This paper presents an approach for extending the constraint model defined for conformity testing of a given method of class to its overriding method in subclass using inheritance principle. The first objective of the...This paper presents an approach for extending the constraint model defined for conformity testing of a given method of class to its overriding method in subclass using inheritance principle. The first objective of the proposed work is to find the relationship between the test model of an overriding method and its overridden method using the constraint propagation. In this context the approach shows that the test cases developed for testing an original method can be used for testing its overriding method in a subclass and then the number of test cases can be reduced considerably. The second objective is the use of invalid data which do not satisfy the precondition constraint and induce valid output values for introducing a new concept of test called secure testing. The implementation of this approach is based on a random generation of test data and analysis by formal proof.展开更多
Generally, the procedure for Solving Security constrained unit commitment (SCUC) problems within Lagrangian Relaxation framework is partitioned into two stages: one is to obtain feasible SCUC states;the other is to so...Generally, the procedure for Solving Security constrained unit commitment (SCUC) problems within Lagrangian Relaxation framework is partitioned into two stages: one is to obtain feasible SCUC states;the other is to solve the economic dispatch of generation power among all the generating units. The core of the two stages is how to determine the feasibility of SCUC states. The existence of ramp rate constraints and security constraints increases the difficulty of obtaining an analytical necessary and sufficient condition for determining the quasi-feasibility of SCUC states at each scheduling time. However, a numerical necessary and sufficient numerical condition is proposed and proven rigorously based on Benders Decomposition Theorem. Testing numerical example shows the effectiveness and efficiency of the condition.展开更多
The COVID-19 outbreak that became a global pandemic in early 2020 is starting to affect agricultural supply chains and leading to a rapid rise in global food prices.As many grain exporting countries announced a ban on...The COVID-19 outbreak that became a global pandemic in early 2020 is starting to affect agricultural supply chains and leading to a rapid rise in global food prices.As many grain exporting countries announced a ban on grain exports,food security issues in China have attracted a significant international attention.Based on the Suitability Distribution Model and Soybean-Cereal Constraint Model,we explored the relationship between soybean production potential and food security.We calculated that the soybean potential planting area in China is 164.3 million ha.If the outbreak prevents China from importing soybeans,soybean planting area will need to be increased by 6.9 times to satisfy the demands.In the meantime,cereal self-sufficiency rate will drop to 63.4%,which will greatly affect food security.Each additional unit of soybean production will reduce 3.9 units of cereal production,and 1%increase in the self-sufficiency rate of soybean will result in a 0.63%drop in the self-sufficiency rate of cereal.Without sacrificing the self-sufficiency rate of cereal,the self-sufficiency rate of soybean is limited to 42%.Consequently,China will still need to import more than 68%of the current import volume of soybean.Although in the short term,the outbreak will not affect food security in China,as soybean imports decrease,insufficient supply of soybeans will affect people’s quality of life.To prevent the impact of the COVID-19 outbreak,China should increase soybean stocks and strengthen international cooperation.In the long term,increasing the self-sufficiency rate is a fundamental solution to solving soybean import dependency.The key to increasing soybean cultivation is by making soybean cultivation profitable and by building a sustainable soybean planting chain.展开更多
In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security mode...In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security model for database systems is pro- posed. According to this method, an analysis by using Coq proof assistant to ensure the correctness and security of the extended model is introduced. Our formal security model has been verified secure. This work demonstrates that our verification method is effective and sufficient.展开更多
A symbol level secure precoding scheme based on band-region constraint of the eavesdropper’s receiving signal is proposed to enhance the energy efficiency of cell-free multiple-input multiple-output(MIMO)networks in ...A symbol level secure precoding scheme based on band-region constraint of the eavesdropper’s receiving signal is proposed to enhance the energy efficiency of cell-free multiple-input multiple-output(MIMO)networks in the presence of an eavesdropper while guaranteeing the quality of service(QoS)of user and the security of system.Moreover,to lighten its high computational complexity,original problem is divided into several cascade sub-problems firstly,and then those sub-problems are handled by combining Lagrangian dual function and improved Hooke-Jeeves method together.Comparative ex-periment with other secure symbol-level precoding schemes demonstrate that proposed scheme can achieve the lower power consumption with almost same symbol error rate and QoS of user.展开更多
With the deepening of the national urban and rural development strategy and the development of urban and rural integration, all levels of government are committed to narrowing the gap between rural and urban subsisten...With the deepening of the national urban and rural development strategy and the development of urban and rural integration, all levels of government are committed to narrowing the gap between rural and urban subsistence allowances. However, the inherent urban and rural differences and path dependence determines the integration of urban and rural low-cost integration is far from the standard can be achieved, the institutional environment and the operating environment are not in the same starting line of the facts, determines the ＂integration＂ will need to go through a long period of time Time of urban and rural development can be gradually achieved. At present, China＇s widespread implementation of the distinction between urban and rural residents minimum riving security system, not only difficult to play its due security ftmction, but further exacerbated the vicious cycle of dual society, the economic and social development is extremely unfavorable.展开更多
Under the influence of extreme natural disasters and man-made cyber attacks,the electricity-gas integrated energy system(EGIES)may experience power failure and gas interruption,which have significant impacts on the na...Under the influence of extreme natural disasters and man-made cyber attacks,the electricity-gas integrated energy system(EGIES)may experience power failure and gas interruption,which have significant impacts on the national economy and social stability.This paper proposes an expansion planning strategy for the EGIES considering N-1 security constraints and restorability capacity.First,the basic expansion planning model for the EGIES,the sub-model of the N-1 security check,and the submodel of restorability capacity verification are respectively proposed.Then,the iterative solution strategy is proposed,in which the solutions of the basic planning model are delivered to the sub-models and the feasible cutting constraints generated by solving the sub-models are delivered to the planning model.Finally,the simulation results of the 9-bus power system with an 8-node gas system and the IEEE 39-bus power system with a 20-node gas system show the effectiveness of the proposed planning method in enhancing the resilience of the EGIES's planning scheme.展开更多
随着分布式新能源和电动汽车等虚拟储能的广泛接入,电力系统的不确定性和低惯量特性变得更加显著,系统的频率运行风险增加,并且主动配电网内部的供需关系呈现出更加灵活多样的特征,导致其与输电网之间的功率交互关系也更加复杂。为此,...随着分布式新能源和电动汽车等虚拟储能的广泛接入,电力系统的不确定性和低惯量特性变得更加显著,系统的频率运行风险增加,并且主动配电网内部的供需关系呈现出更加灵活多样的特征,导致其与输电网之间的功率交互关系也更加复杂。为此,构建了一种基于主动配电网灵活性支撑机制的电-碳-绿证分布式协同优化方法,以充分挖掘输配系统中分布式资源的支撑能力及其碳减排效益。首先,建立了与输配协同系统匹配的动态频率安全约束和基于双向调节模型的主动配电网灵活性支撑机制,提出了输配系统间的电-碳-绿证协同交互框架。为应对新能源出力的不确定性,将两侧子系统中涉及不确定变量的约束建模为联合机会约束。采用交替方向乘子法(alternating direction of multipliers algorithm,ADMM)进行输配系统的分布式协同。仿真结果表明,所提模型能够有效挖掘配电网中分布式资源的支撑潜力,灵活体现主动配电网的向外支撑能力或被支撑需求。与传统方法相比,系统动态频率安全性和输配协同调节灵活性显著提升,总运行成本较输电网单独调度模型降低13.42%,新能源减载量较忽略多市场耦合模型减少16.76%,系统运行经济性和低碳性明显改善。此外,所提出的求解方法比基于传统的样本平均近似方法减少约98%的计算时间,能够实现输配系统的快速分布式协同优化。展开更多
As the proportion of wind power generation increases in power systems,it is necessary to develop new ways for wind power accommodation and improve the existing power dispatch model.The power-to-gas technology,which of...As the proportion of wind power generation increases in power systems,it is necessary to develop new ways for wind power accommodation and improve the existing power dispatch model.The power-to-gas technology,which offers a new approach to accommodate surplus wind power,is an excellent way to solve the former.Hence,this paper proposes to involve power-to-gas technology in the integrated electricity and natural gas systems(IEGSs).To solve the latter,on one hand,a new indicator,the scale factor of wind power integration,is introduced into the wind power stochastic model to better describe the uncertainty of grid-connected wind power;on the other hand,for quantizing and minimizing the impact of the uncertainties of wind power and system loads on system security,security risk constraints are established for the IEGS by the conditional value-at-risk method.By considering these two aspects,an MILP formulation of a security-risk based stochastic dynamic economic dispatch model for an IEGS is established,and GUROBI obtained from GAMS is used for the solution.Case studies are conducted on an IEGS consisting of a modified IEEE 39-bus system and the Belgium 20-node natural gas system to examine the effectiveness of the proposed dispatch model.展开更多
An approach of transmission network expan-sion planning with embedded constraints of short circuit currents and N-1 security is proposed in this paper.The problem brought on by the strong nonlinearity property of shor...An approach of transmission network expan-sion planning with embedded constraints of short circuit currents and N-1 security is proposed in this paper.The problem brought on by the strong nonlinearity property of short circuit currents is solved with a linearization method based on the DC power flow.The model can be converted to a mixed-integer linear programming problem,realizing the optimization of planning model that considers the constraints of linearized short circuit currents and N-1 security.To compensate the error caused by the assump-tions of DC power flow,the compensation factor is pro-posed.With this factor,an iterative algorithm that can compensate the linearization error is then presented.The case study based on the IEEE 118-bus system shows that the proposed model and approach can be utilized to:opti-mize the construction strategy of transmission lines;ensure the N-1 security of the network;and effectively limit the short circuit currents of the system.展开更多
文摘This paper presents an approach for extending the constraint model defined for conformity testing of a given method of class to its overriding method in subclass using inheritance principle. The first objective of the proposed work is to find the relationship between the test model of an overriding method and its overridden method using the constraint propagation. In this context the approach shows that the test cases developed for testing an original method can be used for testing its overriding method in a subclass and then the number of test cases can be reduced considerably. The second objective is the use of invalid data which do not satisfy the precondition constraint and induce valid output values for introducing a new concept of test called secure testing. The implementation of this approach is based on a random generation of test data and analysis by formal proof.
文摘Generally, the procedure for Solving Security constrained unit commitment (SCUC) problems within Lagrangian Relaxation framework is partitioned into two stages: one is to obtain feasible SCUC states;the other is to solve the economic dispatch of generation power among all the generating units. The core of the two stages is how to determine the feasibility of SCUC states. The existence of ramp rate constraints and security constraints increases the difficulty of obtaining an analytical necessary and sufficient condition for determining the quasi-feasibility of SCUC states at each scheduling time. However, a numerical necessary and sufficient numerical condition is proposed and proven rigorously based on Benders Decomposition Theorem. Testing numerical example shows the effectiveness and efficiency of the condition.
基金supported by the National Natural Science Foundation of China(Grant No.41625001,31660233).
文摘The COVID-19 outbreak that became a global pandemic in early 2020 is starting to affect agricultural supply chains and leading to a rapid rise in global food prices.As many grain exporting countries announced a ban on grain exports,food security issues in China have attracted a significant international attention.Based on the Suitability Distribution Model and Soybean-Cereal Constraint Model,we explored the relationship between soybean production potential and food security.We calculated that the soybean potential planting area in China is 164.3 million ha.If the outbreak prevents China from importing soybeans,soybean planting area will need to be increased by 6.9 times to satisfy the demands.In the meantime,cereal self-sufficiency rate will drop to 63.4%,which will greatly affect food security.Each additional unit of soybean production will reduce 3.9 units of cereal production,and 1%increase in the self-sufficiency rate of soybean will result in a 0.63%drop in the self-sufficiency rate of cereal.Without sacrificing the self-sufficiency rate of cereal,the self-sufficiency rate of soybean is limited to 42%.Consequently,China will still need to import more than 68%of the current import volume of soybean.Although in the short term,the outbreak will not affect food security in China,as soybean imports decrease,insufficient supply of soybeans will affect people’s quality of life.To prevent the impact of the COVID-19 outbreak,China should increase soybean stocks and strengthen international cooperation.In the long term,increasing the self-sufficiency rate is a fundamental solution to solving soybean import dependency.The key to increasing soybean cultivation is by making soybean cultivation profitable and by building a sustainable soybean planting chain.
基金the National High Technology Research and Development Program of China (2006AA01Z430)
文摘In order to develop highly secure database systems to meet the requirements for class B2, the BLP （Bell-LaPudula） model is extended according to the features of database systems. A method for verifying security model for database systems is pro- posed. According to this method, an analysis by using Coq proof assistant to ensure the correctness and security of the extended model is introduced. Our formal security model has been verified secure. This work demonstrates that our verification method is effective and sufficient.
基金the National Natural Science Foundation of China(No.61976080)the Key Research Projects in Henan Province of China(No.231111212500).
文摘A symbol level secure precoding scheme based on band-region constraint of the eavesdropper’s receiving signal is proposed to enhance the energy efficiency of cell-free multiple-input multiple-output(MIMO)networks in the presence of an eavesdropper while guaranteeing the quality of service(QoS)of user and the security of system.Moreover,to lighten its high computational complexity,original problem is divided into several cascade sub-problems firstly,and then those sub-problems are handled by combining Lagrangian dual function and improved Hooke-Jeeves method together.Comparative ex-periment with other secure symbol-level precoding schemes demonstrate that proposed scheme can achieve the lower power consumption with almost same symbol error rate and QoS of user.
文摘With the deepening of the national urban and rural development strategy and the development of urban and rural integration, all levels of government are committed to narrowing the gap between rural and urban subsistence allowances. However, the inherent urban and rural differences and path dependence determines the integration of urban and rural low-cost integration is far from the standard can be achieved, the institutional environment and the operating environment are not in the same starting line of the facts, determines the ＂integration＂ will need to go through a long period of time Time of urban and rural development can be gradually achieved. At present, China＇s widespread implementation of the distinction between urban and rural residents minimum riving security system, not only difficult to play its due security ftmction, but further exacerbated the vicious cycle of dual society, the economic and social development is extremely unfavorable.
文摘Under the influence of extreme natural disasters and man-made cyber attacks,the electricity-gas integrated energy system(EGIES)may experience power failure and gas interruption,which have significant impacts on the national economy and social stability.This paper proposes an expansion planning strategy for the EGIES considering N-1 security constraints and restorability capacity.First,the basic expansion planning model for the EGIES,the sub-model of the N-1 security check,and the submodel of restorability capacity verification are respectively proposed.Then,the iterative solution strategy is proposed,in which the solutions of the basic planning model are delivered to the sub-models and the feasible cutting constraints generated by solving the sub-models are delivered to the planning model.Finally,the simulation results of the 9-bus power system with an 8-node gas system and the IEEE 39-bus power system with a 20-node gas system show the effectiveness of the proposed planning method in enhancing the resilience of the EGIES's planning scheme.
文摘随着分布式新能源和电动汽车等虚拟储能的广泛接入,电力系统的不确定性和低惯量特性变得更加显著,系统的频率运行风险增加,并且主动配电网内部的供需关系呈现出更加灵活多样的特征,导致其与输电网之间的功率交互关系也更加复杂。为此,构建了一种基于主动配电网灵活性支撑机制的电-碳-绿证分布式协同优化方法,以充分挖掘输配系统中分布式资源的支撑能力及其碳减排效益。首先,建立了与输配协同系统匹配的动态频率安全约束和基于双向调节模型的主动配电网灵活性支撑机制,提出了输配系统间的电-碳-绿证协同交互框架。为应对新能源出力的不确定性,将两侧子系统中涉及不确定变量的约束建模为联合机会约束。采用交替方向乘子法(alternating direction of multipliers algorithm,ADMM)进行输配系统的分布式协同。仿真结果表明,所提模型能够有效挖掘配电网中分布式资源的支撑潜力,灵活体现主动配电网的向外支撑能力或被支撑需求。与传统方法相比,系统动态频率安全性和输配协同调节灵活性显著提升,总运行成本较输电网单独调度模型降低13.42%,新能源减载量较忽略多市场耦合模型减少16.76%,系统运行经济性和低碳性明显改善。此外,所提出的求解方法比基于传统的样本平均近似方法减少约98%的计算时间,能够实现输配系统的快速分布式协同优化。
基金This work was supported by National Natural Science Foundation of China(No.51777077)Natural Science Foundation of Guangdong Province(2017A030313304).
文摘As the proportion of wind power generation increases in power systems,it is necessary to develop new ways for wind power accommodation and improve the existing power dispatch model.The power-to-gas technology,which offers a new approach to accommodate surplus wind power,is an excellent way to solve the former.Hence,this paper proposes to involve power-to-gas technology in the integrated electricity and natural gas systems(IEGSs).To solve the latter,on one hand,a new indicator,the scale factor of wind power integration,is introduced into the wind power stochastic model to better describe the uncertainty of grid-connected wind power;on the other hand,for quantizing and minimizing the impact of the uncertainties of wind power and system loads on system security,security risk constraints are established for the IEGS by the conditional value-at-risk method.By considering these two aspects,an MILP formulation of a security-risk based stochastic dynamic economic dispatch model for an IEGS is established,and GUROBI obtained from GAMS is used for the solution.Case studies are conducted on an IEGS consisting of a modified IEEE 39-bus system and the Belgium 20-node natural gas system to examine the effectiveness of the proposed dispatch model.
基金This work was supported by National Key Technology R&D Program of China(No.2013BAA01B02)National Natural Science Foundation of China(Nos.51325702,51407100).
文摘An approach of transmission network expan-sion planning with embedded constraints of short circuit currents and N-1 security is proposed in this paper.The problem brought on by the strong nonlinearity property of short circuit currents is solved with a linearization method based on the DC power flow.The model can be converted to a mixed-integer linear programming problem,realizing the optimization of planning model that considers the constraints of linearized short circuit currents and N-1 security.To compensate the error caused by the assump-tions of DC power flow,the compensation factor is pro-posed.With this factor,an iterative algorithm that can compensate the linearization error is then presented.The case study based on the IEEE 118-bus system shows that the proposed model and approach can be utilized to:opti-mize the construction strategy of transmission lines;ensure the N-1 security of the network;and effectively limit the short circuit currents of the system.
