The increasing integration of variable wind generation has aggravated the imbalance between electricity supply and demand. Power-to-hydrogen(P2H) is a promising solution to balance supply and demand in a variable powe...The increasing integration of variable wind generation has aggravated the imbalance between electricity supply and demand. Power-to-hydrogen(P2H) is a promising solution to balance supply and demand in a variable power grid, in which excess wind power is converted into hydrogen via electrolysis and stored for later use. In this study, an energy hub(EH) with both a P2H facility(electrolyzer) and a gas-to-power(G2P) facility(hydrogen gas turbine) is proposed to accommodate a high penetration of wind power. The EH is modeled and integrated into a security-constrained unit commitment(SCUC) problem, and this optimization problem is solved by a mixed-integer linear programming(MILP) method with the Benders decomposition technique. Case studies are presented to validate the proposed model and elaborate on the technological potential of integrating P2H into a power system with a high level of wind penetration(HWP).展开更多
Cyber threats are serious concerns for power systems.For example,hackers may attack power control systems via interconnected enterprise networks.This paper proposes a risk assessment framework to enhance the resilienc...Cyber threats are serious concerns for power systems.For example,hackers may attack power control systems via interconnected enterprise networks.This paper proposes a risk assessment framework to enhance the resilience of power systems against cyber attacks.The duality element relative fuzzy evaluation method is employed to evaluate identified security vulnerabilities within cyber systems of power systems quantitatively.The attack graph is used to identify possible intrusion scenarios that exploit multiple vulnerabilities.An intrusion response system(IRS)is developed to monitor the impact of intrusion scenarios on power system dynamics in real time.IRS calculates the conditional Lyapunov exponents(CLEs)on line based on the phasor measurement unit data.Power system stability is predicted through the values of CLEs.Control actions based on CLEs will be suggested if power system instability is likely to happen.A generic wind farm control system is used for case study.The effectiveness of IRS is illustrated with the IEEE 39 bus system model.展开更多
One of the main factors impacting the reliability of energy systems nowadays is the growing interdependence between electricity and gas networks due to the increase in the installation of gas-fired units. Securitycons...One of the main factors impacting the reliability of energy systems nowadays is the growing interdependence between electricity and gas networks due to the increase in the installation of gas-fired units. Securityconstrained unit commitment(SCUC) models are used to economically schedule generating units without compromising the system reliability. This paper proposes a novel SCUC formulation that includes dynamic gas constraints,such as the line pack, and transmission contingencies in power and gas networks for studying the integrated system reliability. A Benders’ decomposition with linear programming techniques is developed to be able to study large systems. By including dynamic gas constraints into the SCUC, the proposed model accounts for the flexibility and reliability that power systems require from gas systems in the short term. Case studies of different size and complexity are employed to illustrate how the reliability of one system is affected by the reliability of the other. These experiments show how both systems operate in a secure way(by including contingencies) increases operating costs by approximately 9% and also show how these costs can vary by 24% depending on the line pack scheduling.展开更多
The rapid development of economy and society stimulates the increase of power demand. Wind power has received great attention as a typical renewable energy, and the share of wind power is continually increasing in rec...The rapid development of economy and society stimulates the increase of power demand. Wind power has received great attention as a typical renewable energy, and the share of wind power is continually increasing in recent years.However, the high integration of wind power brings challenges to the secure and reliable operation of power grid due to the intermittent characteristic of wind power. In order to solve the operation risk caused by wind power uncertainty, this paper proposes to solve the problem of stochastic security-constrained unit commitment(SCUC) by considering the extreme scenarios of wind power output. Firstly, assuming that the probability density distribution of wind power approximately follows a normal distribution, a great number of scenarios are generated by Monte Carlo(MC) simulation method to capture the stochastic nature of wind power output. Then, the clustering by fast search and find of density peaks(CSFDP) is utilized to separate the generated scenarios into three types: extreme, normal and typical scenarios. The extreme scenarios are identified to determine the on/off statuses of generators, while the typical scenarios are used to solve the day-ahead security-constrained economic dispatch(SCED) problem. The advantage of the proposed method is to ensure the robustness of SCUC solution while reducing the conservativeness of the solution as much as possible.The effectiveness of the proposed method is verified by IEEE test systems.展开更多
Beyond-5G(B5G)aims to meet the growing demands of mobile traffic and expand the communication space.Considering that intelligent applications to B5G wireless communications will involve security issues regarding user ...Beyond-5G(B5G)aims to meet the growing demands of mobile traffic and expand the communication space.Considering that intelligent applications to B5G wireless communications will involve security issues regarding user data and operational data,this paper analyzes the maximum capacity of the multi-watermarking method for multimedia signal hiding as a means of alleviating the information security problem of B5G.The multiwatermarking process employs spread transform dither modulation.During the watermarking procedure,Gram-Schmidt orthogonalization is used to obtain the multiple spreading vectors.Consequently,multiple watermarks can be simultaneously embedded into the same position of a multimedia signal.Moreover,the multiple watermarks can be extracted without affecting one another during the extraction process.We analyze the effect of the size of the spreading vector on the unit maximum capacity,and consequently derive the theoretical relationship between the size of the spreading vector and the unit maximum capacity.A number of experiments are conducted to determine the optimal parameter values for maximum robustness on the premise of high capacity and good imperceptibility.展开更多
Security-constrained unit commitment(SCUC)has been extensively studied as a key decision-making tool to determine optimal power generation schedules in the operation of electricity market.With the development of emerg...Security-constrained unit commitment(SCUC)has been extensively studied as a key decision-making tool to determine optimal power generation schedules in the operation of electricity market.With the development of emerging power grids,fruitful research results on SCUC have been obtained.Therefore,it is essential to review current work and propose future directions for SCUC to meet the needs of developing power systems.In this paper,the basic mathematical model of the standard SCUC is summarized,and the characteristics and application scopes of common solution algorithms are presented.Customized models focusing on diverse mathematical properties are then categorized and the corresponding solving methodologies are discussed.Finally,research trends in the field are prospected based on a summary of the state-of-the-art and latest studies.It is hoped that this paper can be a useful reference to support theoretical research and practical applications of SCUC in the future.展开更多
With the large-scale integration of renewable energy,the traditional maintenance arrangement during the load valley period cannot satisfy the transmission demand of renewable energy generation.Simultaneously,in a mark...With the large-scale integration of renewable energy,the traditional maintenance arrangement during the load valley period cannot satisfy the transmission demand of renewable energy generation.Simultaneously,in a market-oriented operation mode,the power dispatching control center aims to reduce the overall power purchase cost while ensuring the security of the power system.Therefore,a security-constrained transmission maintenance optimization model considering generation and operational risk costs is proposed herein.This model is built on double-layer optimization framework,where the upper-layer model is used for maintenance and generation planning,and the lowerlayer model is primarily used to address the operational security risk arising from the random prediction error and N-1 transmission failure.Correspondingly,a generation-maintenance iterative algorithm based on a defined cost feedback is included to increase solution efficiency.Generation cost is determined using long-term security-constrained unit commitment,and the operational risk cost is obtained using a double-layer N-1 risk assessment model.An electrical correlation coupling coefficient is proposed for the solution process to avoid maintenance of associated equipment simultaneously,thereby improving model convergence efficiency.The IEEE 118-bus system is used as a test case for illustration,and test results suggest that the proposed model and algorithm can reduce the total cost of transmission maintenance and system operation while effectively improving the solution efficiency of the joint optimization model.展开更多
In restructured power systems,the traditional approaches of unit maintenance scheduling(UMS)need to undergo major changes in order to be compatible with new competitive structures.Performing the maintenance on generat...In restructured power systems,the traditional approaches of unit maintenance scheduling(UMS)need to undergo major changes in order to be compatible with new competitive structures.Performing the maintenance on generating units may decrease the security level of transmission network and result in electricity shortage in power system;as a result,it can impose a kind of cost on transmission network as called security cost.Moreover,taking off line a generating unit for performing maintenance can change power flow in some transmission lines,and may lead to network congestion.In this study,generating unit maintenance is scheduled considering security and congestion cost with N-1 examination for transmission lines random failures.The proposed UMS approach would lead to optimum operation of power system in terms of economy and security.To achieve this goal,the optimal power flow(OPF)compatible with market mechanism is implemented.Moreover,the electricity price discovery mechanism as locational marginal pricing(LMP)is restated to analyze the impacts of UMS on nodal electricity price.Considering security and congestion cost simultaneously,this novel approach can reveal some new costs which are imposed to transmission network on behalf of generation units;as a result,it provides a great opportunity to perform maintenance in a fair environment for both generating companies(GenCo)and transmission companies(TransCo).At the end,simulation results on nine-bus test power system demonstrate that by using this method,the proposed UMS can guarantee fairness among market participants including GenCos and TransCo and ensure power system security.展开更多
With the increase in the penetration rate of renewable energy, the planning and operation of power systems will face huge challenges. To ensure the sufficient utilization of renewable energy, the reasonable arrangemen...With the increase in the penetration rate of renewable energy, the planning and operation of power systems will face huge challenges. To ensure the sufficient utilization of renewable energy, the reasonable arrangement for the long-term power generation plan has become more crucial. Security-constrained unit commitment(SCUC) is a critical technical means to optimize the long-term power generation plan. However, the plentiful power sources and the complex grid structure in largescale power systems will bring great difficulties to long-term SCUC. In this paper, we propose a fast calculation method for long-term SCUC of large-scale power systems with renewable energy. First, a method for unit status reduction based on temporal decomposition is proposed, which will reduce plenty of binary variables and intertemporal constraints in SCUC. Then,an efficient redundant constraint identification(RCI) method is developed to reduce the number of network constraints. Furthermore, a joint accelerated calculation framework for status reduction and RCI is formed, which can reduce the complexity of long-term SCUC while ensuring a high-precision feasible solution. In case studies, numerical results based on two test systems ROTS2017 and NREL-118 are analyzed, which verify the effectiveness and scalability of the proposed calculation method.展开更多
Due to the shortage of fossil energy and the pollution caused by combustion of fossil fuels,the proportion of renewable energy in power systems is gradually increasing across the world.Accordingly,the capacity of powe...Due to the shortage of fossil energy and the pollution caused by combustion of fossil fuels,the proportion of renewable energy in power systems is gradually increasing across the world.Accordingly,the capacity of power systems to accommodate renewable energy must be improved.However,integration of a large amount of renewable energy into power grids may result in network congestion.Hence,in this study,optimal transmission switching(OTS)is considered as an important method of accommodating renewable energy.It is incorporated into the operation of a power grid along with deep peak regulation of thermal power units,forming an interactive mode of coordinated operation of source and network.A stochastic unit commitment model consider!ng deep peak regulation and OTS is established,and the role of OTS in promoting the accommodation of renewable energy is analyzed quantitatively.The results of case studies involving the IEEE 30-bus system demonstrate that OTS can enable utilization of the potential of deep peak regulation and facilitate the accommodation of renewable energy.展开更多
China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance ...China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing,research based on nutrition security and broad food systems are increasingly needed in today’s China.Thus,not only grain for human consumption,but also animal foods have been integrated into the Food Equivalent,which is used to analyze China’s current agriculture system and reveal the water resource distribution.The results indicated that the average animal food consumption has risen by 78.6%,and now China’s daily supply of animal food per capita has reached about 50%of that in the USA and 80%of that in the South Korea.So there exist an obvious disparity in animal food supply between China and these two countries.It is impossible for the China’s current agricultural system to achieve the level in the USA.Under China’s current agricultural system,the consumption proportion of feed grain had surpassed the consumption of food grain,increased sharply from 33%in 1992 to 67%in 2011.However,the growth potential of total grain output is approaching an upper limit,so the continued growth of feed grain demand exerts great pressure on the China’s food supply.The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security.China’s current“grain farming”cannot meet the demand of increasing nutrition and appropriate resource utilization.The implementation of grassland agriculture appears feasible and necessary for saving feed grain,providing a large number of high-quality animal foods and appropriate water resource utilization.展开更多
Due to recent technological achievements,stochastic optimization,which inherently captures the uncertainty of intermittent resources,is being used to capture the variability and uncertainty of wind and solar resources...Due to recent technological achievements,stochastic optimization,which inherently captures the uncertainty of intermittent resources,is being used to capture the variability and uncertainty of wind and solar resources.However,due to persistent computational limitations,it is not practical to consider all possible variable generation scenarios.As a result,a reduced number of most likely scenarios is usually considered.While this helps reduce the computational burden,it also leaves the system operator vulnerable to some risk.In order to address this issue,this paper aims at providing insight into using an explicit reserve requirement in a stochastic modeling framework in order to provide system operators with greater confidence in stochastic dispatch solutions.This is accomplished by simulating a modified version of the IEEE 118 bus system in a fully stochastic,multi-timescale framework with flexibility reserve requirements.Results show that utilizing a stochastic flexibility reserve requirement within the stochastic modeling framework offers the most reliability benefit.展开更多
基金supported by National Natural Science Foundation of China(No.51377035)NSFC-RCUK_EPSRC(No.51361130153)
文摘The increasing integration of variable wind generation has aggravated the imbalance between electricity supply and demand. Power-to-hydrogen(P2H) is a promising solution to balance supply and demand in a variable power grid, in which excess wind power is converted into hydrogen via electrolysis and stored for later use. In this study, an energy hub(EH) with both a P2H facility(electrolyzer) and a gas-to-power(G2P) facility(hydrogen gas turbine) is proposed to accommodate a high penetration of wind power. The EH is modeled and integrated into a security-constrained unit commitment(SCUC) problem, and this optimization problem is solved by a mixed-integer linear programming(MILP) method with the Benders decomposition technique. Case studies are presented to validate the proposed model and elaborate on the technological potential of integrating P2H into a power system with a high level of wind penetration(HWP).
文摘Cyber threats are serious concerns for power systems.For example,hackers may attack power control systems via interconnected enterprise networks.This paper proposes a risk assessment framework to enhance the resilience of power systems against cyber attacks.The duality element relative fuzzy evaluation method is employed to evaluate identified security vulnerabilities within cyber systems of power systems quantitatively.The attack graph is used to identify possible intrusion scenarios that exploit multiple vulnerabilities.An intrusion response system(IRS)is developed to monitor the impact of intrusion scenarios on power system dynamics in real time.IRS calculates the conditional Lyapunov exponents(CLEs)on line based on the phasor measurement unit data.Power system stability is predicted through the values of CLEs.Control actions based on CLEs will be suggested if power system instability is likely to happen.A generic wind farm control system is used for case study.The effectiveness of IRS is illustrated with the IEEE 39 bus system model.
文摘One of the main factors impacting the reliability of energy systems nowadays is the growing interdependence between electricity and gas networks due to the increase in the installation of gas-fired units. Securityconstrained unit commitment(SCUC) models are used to economically schedule generating units without compromising the system reliability. This paper proposes a novel SCUC formulation that includes dynamic gas constraints,such as the line pack, and transmission contingencies in power and gas networks for studying the integrated system reliability. A Benders’ decomposition with linear programming techniques is developed to be able to study large systems. By including dynamic gas constraints into the SCUC, the proposed model accounts for the flexibility and reliability that power systems require from gas systems in the short term. Case studies of different size and complexity are employed to illustrate how the reliability of one system is affected by the reliability of the other. These experiments show how both systems operate in a secure way(by including contingencies) increases operating costs by approximately 9% and also show how these costs can vary by 24% depending on the line pack scheduling.
基金supported by the National Key R&D Program of China “Technology and application of wind power/photovoltaic power prediction for promoting renewable energy consumption”(No.2018YFB0904200)eponymous Complement S&T Program of State Grid Corporation of China (No.SGLNDKOOKJJS1800266)。
文摘The rapid development of economy and society stimulates the increase of power demand. Wind power has received great attention as a typical renewable energy, and the share of wind power is continually increasing in recent years.However, the high integration of wind power brings challenges to the secure and reliable operation of power grid due to the intermittent characteristic of wind power. In order to solve the operation risk caused by wind power uncertainty, this paper proposes to solve the problem of stochastic security-constrained unit commitment(SCUC) by considering the extreme scenarios of wind power output. Firstly, assuming that the probability density distribution of wind power approximately follows a normal distribution, a great number of scenarios are generated by Monte Carlo(MC) simulation method to capture the stochastic nature of wind power output. Then, the clustering by fast search and find of density peaks(CSFDP) is utilized to separate the generated scenarios into three types: extreme, normal and typical scenarios. The extreme scenarios are identified to determine the on/off statuses of generators, while the typical scenarios are used to solve the day-ahead security-constrained economic dispatch(SCED) problem. The advantage of the proposed method is to ensure the robustness of SCUC solution while reducing the conservativeness of the solution as much as possible.The effectiveness of the proposed method is verified by IEEE test systems.
基金funded by The National Natural Science Foundation of China under Grant(No.62273108,62306081)The Youth Project of Guangdong Artificial Intelligence and Digital Economy Laboratory(Guangzhou)(PZL2022KF0006)+3 种基金The National Key Research and Development Program of China(2022YFB3604502)Special Fund Project of GuangzhouScience and Technology Innovation Development(202201011307)Guangdong Province Industrial Internet Identity Analysis and Construction Guidance Fund Secondary Node Project(1746312)Special Projects in Key Fields of General Colleges and Universities in Guangdong Province(2021ZDZX1016).
文摘Beyond-5G(B5G)aims to meet the growing demands of mobile traffic and expand the communication space.Considering that intelligent applications to B5G wireless communications will involve security issues regarding user data and operational data,this paper analyzes the maximum capacity of the multi-watermarking method for multimedia signal hiding as a means of alleviating the information security problem of B5G.The multiwatermarking process employs spread transform dither modulation.During the watermarking procedure,Gram-Schmidt orthogonalization is used to obtain the multiple spreading vectors.Consequently,multiple watermarks can be simultaneously embedded into the same position of a multimedia signal.Moreover,the multiple watermarks can be extracted without affecting one another during the extraction process.We analyze the effect of the size of the spreading vector on the unit maximum capacity,and consequently derive the theoretical relationship between the size of the spreading vector and the unit maximum capacity.A number of experiments are conducted to determine the optimal parameter values for maximum robustness on the premise of high capacity and good imperceptibility.
基金supported in part by the National Natural Science Foundation of China(No.51607104)。
文摘Security-constrained unit commitment(SCUC)has been extensively studied as a key decision-making tool to determine optimal power generation schedules in the operation of electricity market.With the development of emerging power grids,fruitful research results on SCUC have been obtained.Therefore,it is essential to review current work and propose future directions for SCUC to meet the needs of developing power systems.In this paper,the basic mathematical model of the standard SCUC is summarized,and the characteristics and application scopes of common solution algorithms are presented.Customized models focusing on diverse mathematical properties are then categorized and the corresponding solving methodologies are discussed.Finally,research trends in the field are prospected based on a summary of the state-of-the-art and latest studies.It is hoped that this paper can be a useful reference to support theoretical research and practical applications of SCUC in the future.
基金supported by the Scientific and Technological Project of State Grid Corporation of China“Multilevel maintenance scheduling and its coordination with medium-term and long-term dispatching decision”(No.5442DZ210012)。
文摘With the large-scale integration of renewable energy,the traditional maintenance arrangement during the load valley period cannot satisfy the transmission demand of renewable energy generation.Simultaneously,in a market-oriented operation mode,the power dispatching control center aims to reduce the overall power purchase cost while ensuring the security of the power system.Therefore,a security-constrained transmission maintenance optimization model considering generation and operational risk costs is proposed herein.This model is built on double-layer optimization framework,where the upper-layer model is used for maintenance and generation planning,and the lowerlayer model is primarily used to address the operational security risk arising from the random prediction error and N-1 transmission failure.Correspondingly,a generation-maintenance iterative algorithm based on a defined cost feedback is included to increase solution efficiency.Generation cost is determined using long-term security-constrained unit commitment,and the operational risk cost is obtained using a double-layer N-1 risk assessment model.An electrical correlation coupling coefficient is proposed for the solution process to avoid maintenance of associated equipment simultaneously,thereby improving model convergence efficiency.The IEEE 118-bus system is used as a test case for illustration,and test results suggest that the proposed model and algorithm can reduce the total cost of transmission maintenance and system operation while effectively improving the solution efficiency of the joint optimization model.
文摘In restructured power systems,the traditional approaches of unit maintenance scheduling(UMS)need to undergo major changes in order to be compatible with new competitive structures.Performing the maintenance on generating units may decrease the security level of transmission network and result in electricity shortage in power system;as a result,it can impose a kind of cost on transmission network as called security cost.Moreover,taking off line a generating unit for performing maintenance can change power flow in some transmission lines,and may lead to network congestion.In this study,generating unit maintenance is scheduled considering security and congestion cost with N-1 examination for transmission lines random failures.The proposed UMS approach would lead to optimum operation of power system in terms of economy and security.To achieve this goal,the optimal power flow(OPF)compatible with market mechanism is implemented.Moreover,the electricity price discovery mechanism as locational marginal pricing(LMP)is restated to analyze the impacts of UMS on nodal electricity price.Considering security and congestion cost simultaneously,this novel approach can reveal some new costs which are imposed to transmission network on behalf of generation units;as a result,it provides a great opportunity to perform maintenance in a fair environment for both generating companies(GenCo)and transmission companies(TransCo).At the end,simulation results on nine-bus test power system demonstrate that by using this method,the proposed UMS can guarantee fairness among market participants including GenCos and TransCo and ensure power system security.
基金supported by the National Key R&D Program of China (No.2017YFB0902200)。
文摘With the increase in the penetration rate of renewable energy, the planning and operation of power systems will face huge challenges. To ensure the sufficient utilization of renewable energy, the reasonable arrangement for the long-term power generation plan has become more crucial. Security-constrained unit commitment(SCUC) is a critical technical means to optimize the long-term power generation plan. However, the plentiful power sources and the complex grid structure in largescale power systems will bring great difficulties to long-term SCUC. In this paper, we propose a fast calculation method for long-term SCUC of large-scale power systems with renewable energy. First, a method for unit status reduction based on temporal decomposition is proposed, which will reduce plenty of binary variables and intertemporal constraints in SCUC. Then,an efficient redundant constraint identification(RCI) method is developed to reduce the number of network constraints. Furthermore, a joint accelerated calculation framework for status reduction and RCI is formed, which can reduce the complexity of long-term SCUC while ensuring a high-precision feasible solution. In case studies, numerical results based on two test systems ROTS2017 and NREL-118 are analyzed, which verify the effectiveness and scalability of the proposed calculation method.
基金the National Natural Science Foundation of China(No.U1966204)the China State Key Lab.of Power System(SKJLD19KM09).
文摘Due to the shortage of fossil energy and the pollution caused by combustion of fossil fuels,the proportion of renewable energy in power systems is gradually increasing across the world.Accordingly,the capacity of power systems to accommodate renewable energy must be improved.However,integration of a large amount of renewable energy into power grids may result in network congestion.Hence,in this study,optimal transmission switching(OTS)is considered as an important method of accommodating renewable energy.It is incorporated into the operation of a power grid along with deep peak regulation of thermal power units,forming an interactive mode of coordinated operation of source and network.A stochastic unit commitment model consider!ng deep peak regulation and OTS is established,and the role of OTS in promoting the accommodation of renewable energy is analyzed quantitatively.The results of case studies involving the IEEE 30-bus system demonstrate that OTS can enable utilization of the potential of deep peak regulation and facilitate the accommodation of renewable energy.
基金supported by the key consultative project“Ecological security of grassland and food security in China”by Chinese Academy of Engineering(2012-ZD-7)Program for Changjiang Scholars and Innovative Research Team in University(IRT13019).
文摘China's food security has a great influence on the world,and has always been the top priority in China.In recent years,as the concept of food security is evolving into one of nutrition security and the importance of food diversity is increasing,research based on nutrition security and broad food systems are increasingly needed in today’s China.Thus,not only grain for human consumption,but also animal foods have been integrated into the Food Equivalent,which is used to analyze China’s current agriculture system and reveal the water resource distribution.The results indicated that the average animal food consumption has risen by 78.6%,and now China’s daily supply of animal food per capita has reached about 50%of that in the USA and 80%of that in the South Korea.So there exist an obvious disparity in animal food supply between China and these two countries.It is impossible for the China’s current agricultural system to achieve the level in the USA.Under China’s current agricultural system,the consumption proportion of feed grain had surpassed the consumption of food grain,increased sharply from 33%in 1992 to 67%in 2011.However,the growth potential of total grain output is approaching an upper limit,so the continued growth of feed grain demand exerts great pressure on the China’s food supply.The discordance of the spatial distribution of water resource and virtual water revealed that China’s current agriculture system had a low efficiency in being able to achieve food and nutrition security.China’s current“grain farming”cannot meet the demand of increasing nutrition and appropriate resource utilization.The implementation of grassland agriculture appears feasible and necessary for saving feed grain,providing a large number of high-quality animal foods and appropriate water resource utilization.
基金supported by the National Renewable Energy Laboratory operated for DOE by the Alliance for Sustainable Energy,LLC under Contract No.DOE-AC36-08-GO28308.
文摘Due to recent technological achievements,stochastic optimization,which inherently captures the uncertainty of intermittent resources,is being used to capture the variability and uncertainty of wind and solar resources.However,due to persistent computational limitations,it is not practical to consider all possible variable generation scenarios.As a result,a reduced number of most likely scenarios is usually considered.While this helps reduce the computational burden,it also leaves the system operator vulnerable to some risk.In order to address this issue,this paper aims at providing insight into using an explicit reserve requirement in a stochastic modeling framework in order to provide system operators with greater confidence in stochastic dispatch solutions.This is accomplished by simulating a modified version of the IEEE 118 bus system in a fully stochastic,multi-timescale framework with flexibility reserve requirements.Results show that utilizing a stochastic flexibility reserve requirement within the stochastic modeling framework offers the most reliability benefit.
