The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates signi...The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.展开更多
High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic fie...High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic field is a promising solution for improvement in the slag resistance of refractory.The wetting of alumina refractory ceramics with different basicities of high alumina slags under a weak static magnetic field was analyzed,given that a weak static magnetic field can affect the corrosion behavior of refractory ceramics.Taking slag S_(3) as an example,when there was an external static magnetic field of 1.0 mT at 1600 ℃,the thickness of calcium aluminate reaction layer at the interface decreased by 36.7%,the denting depth of interface decreased by 35.6%,and the apparent wetting angle increased by 20%.The living radicals and their formation path in oxide melts were verified by first-principles calculation combined with electron paramagnetic resonance spectroscopy analysis.The influence of the flux density of a weak static magnetic field on the wetting behavior of slags was also explored.The contact angle of the slags increased owing to the inhibitory effect of magnetic field on the radicalinvolved reaction at the interface of the slag and the alumina refractory ceramic.The relationships between the magnetic flux density,diffusion coefficient,slag microstructure(hyperfine coupling constant),and contact angle were established.This provides a theoretical basis for the field control of radical involved reactive wetting between inorganic oxide slags and solid oxide ceramics.展开更多
In this paper,an elasto-plastic constitutive model is employed to capture the shear failure that may occur in a rock mass presenting mechanical discontinuities,such as faults,fractures,bedding planes or other planar w...In this paper,an elasto-plastic constitutive model is employed to capture the shear failure that may occur in a rock mass presenting mechanical discontinuities,such as faults,fractures,bedding planes or other planar weak structures.The failure may occur in two modes:a sliding failure on the weak plane or an intrinsic failure of the rock mass.The rock matrix is expected to behave elastically or fail in a brittle manner,being represented by a non-associated Mohr-Coulomb behavior,while the sliding failure is represented by the evaluation of the Coulomb criterion on an explicitly defined plane.Failure may furthermore affect the hydraulic properties of the rock mass:the shearing of the weakness plane may create a transmissive fluid pathway.Verification of the mechanical submodel is conducted by comparison with an analytical solution,while the coupled hydro-mechanical behavior is validated with field data and will be applied within a model and code validation initiative.The work presented here aims at documenting the progress in code development,while accurate match of the field data with the numerical results is current work in progress.展开更多
光伏发电系统大量接入电网,会导致电网强度下降,进而限制光伏并网逆变器(grid-connected inverter,GCI)功率输出能力。因此,需要对弱电网下GCI静态功率稳定运行区域与优化控制开展研究。以GCI静态功率稳定运行为目标,以输出电流幅值和...光伏发电系统大量接入电网,会导致电网强度下降,进而限制光伏并网逆变器(grid-connected inverter,GCI)功率输出能力。因此,需要对弱电网下GCI静态功率稳定运行区域与优化控制开展研究。以GCI静态功率稳定运行为目标,以输出电流幅值和公共连接点(point of common coupling,PCC)电压允许范围为约束,确定了GCI在不同短路比(short circuit ratio,SCR)区间内的运行方式,并给出了相应的电流参考值计算方法;为提高GCI在低SCR下运行的稳定性,提出了一种阻抗重塑优化控制方法。该方法在锁相环前级增加了基于准降阶谐振控制器的正负序分离环节,使得系统中频段相位整体较为平稳。同时在电流环引入幅值相位补偿环节,整体增大了系统中频段相位;搭建了仿真模型,在SCR值为1的情况下,所提阻抗重塑优化控制方法仍能保证GCI的稳定性,并基于所提阻抗重塑优化控制方法,验证了GCI静态功率稳定运行区域的正确性。展开更多
基金supported by the National Natural Science Foundation of China under Grant 52407069the Science and Technology Project of Zhejiang Province under Grant 2024C01254the China Postdoctoral Science Foundation under Grant 2024T170766 and 2024M762824。
文摘The phase-locked loop(PLL)plays an essential role for synchronizing renewable power generation to the grid.However,as per the grid-code compliance for reactive current support,the PLL output frequency fluctuates significantly and exceeds the limitation,which seriously threaten the safe supply of electricity.In this paper,the underlying theoretical mechanism and dominant force behind the maximum PLL frequency deviation are revealed.Accordingly,two feasible approaches are proposed to enhance the PLL frequency stability with validations in experimental results.
基金supported by the National Natural Science Foundation of China(52272022)Key Program of the Natural Science Foundation of Hubei Province of China(2021CFA071).
文摘High alumina slag will cause severe corrosion at the interface of alumina refractory,and the wetting behavior of slag is a key factor influencing the corrosion resistance of refractory ceramics.The static magnetic field is a promising solution for improvement in the slag resistance of refractory.The wetting of alumina refractory ceramics with different basicities of high alumina slags under a weak static magnetic field was analyzed,given that a weak static magnetic field can affect the corrosion behavior of refractory ceramics.Taking slag S_(3) as an example,when there was an external static magnetic field of 1.0 mT at 1600 ℃,the thickness of calcium aluminate reaction layer at the interface decreased by 36.7%,the denting depth of interface decreased by 35.6%,and the apparent wetting angle increased by 20%.The living radicals and their formation path in oxide melts were verified by first-principles calculation combined with electron paramagnetic resonance spectroscopy analysis.The influence of the flux density of a weak static magnetic field on the wetting behavior of slags was also explored.The contact angle of the slags increased owing to the inhibitory effect of magnetic field on the radicalinvolved reaction at the interface of the slag and the alumina refractory ceramic.The relationships between the magnetic flux density,diffusion coefficient,slag microstructure(hyperfine coupling constant),and contact angle were established.This provides a theoretical basis for the field control of radical involved reactive wetting between inorganic oxide slags and solid oxide ceramics.
基金the DECOVALEX-2019 funding organisations of Andra,BGR/UFZ,CNSC,US DOE,ENSI,JAEA,IRSN,KAERI,NWMO,RWM,SURAO,SSM and Taipower for their financial and technical support of the work described in this paper。
文摘In this paper,an elasto-plastic constitutive model is employed to capture the shear failure that may occur in a rock mass presenting mechanical discontinuities,such as faults,fractures,bedding planes or other planar weak structures.The failure may occur in two modes:a sliding failure on the weak plane or an intrinsic failure of the rock mass.The rock matrix is expected to behave elastically or fail in a brittle manner,being represented by a non-associated Mohr-Coulomb behavior,while the sliding failure is represented by the evaluation of the Coulomb criterion on an explicitly defined plane.Failure may furthermore affect the hydraulic properties of the rock mass:the shearing of the weakness plane may create a transmissive fluid pathway.Verification of the mechanical submodel is conducted by comparison with an analytical solution,while the coupled hydro-mechanical behavior is validated with field data and will be applied within a model and code validation initiative.The work presented here aims at documenting the progress in code development,while accurate match of the field data with the numerical results is current work in progress.
文摘光伏发电系统大量接入电网,会导致电网强度下降,进而限制光伏并网逆变器(grid-connected inverter,GCI)功率输出能力。因此,需要对弱电网下GCI静态功率稳定运行区域与优化控制开展研究。以GCI静态功率稳定运行为目标,以输出电流幅值和公共连接点(point of common coupling,PCC)电压允许范围为约束,确定了GCI在不同短路比(short circuit ratio,SCR)区间内的运行方式,并给出了相应的电流参考值计算方法;为提高GCI在低SCR下运行的稳定性,提出了一种阻抗重塑优化控制方法。该方法在锁相环前级增加了基于准降阶谐振控制器的正负序分离环节,使得系统中频段相位整体较为平稳。同时在电流环引入幅值相位补偿环节,整体增大了系统中频段相位;搭建了仿真模型,在SCR值为1的情况下,所提阻抗重塑优化控制方法仍能保证GCI的稳定性,并基于所提阻抗重塑优化控制方法,验证了GCI静态功率稳定运行区域的正确性。
