Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new...Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new solution for the frequency control of the AMG.In this paper,a novel decentralized demand control strategy(DDC) for family-friendly controllable refrigerators considering customer comfort level is proposed to regulate the frequency of AMG in coordination with the energy storage system(ESS).The refrigerator under DDC responds to the local frequency signals quickly and adjusts its operation cycle dynamically.Meanwhile,a customer participation degree which is proportional to the frequency deviation is introduced to evaluate the customer comforts when responding to the frequency of AMG.Finally,a benchmark low voltage AMG is established as a test system to verify the effectiveness of the proposed DDC strategy.Simulation results show that the DDC strategy can not only improve the frequency control effect of AMG effectively but also guarantee the customer comforts as well as reduce the capacity of ESS.展开更多
Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are op...Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are optimized by taking minimum entransy dissipation rate as optimization objective.The optimal constructs of the three "volume-point" heat conduction models with minimum dimensionless equivalent thermal resistance are obtained.The results show that the optimal constructs of the three-dimensional cylindrical assembly based on the minimizations of dimensionless equivalent thermal resistance and dimensionless maximum thermal resistance are different,which is obviously different from the comparison between those of the corresponding two-dimensional rectangular assembly based on the minimizations of these two objectives.The optimal constructs based on rectangular and triangular elements on microscale and nanoscale when the size effect takes effect are obviously different from those when the size effect does not take effect.Because the thermal current density in the high conductivity channel of the rectangular and triangular second order assemblies are not linear with the length,the optimal constructs of these assemblies based on the minimization of entransy dissipation rate are different from those based on the minimization of maximum temperature difference.The dimensionless equivalent thermal resistance defined based on entransy dissipation rate reflects the average heat transfer performance of the construct.The studies on "volume-point" heat conduction constructal problems at three-dimensional conditions and microscale and nanoscale by taking minimum entransy dissipation rate as optimization objective extend the application range of the entransy dissipation extremum principle.展开更多
基金supported by the Special Fund of the National Basic Research Program of China ("973" Project) (Grant Nos. 2009CB219701,2010CB234608)the National Natural Science Foundation of China (Grant No. 51277128)+1 种基金the Tianjin Municipal Science and Technology Development Program of China (Grant No. 09JCZDJC25000)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090032110064)
文摘Frequency is a key issue for the stable operation of autonomous microgrid(AMG) with a large penetration of intermittent renewable energy resources.The fast development of demand-side response technology provides a new solution for the frequency control of the AMG.In this paper,a novel decentralized demand control strategy(DDC) for family-friendly controllable refrigerators considering customer comfort level is proposed to regulate the frequency of AMG in coordination with the energy storage system(ESS).The refrigerator under DDC responds to the local frequency signals quickly and adjusts its operation cycle dynamically.Meanwhile,a customer participation degree which is proportional to the frequency deviation is introduced to evaluate the customer comforts when responding to the frequency of AMG.Finally,a benchmark low voltage AMG is established as a test system to verify the effectiveness of the proposed DDC strategy.Simulation results show that the DDC strategy can not only improve the frequency control effect of AMG effectively but also guarantee the customer comforts as well as reduce the capacity of ESS.
基金supported by the National Natural Science Foundation of China (Grant No. 51176203)the Natural Science Foundation of Naval University of Engineering (Grant No. HGDYDJJ10011)the Natural Science Foundation for Youngsters of Naval University of Engineering (Grant No. HGDQNJJ10017)
文摘Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are optimized by taking minimum entransy dissipation rate as optimization objective.The optimal constructs of the three "volume-point" heat conduction models with minimum dimensionless equivalent thermal resistance are obtained.The results show that the optimal constructs of the three-dimensional cylindrical assembly based on the minimizations of dimensionless equivalent thermal resistance and dimensionless maximum thermal resistance are different,which is obviously different from the comparison between those of the corresponding two-dimensional rectangular assembly based on the minimizations of these two objectives.The optimal constructs based on rectangular and triangular elements on microscale and nanoscale when the size effect takes effect are obviously different from those when the size effect does not take effect.Because the thermal current density in the high conductivity channel of the rectangular and triangular second order assemblies are not linear with the length,the optimal constructs of these assemblies based on the minimization of entransy dissipation rate are different from those based on the minimization of maximum temperature difference.The dimensionless equivalent thermal resistance defined based on entransy dissipation rate reflects the average heat transfer performance of the construct.The studies on "volume-point" heat conduction constructal problems at three-dimensional conditions and microscale and nanoscale by taking minimum entransy dissipation rate as optimization objective extend the application range of the entransy dissipation extremum principle.
