The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are add...The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.展开更多
Network frequency control function is incorporated into a grid-connected wind farm-dual battery energy storage system(BESS)scheme.The design of the scheme takes advantage of the rapid response characteristics of the B...Network frequency control function is incorporated into a grid-connected wind farm-dual battery energy storage system(BESS)scheme.The design of the scheme takes advantage of the rapid response characteristics of the BESS and the in-built short-term overloading capability of the associated power conversion devices.A control strategy to regulate the BESS output power is then proposed.It is shown that the frequency control action offered by the BESS complements amicably with that of conventional generators in enhancing the frequency regulation attribute of the grid system.展开更多
-The Danish government set an ambitious goal to achieve a fully renewable-based energy system by 2050.In this context,the integrated electricity and heating system is undergoing rapid development in Denmark as a promi...-The Danish government set an ambitious goal to achieve a fully renewable-based energy system by 2050.In this context,the integrated electricity and heating system is undergoing rapid development in Denmark as a promising way to accommodate the ever-growing renewable energy sources(RESs).The electric heat pumps(HPs),coupled with the power and heat sectors,can propagate the flexibility on the heat consumer side to the power system operations,playing an important role of improving system flexibility and balancing the variability of the RES.In this paper,the current development situation of HPs in Denmark is analyzed,including both the large-scale HPs in the district heating system and individual HPs on the residential side.The possibility of using HPs to provide frequency control ancillary service(FCAS)is analyzed according to the market and technical requirements of the FCAS in the Danish transmission system and experimental results of representative demonstration projects of HPs.A comprehensive analysis of the advantages,barriers,future prospects,and challenges for using HPs to provide the FCAS are carried out from the perspectives of different entities.展开更多
An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and aband...An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and abandoned if they are from the same flow.But MCHOKeM uses multiple virtual queues for different priority packets and enhances the drawing function by adjusting the maximum number of draws based on the current status of virtual queue length.The number of parameters that MCHOKeM needs to maintain is determined by the number of priority levels being supported by the router,which usually has a small limited value.In order to explain the features of MCHOKeM,an analytical model is used.A series of simulation tests to evaluate the performance are given.展开更多
Aiming to provide a measurable service Quality of Service （ QoS） evaluating method for service inventory management, this paper proposes a new mobile Service Utility Model （SUM）, considers the service and business...Aiming to provide a measurable service Quality of Service （ QoS） evaluating method for service inventory management, this paper proposes a new mobile Service Utility Model （SUM）, considers the service and business layer elements into the service utility influence profile, and proposes an self-adaptive service inventory management algorithm as a QoS control scheme based on SUM. It can be concluded from the simulation result that the service inventory utility can be fully reflected by SUM and the whole system efficiency is greatly increased by using SUM as the adaptive rule.展开更多
in order to project a reliable telecommunication network ,we have to measure the call lossrate of present traffic and to predzct the traffic of hajective network. In this paper we point out that afactor of real commun...in order to project a reliable telecommunication network ,we have to measure the call lossrate of present traffic and to predzct the traffic of hajective network. In this paper we point out that afactor of real communication needs for subscrihas should be added in studying the traffic source char-acterization. Generally, the predicted traffic does not equal to the real demends, Considered asubscriber's psychological facter for attempts in busy-hour, a mathematical medel of probable dertva-tive calls from each real communication demand is given,with which the calling-up probabity, andthe repeating attempt probability of original subscribers on line occupation are calculated and the rela-tionship between the traffic and the real cammunication need is predicted.展开更多
The network traffic prediction is important for service quality control in computer network.The performance of the traditional prediction method significantly degrades for the burst short-term flow.In view of the prob...The network traffic prediction is important for service quality control in computer network.The performance of the traditional prediction method significantly degrades for the burst short-term flow.In view of the problem,this paper proposes a double LSTMs structure,one of which acts as the main flow predictor,another as the detector of the time the burst flow starts at.The two LSTM units can exchange information about their internal states,and the predictor uses the detector’s information to improve the accuracy of the prediction.A training algorithm is developed specially to train the structure offline.To obtain the prediction online,a pulse series is used as a simulant of the burst event.A simulation experiment is designed to test performance of the predictor.The results of the experiment show that the prediction accuracy of the double LSTM structure is significantly improved,compared with the traditional single LSTM structure.展开更多
基金supported by the National Natural Science Foundation of China(11302010)
文摘The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.
文摘Network frequency control function is incorporated into a grid-connected wind farm-dual battery energy storage system(BESS)scheme.The design of the scheme takes advantage of the rapid response characteristics of the BESS and the in-built short-term overloading capability of the associated power conversion devices.A control strategy to regulate the BESS output power is then proposed.It is shown that the frequency control action offered by the BESS complements amicably with that of conventional generators in enhancing the frequency regulation attribute of the grid system.
基金supported in part by the Innovationsfond,Denmark,through the project Using flexible district heating with heat pumps for integrated electricity and heat dispatch with renewables(HEAT4RES)(8087-00003 A)in part by the Ministry of Science and Technology,China under the project(2018YFE0106600).
文摘-The Danish government set an ambitious goal to achieve a fully renewable-based energy system by 2050.In this context,the integrated electricity and heating system is undergoing rapid development in Denmark as a promising way to accommodate the ever-growing renewable energy sources(RESs).The electric heat pumps(HPs),coupled with the power and heat sectors,can propagate the flexibility on the heat consumer side to the power system operations,playing an important role of improving system flexibility and balancing the variability of the RES.In this paper,the current development situation of HPs in Denmark is analyzed,including both the large-scale HPs in the district heating system and individual HPs on the residential side.The possibility of using HPs to provide frequency control ancillary service(FCAS)is analyzed according to the market and technical requirements of the FCAS in the Danish transmission system and experimental results of representative demonstration projects of HPs.A comprehensive analysis of the advantages,barriers,future prospects,and challenges for using HPs to provide the FCAS are carried out from the perspectives of different entities.
基金supported by the Beijing Natural Science Foundation(4102050)USFC-KOSEF Joint Research Project of China and Korea(60811140343)
文摘An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and abandoned if they are from the same flow.But MCHOKeM uses multiple virtual queues for different priority packets and enhances the drawing function by adjusting the maximum number of draws based on the current status of virtual queue length.The number of parameters that MCHOKeM needs to maintain is determined by the number of priority levels being supported by the router,which usually has a small limited value.In order to explain the features of MCHOKeM,an analytical model is used.A series of simulation tests to evaluate the performance are given.
基金This workis supported by Specialized Research Fundfor the Doctoral Programof Higher Education(20030013006) ,and National Specialized R&DPro-ject for the Product of Mobile Communications.
基金The workis supported by National Science Foundation of China(60372098) .
文摘Aiming to provide a measurable service Quality of Service （ QoS） evaluating method for service inventory management, this paper proposes a new mobile Service Utility Model （SUM）, considers the service and business layer elements into the service utility influence profile, and proposes an self-adaptive service inventory management algorithm as a QoS control scheme based on SUM. It can be concluded from the simulation result that the service inventory utility can be fully reflected by SUM and the whole system efficiency is greatly increased by using SUM as the adaptive rule.
文摘in order to project a reliable telecommunication network ,we have to measure the call lossrate of present traffic and to predzct the traffic of hajective network. In this paper we point out that afactor of real communication needs for subscrihas should be added in studying the traffic source char-acterization. Generally, the predicted traffic does not equal to the real demends, Considered asubscriber's psychological facter for attempts in busy-hour, a mathematical medel of probable dertva-tive calls from each real communication demand is given,with which the calling-up probabity, andthe repeating attempt probability of original subscribers on line occupation are calculated and the rela-tionship between the traffic and the real cammunication need is predicted.
基金the research plan of State Grid Sichuan Electric Power Company,Chinathe research plan of the 10th Research Institute of China Electronics Technology Group Corporation(KTYT-XY-002).
文摘The network traffic prediction is important for service quality control in computer network.The performance of the traditional prediction method significantly degrades for the burst short-term flow.In view of the problem,this paper proposes a double LSTMs structure,one of which acts as the main flow predictor,another as the detector of the time the burst flow starts at.The two LSTM units can exchange information about their internal states,and the predictor uses the detector’s information to improve the accuracy of the prediction.A training algorithm is developed specially to train the structure offline.To obtain the prediction online,a pulse series is used as a simulant of the burst event.A simulation experiment is designed to test performance of the predictor.The results of the experiment show that the prediction accuracy of the double LSTM structure is significantly improved,compared with the traditional single LSTM structure.
