Considering the additional electric energy generated after the full operation of the underground hydropower station, the electric energy accommodation of the Three Gorges Project (TGP) is reviewed. It is focused on th...Considering the additional electric energy generated after the full operation of the underground hydropower station, the electric energy accommodation of the Three Gorges Project (TGP) is reviewed. It is focused on the additional electricity accommodation, based on the research at the early stage. The electric energy accommodation solutions are recommended as that, based on the cost-benefit analysis of the power distribution area, the additional electric energy of the Three Gorges should be given priority to meet the needs at the supply end of Hubei and Chongqing. The results of this research has a reference value on the implementation of the Three Gorges electric power accommodation, after the further optimization of the transmission curves in both wet and dry seasons.展开更多
In order to build a power plant with high efficiency,low investment and zero warm water discharge,a series of innovations are applied to the two 1 000-MW units of Ninghai Power Plant.The new technologies include the c...In order to build a power plant with high efficiency,low investment and zero warm water discharge,a series of innovations are applied to the two 1 000-MW units of Ninghai Power Plant.The new technologies include the closed-circuit system for seawater cooling tower with a spraying area of 13 000 m2,the main buildings with reinforced concrete structure,the plasma ignition system for tower boiler and the fieldbus control system.Optimization measures are taken in some aspects,such as the open point of the turbine overload valves,the boiler dimensions,the technical process,the electric system,the building structures and the layout of the power plant.The units have been running for more than half a year with the thermal efficiency as high as 45.79% and without warm water discharged,which indicates that all the systems are safe and steady and the original purpose of optimization has been realized.展开更多
The triggering mechanisms of debris flows were explored in the field using artificial rainfall experiments in two gullies, Dawazi Gully and Aizi Gully, in Yunnan and Sichuan Provinces, China,respectively. The soils at...The triggering mechanisms of debris flows were explored in the field using artificial rainfall experiments in two gullies, Dawazi Gully and Aizi Gully, in Yunnan and Sichuan Provinces, China,respectively. The soils at both sites are bare, loose and cohesive gravel-dominated. The results of a direct shear test, rheological test and back-analysis using soil mass stability calculations indicate that the mechanisms responsible for triggering debris flows involved the decreases in static and dynamic resistance of the soil. The triggering processes can be divided into 7 stages: rainfall infiltration, generation of excess runoff, high pore water pressure, surface erosion, soil creep, soil slipping, debris flow triggering and debris flow increment. In addition, two critical steps are evident:(i) During the process of the soil mass changing from a static to a mobile state, its cohesion decreased sharply(e.g., the cohesion of the soil mass in Dawazi Gully decreased from 0.520 to0.090 k Pa, a decrease of 83%). This would have reduced the soil strength and the kinetic energy during slipping, eventually triggered the debris flow.(ii) When the soil mass began to slip, the velocity and the volume increment of the debris flow fluctuated as a result of the interaction of soil resistance and the sliding force. The displaced soil mass from the source area of the slope resulted in the deposition of a volume of soil more than 7-8 times greater than that in the source area.展开更多
The uneven distribution of economic development and energy resources in the Southern Power Grid, yet with stronger complementary superiority has determined the necessity to actively push forward power transmission fro...The uneven distribution of economic development and energy resources in the Southern Power Grid, yet with stronger complementary superiority has determined the necessity to actively push forward power transmission from west to east in the Southern Power Grid and realize optimal disposition in even greater scope. To further promote transmission capability and operational security from west to east, measures including power sources disposition, unit starting schemes, power grid configuration, DC modulation and application of new transmission technologies are analyzed in this paper.展开更多
The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventila...The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventilation as much as possible. Then,it comes to a conclusion by the field test that natural ventilation has certain practical effect on improving indoor thermal environment. CFD simulation software is employed to verify the test result. Based on PMV modified model,and according to norms,geography and climate combined with the measured and simulated results,the application of the time and effectiveness of natural ventilation in hot and humid region were analyzed,to some extent,providing a basis for reducing the air-conditioner's runtime with natural ventilation.展开更多
For active distribution networks(ADNs)integrated with massive inverter-based energy resources,it is impractical to maintain the accurate model and deploy measurements at all nodes due to the large-scale of ADNs.Thus,c...For active distribution networks(ADNs)integrated with massive inverter-based energy resources,it is impractical to maintain the accurate model and deploy measurements at all nodes due to the large-scale of ADNs.Thus,current models of ADNs usually involve significant errors or even unknown occurances.Moreover,ADNs are usually partially observable since only a few measurements are available at pilot nodes or nodes with significant users.To provide a practical Volt/Var control(VVC)strategy for such networks,a data-driven VVC method is proposed in this paper.First,the system response policy,approximating the relationship between the control variables and states of monitoring nodes,is estimated by a recursive regression closed-form solution.Then,based on real-time measurements and the newly updated system response policy,a VVC strategy with convergence guarantee is realized.Since the recursive regression solution is embedded in the control stage,a data-driven closedloop VVC framework is established.The effectiveness of the proposed method is validated in an unbalanced distribution system considering nonlinear loads,where not only the rapid and self-adaptive voltage regulation is realized,but also systemwide optimization is achieved.展开更多
The primary cracks in the rock block undergo series of steps and finally disintegrate,during this procession,the radius affects the impact force of rock block in clastic flow.Therefore,it is essential to figure out th...The primary cracks in the rock block undergo series of steps and finally disintegrate,during this procession,the radius affects the impact force of rock block in clastic flow.Therefore,it is essential to figure out the evolution mechanism of crack propagation for the design of engineering protection.In this study,based on fracture mechanics and Hertz contact theory,collision happened between rock block and slope surface is assumed to be elastic contact.Based on the above assumption,the critical impact force of crack propagation is obtained,and a model used to calculate the crack propagation length in a single collision is established.Besides,a rock fall site in Jiuzhai Valley was used to verify the calculation model.According to the model,several key factors were identified to influence crack propagation length including falling height,initial equivalent radius,and recovery coefficient of slope surface.Moreover,as a result of the orthogonal experiment,the influence of those factors on the crack propagation length was ranked,normal recovery coefficient>initial radius>initial falling height.In addition,the kinetic energy of the rock block in the compression stage is transformed into elastic deformation energy,angular kinetic energy,and dissipated energy of crack propagation.Due to the increase of collisions,the kinetic energy is gradually transformed into angular kinetic energy,and the dissipated energy of crack propagation weights is reduced.In conclusion,the crack propagation in rock block is a complicated progress,which is affected by multiple factors,especially falling height,initial equivalent radius,and recovery coefficient of slope surface.Our study may provide guidance for the design of protective structure of clastic flows.展开更多
A time-delay-dependent wide-area damping controller synthesis approach,based on Jensen’s integral inequality and evolution algorithm,is developed to suppress the adverse effect of time delay on the supplemental contr...A time-delay-dependent wide-area damping controller synthesis approach,based on Jensen’s integral inequality and evolution algorithm,is developed to suppress the adverse effect of time delay on the supplemental control of high-voltage direct current(DC)transmission systems.Initially,the state-space model of hybrid AC/DC systems with time delay is derived and the delay-dependent criteria for the stability of the closed-loop system are provided based on Jensen’s integral inequality.Subsequently,initial solutions are randomly generated to overcome the difficulty of solving the nonlinear matrix inequality.Finally,the time-delay stability upper bound of the controller is optimized using the differential evolution algorithm.In comparison to popular time-delay stable controller design methods,such as the free-weighting-matrix approach,the proposed method based on output feedback realization requires fewer decision variables and is more suitable for large-scale hybrid AC/DC systems.Three examples are introduced to verify the effectiveness of the proposed method.展开更多
What has become known as Stahl's Theorem in power-engineering circles has been used to justify a convergence guarantee of the Holomorphic Embedding Method(HEM)as it applies to the power-flow problem.In this,the se...What has become known as Stahl's Theorem in power-engineering circles has been used to justify a convergence guarantee of the Holomorphic Embedding Method(HEM)as it applies to the power-flow problem.In this,the second part of a two-part paper,we examine implications to numerical convergence of the HEM and the numerical properties of a Pade approximant algorithm.We show that even if the point of interest is within the convergence domain,numerical convergence of the sequence of Pade approximants computed with finite precision is not guaranteed.We propose a convergence factor equation that can be used to both estimate the convergence rate and the capacity of the branch cut.We also show that the study of convergence properties of the Pade approximant is the study of the location of the branch-points of the function,which in turn dictate branch-cut topology and capacity and,therefore,convergence rate.展开更多
文摘Considering the additional electric energy generated after the full operation of the underground hydropower station, the electric energy accommodation of the Three Gorges Project (TGP) is reviewed. It is focused on the additional electricity accommodation, based on the research at the early stage. The electric energy accommodation solutions are recommended as that, based on the cost-benefit analysis of the power distribution area, the additional electric energy of the Three Gorges should be given priority to meet the needs at the supply end of Hubei and Chongqing. The results of this research has a reference value on the implementation of the Three Gorges electric power accommodation, after the further optimization of the transmission curves in both wet and dry seasons.
文摘In order to build a power plant with high efficiency,low investment and zero warm water discharge,a series of innovations are applied to the two 1 000-MW units of Ninghai Power Plant.The new technologies include the closed-circuit system for seawater cooling tower with a spraying area of 13 000 m2,the main buildings with reinforced concrete structure,the plasma ignition system for tower boiler and the fieldbus control system.Optimization measures are taken in some aspects,such as the open point of the turbine overload valves,the boiler dimensions,the technical process,the electric system,the building structures and the layout of the power plant.The units have been running for more than half a year with the thermal efficiency as high as 45.79% and without warm water discharged,which indicates that all the systems are safe and steady and the original purpose of optimization has been realized.
基金supported by the National Natural Science Foundation of China(Grant No.41190084Grant No.41671112+2 种基金Grant No.41661134012)the Technology Program of Housing and Urban-Rural Development of P.R.China(Grant No.2015-K6-016)the key projects of Education Department of Sichuan Province,China(Grant No.15ZA0053)
文摘The triggering mechanisms of debris flows were explored in the field using artificial rainfall experiments in two gullies, Dawazi Gully and Aizi Gully, in Yunnan and Sichuan Provinces, China,respectively. The soils at both sites are bare, loose and cohesive gravel-dominated. The results of a direct shear test, rheological test and back-analysis using soil mass stability calculations indicate that the mechanisms responsible for triggering debris flows involved the decreases in static and dynamic resistance of the soil. The triggering processes can be divided into 7 stages: rainfall infiltration, generation of excess runoff, high pore water pressure, surface erosion, soil creep, soil slipping, debris flow triggering and debris flow increment. In addition, two critical steps are evident:(i) During the process of the soil mass changing from a static to a mobile state, its cohesion decreased sharply(e.g., the cohesion of the soil mass in Dawazi Gully decreased from 0.520 to0.090 k Pa, a decrease of 83%). This would have reduced the soil strength and the kinetic energy during slipping, eventually triggered the debris flow.(ii) When the soil mass began to slip, the velocity and the volume increment of the debris flow fluctuated as a result of the interaction of soil resistance and the sliding force. The displaced soil mass from the source area of the slope resulted in the deposition of a volume of soil more than 7-8 times greater than that in the source area.
文摘The uneven distribution of economic development and energy resources in the Southern Power Grid, yet with stronger complementary superiority has determined the necessity to actively push forward power transmission from west to east in the Southern Power Grid and realize optimal disposition in even greater scope. To further promote transmission capability and operational security from west to east, measures including power sources disposition, unit starting schemes, power grid configuration, DC modulation and application of new transmission technologies are analyzed in this paper.
基金Project(50838009) supported by the National Natural Science Foundation of ChinaProject(2006BAJ01A05) supported by the National Key Technologies R&D Program of ChinaProject(CSTC,2008AB7110) supported by Key Technologies R & D Program of Chongqing City,China
文摘The current ventilation condition of the hot and humid regions was analyzed through on-site investigation. It is found that residents in this region expect to improve indoor thermal environment through natural ventilation as much as possible. Then,it comes to a conclusion by the field test that natural ventilation has certain practical effect on improving indoor thermal environment. CFD simulation software is employed to verify the test result. Based on PMV modified model,and according to norms,geography and climate combined with the measured and simulated results,the application of the time and effectiveness of natural ventilation in hot and humid region were analyzed,to some extent,providing a basis for reducing the air-conditioner's runtime with natural ventilation.
基金supported by the Research Project of China Southern Power Grid Corporation:The demonstration and application of the virtual power plant intelligent operation and management platform with source-grid coordination,No.GDKJXM20185069 (032000KK 52180069)。
文摘For active distribution networks(ADNs)integrated with massive inverter-based energy resources,it is impractical to maintain the accurate model and deploy measurements at all nodes due to the large-scale of ADNs.Thus,current models of ADNs usually involve significant errors or even unknown occurances.Moreover,ADNs are usually partially observable since only a few measurements are available at pilot nodes or nodes with significant users.To provide a practical Volt/Var control(VVC)strategy for such networks,a data-driven VVC method is proposed in this paper.First,the system response policy,approximating the relationship between the control variables and states of monitoring nodes,is estimated by a recursive regression closed-form solution.Then,based on real-time measurements and the newly updated system response policy,a VVC strategy with convergence guarantee is realized.Since the recursive regression solution is embedded in the control stage,a data-driven closedloop VVC framework is established.The effectiveness of the proposed method is validated in an unbalanced distribution system considering nonlinear loads,where not only the rapid and self-adaptive voltage regulation is realized,but also systemwide optimization is achieved.
基金funded by the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA23090403)the Scientific Foundation of the Chinese Academy of Sciences(Grant No.KFZD-SW-425)the Key Research and Development Program of Sichuan Province(Grant No.2019YFG0460)。
文摘The primary cracks in the rock block undergo series of steps and finally disintegrate,during this procession,the radius affects the impact force of rock block in clastic flow.Therefore,it is essential to figure out the evolution mechanism of crack propagation for the design of engineering protection.In this study,based on fracture mechanics and Hertz contact theory,collision happened between rock block and slope surface is assumed to be elastic contact.Based on the above assumption,the critical impact force of crack propagation is obtained,and a model used to calculate the crack propagation length in a single collision is established.Besides,a rock fall site in Jiuzhai Valley was used to verify the calculation model.According to the model,several key factors were identified to influence crack propagation length including falling height,initial equivalent radius,and recovery coefficient of slope surface.Moreover,as a result of the orthogonal experiment,the influence of those factors on the crack propagation length was ranked,normal recovery coefficient>initial radius>initial falling height.In addition,the kinetic energy of the rock block in the compression stage is transformed into elastic deformation energy,angular kinetic energy,and dissipated energy of crack propagation.Due to the increase of collisions,the kinetic energy is gradually transformed into angular kinetic energy,and the dissipated energy of crack propagation weights is reduced.In conclusion,the crack propagation in rock block is a complicated progress,which is affected by multiple factors,especially falling height,initial equivalent radius,and recovery coefficient of slope surface.Our study may provide guidance for the design of protective structure of clastic flows.
基金supported by the National Key Research and Development Program of China(2016YFB0901001).
文摘A time-delay-dependent wide-area damping controller synthesis approach,based on Jensen’s integral inequality and evolution algorithm,is developed to suppress the adverse effect of time delay on the supplemental control of high-voltage direct current(DC)transmission systems.Initially,the state-space model of hybrid AC/DC systems with time delay is derived and the delay-dependent criteria for the stability of the closed-loop system are provided based on Jensen’s integral inequality.Subsequently,initial solutions are randomly generated to overcome the difficulty of solving the nonlinear matrix inequality.Finally,the time-delay stability upper bound of the controller is optimized using the differential evolution algorithm.In comparison to popular time-delay stable controller design methods,such as the free-weighting-matrix approach,the proposed method based on output feedback realization requires fewer decision variables and is more suitable for large-scale hybrid AC/DC systems.Three examples are introduced to verify the effectiveness of the proposed method.
基金supported by the Science and Technology Project of SGCC(No.5455HJ160007).
文摘What has become known as Stahl's Theorem in power-engineering circles has been used to justify a convergence guarantee of the Holomorphic Embedding Method(HEM)as it applies to the power-flow problem.In this,the second part of a two-part paper,we examine implications to numerical convergence of the HEM and the numerical properties of a Pade approximant algorithm.We show that even if the point of interest is within the convergence domain,numerical convergence of the sequence of Pade approximants computed with finite precision is not guaranteed.We propose a convergence factor equation that can be used to both estimate the convergence rate and the capacity of the branch cut.We also show that the study of convergence properties of the Pade approximant is the study of the location of the branch-points of the function,which in turn dictate branch-cut topology and capacity and,therefore,convergence rate.