An energy-saving control strategy based on predictive control for central air-conditioning systems is proposed in this paper. The cold load model is developed to describe the dynamic characteristics of temperature con...An energy-saving control strategy based on predictive control for central air-conditioning systems is proposed in this paper. The cold load model is developed to describe the dynamic characteristics of temperature control systems, and then parameters in the cold load model and in the central air-conditioning system model are estimated. Generalized predictive control (GPC) is used to establish an optimization model to minimize the consumption of energy and the control error of temperature. The simulated annealing (SA) algorithm, combined with quadratic programming, is adopted to solve the optimal problem. Contrasted with the simulation of traditional PID control, the results prove the effectiveness of this proposed strategy.展开更多
Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipmen...Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.展开更多
The central solenoid is an important part of the HT-7U device. In this paper， the computational analysis of the stress and the displacement on the pre-load structures of the central solenoid have been made by the fin...The central solenoid is an important part of the HT-7U device. In this paper， the computational analysis of the stress and the displacement on the pre-load structures of the central solenoid have been made by the finite element analysis system COSMOS/M2.0 under room and/or operating temperature. According to the analytical results, the clip aprons and compression plates are all satisfied with safety design criteria.展开更多
风洞天平的校准精度直接决定了风洞试验的气动载荷测量精度,为了提升天平校准的质量和效率,以BCS-100天平校准系统为研究对象,基于现代试验设计方法(modern design of experiments,MDOE)开展了风洞天平校准研究。针对单因子变量法(one f...风洞天平的校准精度直接决定了风洞试验的气动载荷测量精度,为了提升天平校准的质量和效率,以BCS-100天平校准系统为研究对象,基于现代试验设计方法(modern design of experiments,MDOE)开展了风洞天平校准研究。针对单因子变量法(one factor at a time,OFAT)天平校准中存在系统误差与响应量耦合的问题,采用MDOE的随机、重复和分块策略控制校准的系统误差,并选定响应面理论的中心复合设计方法生成校准矩阵。校准矩阵共计86个样本点,包括64个分级因子点、12个轴向因子点和10个中心因子点,其中所有样本点的加载顺序做随机化处理,并作为一个样本块在短时间内集中完成加载,中心因子点则用于满足重复原则。最后开展了OFAT和MDOE的对比校准,拟合载荷的残差正态概率分布显示MDOE校准中横侧向分量的样本点独立性更强,样本点残差最高可降低84%;检验载荷显示MDOE和OFAT两种方法中天平所有分量的综合加载重复性持平,MDOE校准中横侧向分量的综合加载误差最高可降低54%。研究表明MDOE能够有效降低校准的系统误差,提升横侧向小量的预测能力。展开更多
针对混合微电网集中控制对中央控制器依赖严重、通信需求量大、扰动调节能力差的问题,提出一种微电网中央控制器(microgrid central control,MGCC)参与的分层事件触发控制策略,有效降低分布式集群的冗余通信并减少中央控制器计算负担,...针对混合微电网集中控制对中央控制器依赖严重、通信需求量大、扰动调节能力差的问题,提出一种微电网中央控制器(microgrid central control,MGCC)参与的分层事件触发控制策略,有效降低分布式集群的冗余通信并减少中央控制器计算负担,改进策略可靠性。该策略将控制系统分为2层,其中,设备层为本地控制层,采用分布式协同控制,所设计的本地控制器可就地控制更新输出状态,实现混合微电网的分散自治运行;另外,在控制层建立微电网控制层,引入事件触发策略,协调MGCC获取混合微电网的全局信息,从而向本地控制器发出预定义的调控指令,实现“源网荷储”灵活调度,尤其是应对突发事件而引发的电网振荡。最后,采用Matlab搭建混合微电网模型并进行仿真,利用Stateflow模块实现了事件触发算法,验证控制策略在满足并网/孤岛模式可靠性、稳定性的前提下,系统通信量可降低56.4%。展开更多
Power grids,due to their lack of network redundancy and structural interdependence,are particularly vulnerable to cascading failures,a phenomenon where a few failed nodes—having their loads exceeding their capacities...Power grids,due to their lack of network redundancy and structural interdependence,are particularly vulnerable to cascading failures,a phenomenon where a few failed nodes—having their loads exceeding their capacities—can trigger a widespread collapse of all nodes.Here,we extend the cascading failure(Motter-Lai)model to a more realistic perspective,where each node’s load capacity is determined to be nonlinearly correlated with the node’s centrality.Our analysis encompasses a range of synthetic networks featuring small-world or scale-free properties,as well as real-world network configurations like the IEEE bus systems and the US power grid.We find that fine-tuning this nonlinear relationship can significantly enhance a network’s robustness against cascading failures when the network nodes are under attack.Additionally,the selection of initial nodes and the attack strategies also impact overall network robustness.Our findings offer valuable insights for improving the safety and resilience of power grids,bringing us closer to understanding cascading failures in a more realistic context.展开更多
文摘An energy-saving control strategy based on predictive control for central air-conditioning systems is proposed in this paper. The cold load model is developed to describe the dynamic characteristics of temperature control systems, and then parameters in the cold load model and in the central air-conditioning system model are estimated. Generalized predictive control (GPC) is used to establish an optimization model to minimize the consumption of energy and the control error of temperature. The simulated annealing (SA) algorithm, combined with quadratic programming, is adopted to solve the optimal problem. Contrasted with the simulation of traditional PID control, the results prove the effectiveness of this proposed strategy.
基金Project(2011B061200043)supported by the Guangdong Provincial Department of Science and Technology,China
文摘Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.
文摘The central solenoid is an important part of the HT-7U device. In this paper， the computational analysis of the stress and the displacement on the pre-load structures of the central solenoid have been made by the finite element analysis system COSMOS/M2.0 under room and/or operating temperature. According to the analytical results, the clip aprons and compression plates are all satisfied with safety design criteria.
文摘风洞天平的校准精度直接决定了风洞试验的气动载荷测量精度,为了提升天平校准的质量和效率,以BCS-100天平校准系统为研究对象,基于现代试验设计方法(modern design of experiments,MDOE)开展了风洞天平校准研究。针对单因子变量法(one factor at a time,OFAT)天平校准中存在系统误差与响应量耦合的问题,采用MDOE的随机、重复和分块策略控制校准的系统误差,并选定响应面理论的中心复合设计方法生成校准矩阵。校准矩阵共计86个样本点,包括64个分级因子点、12个轴向因子点和10个中心因子点,其中所有样本点的加载顺序做随机化处理,并作为一个样本块在短时间内集中完成加载,中心因子点则用于满足重复原则。最后开展了OFAT和MDOE的对比校准,拟合载荷的残差正态概率分布显示MDOE校准中横侧向分量的样本点独立性更强,样本点残差最高可降低84%;检验载荷显示MDOE和OFAT两种方法中天平所有分量的综合加载重复性持平,MDOE校准中横侧向分量的综合加载误差最高可降低54%。研究表明MDOE能够有效降低校准的系统误差,提升横侧向小量的预测能力。
文摘针对混合微电网集中控制对中央控制器依赖严重、通信需求量大、扰动调节能力差的问题,提出一种微电网中央控制器(microgrid central control,MGCC)参与的分层事件触发控制策略,有效降低分布式集群的冗余通信并减少中央控制器计算负担,改进策略可靠性。该策略将控制系统分为2层,其中,设备层为本地控制层,采用分布式协同控制,所设计的本地控制器可就地控制更新输出状态,实现混合微电网的分散自治运行;另外,在控制层建立微电网控制层,引入事件触发策略,协调MGCC获取混合微电网的全局信息,从而向本地控制器发出预定义的调控指令,实现“源网荷储”灵活调度,尤其是应对突发事件而引发的电网振荡。最后,采用Matlab搭建混合微电网模型并进行仿真,利用Stateflow模块实现了事件触发算法,验证控制策略在满足并网/孤岛模式可靠性、稳定性的前提下,系统通信量可降低56.4%。
基金supported by the National Key R&D Program of China for International S&T Cooperation Projects(No.2019YFE0118700)National Natural Science Foundation of China(Nos.62222306 and 61973110)+1 种基金Hunan Young Talents Science and Technology Innovation Project(No.2020RC3048)Natural Science Found for Distinguished Young Scholars of Hunan Province(No.2021JJ10030).
文摘Power grids,due to their lack of network redundancy and structural interdependence,are particularly vulnerable to cascading failures,a phenomenon where a few failed nodes—having their loads exceeding their capacities—can trigger a widespread collapse of all nodes.Here,we extend the cascading failure(Motter-Lai)model to a more realistic perspective,where each node’s load capacity is determined to be nonlinearly correlated with the node’s centrality.Our analysis encompasses a range of synthetic networks featuring small-world or scale-free properties,as well as real-world network configurations like the IEEE bus systems and the US power grid.We find that fine-tuning this nonlinear relationship can significantly enhance a network’s robustness against cascading failures when the network nodes are under attack.Additionally,the selection of initial nodes and the attack strategies also impact overall network robustness.Our findings offer valuable insights for improving the safety and resilience of power grids,bringing us closer to understanding cascading failures in a more realistic context.
