The power system restoration control has a higher uncertainty level than the preventive control of cascading failures. In order to ensure the feasibility of the decision support system of restoration control, a decisi...The power system restoration control has a higher uncertainty level than the preventive control of cascading failures. In order to ensure the feasibility of the decision support system of restoration control, a decision support framework for adaptive restoration control of transmission system is proposed, which can support the coordinated restoration of multiple partitions, coordinated restoration of units and loads, and coordination of multi-partition decision-making process and actual restoration process. The proposed framework is divided into two layers, global coordination layer and partition optimization layer. The upper layer partitions the transmission system according to the power outage scenario, constantly and dynamically adjusts the partitions during the restoration process, and optimizes the time-space decision-making of inter-partition connectivity. For each partition, the lower layer pre-selects restoration targets according to the estimated restoration income, optimizes the corresponding restoration paths, and evaluates the restoration plans according to the expected net income per unit of power consumption. During the restoration process, if the restoration operation such as energizing the outage branch fails, the current restoration plan will be adaptively switched to the sub-optimal one or re-optimized if necessary. The framework includes two operation modes, i.e., the on-line operation mode and training simulation mode, and provides an information interaction interface for collaborative restoration with related distribution systems. The effectiveness and adaptability of the proposed framework is demonstrated by simulations using the modified IEEE 118-bus system.展开更多
The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process o...The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process of collision that often occurs in gear system. Focus on the contact-impact events, this paper proposes an improved gear contact force model for dynamic analysis in helical gear transmission system. In this model, a new factor associated with hysteresis damping is developed for contact-impact state, whereas the traditional linear damping factor is utilized for normal meshing state. For determining the selection strategy of these two damping factors, the fundamental contact mechanics of contact-impact event a ected by supporting forces are analyzed. During this analysis, an e ect factor is proposed for evaluating the influence of supporting forces on collision. Meanwhile, a new restitution of coe cient is deduced for calculating hysteresis damping factor, which suitable for both separation and non-separation states at the end of collision. In addition, the time-varying meshing sti ness(TVMS) is obtained based on the potential energy approach and the slice theory. Finally, a dynamic analysis of a helical gear system is carried out to better understand the contact force model proposed in this paper. The analysis results show that the contribution of supporting forces to the dynamic response of contact-impact event within gear pair is important. The supporting forces and dissipative energy are the main reasons for gear system to enter a steady contact state from repeated contact-impact state. This research proposes an improved contact force model which distinguishes meshing and collision states in gear system.展开更多
For the high-temperature catalytic reaction,revealing the interface of catalyst–support and its evolution under reactive conditions is of crucial importance for understanding the reaction mechanism.However,much less ...For the high-temperature catalytic reaction,revealing the interface of catalyst–support and its evolution under reactive conditions is of crucial importance for understanding the reaction mechanism.However,much less is known about the atomic-scale interface of the hard-to-reduce silica-metal compared to that of reducible oxide systems.Here we reported the general behaviors of SiO_(2)migration onto various metal(Pt,Co,Rh,Pd,Ru,and Ni)nanocrystals supported on silica.Typically,the Pt/SiO_(2)catalytic system,which boosted the CO_(2)hydrogenation to CO,exhibited the reduction of Si0 at the Pt-SiO2 interface under H2 and further Si diffusion into the near surface of Pt nanoparticles,which was unveiled by in-situ environmental transmission electron microscopy coupled with spectroscopies.This reconstructed interface with Si diffused into Pt increased the sinter resistance of catalyst and thus improved the catalytic stability.The morphology of metal nanoparticles with SiO_(2)overlayer were dynamically evolved under reducing,vacuum,and oxidizing atmospheres,with a thicker SiO_(2)layer under oxidizing condition.The theoretical calculations revealed the mechanism that the Si-Pt surface provided synergistic sites for the activation of CO_(2)/H_(2)to produce CO with lower energy barriers,consequently boosting the high-temperature reverse water-gas shift reaction.These findings deepen the understanding toward the interface structure of inert oxide supported catalysts.展开更多
There is a new public health catastrophe forbidding the world.With the advent and spread of 2019 novel coro-navirus(2019-nCoV).Learning from the experiences of various countries and the World Health Organization(WHO)g...There is a new public health catastrophe forbidding the world.With the advent and spread of 2019 novel coro-navirus(2019-nCoV).Learning from the experiences of various countries and the World Health Organization(WHO)guidelines,social distancing,use of sanitizers,thermal screening,quarantining,and provision of lock-down in the cities being the effective measure that can contain the spread of the pandemic.Though complete lockdown helps in containing the spread,it generates complexity by breaking the economic activity chain.Besides,laborers,farmers,and workers may lose their daily earnings.Owing to these detrimental effects,the government has to open the lockdown strategically.Prediction of the COVID-19 spread and analyzing when the cases would stop increasing helps in developing a strategy.An attempt is made in this paper to predict the time after which the number of new cases stops rising,considering the strong implementation of lockdown conditions using three different techniques such as Decision Tree,Support Vector Machine,and Gaussian Process Regression algorithm are used to project the number of cases.Thus,the projections are used in identifying inflection points,which would help in planning the easing of lockdown in a few of the areas strategically.The criticality in a region is evaluated using the criticality index(CI),which is proposed by authors in one of the past of research works.This research work is made available in a dashboard to enable the decision-makers to combat the pandemic.展开更多
根据实际工程需求,将统一潮流控制器(Unified Power Flow Controller,UPFC)的拓扑结构进行变换。将UPFC系统的串联换流器和并联换流器接在不同的线路中,为了提高串联侧的输电能力,提出一种可再生能源对UPFC系统提供有功功率支持的方案...根据实际工程需求,将统一潮流控制器(Unified Power Flow Controller,UPFC)的拓扑结构进行变换。将UPFC系统的串联换流器和并联换流器接在不同的线路中,为了提高串联侧的输电能力,提出一种可再生能源对UPFC系统提供有功功率支持的方案。由于可再生能源的不确定性,为了系统的安全和稳定,可再生能源提供的功率先由电池储能进行存储,再做接入;对含新型UPFC拓扑结构的输电系统进行数学建模,以传输功率最大化为目标函数,通过遗传算法进行求解;最后通过算例仿真验证所提方案的正确性和有效性。展开更多
基金This work was supported in part by the China State Grid Corporation project of the Key Technologies of Power Grid Proactive Support for Energy Transition (No. 5100-202040325A-0-0-00).
文摘The power system restoration control has a higher uncertainty level than the preventive control of cascading failures. In order to ensure the feasibility of the decision support system of restoration control, a decision support framework for adaptive restoration control of transmission system is proposed, which can support the coordinated restoration of multiple partitions, coordinated restoration of units and loads, and coordination of multi-partition decision-making process and actual restoration process. The proposed framework is divided into two layers, global coordination layer and partition optimization layer. The upper layer partitions the transmission system according to the power outage scenario, constantly and dynamically adjusts the partitions during the restoration process, and optimizes the time-space decision-making of inter-partition connectivity. For each partition, the lower layer pre-selects restoration targets according to the estimated restoration income, optimizes the corresponding restoration paths, and evaluates the restoration plans according to the expected net income per unit of power consumption. During the restoration process, if the restoration operation such as energizing the outage branch fails, the current restoration plan will be adaptively switched to the sub-optimal one or re-optimized if necessary. The framework includes two operation modes, i.e., the on-line operation mode and training simulation mode, and provides an information interaction interface for collaborative restoration with related distribution systems. The effectiveness and adaptability of the proposed framework is demonstrated by simulations using the modified IEEE 118-bus system.
基金Supported by National Natural Science Foundation of China(Grant No.51475263)
文摘The current research on gear system dynamics mainly utilizes linear spring damping model to calculate the contact force between gears. However, this linear model cannot correctly describe the energy transfer process of collision that often occurs in gear system. Focus on the contact-impact events, this paper proposes an improved gear contact force model for dynamic analysis in helical gear transmission system. In this model, a new factor associated with hysteresis damping is developed for contact-impact state, whereas the traditional linear damping factor is utilized for normal meshing state. For determining the selection strategy of these two damping factors, the fundamental contact mechanics of contact-impact event a ected by supporting forces are analyzed. During this analysis, an e ect factor is proposed for evaluating the influence of supporting forces on collision. Meanwhile, a new restitution of coe cient is deduced for calculating hysteresis damping factor, which suitable for both separation and non-separation states at the end of collision. In addition, the time-varying meshing sti ness(TVMS) is obtained based on the potential energy approach and the slice theory. Finally, a dynamic analysis of a helical gear system is carried out to better understand the contact force model proposed in this paper. The analysis results show that the contribution of supporting forces to the dynamic response of contact-impact event within gear pair is important. The supporting forces and dissipative energy are the main reasons for gear system to enter a steady contact state from repeated contact-impact state. This research proposes an improved contact force model which distinguishes meshing and collision states in gear system.
基金supported by the National Natural Science Foundation of China revise to(Nos.22222504,92161124,and 52002165)the National Key Research and Development Program of China(No.2021YFA0717400)+4 种基金the Beijing National Laboratory for Molecular Sciences(No.BNLMS202013)the Guangdong Provincial Natural Science Foundation(No.2021A1515010229)the Shenzhen Basic Research Project(No.JCYJ20210324104808022)the Guangdong Provincial Key Laboratory of Catalysis(No.2020B121201002)L.W.acknowledges the China Postdoctoral Science Foundation(No.2020M682764).
文摘For the high-temperature catalytic reaction,revealing the interface of catalyst–support and its evolution under reactive conditions is of crucial importance for understanding the reaction mechanism.However,much less is known about the atomic-scale interface of the hard-to-reduce silica-metal compared to that of reducible oxide systems.Here we reported the general behaviors of SiO_(2)migration onto various metal(Pt,Co,Rh,Pd,Ru,and Ni)nanocrystals supported on silica.Typically,the Pt/SiO_(2)catalytic system,which boosted the CO_(2)hydrogenation to CO,exhibited the reduction of Si0 at the Pt-SiO2 interface under H2 and further Si diffusion into the near surface of Pt nanoparticles,which was unveiled by in-situ environmental transmission electron microscopy coupled with spectroscopies.This reconstructed interface with Si diffused into Pt increased the sinter resistance of catalyst and thus improved the catalytic stability.The morphology of metal nanoparticles with SiO_(2)overlayer were dynamically evolved under reducing,vacuum,and oxidizing atmospheres,with a thicker SiO_(2)layer under oxidizing condition.The theoretical calculations revealed the mechanism that the Si-Pt surface provided synergistic sites for the activation of CO_(2)/H_(2)to produce CO with lower energy barriers,consequently boosting the high-temperature reverse water-gas shift reaction.These findings deepen the understanding toward the interface structure of inert oxide supported catalysts.
文摘There is a new public health catastrophe forbidding the world.With the advent and spread of 2019 novel coro-navirus(2019-nCoV).Learning from the experiences of various countries and the World Health Organization(WHO)guidelines,social distancing,use of sanitizers,thermal screening,quarantining,and provision of lock-down in the cities being the effective measure that can contain the spread of the pandemic.Though complete lockdown helps in containing the spread,it generates complexity by breaking the economic activity chain.Besides,laborers,farmers,and workers may lose their daily earnings.Owing to these detrimental effects,the government has to open the lockdown strategically.Prediction of the COVID-19 spread and analyzing when the cases would stop increasing helps in developing a strategy.An attempt is made in this paper to predict the time after which the number of new cases stops rising,considering the strong implementation of lockdown conditions using three different techniques such as Decision Tree,Support Vector Machine,and Gaussian Process Regression algorithm are used to project the number of cases.Thus,the projections are used in identifying inflection points,which would help in planning the easing of lockdown in a few of the areas strategically.The criticality in a region is evaluated using the criticality index(CI),which is proposed by authors in one of the past of research works.This research work is made available in a dashboard to enable the decision-makers to combat the pandemic.
文摘根据实际工程需求,将统一潮流控制器(Unified Power Flow Controller,UPFC)的拓扑结构进行变换。将UPFC系统的串联换流器和并联换流器接在不同的线路中,为了提高串联侧的输电能力,提出一种可再生能源对UPFC系统提供有功功率支持的方案。由于可再生能源的不确定性,为了系统的安全和稳定,可再生能源提供的功率先由电池储能进行存储,再做接入;对含新型UPFC拓扑结构的输电系统进行数学建模,以传输功率最大化为目标函数,通过遗传算法进行求解;最后通过算例仿真验证所提方案的正确性和有效性。
