针对无线电能传输(wireless power transfer,WPT)系统中等效负载变化而导致系统效率低下的问题,在保证系统恒压输出的前提下,通过最小化输入功率来实现最优效率点跟踪。首先,基于电路理论分别得到最优效率输出和最大功率输出对应的Buck-...针对无线电能传输(wireless power transfer,WPT)系统中等效负载变化而导致系统效率低下的问题,在保证系统恒压输出的前提下,通过最小化输入功率来实现最优效率点跟踪。首先,基于电路理论分别得到最优效率输出和最大功率输出对应的Buck-Boost调压电路的占空比,通过对比分析确定稳压输出控制策略。在此基础上,基于模糊控制理论,通过控制原边逆变器的移相角来最小化输入功率,实现最优效率点跟踪。最后,搭建仿真平台进行了相关验证,证明该方法寻优过程快速而稳定,不需要原、副边通信,既能保证恒压输出,也能实现最大效率跟踪。展开更多
Buildings contribute to a major part of energy consumption in urban areas, especially in areas like Hong Kong which is full of high-rise buildings. Smart buildings with high efficiency can reduce the energy consumptio...Buildings contribute to a major part of energy consumption in urban areas, especially in areas like Hong Kong which is full of high-rise buildings. Smart buildings with high efficiency can reduce the energy consumption largely and help achieve green cities or smart cities. Design and control optimization of building energy systems therefore plays a significant role to obtain the optimal performance. This paper introduces a general methodology for the design and control optimization of building energy systems in the life cycle. When the design scheme of building energy systems is optimized, primary steps and related issues are introduced. To improve the operation performance, the optimal control strategies that can be used by different systems are presented and key issues are discussed. To demonstrate the effect of the methods, the energy system of a high-rise building is introduced. The design on the chilled water pump system and cooling towers is improved. The control strategies for chillers,pumps and fresh air systems are optimized. The energy saving and cost from the design and control optimization methods are analyzed. The presented methodology will provide users and stakeholders an effective approach to improve the energy efficiency of building energy systems and promote the development of smart buildings and smart cities.展开更多
This paper analyzes fault-tolerance over the entire design life of a class of multiple-hop wireless networks, where cooperative transmission schemes are used. The networks are subject to both node failure and random c...This paper analyzes fault-tolerance over the entire design life of a class of multiple-hop wireless networks, where cooperative transmission schemes are used. The networks are subject to both node failure and random channel fading. A node lifetime distribution is modeled with an increasing failure rate, where the node power consumption level enters the parameters of the distribution. A method for assessing both link and network reliabilities projected at the network＇s design life is developed. Link reliability is enhanced through use of redundant nodes. The number of redundant nodes is restricted by the cooperative transmission scheme used. The link reliability is then used to establish a re-transmission control policy that minimizes an expected cost involving power, bandwidth expenditures, and packet loss. The benefit and cost of feedback in network operations are examined. The results of a simulation study under specific node processing times are presented. The study quantifies the effect of loop closure frequency, acknowledgment deadline, and nodes＇ storage capacity on the performance of the network in terms of network lifetime, packet loss rate, and false alarm rate. The study concludes that in a network where energy is severely constrained, feedback must be applied judiciously.展开更多
文摘针对无线电能传输(wireless power transfer,WPT)系统中等效负载变化而导致系统效率低下的问题,在保证系统恒压输出的前提下,通过最小化输入功率来实现最优效率点跟踪。首先,基于电路理论分别得到最优效率输出和最大功率输出对应的Buck-Boost调压电路的占空比,通过对比分析确定稳压输出控制策略。在此基础上,基于模糊控制理论,通过控制原边逆变器的移相角来最小化输入功率,实现最优效率点跟踪。最后,搭建仿真平台进行了相关验证,证明该方法寻优过程快速而稳定,不需要原、副边通信,既能保证恒压输出,也能实现最大效率跟踪。
文摘Buildings contribute to a major part of energy consumption in urban areas, especially in areas like Hong Kong which is full of high-rise buildings. Smart buildings with high efficiency can reduce the energy consumption largely and help achieve green cities or smart cities. Design and control optimization of building energy systems therefore plays a significant role to obtain the optimal performance. This paper introduces a general methodology for the design and control optimization of building energy systems in the life cycle. When the design scheme of building energy systems is optimized, primary steps and related issues are introduced. To improve the operation performance, the optimal control strategies that can be used by different systems are presented and key issues are discussed. To demonstrate the effect of the methods, the energy system of a high-rise building is introduced. The design on the chilled water pump system and cooling towers is improved. The control strategies for chillers,pumps and fresh air systems are optimized. The energy saving and cost from the design and control optimization methods are analyzed. The presented methodology will provide users and stakeholders an effective approach to improve the energy efficiency of building energy systems and promote the development of smart buildings and smart cities.
基金This work was partly supported by the US AFOSR (No. FA9550-06-0456 and FA9550-06-10249).
文摘This paper analyzes fault-tolerance over the entire design life of a class of multiple-hop wireless networks, where cooperative transmission schemes are used. The networks are subject to both node failure and random channel fading. A node lifetime distribution is modeled with an increasing failure rate, where the node power consumption level enters the parameters of the distribution. A method for assessing both link and network reliabilities projected at the network＇s design life is developed. Link reliability is enhanced through use of redundant nodes. The number of redundant nodes is restricted by the cooperative transmission scheme used. The link reliability is then used to establish a re-transmission control policy that minimizes an expected cost involving power, bandwidth expenditures, and packet loss. The benefit and cost of feedback in network operations are examined. The results of a simulation study under specific node processing times are presented. The study quantifies the effect of loop closure frequency, acknowledgment deadline, and nodes＇ storage capacity on the performance of the network in terms of network lifetime, packet loss rate, and false alarm rate. The study concludes that in a network where energy is severely constrained, feedback must be applied judiciously.
