Load flow is an important tool used by power engineers for planning, to determine the best operation for a power system and exchange of power between utility companies. In order to have an efficient operating power sy...Load flow is an important tool used by power engineers for planning, to determine the best operation for a power system and exchange of power between utility companies. In order to have an efficient operating power system, it is necessary to determine which method is suitable and efficient for the system’s load flow analysis. A power flow analysis method may take a long time and therefore prevent achieving an accurate result to a power flow solution because of continuous changes in power demand and generations. This paper presents analysis of the load flow problem in power system planning studies. The numerical methods: Gauss-Seidel, Newton-Raphson and Fast Decoupled methods were compared for a power flow analysis solution. Simulation is carried out using Matlab for test cases of IEEE 9-Bus, IEEE 30-Bus and IEEE 57-Bus system. The simulation results were compared for number of iteration, computational time, tolerance value and convergence. The compared results show that Newton-Raphson is the most reliable method because it has the least number of iteration and converges faster.展开更多
Recently,the fast frequency response(FFR)service by large-scale battery energy storage systems(BESSs)has been successfully proved to arrest the frequency excursion during an unexpected power outage.However,adequate fr...Recently,the fast frequency response(FFR)service by large-scale battery energy storage systems(BESSs)has been successfully proved to arrest the frequency excursion during an unexpected power outage.However,adequate frequency response relies on proper evaluation of the contingency reserve of BESSs.The BESS FFR reserve is commonly managed under fixed contracts,ignoring various response characteristics of different BESSs and their coexisting interactions.This paper proposes a new methodology based on dynamic grid response and various BESS response characteristics to optimise the FFR reserves and prevent the frequency from breaching the under-frequency load shedding(UFLS)thresholds.The superiority of the proposed method is demonstrated to manage three large-scale BESSs operating simultaneously in an Australian power grid under high renewable penetration scenarios.Further,the proposed method can identify remaining battery power and energy reserve to be safely utilised for other grid services(e.g.,energy arbitrage).The results can provide valuable insights for integrating FFR into conventional ancillary services and techno-effective management of multiple BESSs.展开更多
The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In th...The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In this paper,the 1200 MWe large pool SFR(CFR1200)is used as the heat source of the system,and the sodium circuit temperature and the heat load are the operating boundaries of the cycle system.The performance of different SCO_(2) Brayton cycle systems and changes in key equipment performance are compared.The study indicates that the inter-stage cooling and recompression cycle has the best match with the heat source characteristics of the SFR,and the cycle efficiency is the highest(40.7%).Then,based on the developed system transient analysis program(FR-Sdaso),a pool-type SFR power plant system analysis model based on the inter-stage cooling and recompression cycle is established.In addition,the matching between the inter-stage cooling recompression cycle and the SFR during the load cycle of the power plant is studied.The analysis shows that when the nuclear island adopts the flow-advanced operation strategy and the carbon dioxide flowrate in the SCO_(2) power conversion system is adjusted with the goal of maintaining the sodium-carbon dioxide heat exchanger sodium side outlet temperature unchanged,the inter-stage cooling recompression cycle can match the operation of the SFR very well.展开更多
Fast walking and jogging are two common exercises for people to maintain health in daily life.But the differences in loading patterns of fast walking and jogging are still unclear.The purpose of this study was to comp...Fast walking and jogging are two common exercises for people to maintain health in daily life.But the differences in loading patterns of fast walking and jogging are still unclear.The purpose of this study was to compare loading patterns in fast walking and jogging at the same speed,and to identify how differences in foot mechanics influence plantar pressure distribution between the two modes of gait.Totally,49 healthy males participated in this study.Data of pressure parameters,including maximum force(MF),peak pressure(PP),contact area(CA),force-time integral(FTI),were recorded by Pedar-X insole plantar pressure measurement system in participants’fast walking and jogging process at 7 km/h.A Load transfer analysis method was used to quantify the plantar load transference from fast walking to jogging.The results showed that MF,PP and CA increased in metatarsal regions and midfoot regions while decreased in toes regions and heel during jogging when compared with fast walking.FTI decreased in all foot regions during jogging compared to fast walking.Under the effects of spring mechanics and the varus of rearfoot during jogging,fast walking and jogging reveal different loading patterns.Compared jogging to fast walking,load transferred as follow:1)in transverse direction,load transferred from lateral foot to medial foot in metatarsal regions and midfoot regions,2)in longitudinal direction,load transferred from toes to the metatarsal,and from heel to the metatarsal and midfoot.These results also provide suggestions for footwear designs.展开更多
文摘Load flow is an important tool used by power engineers for planning, to determine the best operation for a power system and exchange of power between utility companies. In order to have an efficient operating power system, it is necessary to determine which method is suitable and efficient for the system’s load flow analysis. A power flow analysis method may take a long time and therefore prevent achieving an accurate result to a power flow solution because of continuous changes in power demand and generations. This paper presents analysis of the load flow problem in power system planning studies. The numerical methods: Gauss-Seidel, Newton-Raphson and Fast Decoupled methods were compared for a power flow analysis solution. Simulation is carried out using Matlab for test cases of IEEE 9-Bus, IEEE 30-Bus and IEEE 57-Bus system. The simulation results were compared for number of iteration, computational time, tolerance value and convergence. The compared results show that Newton-Raphson is the most reliable method because it has the least number of iteration and converges faster.
文摘Recently,the fast frequency response(FFR)service by large-scale battery energy storage systems(BESSs)has been successfully proved to arrest the frequency excursion during an unexpected power outage.However,adequate frequency response relies on proper evaluation of the contingency reserve of BESSs.The BESS FFR reserve is commonly managed under fixed contracts,ignoring various response characteristics of different BESSs and their coexisting interactions.This paper proposes a new methodology based on dynamic grid response and various BESS response characteristics to optimise the FFR reserves and prevent the frequency from breaching the under-frequency load shedding(UFLS)thresholds.The superiority of the proposed method is demonstrated to manage three large-scale BESSs operating simultaneously in an Australian power grid under high renewable penetration scenarios.Further,the proposed method can identify remaining battery power and energy reserve to be safely utilised for other grid services(e.g.,energy arbitrage).The results can provide valuable insights for integrating FFR into conventional ancillary services and techno-effective management of multiple BESSs.
基金the International Cooperative Research and Development Project on Key Technologies of the Fourth Generation Nuclear Energy System Sodium-cooled Fast Reactor(2016YFE0100800).
文摘The supercritical carbon dioxide(SCO_(2))Brayton cycle has become an ideal power conversion system for sodium-cooled fast reactors(SFR)due to its high efficiency,compactness,and avoidance of sodiumwater reaction.In this paper,the 1200 MWe large pool SFR(CFR1200)is used as the heat source of the system,and the sodium circuit temperature and the heat load are the operating boundaries of the cycle system.The performance of different SCO_(2) Brayton cycle systems and changes in key equipment performance are compared.The study indicates that the inter-stage cooling and recompression cycle has the best match with the heat source characteristics of the SFR,and the cycle efficiency is the highest(40.7%).Then,based on the developed system transient analysis program(FR-Sdaso),a pool-type SFR power plant system analysis model based on the inter-stage cooling and recompression cycle is established.In addition,the matching between the inter-stage cooling recompression cycle and the SFR during the load cycle of the power plant is studied.The analysis shows that when the nuclear island adopts the flow-advanced operation strategy and the carbon dioxide flowrate in the SCO_(2) power conversion system is adjusted with the goal of maintaining the sodium-carbon dioxide heat exchanger sodium side outlet temperature unchanged,the inter-stage cooling recompression cycle can match the operation of the SFR very well.
基金supported by National Natural Science Foundation of China,grant number:11502154.
文摘Fast walking and jogging are two common exercises for people to maintain health in daily life.But the differences in loading patterns of fast walking and jogging are still unclear.The purpose of this study was to compare loading patterns in fast walking and jogging at the same speed,and to identify how differences in foot mechanics influence plantar pressure distribution between the two modes of gait.Totally,49 healthy males participated in this study.Data of pressure parameters,including maximum force(MF),peak pressure(PP),contact area(CA),force-time integral(FTI),were recorded by Pedar-X insole plantar pressure measurement system in participants’fast walking and jogging process at 7 km/h.A Load transfer analysis method was used to quantify the plantar load transference from fast walking to jogging.The results showed that MF,PP and CA increased in metatarsal regions and midfoot regions while decreased in toes regions and heel during jogging when compared with fast walking.FTI decreased in all foot regions during jogging compared to fast walking.Under the effects of spring mechanics and the varus of rearfoot during jogging,fast walking and jogging reveal different loading patterns.Compared jogging to fast walking,load transferred as follow:1)in transverse direction,load transferred from lateral foot to medial foot in metatarsal regions and midfoot regions,2)in longitudinal direction,load transferred from toes to the metatarsal,and from heel to the metatarsal and midfoot.These results also provide suggestions for footwear designs.
