To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for powe...To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for power scheduling in hydrogen production systems under the scenario of photovoltaic(PV)electrolysis of water.First,voltage and performance attenuation models of the PEMEL are proposed,and the degradation cost of the electrolyzer under a fluctuating input is considered.Then,the calculation of the investment and operating costs of the hydrogen production system for a typical day is based on the life cycle cost.Finally,a layered power scheduling optimization method is proposed to reasonably distribute the power of the electrolyzer and energy storage system in a hydrogen production system.In the up-layer optimization,the PV power absorbed by the hydrogen production system was optimized using MALTAB+Gurobi.In low-layer optimization,the power allocation between the PEMEL and battery energy storage system(BESS)is optimized using a non-dominated sorting genetic algorithm(NSGA-Ⅱ)combined with the firefly algorithm(FA).A better optimization result,characterized by lower degradation and total costs,was obtained using the method proposed in this study.The improved algorithm can search for a better population and obtain optimization results in fewer iterations.As a calculation example,data from a PV power station in northwest China were used for optimization,and the effectiveness and rationality of the proposed optimization method were verified.展开更多
With the rapid development of cloud computing,edge computing,and smart devices,computing power resources indicate a trend of ubiquitous deployment.The traditional network architecture cannot efficiently leverage these...With the rapid development of cloud computing,edge computing,and smart devices,computing power resources indicate a trend of ubiquitous deployment.The traditional network architecture cannot efficiently leverage these distributed computing power resources due to computing power island effect.To overcome these problems and improve network efficiency,a new network computing paradigm is proposed,i.e.,Computing Power Network(CPN).Computing power network can connect ubiquitous and heterogenous computing power resources through networking to realize computing power scheduling flexibly.In this survey,we make an exhaustive review on the state-of-the-art research efforts on computing power network.We first give an overview of computing power network,including definition,architecture,and advantages.Next,a comprehensive elaboration of issues on computing power modeling,information awareness and announcement,resource allocation,network forwarding,computing power transaction platform and resource orchestration platform is presented.The computing power network testbed is built and evaluated.The applications and use cases in computing power network are discussed.Then,the key enabling technologies for computing power network are introduced.Finally,open challenges and future research directions are presented as well.展开更多
Increasing interest has been directed toward the potential of heterogeneous flexible loads to mitigate the challenges associated with the increasing variability and uncertainty of renewable generation.Evaluating the a...Increasing interest has been directed toward the potential of heterogeneous flexible loads to mitigate the challenges associated with the increasing variability and uncertainty of renewable generation.Evaluating the aggregated flexible region of load clusters managed by load aggregators is the crucial basis of power system scheduling for the system operator.This is because the aggregation result affects the qual-ity of the scheduling schemes.A stringent computation based on the Minkowski sum is NP-hard,whereas existing approximation meth-ods that use a special type of polytope exhibit limited adaptability when aggregating heterogeneous loads.This study proposes a stringent internal approximation method based on the convex hull of multiple layers of maximum volume boxes and embeds it into a day-ahead scheduling optimization model.The numerical results indicate that the aggregation accuracy can be improved compared with methods based on one type of special polytope,including boxes,zonotopes,and homothets.Hence,the reliability and economy of the power sys-tem scheduling can be enhanced.展开更多
In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throt...In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throttle movement as well as the safety of the engine,a method used to design a constant thrust power schedule was proposed.The research was based on a simulink turbofan engine model and the results were organized as look-up tables in different structures with limitations.Simulation was done to confirm the validity and demonstrate the effectiveness of the schedule obtained with the approach.The constant thrust takeoff schedule,constant thrust idle schedule and constant thrust part power schedule with the present constant thrust control(CTC)method were proved to be valid.The results can be applied to this specific engine but the method can be applied to any areoengine and can be even extended to the unmanned plane.展开更多
Retraction： LIU Shuanggen, NI Haiying, HU Yupu, LIAO Yunyan. An Improved Simple Power Attack against Camellia＇s Key Schedule. Wuhan University Journal of Natural Sciences, 2008, 13（5）： 591-594. DOI： 10.1007/s 11...Retraction： LIU Shuanggen, NI Haiying, HU Yupu, LIAO Yunyan. An Improved Simple Power Attack against Camellia＇s Key Schedule. Wuhan University Journal of Natural Sciences, 2008, 13（5）： 591-594. DOI： 10.1007/s 11859-008-0516-3展开更多
Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in t...Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in the project were given official notice that both sides should start to implement the contracts. "The move marked a significant step forward in the project’s construction," said Zeng Wenxing, General Manager of Ling’ ao Nuclear Power Co Ltd, set up in展开更多
In traditional power systems,besides the conventional power plants that provide the necessary reactive power in transmission system,the shunt capacitors along with the tap changers of transformers are also employed in...In traditional power systems,besides the conventional power plants that provide the necessary reactive power in transmission system,the shunt capacitors along with the tap changers of transformers are also employed in distribution networks.In future years,because of the high number of distributed resources integrated into the distribution networks,it will be essential to schedule complete active-reactive power at distribution level.In this research work,an economic framework based on the active-reactive power bids has been developed for complete active-reactive power dispatch scheduling of smart distribution networks.The economical complete active-reactive power scheduling approach suggested in this study motivates distributed energy resources(DERs)to cooperate in both active power markets and the Volt/Var control scheme.To this end,using DER’s reactive power capability,a generic framework of reactive power offers for DERs is extracted.A 22-bus distribution test system is implemented to verify the impressiveness of the suggested active-reactive power scheduling approach.展开更多
With the improvement of electricity markets,the gradual aggravation of energy shortage and the environment pollution,it is urgent to formulate a new model to precisely satisfy the system demand for energy and reserve....With the improvement of electricity markets,the gradual aggravation of energy shortage and the environment pollution,it is urgent to formulate a new model to precisely satisfy the system demand for energy and reserve.Currently,power system opti-mization dispatching is always formulated as a discrete-time scheduling model.In this paper,we first demonstrate through an example that the upper and lower bounds of spinning reserve offered by a unit,given in the discrete-time model framework as constraints,is unreachable.This causes the problem that the reserve delivery obtained by the discrete-time scheduling model cannot be carried out precisely.From the detailed analysis of the ramp rate constraints,it is proved that the reachable upper and lower bounds of spinning reserve in every period can be expressed as functions of two variables,i.e.,generation level of unit at the start and end of this period.Thus,a new method is provided to calculate the upper and lower bounds of spinning reserve which are reachable in average.Furthermore,a new model based on this proposed method for joint scheduling of generation and reserve is presented,which considers the ability to realize the scheduled energy and reserve delivery.It converts the opti-mization based accurate scheduling for generation and reserve of power system from a continuous-time optimal control prob-lem to a nonlinear programming problem.Therefore,the proposed model can avoid the difficulties in solving a continu-ous-time optimal control problem.Based on the sequential quadratic programming method,numerical experiments for sched-uling electric power production systems are performed to evaluate the model and the results show that the new model is highly effective.展开更多
As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new ...As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.展开更多
While the size and complexity of software are rapidly increasing,not only is the number of vulnerabilities increasing,but their forms are diversifying.Vulnerability has become an important factor in network attack and...While the size and complexity of software are rapidly increasing,not only is the number of vulnerabilities increasing,but their forms are diversifying.Vulnerability has become an important factor in network attack and defense.Therefore,automatic vulnerability discovery has become critical to ensure software security.Fuzzing is one of the most important methods of vulnerability discovery.It is based on the initial input,i.e.,a seed,to generate mutated test cases as new inputs of a tested program in the next execution loop.By monitoring the path coverage,fuzzing can choose high-value test cases for inclusion in the new seed set and capture crashes used for triggering vulnerabilities.Although there have been remarkable achievements in terms of the number of discovered vulnerabilities,the reduction of time cost is still inadequate.This paper proposes a fast directed greybox fuzzing model,FastAFLGo.A fast convergence formula of temperature is designed,and the energy scheduling scheme can quickly determine the best seed to make the program execute toward the target basic blocks.Experimental results show that FastAFLGo can discover more vulnerabilities than the traditional fuzzing method in the same execution time.展开更多
As transmission power among interconnected re-gional grids is increasing rapidly,formulating the power distri-bution and maintenance schedules of multiple paralleled trans-mission channels is critical to ensure the se...As transmission power among interconnected re-gional grids is increasing rapidly,formulating the power distri-bution and maintenance schedules of multiple paralleled trans-mission channels is critical to ensure the secure and economic operation in an AC/DC power system.A coordinated optimiza-tion for power distribution and maintenance schedules(COPD-MS)of multiple paralleled transmission channels is proposed,and the active power losses of the resistances of earth line in the high-voltage direct current(HVDC)transmission lines are taken into account when one pole is under maintenance while the other pole is operating under monopolar ground circuit.To solve the proposed COPD-MS model efficiently,the generalized Benders decomposition(GBD)algorithm is used to decompose the proposed COPD-MS model into master problem of mainte-nance scheduling and sub-problems of power distribution sched-uling,and the optimal solution to the original model is obtained by the alternative iteration between them.Moreover,a recur-sive acceleration(RA)algorithm is proposed to solve the master problem,which can directly obtain its solution in the new itera-tion by using the solution in the last iteration and the newly added Benders cut.Convex relaxation techniques are applied to the nonlinear constraints in the sub-problem to ensure the reli-able convergence.Additionally,since there is no coupling among the power distributions during each time interval in the sub-problem,parallel computing technology is used to improve the computational efficiency.Finally,case studies on the modi-fied IEEE 39-bus system and an actual 1524-bus large-scale AC/DC hybrid power system demonstrate the effectiveness of the proposed COPD-MS model.展开更多
Reliability level of HVDC power transmission systems becomes an important factor impacting the entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by SGCC since 2003 in respe...Reliability level of HVDC power transmission systems becomes an important factor impacting the entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by SGCC since 2003 in respect of forced outage times,forced energy unavailability,scheduled energy unavailability and energy utilization eff iciency.The results show that the reliability level of HVDC power transmission systems owned by SGCC is improving.By analyzing different reliability indices of HVDC power transmission system,the maximum asset benef its of power grid can be achieved through building a scientif ic and reasonable reliability evaluation system.展开更多
This paper presents an effective power scheduling strategy for energy efficient multiple objects identification and association. The proposed method can be utilized in many heterogeneous surveillance systems with visu...This paper presents an effective power scheduling strategy for energy efficient multiple objects identification and association. The proposed method can be utilized in many heterogeneous surveillance systems with visual sensors and RFID （radio-frequency identification） readers where energy efficiency as well as association rate are critical Multiple objects positions and trajectory estimates are used to decide the power level of RFID readers. Several key parameters including the time windows and the distance separations are defined in the method in order to minimize the effects of RFID coverage uncertainty. The power cost model is defined and incorporated into the method to minimize energy consumption and to maximize association performance. The proposed method computes the power cost using the range of the outermost position for possible single association and group associations at every sampling time. An RFID reader is activated with the proper coverage range when the power cost for the current time is lower than the power cost for the next time sample. The simplicity of the power cost model relieves the problematic combinatorial comparisons in multiple object cases. The performance comparison simulation with the minimum and maximum energy consumption shows that the proposed method achieves fast single associations with less energy consumption. Finally, the realistic comparison simulation with the fixed range RFID readers demonstrates that the proposed method outperforms the fixed ranges in terms of single association rate and energy consumption.展开更多
Phase change memory （PCM） is a promising can- didate to replace DRAM as main memory, thanks to its bet- ter scalability and lower static power than DRAM. However, PCM also presents a few drawbacks, such as long writ...Phase change memory （PCM） is a promising can- didate to replace DRAM as main memory, thanks to its bet- ter scalability and lower static power than DRAM. However, PCM also presents a few drawbacks, such as long write la- tency and high write power. Moreover, the write commands parallelism of PCM is restricted by instantaneous power con- straints, which degrades write bandwidth and overall perfor- mance. The write power of PCM is asymmetric： writing a zero consumes more power than writing a one. In this paper, we propose a new scheduling policy, write power asymme- try scheduling （WPAS）, that exploits the asymmetry of write power. WPAS improves write commands parallelism of PCM memory without violating power constraint. The evaluation results show that WPAS can improve performance by up to 35.5%, and 18.5% on average. The effective read latency can be reduced by up to 33.0%, and 17.1% on average.展开更多
Grid structures are rapidly evolving in view of contemporary energy policies which ensure the addition of more renewable sources to reduce the carbon footprint.Compared to a centralized approach,low voltage grids(dece...Grid structures are rapidly evolving in view of contemporary energy policies which ensure the addition of more renewable sources to reduce the carbon footprint.Compared to a centralized approach,low voltage grids(decentralized and distributed)are promising approaches to integrating nondispatchable renewable energy sources(RESs).Installing local micro level power generation sources such as fuel cells,microturbines,and energy storage systems are a recent trend which helps in the intermittent effects of RESs and makes microgrids less dependable on the main grid.Due to the increasing variety of distributed generation sources having diverse characteristics,power dispatch scheduling of distributed microgrids is becoming challenging.A dispatch scheduling solution from an operator’s point of view is presented by the authors.The core objective of this study is to minimize the carbon emissions and the cost of each microgrid.Further,it is observed that sales and purchases from the main grid are reduced.Consequently,transmission losses are also decreased.展开更多
As power systems scale up and uncertainties deepen,traditional centralized optimization approaches impose significant computation burdens on large-scale optimization problems,introducing new challenges for power syste...As power systems scale up and uncertainties deepen,traditional centralized optimization approaches impose significant computation burdens on large-scale optimization problems,introducing new challenges for power system scheduling.To address these challenges,this study formulates a distributionally robust optimization(DRO)scheduling model that considers source-load uncertainty and is solved using a novel distributed approach that considers the distribution of tie-line endpoints.The proposed model includes a constraint related to the transmission interface,which consists of several tie-lines between two subsystems and is specifically designed to ensure technical operation security.In addition,we find that tie-line endpoints enhance the speed of distributed computation,leading to the development of a power system partitioning approach that considers the distribution of these endpoints.Further,this study proposes a distributed approach that employs an integrated algorithm of column-and-constraint generation(C&CG)and subgradient descent(IACS)to address the proposed model across multiple subsystems.A case study of two IEEE test systems and a practical provincial power system demonstrates that the proposed model effectively ensures system security.Finally,the scalability and effectiveness of the distributed approach in accelerating problem-solving are confirmed.展开更多
This paper describes the effect of channel estimation error （CEE） on the performance of distributed estimations of an unknown parameter in a wireless sensor network. Both the classical and Bayesian estimators are de...This paper describes the effect of channel estimation error （CEE） on the performance of distributed estimations of an unknown parameter in a wireless sensor network. Both the classical and Bayesian estimators are derived to mitigate the adverse effects caused by the CEE. Power scheduling among sensors and the power ratio between the training and data transmission at each individual node are optimized by directly minimizing the final average mean squared error to compensate for the CEE. A closed-form power scheduling policy is given for a homogeneous environment, which shows that more than 50% of the power should be allocated to sensor observation transmissions. For an inhomogeneous environment, a multilevel waterfilling type solution is developed for the power scheduling among sensors for only the sum power constraint with a ＂cave＂ waterfilling solution for both the sum and individual power constraints. Simulations show that the proposed power scheduling schemes achieve better performance than the equal power scheduling scheme.展开更多
The allocation of bandwidth to unlicensed users, without significantly increasing the interference on the existing licensed users, is a challenge for Ultra Wideband （UWB） networks. Our research work presents a novel...The allocation of bandwidth to unlicensed users, without significantly increasing the interference on the existing licensed users, is a challenge for Ultra Wideband （UWB） networks. Our research work presents a novel Rake Optimization and Power Aware Scheduling （ROPAS） architecture for UWB networks. Since UWB communication is rich in multipath effects, a Rake receiver is used for path diversity. Our idea of developing an optimized Rake receiver in our ROPAS architecture stems from the intention of reducing the computation complexity in terms of the number of multiplications and additions needed for the weight derivation attached to each finger of the Rake receiver. Our proposed work uses the Cognitive Radio （CR） for dynamic channel allocation among the requesting users while limiting the average power transmitted in each sub-band. In our proposed novel ROPAS architecture, dynamic channel allocation is achieved by a CR-based cross-layer design between the PHY and Medium Access Control （MAC） layers. Additionally, the maximum number of parallel transmissions within a frame interval is formulated as an optimization problem. This optimal decision is based on the distance parameter between a transmitter-receiver pair, bit error rate and frequency of request by a particular application. Moreover, the optimization problem improvises a differentiation technique among the requesting applications by incorporating priority levels among user applications. This provides fairness and higher throughput among services with varying power constraint and data rates required for a UWB network.展开更多
基金supported by the National Key Research and Development Program of China(Materials and Process Basis of Electrolytic Hydrogen Production from Fluctuating Power Sources such as Photovoltaic/Wind Power,No.2021YFB4000100)。
文摘To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for power scheduling in hydrogen production systems under the scenario of photovoltaic(PV)electrolysis of water.First,voltage and performance attenuation models of the PEMEL are proposed,and the degradation cost of the electrolyzer under a fluctuating input is considered.Then,the calculation of the investment and operating costs of the hydrogen production system for a typical day is based on the life cycle cost.Finally,a layered power scheduling optimization method is proposed to reasonably distribute the power of the electrolyzer and energy storage system in a hydrogen production system.In the up-layer optimization,the PV power absorbed by the hydrogen production system was optimized using MALTAB+Gurobi.In low-layer optimization,the power allocation between the PEMEL and battery energy storage system(BESS)is optimized using a non-dominated sorting genetic algorithm(NSGA-Ⅱ)combined with the firefly algorithm(FA).A better optimization result,characterized by lower degradation and total costs,was obtained using the method proposed in this study.The improved algorithm can search for a better population and obtain optimization results in fewer iterations.As a calculation example,data from a PV power station in northwest China were used for optimization,and the effectiveness and rationality of the proposed optimization method were verified.
基金supported by the National Science Foundation of China under Grant 62271062 and 62071063by the Zhijiang Laboratory Open Project Fund 2020LCOAB01。
文摘With the rapid development of cloud computing,edge computing,and smart devices,computing power resources indicate a trend of ubiquitous deployment.The traditional network architecture cannot efficiently leverage these distributed computing power resources due to computing power island effect.To overcome these problems and improve network efficiency,a new network computing paradigm is proposed,i.e.,Computing Power Network(CPN).Computing power network can connect ubiquitous and heterogenous computing power resources through networking to realize computing power scheduling flexibly.In this survey,we make an exhaustive review on the state-of-the-art research efforts on computing power network.We first give an overview of computing power network,including definition,architecture,and advantages.Next,a comprehensive elaboration of issues on computing power modeling,information awareness and announcement,resource allocation,network forwarding,computing power transaction platform and resource orchestration platform is presented.The computing power network testbed is built and evaluated.The applications and use cases in computing power network are discussed.Then,the key enabling technologies for computing power network are introduced.Finally,open challenges and future research directions are presented as well.
基金supported by State Grid science and technology projects“Research on energy and power sup-ply and demand interactive simulation technology for new power system(5100-202257028A-1-1-ZN)”.
文摘Increasing interest has been directed toward the potential of heterogeneous flexible loads to mitigate the challenges associated with the increasing variability and uncertainty of renewable generation.Evaluating the aggregated flexible region of load clusters managed by load aggregators is the crucial basis of power system scheduling for the system operator.This is because the aggregation result affects the qual-ity of the scheduling schemes.A stringent computation based on the Minkowski sum is NP-hard,whereas existing approximation meth-ods that use a special type of polytope exhibit limited adaptability when aggregating heterogeneous loads.This study proposes a stringent internal approximation method based on the convex hull of multiple layers of maximum volume boxes and embeds it into a day-ahead scheduling optimization model.The numerical results indicate that the aggregation accuracy can be improved compared with methods based on one type of special polytope,including boxes,zonotopes,and homothets.Hence,the reliability and economy of the power sys-tem scheduling can be enhanced.
文摘In order to make the power level angle(PLA)have the same bijection relationship with the thrust when the environment changes before operational limit exceedance,and ensure the pilot's ability of unrestricted throttle movement as well as the safety of the engine,a method used to design a constant thrust power schedule was proposed.The research was based on a simulink turbofan engine model and the results were organized as look-up tables in different structures with limitations.Simulation was done to confirm the validity and demonstrate the effectiveness of the schedule obtained with the approach.The constant thrust takeoff schedule,constant thrust idle schedule and constant thrust part power schedule with the present constant thrust control(CTC)method were proved to be valid.The results can be applied to this specific engine but the method can be applied to any areoengine and can be even extended to the unmanned plane.
文摘Retraction： LIU Shuanggen, NI Haiying, HU Yupu, LIAO Yunyan. An Improved Simple Power Attack against Camellia＇s Key Schedule. Wuhan University Journal of Natural Sciences, 2008, 13（5）： 591-594. DOI： 10.1007/s 11859-008-0516-3
文摘Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in the project were given official notice that both sides should start to implement the contracts. "The move marked a significant step forward in the project’s construction," said Zeng Wenxing, General Manager of Ling’ ao Nuclear Power Co Ltd, set up in
文摘In traditional power systems,besides the conventional power plants that provide the necessary reactive power in transmission system,the shunt capacitors along with the tap changers of transformers are also employed in distribution networks.In future years,because of the high number of distributed resources integrated into the distribution networks,it will be essential to schedule complete active-reactive power at distribution level.In this research work,an economic framework based on the active-reactive power bids has been developed for complete active-reactive power dispatch scheduling of smart distribution networks.The economical complete active-reactive power scheduling approach suggested in this study motivates distributed energy resources(DERs)to cooperate in both active power markets and the Volt/Var control scheme.To this end,using DER’s reactive power capability,a generic framework of reactive power offers for DERs is extracted.A 22-bus distribution test system is implemented to verify the impressiveness of the suggested active-reactive power scheduling approach.
基金supported by the National Natural Science Foundation of China(Grant Nos.60921003,60736027,61174161,60974101)the Spe-cialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20090121110022)+3 种基金the Fundamental Research Funds for the Central Universities of Xiamen University(Grant Nos.2011121047,201112G018,CXB2011035)the Key Research Project of Fujian Province of China(Grant No.2009H0044)Xiamen University National 211 3rd Period Project of China)(Grant No.0630-E72000)the Natural Sci-ence Foundation of Fujian Province,China(Grant No.2011J05154)
文摘With the improvement of electricity markets,the gradual aggravation of energy shortage and the environment pollution,it is urgent to formulate a new model to precisely satisfy the system demand for energy and reserve.Currently,power system opti-mization dispatching is always formulated as a discrete-time scheduling model.In this paper,we first demonstrate through an example that the upper and lower bounds of spinning reserve offered by a unit,given in the discrete-time model framework as constraints,is unreachable.This causes the problem that the reserve delivery obtained by the discrete-time scheduling model cannot be carried out precisely.From the detailed analysis of the ramp rate constraints,it is proved that the reachable upper and lower bounds of spinning reserve in every period can be expressed as functions of two variables,i.e.,generation level of unit at the start and end of this period.Thus,a new method is provided to calculate the upper and lower bounds of spinning reserve which are reachable in average.Furthermore,a new model based on this proposed method for joint scheduling of generation and reserve is presented,which considers the ability to realize the scheduled energy and reserve delivery.It converts the opti-mization based accurate scheduling for generation and reserve of power system from a continuous-time optimal control prob-lem to a nonlinear programming problem.Therefore,the proposed model can avoid the difficulties in solving a continu-ous-time optimal control problem.Based on the sequential quadratic programming method,numerical experiments for sched-uling electric power production systems are performed to evaluate the model and the results show that the new model is highly effective.
基金supported by the National Key Research and Development Program of China(No.2021YFB2400500)the Science and Technology Project of State Grid Corporation of China“Fast control of photovoltaic and wind power plant for transient frequency/voltage support”.
文摘As the proportion of renewable energy(RE)increases,the inertia and the primary frequency regulation(FR)capability of the power system decrease.Thus,ensuring frequency security in the scheduling model has become a new technical requirement in power systems with a high share of RE.Due to a shortage of conventional synchronous generators,the frequency support of multi-source converters has become an indispensable part of the system frequency resources,especially variable-speed wind turbine generation(WTG)and battery energy storage(BES).Quantitative expression of the FR capability of multi-source converters is necessary to construct frequency-constrained scheduling model.However,the frequency support performance of these converter-interfaced devices is related to their working states,operation modes,and parameters,and the complex coupling of these factors has not been fully exploited in existing models.In this study,we propose an integrated frequency-constrained scheduling model considering the coordination of FR capabilities from multi-source converters.Switchable FR control strategies and variable FR parameters for WTG with or without reserved power are modeled,and multi-target allocation of BES capacity between tracking dispatch instruction and emergency FR is analyzed.Then,the variable FR capabilities of WTG and BES are embedded into the integrated frequency-constrained scheduling model.The nonlinear constraints for frequency security are precisely linearized through an improved iteration-based strategy.The effectiveness of the proposed model is verified in a modified IEEE 24-bus standard system.The results suggest that the coordinated participation of BES and WTG in FR can effectively reduce the cost of the scheduling model while meeting frequency security constraints.
基金This work was supported by the Natural Science Foundation of China(Grant No.61702013)National Key Research and Development Plan(Grant Nos.2018YFB1800302 and 2019YFA0706404)+1 种基金Beijing Natural Science Foundation(Grant Nos.KZ201810009011,4202020,and 19L2021)Science and Technology Innovation Project of North China University of Technology(19XN108).
文摘While the size and complexity of software are rapidly increasing,not only is the number of vulnerabilities increasing,but their forms are diversifying.Vulnerability has become an important factor in network attack and defense.Therefore,automatic vulnerability discovery has become critical to ensure software security.Fuzzing is one of the most important methods of vulnerability discovery.It is based on the initial input,i.e.,a seed,to generate mutated test cases as new inputs of a tested program in the next execution loop.By monitoring the path coverage,fuzzing can choose high-value test cases for inclusion in the new seed set and capture crashes used for triggering vulnerabilities.Although there have been remarkable achievements in terms of the number of discovered vulnerabilities,the reduction of time cost is still inadequate.This paper proposes a fast directed greybox fuzzing model,FastAFLGo.A fast convergence formula of temperature is designed,and the energy scheduling scheme can quickly determine the best seed to make the program execute toward the target basic blocks.Experimental results show that FastAFLGo can discover more vulnerabilities than the traditional fuzzing method in the same execution time.
基金This work was supported by the National Natural Science Foundation of China(No.51977080)the Natural Science Foundation of Guangdong Province(No.2022A1515010332).
文摘As transmission power among interconnected re-gional grids is increasing rapidly,formulating the power distri-bution and maintenance schedules of multiple paralleled trans-mission channels is critical to ensure the secure and economic operation in an AC/DC power system.A coordinated optimiza-tion for power distribution and maintenance schedules(COPD-MS)of multiple paralleled transmission channels is proposed,and the active power losses of the resistances of earth line in the high-voltage direct current(HVDC)transmission lines are taken into account when one pole is under maintenance while the other pole is operating under monopolar ground circuit.To solve the proposed COPD-MS model efficiently,the generalized Benders decomposition(GBD)algorithm is used to decompose the proposed COPD-MS model into master problem of mainte-nance scheduling and sub-problems of power distribution sched-uling,and the optimal solution to the original model is obtained by the alternative iteration between them.Moreover,a recur-sive acceleration(RA)algorithm is proposed to solve the master problem,which can directly obtain its solution in the new itera-tion by using the solution in the last iteration and the newly added Benders cut.Convex relaxation techniques are applied to the nonlinear constraints in the sub-problem to ensure the reli-able convergence.Additionally,since there is no coupling among the power distributions during each time interval in the sub-problem,parallel computing technology is used to improve the computational efficiency.Finally,case studies on the modi-fied IEEE 39-bus system and an actual 1524-bus large-scale AC/DC hybrid power system demonstrate the effectiveness of the proposed COPD-MS model.
文摘Reliability level of HVDC power transmission systems becomes an important factor impacting the entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by SGCC since 2003 in respect of forced outage times,forced energy unavailability,scheduled energy unavailability and energy utilization eff iciency.The results show that the reliability level of HVDC power transmission systems owned by SGCC is improving.By analyzing different reliability indices of HVDC power transmission system,the maximum asset benef its of power grid can be achieved through building a scientif ic and reasonable reliability evaluation system.
基金supported by the International Collaborative Research and Development Program of the Ministry of Knowledge Economy(MKE)of Korea under the Grant No.2010-TD-300802-002
文摘This paper presents an effective power scheduling strategy for energy efficient multiple objects identification and association. The proposed method can be utilized in many heterogeneous surveillance systems with visual sensors and RFID （radio-frequency identification） readers where energy efficiency as well as association rate are critical Multiple objects positions and trajectory estimates are used to decide the power level of RFID readers. Several key parameters including the time windows and the distance separations are defined in the method in order to minimize the effects of RFID coverage uncertainty. The power cost model is defined and incorporated into the method to minimize energy consumption and to maximize association performance. The proposed method computes the power cost using the range of the outermost position for possible single association and group associations at every sampling time. An RFID reader is activated with the proper coverage range when the power cost for the current time is lower than the power cost for the next time sample. The simplicity of the power cost model relieves the problematic combinatorial comparisons in multiple object cases. The performance comparison simulation with the minimum and maximum energy consumption shows that the proposed method achieves fast single associations with less energy consumption. Finally, the realistic comparison simulation with the fixed range RFID readers demonstrates that the proposed method outperforms the fixed ranges in terms of single association rate and energy consumption.
文摘Phase change memory （PCM） is a promising can- didate to replace DRAM as main memory, thanks to its bet- ter scalability and lower static power than DRAM. However, PCM also presents a few drawbacks, such as long write la- tency and high write power. Moreover, the write commands parallelism of PCM is restricted by instantaneous power con- straints, which degrades write bandwidth and overall perfor- mance. The write power of PCM is asymmetric： writing a zero consumes more power than writing a one. In this paper, we propose a new scheduling policy, write power asymme- try scheduling （WPAS）, that exploits the asymmetry of write power. WPAS improves write commands parallelism of PCM memory without violating power constraint. The evaluation results show that WPAS can improve performance by up to 35.5%, and 18.5% on average. The effective read latency can be reduced by up to 33.0%, and 17.1% on average.
基金This work was supported by the National Natural Science Foundation of China(U1866206).
文摘Grid structures are rapidly evolving in view of contemporary energy policies which ensure the addition of more renewable sources to reduce the carbon footprint.Compared to a centralized approach,low voltage grids(decentralized and distributed)are promising approaches to integrating nondispatchable renewable energy sources(RESs).Installing local micro level power generation sources such as fuel cells,microturbines,and energy storage systems are a recent trend which helps in the intermittent effects of RESs and makes microgrids less dependable on the main grid.Due to the increasing variety of distributed generation sources having diverse characteristics,power dispatch scheduling of distributed microgrids is becoming challenging.A dispatch scheduling solution from an operator’s point of view is presented by the authors.The core objective of this study is to minimize the carbon emissions and the cost of each microgrid.Further,it is observed that sales and purchases from the main grid are reduced.Consequently,transmission losses are also decreased.
基金supported by the National Key R&D Program of China(No.2022YFB2403400)。
文摘As power systems scale up and uncertainties deepen,traditional centralized optimization approaches impose significant computation burdens on large-scale optimization problems,introducing new challenges for power system scheduling.To address these challenges,this study formulates a distributionally robust optimization(DRO)scheduling model that considers source-load uncertainty and is solved using a novel distributed approach that considers the distribution of tie-line endpoints.The proposed model includes a constraint related to the transmission interface,which consists of several tie-lines between two subsystems and is specifically designed to ensure technical operation security.In addition,we find that tie-line endpoints enhance the speed of distributed computation,leading to the development of a power system partitioning approach that considers the distribution of these endpoints.Further,this study proposes a distributed approach that employs an integrated algorithm of column-and-constraint generation(C&CG)and subgradient descent(IACS)to address the proposed model across multiple subsystems.A case study of two IEEE test systems and a practical provincial power system demonstrates that the proposed model effectively ensures system security.Finally,the scalability and effectiveness of the distributed approach in accelerating problem-solving are confirmed.
文摘This paper describes the effect of channel estimation error （CEE） on the performance of distributed estimations of an unknown parameter in a wireless sensor network. Both the classical and Bayesian estimators are derived to mitigate the adverse effects caused by the CEE. Power scheduling among sensors and the power ratio between the training and data transmission at each individual node are optimized by directly minimizing the final average mean squared error to compensate for the CEE. A closed-form power scheduling policy is given for a homogeneous environment, which shows that more than 50% of the power should be allocated to sensor observation transmissions. For an inhomogeneous environment, a multilevel waterfilling type solution is developed for the power scheduling among sensors for only the sum power constraint with a ＂cave＂ waterfilling solution for both the sum and individual power constraints. Simulations show that the proposed power scheduling schemes achieve better performance than the equal power scheduling scheme.
基金the National Science Foundation(NSF)of USA under Grant No.NeTS-WN0721641.
文摘The allocation of bandwidth to unlicensed users, without significantly increasing the interference on the existing licensed users, is a challenge for Ultra Wideband （UWB） networks. Our research work presents a novel Rake Optimization and Power Aware Scheduling （ROPAS） architecture for UWB networks. Since UWB communication is rich in multipath effects, a Rake receiver is used for path diversity. Our idea of developing an optimized Rake receiver in our ROPAS architecture stems from the intention of reducing the computation complexity in terms of the number of multiplications and additions needed for the weight derivation attached to each finger of the Rake receiver. Our proposed work uses the Cognitive Radio （CR） for dynamic channel allocation among the requesting users while limiting the average power transmitted in each sub-band. In our proposed novel ROPAS architecture, dynamic channel allocation is achieved by a CR-based cross-layer design between the PHY and Medium Access Control （MAC） layers. Additionally, the maximum number of parallel transmissions within a frame interval is formulated as an optimization problem. This optimal decision is based on the distance parameter between a transmitter-receiver pair, bit error rate and frequency of request by a particular application. Moreover, the optimization problem improvises a differentiation technique among the requesting applications by incorporating priority levels among user applications. This provides fairness and higher throughput among services with varying power constraint and data rates required for a UWB network.
