为提高风电并网效益,减少弃风,在电网中接入电池储能电站(battery energy storage power station,BESPS)。首先,建立了考虑损耗成本的BESPS调度特性模型,该损耗成本由BESPS投资成本与调度区间内的充放电循环次数估算;然后,在考虑风电可...为提高风电并网效益,减少弃风,在电网中接入电池储能电站(battery energy storage power station,BESPS)。首先,建立了考虑损耗成本的BESPS调度特性模型,该损耗成本由BESPS投资成本与调度区间内的充放电循环次数估算;然后,在考虑风电可信容量的基础上构建了BESPS调度模型。某些情况下,系统很难全额消纳风电,因此,调度模型具有运行成本最小与风电接纳最大2个不同维度的优化目标。为求解此问题,基于隶属度函数将2个子优化目标模糊化,构建了基于最大满意度的单目标优化模型,并采用GAMS软件提供的CPLEX求解器对其进行求解。基于我国东北某实际省级电网的仿真实验说明:BESPS接入可显著提升系统风电接纳能力,且基于最大满意度的优化调度可给出更为合理的结果。展开更多
在高风电渗透率的刚性源端系统中,风电参与调度运行的模式需从负负荷向部分可控电源转变,而集群风电以虚拟机组(wind farm cluster virtual power generation unit,WCVPG)形式参与调度运行是提高风电可调度性的可行方案。该文作为系列...在高风电渗透率的刚性源端系统中,风电参与调度运行的模式需从负负荷向部分可控电源转变,而集群风电以虚拟机组(wind farm cluster virtual power generation unit,WCVPG)形式参与调度运行是提高风电可调度性的可行方案。该文作为系列文章的第2部分,基于文章第1部分建立的WCVPG时变概率模型,提出一种WCVPG调度特性与风险指标量化方法,为其以电源形式参与调度模型做出定量化的性能评价。首先,从可发功率、可发功率极限、出力调节范围和爬坡率四个方面提出WCVPG调度特性指标概率量化方法;然后,基于条件风险价值理论,提出WCVPG的安全性和经济性风险指标量化方法;进而,基于多状态概率分布基本运算,提出调度特性与风险指标计算方法;最后,基于实测数据比较了单个风电场与同一风电场公共连接点(point of common coupling,PCC)的风电场组合WCVPG调度特性指标和风险指标差异;分析了风电不确定性和波动性概率分布时变特性对WCVPG调度特性和风险指标的影响。展开更多
In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix...In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix are stressed. The FEM equations of mechanics characteristics, natural frequency and main mode are set up based on the first order matrix perturbation theory. Applicantion of the proposed model to analyze a real arch bridge proved the improvement in the simulation precision of dynamical characteristics of the arch bridge by considering the effects of suspender length variation.展开更多
Nitrogen-controlled atmosphere has been internationally recognized as a green grain storage technology.This study used Jiangsu ordinary late japonica rice as the test material and investigated the effects of different...Nitrogen-controlled atmosphere has been internationally recognized as a green grain storage technology.This study used Jiangsu ordinary late japonica rice as the test material and investigated the effects of different nitrogen concentrations(88%,93%,and 98%)and different storage temperatures(10,20,and 30℃)on the rice quality indexes during nitrogen-controlled atmosphere storage.The results showed that the water content of rice in different nitrogen-controlled atmosphere groups fluctuated between 12.85%~13.15%at 20℃,which was significantly lower than that in the control group.High-concentration nitrogen-controlled atmosphere treatment(93%and 98%)effectively slowed down the fatty acid value,malondialdehyde(MDA)content,and electrical conductivity of rice,and also significantly inhibited the rapid increase in the final viscosity and water absorption of rice starch,while the changes in the peak viscosity and attenuation value of rice were not significantly different from those of the control group.Meanwhile,the impacts of controlled atmosphere storage with 98%nitrogen concentration on the water content,fatty acid value,MDA content,electrical conductivity,gelatinization characteristics,and water absorption of rice at 10,20,and 30℃were studied.It was found that all quality parameters,except the MDA content,changed most gently at 10℃.In conclusion,the combined treatment of nitrogen-controlled atmosphere storage(98%)and low temperature(10℃)can effectively delay the quality deterioration of ordinary late japonica rice.展开更多
A large number of debris flows occurred simultaneously at around 8:30 to 8:50 a.m.on July 27,2011,at the center of Seoul,Korea.This area is located in the southern part of Seoul and is a densely populated district.As ...A large number of debris flows occurred simultaneously at around 8:30 to 8:50 a.m.on July 27,2011,at the center of Seoul,Korea.This area is located in the southern part of Seoul and is a densely populated district.As a result of the debris flow event,16 people were killed,30 houses were buried,and 116 houses were damaged around Umyeon Mountain,a relatively small mountain with a height of 312.6 m.Since the debris flow event,field investigations on the initiation and transportation zones of debris flows have been carried out.Rainfall data were collected from the automatic weather stations(AWSs) which are operated by the Korea Meteorological Administration(KMA).Video files recorded by residents were also acquired and used to analyze the flow characteristics of the debris flow.Field investigation shows that about 40 debris flows occurred around Umyeon Mountain and most of the debris flows were initiated by small slope failures.The effects of the precipitation that triggered the debris flows were analyzed as well.A landslide hazard map which considers slope gradient and aspect,strength of soil,hazard record,rainfall conditions,and vegetation,was constructed and compared with the initiation zones of debris flows.展开更多
Absrtact: The principle of ZVS - PWM inverting circuit is first described by means of inverting welder supply. The contrastive study is made on switching characte -ristics and switching losses of IGBT between ZVS - PW...Absrtact: The principle of ZVS - PWM inverting circuit is first described by means of inverting welder supply. The contrastive study is made on switching characte -ristics and switching losses of IGBT between ZVS - PWM and hard - switching.展开更多
文摘为提高风电并网效益,减少弃风,在电网中接入电池储能电站(battery energy storage power station,BESPS)。首先,建立了考虑损耗成本的BESPS调度特性模型,该损耗成本由BESPS投资成本与调度区间内的充放电循环次数估算;然后,在考虑风电可信容量的基础上构建了BESPS调度模型。某些情况下,系统很难全额消纳风电,因此,调度模型具有运行成本最小与风电接纳最大2个不同维度的优化目标。为求解此问题,基于隶属度函数将2个子优化目标模糊化,构建了基于最大满意度的单目标优化模型,并采用GAMS软件提供的CPLEX求解器对其进行求解。基于我国东北某实际省级电网的仿真实验说明:BESPS接入可显著提升系统风电接纳能力,且基于最大满意度的优化调度可给出更为合理的结果。
文摘在高风电渗透率的刚性源端系统中,风电参与调度运行的模式需从负负荷向部分可控电源转变,而集群风电以虚拟机组(wind farm cluster virtual power generation unit,WCVPG)形式参与调度运行是提高风电可调度性的可行方案。该文作为系列文章的第2部分,基于文章第1部分建立的WCVPG时变概率模型,提出一种WCVPG调度特性与风险指标量化方法,为其以电源形式参与调度模型做出定量化的性能评价。首先,从可发功率、可发功率极限、出力调节范围和爬坡率四个方面提出WCVPG调度特性指标概率量化方法;然后,基于条件风险价值理论,提出WCVPG的安全性和经济性风险指标量化方法;进而,基于多状态概率分布基本运算,提出调度特性与风险指标计算方法;最后,基于实测数据比较了单个风电场与同一风电场公共连接点(point of common coupling,PCC)的风电场组合WCVPG调度特性指标和风险指标差异;分析了风电不确定性和波动性概率分布时变特性对WCVPG调度特性和风险指标的影响。
基金Supported by the Key Teacher Foundation of Chongqing University (No. 717411067)
文摘In this paper, we established a finite element (FEM) model to analyze the dynamic characteristics of arch bridges. In this model, the effects of adjustment to the length of a suspender on its geometry stiffness matrix are stressed. The FEM equations of mechanics characteristics, natural frequency and main mode are set up based on the first order matrix perturbation theory. Applicantion of the proposed model to analyze a real arch bridge proved the improvement in the simulation precision of dynamical characteristics of the arch bridge by considering the effects of suspender length variation.
文摘Nitrogen-controlled atmosphere has been internationally recognized as a green grain storage technology.This study used Jiangsu ordinary late japonica rice as the test material and investigated the effects of different nitrogen concentrations(88%,93%,and 98%)and different storage temperatures(10,20,and 30℃)on the rice quality indexes during nitrogen-controlled atmosphere storage.The results showed that the water content of rice in different nitrogen-controlled atmosphere groups fluctuated between 12.85%~13.15%at 20℃,which was significantly lower than that in the control group.High-concentration nitrogen-controlled atmosphere treatment(93%and 98%)effectively slowed down the fatty acid value,malondialdehyde(MDA)content,and electrical conductivity of rice,and also significantly inhibited the rapid increase in the final viscosity and water absorption of rice starch,while the changes in the peak viscosity and attenuation value of rice were not significantly different from those of the control group.Meanwhile,the impacts of controlled atmosphere storage with 98%nitrogen concentration on the water content,fatty acid value,MDA content,electrical conductivity,gelatinization characteristics,and water absorption of rice at 10,20,and 30℃were studied.It was found that all quality parameters,except the MDA content,changed most gently at 10℃.In conclusion,the combined treatment of nitrogen-controlled atmosphere storage(98%)and low temperature(10℃)can effectively delay the quality deterioration of ordinary late japonica rice.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education,Science and Technology (2012014940)supported by a grant(Code#’08 RTIP B01-01) from the Regional Technology Innovation Program (RTIP)funded by the Ministry of Land Transport and Maritime Affairs of the Korean government
文摘A large number of debris flows occurred simultaneously at around 8:30 to 8:50 a.m.on July 27,2011,at the center of Seoul,Korea.This area is located in the southern part of Seoul and is a densely populated district.As a result of the debris flow event,16 people were killed,30 houses were buried,and 116 houses were damaged around Umyeon Mountain,a relatively small mountain with a height of 312.6 m.Since the debris flow event,field investigations on the initiation and transportation zones of debris flows have been carried out.Rainfall data were collected from the automatic weather stations(AWSs) which are operated by the Korea Meteorological Administration(KMA).Video files recorded by residents were also acquired and used to analyze the flow characteristics of the debris flow.Field investigation shows that about 40 debris flows occurred around Umyeon Mountain and most of the debris flows were initiated by small slope failures.The effects of the precipitation that triggered the debris flows were analyzed as well.A landslide hazard map which considers slope gradient and aspect,strength of soil,hazard record,rainfall conditions,and vegetation,was constructed and compared with the initiation zones of debris flows.
文摘Absrtact: The principle of ZVS - PWM inverting circuit is first described by means of inverting welder supply. The contrastive study is made on switching characte -ristics and switching losses of IGBT between ZVS - PWM and hard - switching.
