At present, the problem of abandoning wind and PV power in “Three North” region of China is particularly significant, and how to alleviate this problem has become the focus of universal attention. Calculation of ren...At present, the problem of abandoning wind and PV power in “Three North” region of China is particularly significant, and how to alleviate this problem has become the focus of universal attention. Calculation of renewable energy accommodation capacity is the basis to solve the problem of abandoning wind and PV power. Main problems of Chinese renewable energy accommodation is analyzed from power supply, power grid and load side aspects, and it focuses on the effect of inter-provincial tie-line to renewable energy accommodation capacity. At present, the inter-provincial tie-line utilization level is limited, which affected renewable energy accommodation to a certain extent. Based on the sequential production simulation model, a new kind of renewable energy accommodation capacity model is put forward considering the utilization level of inter-provincial tie-line. According to different system stability constraints and different electricity constraints of inter-provincial tie-line, 4 schemes are designed for comparative analysis, and the evaluation model is used to calculate renewable energy accommodation capacity of “Three North” region of China in 2020. Example analysis results verify validity of the model that releasing curve constraints, electricity constraints and stability constraints in turn can significantly enhance renewable energy accommodation capacity through effective use of inter-provincial tie-line transmission capacity. Research work in this paper can provide strong support for the planning and scheduling control of power grid.展开更多
This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, an...This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, and then pressed to fill cavity by an upper mold being lowered down. For complex liquid flow during pressing, the liquid＇s pressure changing inside vertical path with various contraction and expansion geometries is newly modeled via the unstationary Bernoulli equation. The mathematical model is derived for a control design of pressing. To conduct the pressing velocity design algorithm, an unknown parameter of proposed model considering viscous flow is identified by using CFD （Computational Fluid Dynamics） with heat flow calculation. Control performance using a multi-switching velocity pattern is confirmed as an effective control design using the pressure model, because the pressure fluctuation has discontinuous variation points. Substituting detailed information for mold shape, poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the design algorithm based on the construction of an inverse system comprised of the sequential switching from higher to lower speed. Consequently, the effectiveness of the pressing control with reasonable pressure suppression has been demonstrated through CFD.展开更多
In this paper we demonstrate the need for risk-adjusted approaches to planning expansion of livestock production. In particular, we illustrate that under exposure to risk, a portfolio of producers is needed where more...In this paper we demonstrate the need for risk-adjusted approaches to planning expansion of livestock production. In particular, we illustrate that under exposure to risk, a portfolio of producers is needed where more efficient producers co-exist and cooperate with less efficient ones given that the latter are associated with lower, uncorre, lated or even negatively correlated contingencies. This raises important issues of cooperation and risk sharing among diverse producers. For large-scale practical allocation problems when information on the contingencies may be disperse, not analytically tractable, or be available on aggregate levels, we propose a downscaling procedure based on behavioral principles utilizing spatial risk preference structure, It allows for estimation of production allocation at required resolutions accounting for location specific risks and suitability constraints. The approach provides a tool for harmonization of data from various spatial levels. We applied the method in a case study of livestock production allocation in China to 2030.展开更多
传统电力系统随机生产模拟难以准确描述负荷、风电出力和储能荷电状态(state of charge,SOC)的时序变化特性,也难以反映灵活多样的系统运行调度策略,导致生产模拟准确性欠佳。为此,提出了含风电和储能电力系统时序随机生产模拟方法。该...传统电力系统随机生产模拟难以准确描述负荷、风电出力和储能荷电状态(state of charge,SOC)的时序变化特性,也难以反映灵活多样的系统运行调度策略,导致生产模拟准确性欠佳。为此,提出了含风电和储能电力系统时序随机生产模拟方法。该方法计及了系统运行调度策略,将运行调度策略与随机生产模拟中的各机组加载顺序和储能充放电条件等对应起来,有效地描述了各种运行调度策略。为保留元件出力和负荷的时序变化特性,采用可用容量状态刻画各时刻的机组出力状态,将储能充放电分别等效为负荷和机组2部分分别计入基于时序负荷曲线的随机生产模拟中,并建立了描述储能容量状态变化的时变SOC概率分布模型。基于修改的RBTS测试系统进行分析,验证了所提方法的有效性。展开更多
基金supported by project of the National Key Research and Development Program Foundation of China(2016YFB0900100).
文摘At present, the problem of abandoning wind and PV power in “Three North” region of China is particularly significant, and how to alleviate this problem has become the focus of universal attention. Calculation of renewable energy accommodation capacity is the basis to solve the problem of abandoning wind and PV power. Main problems of Chinese renewable energy accommodation is analyzed from power supply, power grid and load side aspects, and it focuses on the effect of inter-provincial tie-line to renewable energy accommodation capacity. At present, the inter-provincial tie-line utilization level is limited, which affected renewable energy accommodation to a certain extent. Based on the sequential production simulation model, a new kind of renewable energy accommodation capacity model is put forward considering the utilization level of inter-provincial tie-line. According to different system stability constraints and different electricity constraints of inter-provincial tie-line, 4 schemes are designed for comparative analysis, and the evaluation model is used to calculate renewable energy accommodation capacity of “Three North” region of China in 2020. Example analysis results verify validity of the model that releasing curve constraints, electricity constraints and stability constraints in turn can significantly enhance renewable energy accommodation capacity through effective use of inter-provincial tie-line transmission capacity. Research work in this paper can provide strong support for the planning and scheduling control of power grid.
文摘This paper presents a modeling and control of molten metal＇s pressure in pressing process using an innovative iron casting developed by our group. In this method, molten metal is directly poured into a lower mold, and then pressed to fill cavity by an upper mold being lowered down. For complex liquid flow during pressing, the liquid＇s pressure changing inside vertical path with various contraction and expansion geometries is newly modeled via the unstationary Bernoulli equation. The mathematical model is derived for a control design of pressing. To conduct the pressing velocity design algorithm, an unknown parameter of proposed model considering viscous flow is identified by using CFD （Computational Fluid Dynamics） with heat flow calculation. Control performance using a multi-switching velocity pattern is confirmed as an effective control design using the pressure model, because the pressure fluctuation has discontinuous variation points. Substituting detailed information for mold shape, poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the design algorithm based on the construction of an inverse system comprised of the sequential switching from higher to lower speed. Consequently, the effectiveness of the pressing control with reasonable pressure suppression has been demonstrated through CFD.
文摘In this paper we demonstrate the need for risk-adjusted approaches to planning expansion of livestock production. In particular, we illustrate that under exposure to risk, a portfolio of producers is needed where more efficient producers co-exist and cooperate with less efficient ones given that the latter are associated with lower, uncorre, lated or even negatively correlated contingencies. This raises important issues of cooperation and risk sharing among diverse producers. For large-scale practical allocation problems when information on the contingencies may be disperse, not analytically tractable, or be available on aggregate levels, we propose a downscaling procedure based on behavioral principles utilizing spatial risk preference structure, It allows for estimation of production allocation at required resolutions accounting for location specific risks and suitability constraints. The approach provides a tool for harmonization of data from various spatial levels. We applied the method in a case study of livestock production allocation in China to 2030.
文摘传统电力系统随机生产模拟难以准确描述负荷、风电出力和储能荷电状态(state of charge,SOC)的时序变化特性,也难以反映灵活多样的系统运行调度策略,导致生产模拟准确性欠佳。为此,提出了含风电和储能电力系统时序随机生产模拟方法。该方法计及了系统运行调度策略,将运行调度策略与随机生产模拟中的各机组加载顺序和储能充放电条件等对应起来,有效地描述了各种运行调度策略。为保留元件出力和负荷的时序变化特性,采用可用容量状态刻画各时刻的机组出力状态,将储能充放电分别等效为负荷和机组2部分分别计入基于时序负荷曲线的随机生产模拟中,并建立了描述储能容量状态变化的时变SOC概率分布模型。基于修改的RBTS测试系统进行分析,验证了所提方法的有效性。
