energy sup...Microgrid (MG) is a small entity of electrical network which comprises of various Distributed Generation (DG) sources, storage devices, and group of loads in various classes. MG provides reliable and secure energy supply to the critical loads of communities while operating either in on-grid or off-grid mode. In this study, a coordinated power management control strategy for a typical low voltage (LV) MG network with integration of solar Photovoltaic (PV) and storage facility has been developed and analysed in Matlab-Simu-link software environment at various modes (on-grid, off-grid, and on-grid to off-grid transition) of MG operation. Solar PV and battery power inverters are considered as grid-support grid-forming (GsGfm) Voltage Source Inverter (VSI) with the implementation of modified droop and virtual output impedance control strategies. Proposed control strategy supports coordinated control operation between PV units and battery storage, equal power sharing among the DG sources, and smooth MG mode transition with regulation of voltage and frequency level in MG network. In addition, voltage and current THD level were analysed and verified as per the standard of AS4777.展开更多
An ultraviolet（UV） curable support material pre-polymer for three dimensional printing was prepared based on the synergistic effect between PEO-PPO-PEO tri-block copolymer（F127） and polyethylene glycol （400） di-...An ultraviolet（UV） curable support material pre-polymer for three dimensional printing was prepared based on the synergistic effect between PEO-PPO-PEO tri-block copolymer（F127） and polyethylene glycol （400） di-acrylate（SR344）. The effects of jetting conditions, thermal stability, curing time, mechanical properties and shrinking rate on printing models were studied. The situation of removing support material from build model was investigated after building progress was completed. The experimental result shows that when F127 is 6.0wt%, SR344 is 20.0wt%, 4-Methoxy phenol is 0.15wt% and Irgacure 2959 is 1.5wt%, the support material pre-polymer could be jetted out from the nozzles smoothly during building up of three dimensional printing models at 50-55 ℃. In addition, the support material could be removed easily from building model without spoiling the model; furthermore, the forming precision of building model is improved.展开更多
【目的】“双高”电力系统(高比例可再生能源和高比例电力电子设备)低惯性、低阻尼的特征使电网在频率、电压等稳定问题面临着严峻的挑战。构网型储能(grid-forming energy storage,GFM-ES)具有频率调节和电压控制的能力,针对其特性、...【目的】“双高”电力系统(高比例可再生能源和高比例电力电子设备)低惯性、低阻尼的特征使电网在频率、电压等稳定问题面临着严峻的挑战。构网型储能(grid-forming energy storage,GFM-ES)具有频率调节和电压控制的能力,针对其特性、应用场景和研究展望等方面进行综述。【方法】首先从GFM-ES和跟网型储能的区别以及控制方法等方面阐述了GFM-ES的主要特点;然后从频率支撑、电压支撑和黑启动等方面介绍了GFM-ES的主要应用场景;最后从GFM-ES的稳定性、优化配置和实际工程应用等方面提出了研究展望。【结论】构网型变流器的稳定性对储能机组的运行特性具有重要影响,需要进一步关注稳定问题的诱导原因、参数整定、控制和限流策略切换等;GFM-ES规划配置中,需要在功能性、复杂性、成本等方面进行权衡,以及构网型和跟网型储能的混合配置有待继续研究;加强GFM-ES机组之间的协调性和运行交互性,完善工程测试规范和标准,推动其在交直流混合电网及高压输电网络的应用。展开更多
This paper describes an analytical investigation into synchrophasing,a vibration control strategy on a machinery installation in which two rotational machines are attached to a beam-like raft by discrete resilient iso...This paper describes an analytical investigation into synchrophasing,a vibration control strategy on a machinery installation in which two rotational machines are attached to a beam-like raft by discrete resilient isolators.Forces and moments introduced by sources are considered,which effectively represent a practical engineering system.Adjusting the relative phase angle between the machines has been theoretically demonstrated to greatly reduce the cost function,which is defined as the sum of velocity squares of attaching points on the raft at each frequency of interest.The effect of the position of the machine is also investigated.Results show that altering the position of the secondary source may cause a slight change to the mode shape of the composite system and therefore change the optimum phase between the two machines.Although the analysis is based on a one-dimensional Euler– Bernoulli beam and each machine is considered as a rigid-body,a key principle can be derived from the results.However,the factors that can influence the synchrophasing control performance would become coupled and highly complicated.This condition has to be considered in practice.展开更多
为充分利用构网控制的电压源特性,协同场站内多无功源进一步提升新能源场站对高比例新能源电力系统的暂态电压主动支撑能力,提出了基于构网变流器的新能源场站暂态电压分散协同控制策略,包括多无功源暂态电压控制改进策略和容量配置方...为充分利用构网控制的电压源特性,协同场站内多无功源进一步提升新能源场站对高比例新能源电力系统的暂态电压主动支撑能力,提出了基于构网变流器的新能源场站暂态电压分散协同控制策略,包括多无功源暂态电压控制改进策略和容量配置方法两方面。首先,对场站无功源的基本特性进行分析。然后,构网变流器增加了基于无功补偿的暂态控制,提高暂态内电势电压。跟网变流器和静止同步补偿器(static var generator, SVG)分别通过暂态有功/无功自适应变化控制策略、暂态参考值变化策略,增大两者的暂态无功出力。静止无功补偿器(static var compensator, SVC)采用暂稳态切换控制策略,由稳态的无功控制切换为电压控制,以进一步提高电压调节水平。同时基于最大暂态电流和补偿容量需求提出多无功源的容量配置方法。最后,构建弱电网下暂态电压主动支撑典型场景,验证了所提分散协同控制策略提高了场站的暂态电压支撑能力,挖掘了构网控制在场站主动暂态电压支撑方面的作用。展开更多
The Meshless Local Petrov-Galerkin (MLPG) with Laplace transform is used for solving partial differential equation. Local weak form is developed using the weighted residual method locally from the dynamic partial diff...The Meshless Local Petrov-Galerkin (MLPG) with Laplace transform is used for solving partial differential equation. Local weak form is developed using the weighted residual method locally from the dynamic partial differential equation and using the moving least square (MLS) method to construct shape function. This method is a more effective alternative than the finite element method for computer modelling and simulation of problems in engineering;however, the accuracy of the present method depends on a number of parameters deriving from local weak form and different subdomains. In this paper, the meshless local Petrov-Galerkin (MLPG) formulation is proposed for forced vibration analysis. First, the results are presented for different values of as, and aq?with regular distribution of nodes nt=55. After, the results are presented with fixed values of?as?and aq?for different time-step.展开更多
随着近海风电资源开发饱和,远海风电的开发利用日益受到重视。柔性直流输电技术(voltage source converter based-high voltage direct current transmission,VSC-HVDC)凭借其灵活可控、可孤岛运行及适应远距离输电等优势,成为规模化远...随着近海风电资源开发饱和,远海风电的开发利用日益受到重视。柔性直流输电技术(voltage source converter based-high voltage direct current transmission,VSC-HVDC)凭借其灵活可控、可孤岛运行及适应远距离输电等优势,成为规模化远海风电输送的首选技术。然而,大容量的海上风电柔直工程大规模接入,将给电网带来弱系统、低惯量和电压支撑不足等稳定性挑战。因此,提升海上风电柔性直流外送系统的主动支撑能力成为国内外研究热点。为此,首先介绍了海上风电柔直外送系统拓扑结构和传统控制策略。接着,从有功和无功支撑2个层面,讨论了跟网型控制结构下通过附加控制策略实现主动支撑的方法及其局限性。然后,探讨了对构网型主动支撑技术的需求与相关标准,并梳理分析了构网型控制结构下不同的技术路线及其特点。最后,展望了技术发展趋势,并指出了当前研究及工程应用中面临的关键问题及挑战。展开更多
基金Projects(51409154,41372289)supported by the National Natural Science Foundation of ChinaProjects(2015JQJH106,2014TDJH103)supported by Research Fund of Shandong University of Science and Technology,China
文摘Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.
文摘Microgrid (MG) is a small entity of electrical network which comprises of various Distributed Generation (DG) sources, storage devices, and group of loads in various classes. MG provides reliable and secure energy supply to the critical loads of communities while operating either in on-grid or off-grid mode. In this study, a coordinated power management control strategy for a typical low voltage (LV) MG network with integration of solar Photovoltaic (PV) and storage facility has been developed and analysed in Matlab-Simu-link software environment at various modes (on-grid, off-grid, and on-grid to off-grid transition) of MG operation. Solar PV and battery power inverters are considered as grid-support grid-forming (GsGfm) Voltage Source Inverter (VSI) with the implementation of modified droop and virtual output impedance control strategies. Proposed control strategy supports coordinated control operation between PV units and battery storage, equal power sharing among the DG sources, and smooth MG mode transition with regulation of voltage and frequency level in MG network. In addition, voltage and current THD level were analysed and verified as per the standard of AS4777.
基金Funded by National High-tech Research and Development Projects of China(No. 2002AA6Z3083)
文摘An ultraviolet（UV） curable support material pre-polymer for three dimensional printing was prepared based on the synergistic effect between PEO-PPO-PEO tri-block copolymer（F127） and polyethylene glycol （400） di-acrylate（SR344）. The effects of jetting conditions, thermal stability, curing time, mechanical properties and shrinking rate on printing models were studied. The situation of removing support material from build model was investigated after building progress was completed. The experimental result shows that when F127 is 6.0wt%, SR344 is 20.0wt%, 4-Methoxy phenol is 0.15wt% and Irgacure 2959 is 1.5wt%, the support material pre-polymer could be jetted out from the nozzles smoothly during building up of three dimensional printing models at 50-55 ℃. In addition, the support material could be removed easily from building model without spoiling the model; furthermore, the forming precision of building model is improved.
文摘【目的】“双高”电力系统(高比例可再生能源和高比例电力电子设备)低惯性、低阻尼的特征使电网在频率、电压等稳定问题面临着严峻的挑战。构网型储能(grid-forming energy storage,GFM-ES)具有频率调节和电压控制的能力,针对其特性、应用场景和研究展望等方面进行综述。【方法】首先从GFM-ES和跟网型储能的区别以及控制方法等方面阐述了GFM-ES的主要特点;然后从频率支撑、电压支撑和黑启动等方面介绍了GFM-ES的主要应用场景;最后从GFM-ES的稳定性、优化配置和实际工程应用等方面提出了研究展望。【结论】构网型变流器的稳定性对储能机组的运行特性具有重要影响,需要进一步关注稳定问题的诱导原因、参数整定、控制和限流策略切换等;GFM-ES规划配置中,需要在功能性、复杂性、成本等方面进行权衡,以及构网型和跟网型储能的混合配置有待继续研究;加强GFM-ES机组之间的协调性和运行交互性,完善工程测试规范和标准,推动其在交直流混合电网及高压输电网络的应用。
文摘This paper describes an analytical investigation into synchrophasing,a vibration control strategy on a machinery installation in which two rotational machines are attached to a beam-like raft by discrete resilient isolators.Forces and moments introduced by sources are considered,which effectively represent a practical engineering system.Adjusting the relative phase angle between the machines has been theoretically demonstrated to greatly reduce the cost function,which is defined as the sum of velocity squares of attaching points on the raft at each frequency of interest.The effect of the position of the machine is also investigated.Results show that altering the position of the secondary source may cause a slight change to the mode shape of the composite system and therefore change the optimum phase between the two machines.Although the analysis is based on a one-dimensional Euler– Bernoulli beam and each machine is considered as a rigid-body,a key principle can be derived from the results.However,the factors that can influence the synchrophasing control performance would become coupled and highly complicated.This condition has to be considered in practice.
文摘为充分利用构网控制的电压源特性,协同场站内多无功源进一步提升新能源场站对高比例新能源电力系统的暂态电压主动支撑能力,提出了基于构网变流器的新能源场站暂态电压分散协同控制策略,包括多无功源暂态电压控制改进策略和容量配置方法两方面。首先,对场站无功源的基本特性进行分析。然后,构网变流器增加了基于无功补偿的暂态控制,提高暂态内电势电压。跟网变流器和静止同步补偿器(static var generator, SVG)分别通过暂态有功/无功自适应变化控制策略、暂态参考值变化策略,增大两者的暂态无功出力。静止无功补偿器(static var compensator, SVC)采用暂稳态切换控制策略,由稳态的无功控制切换为电压控制,以进一步提高电压调节水平。同时基于最大暂态电流和补偿容量需求提出多无功源的容量配置方法。最后,构建弱电网下暂态电压主动支撑典型场景,验证了所提分散协同控制策略提高了场站的暂态电压支撑能力,挖掘了构网控制在场站主动暂态电压支撑方面的作用。
文摘The Meshless Local Petrov-Galerkin (MLPG) with Laplace transform is used for solving partial differential equation. Local weak form is developed using the weighted residual method locally from the dynamic partial differential equation and using the moving least square (MLS) method to construct shape function. This method is a more effective alternative than the finite element method for computer modelling and simulation of problems in engineering;however, the accuracy of the present method depends on a number of parameters deriving from local weak form and different subdomains. In this paper, the meshless local Petrov-Galerkin (MLPG) formulation is proposed for forced vibration analysis. First, the results are presented for different values of as, and aq?with regular distribution of nodes nt=55. After, the results are presented with fixed values of?as?and aq?for different time-step.
文摘随着近海风电资源开发饱和,远海风电的开发利用日益受到重视。柔性直流输电技术(voltage source converter based-high voltage direct current transmission,VSC-HVDC)凭借其灵活可控、可孤岛运行及适应远距离输电等优势,成为规模化远海风电输送的首选技术。然而,大容量的海上风电柔直工程大规模接入,将给电网带来弱系统、低惯量和电压支撑不足等稳定性挑战。因此,提升海上风电柔性直流外送系统的主动支撑能力成为国内外研究热点。为此,首先介绍了海上风电柔直外送系统拓扑结构和传统控制策略。接着,从有功和无功支撑2个层面,讨论了跟网型控制结构下通过附加控制策略实现主动支撑的方法及其局限性。然后,探讨了对构网型主动支撑技术的需求与相关标准,并梳理分析了构网型控制结构下不同的技术路线及其特点。最后,展望了技术发展趋势,并指出了当前研究及工程应用中面临的关键问题及挑战。
