In the paper, the method to optimize the rotor structure in variable frequency speed control motors is introduced. The saturation and the skin effect are considered and 2D no-load and load electromagnetic field is cal...In the paper, the method to optimize the rotor structure in variable frequency speed control motors is introduced. The saturation and the skin effect are considered and 2D no-load and load electromagnetic field is calculated in finite elements for a variable frequency speed control motor before and after optimization. Finally, no-load current and operation performance before and after optimization are obtained and the two results are contrasted.展开更多
Variable speed limits(VSL)stands out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways.It allows variable message signs(VMSs)to dynamically determine ...Variable speed limits(VSL)stands out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways.It allows variable message signs(VMSs)to dynamically determine the speed limits according to real-time traffic states.This paper introduces an innovative online feedback control approach designed to regulate speed limit values on VMSs,addressing multiple bottlenecks while considering their spatiotemporal constraints.Moreover,we offline optimize the gain coefficients of this feedback control approach in the simulation-based optimization(SBO)framework.Specifically,with average and variance of space-mean speeds as bi-objectives,a stochastic SBO model considering uncertain traffic demands and compliance behaviours is established and solved by a bi-objective surrogate-based promising area search(BOSPAS)algorithm.Real-field experiments conducted in Edmonton,Canada,demonstrate the well-performing bi-objectives of the proposed approach,especially in handling uncertain compliance behaviours and traffic demands.Compared with the uncontrolled scenario,the feedback control schemes with the offline optimized gain coefficients improve the average and variance of space-mean speeds by up to 16.2%and 20.8%,respectively.Meanwhile,by the comparison of detailed performances,it is found that the optimized control schemes perform better than the uncontrolled scheme from the overall and local aspects.In conclusion,this study puts forward a general framework that applies an online feedback control approach with gain coefficients optimized offline by an SBO method to deal with real-time decision-making problems under uncertainties.展开更多
The emergence of building condenser water systems with all-variable speed pumps and tower fans allows for increased efficiency and flexibility of chiller plants in partial load operation but also increases the control...The emergence of building condenser water systems with all-variable speed pumps and tower fans allows for increased efficiency and flexibility of chiller plants in partial load operation but also increases the control complexity of condenser water systems.This study aims to develop an integrated modeling technique for evaluating and optimizing the energy performance of such a condenser water system.The proposed system model is based on the semi-physical semi-empirical chiller,pump,and cooling tower models,with capabilities of fully considering the hydraulic and thermal interactions in the condenser water loop,being solved analytically and much faster than iterative solvers and supporting the explicit optimization of the pump and tower fan frequency.A mathematical approach,based on the system model and constrained optimization technique,is subsequently established to evaluate the energy performance of a typical dual setpoint-based variable speed strategy and find its energy-saving potential and most efficient operation by jointly optimizing pumps and tower fans.An all-variable speed chiller plant from Wuhan,China,is used for a case study to validate the system model’s accuracy and explore its applicability.The results showed that the system model can accurately simulate the condenser water system’s performance under various operating conditions.By optimizing the frequencies of pumps and tower fans,the total system energy consumption can be reduced by 12%–13%compared to the fixed dual setpoint-based strategy with range and approach setpoints of 4℃and 2℃.In contrast,the energy-saving potential of optimizing the cooling tower sequencing is insignificant.A simple joint speed control method for optimizing the pumps and tower fans emerged,i.e.,the optimal pump and fan frequency are linearly correlated(if both are non-extremes)and depend on the chiller part load ratio only,irrespective of the ambient wet-bulb temperature and chilled water supply temperature.It was also found that the oversizing issue has further limited the energy-saving space of the studied system and results in the range and approach setpoints being inaccessible.The study’s findings can serve as references to the operation optimization of all-variable speed condenser water systems in the future.展开更多
文摘In the paper, the method to optimize the rotor structure in variable frequency speed control motors is introduced. The saturation and the skin effect are considered and 2D no-load and load electromagnetic field is calculated in finite elements for a variable frequency speed control motor before and after optimization. Finally, no-load current and operation performance before and after optimization are obtained and the two results are contrasted.
基金supported by the National Natural Science Foundation of China(Grant No.72371251)the Excellent Youth Foundation of Hunan Education Department(Grant No.21B0015)Fundamental Research Funds for the Central Universities of Central South University。
文摘Variable speed limits(VSL)stands out as a well-established and effective strategy to alleviate traffic congestion and enhance traffic safety on motorways.It allows variable message signs(VMSs)to dynamically determine the speed limits according to real-time traffic states.This paper introduces an innovative online feedback control approach designed to regulate speed limit values on VMSs,addressing multiple bottlenecks while considering their spatiotemporal constraints.Moreover,we offline optimize the gain coefficients of this feedback control approach in the simulation-based optimization(SBO)framework.Specifically,with average and variance of space-mean speeds as bi-objectives,a stochastic SBO model considering uncertain traffic demands and compliance behaviours is established and solved by a bi-objective surrogate-based promising area search(BOSPAS)algorithm.Real-field experiments conducted in Edmonton,Canada,demonstrate the well-performing bi-objectives of the proposed approach,especially in handling uncertain compliance behaviours and traffic demands.Compared with the uncontrolled scenario,the feedback control schemes with the offline optimized gain coefficients improve the average and variance of space-mean speeds by up to 16.2%and 20.8%,respectively.Meanwhile,by the comparison of detailed performances,it is found that the optimized control schemes perform better than the uncontrolled scheme from the overall and local aspects.In conclusion,this study puts forward a general framework that applies an online feedback control approach with gain coefficients optimized offline by an SBO method to deal with real-time decision-making problems under uncertainties.
基金supported by the State Key Laboratory of Air-Conditioning Equipment and System Energy Conservation(No.ACSKL2019KT13)National Natural Science Foundation of China(No.51608297)+3 种基金Scientific Research Project of Beijing Municipal Education Commission(No.KM201910016009 and No.KZ202110016022)Beijing Advanced Innovation Center for Future Urban Design(No.UDC2019011121)Pyramid Talent Training Project(No.JDYC20220815)Post-Graduate Innovation Project(No.PG2024077)of Beijing University of Civil Engineering and Architecture.
文摘The emergence of building condenser water systems with all-variable speed pumps and tower fans allows for increased efficiency and flexibility of chiller plants in partial load operation but also increases the control complexity of condenser water systems.This study aims to develop an integrated modeling technique for evaluating and optimizing the energy performance of such a condenser water system.The proposed system model is based on the semi-physical semi-empirical chiller,pump,and cooling tower models,with capabilities of fully considering the hydraulic and thermal interactions in the condenser water loop,being solved analytically and much faster than iterative solvers and supporting the explicit optimization of the pump and tower fan frequency.A mathematical approach,based on the system model and constrained optimization technique,is subsequently established to evaluate the energy performance of a typical dual setpoint-based variable speed strategy and find its energy-saving potential and most efficient operation by jointly optimizing pumps and tower fans.An all-variable speed chiller plant from Wuhan,China,is used for a case study to validate the system model’s accuracy and explore its applicability.The results showed that the system model can accurately simulate the condenser water system’s performance under various operating conditions.By optimizing the frequencies of pumps and tower fans,the total system energy consumption can be reduced by 12%–13%compared to the fixed dual setpoint-based strategy with range and approach setpoints of 4℃and 2℃.In contrast,the energy-saving potential of optimizing the cooling tower sequencing is insignificant.A simple joint speed control method for optimizing the pumps and tower fans emerged,i.e.,the optimal pump and fan frequency are linearly correlated(if both are non-extremes)and depend on the chiller part load ratio only,irrespective of the ambient wet-bulb temperature and chilled water supply temperature.It was also found that the oversizing issue has further limited the energy-saving space of the studied system and results in the range and approach setpoints being inaccessible.The study’s findings can serve as references to the operation optimization of all-variable speed condenser water systems in the future.
