In this paper,a model free volt/var control(VVC)algorithm is developed by using deep reinforcement learning(DRL).We transform the VVC problem of distribution networks into the network framework of PPO algorithm,in ord...In this paper,a model free volt/var control(VVC)algorithm is developed by using deep reinforcement learning(DRL).We transform the VVC problem of distribution networks into the network framework of PPO algorithm,in order to avoid directly solving a large-scale nonlinear optimization problem.We select photovoltaic inverters as agents to adjust system voltage in a distribution network,taking the reactive power output of inverters as action variables.An appropriate reward function is designed to guide the interaction between photovoltaic inverters and the distribution network environment.OPENDSS is used to output system node voltage and network loss.This method realizes the goal of optimal VVC in distribution network.The IEEE 13-bus three phase unbalanced distribution system is used to verify the effectiveness of the proposed algorithm.Simulation results demonstrate that the proposed method has excellent performance in voltage and reactive power regulation of a distribution network.展开更多
The European power grid is one of the largest regional interconnected power grids in the world.It realizes a multinational grid operation,which is rare.The total installed capacity of the European power grid is the la...The European power grid is one of the largest regional interconnected power grids in the world.It realizes a multinational grid operation,which is rare.The total installed capacity of the European power grid is the largest throughout the world.In addition,the integration and utilization of renewable energy in this grid is a great benchmark for other countries and can help promote energy transformation and achieve a high proportion of renewable energy consumption.Based on the analysis of the existing status of the European interconnected power grid and the development history of this power grid,this paper summarizes four key development stages of the European power grid.In addition,the characteristics of each stage and the development prospect of the European power grid are analyzed.On this basis,this paper gives suggestions for the development and construction of China’s energy internet;this can provide valuable reference for further studies on China’s energy internet.展开更多
In a multi-energy collaboration system, cooling, heating, electricity, and other energy components are coupled to complement each other. Through multi-energy coordination and cooperation, they can significantly improv...In a multi-energy collaboration system, cooling, heating, electricity, and other energy components are coupled to complement each other. Through multi-energy coordination and cooperation, they can significantly improve their individual operating efficiency and overall economic benefits. Demand response, as a multi-energy supply and demand balance method, can further improve system flexibility and economy. Therefore, a multi-energy cooperative system optimization model has been proposed, which is driven by price-based demand response to determine the impact of power-demand response on the optimal operating mode of a multi-energy cooperative system. The main components of the multi-energy collaborative system have been analyzed. The multi-energy coupling characteristics have been identified based on the energy hub model. Using market elasticity as a basis, a price-based demand response model has been built. The model has been optimized to minimize daily operating cost of the multi-energy collaborative system. Using data from an actual situation, the model has been verified, and we have shown that the adoption of price-based demand response measures can significantly improve the economy of multi-energy collaborative systems.展开更多
To address the issue of climate change caused by the use of polluting, non-renewable energy sources, the use of renewable energy has gained momentum worldwide. Consequently, the increased integration of renewable ener...To address the issue of climate change caused by the use of polluting, non-renewable energy sources, the use of renewable energy has gained momentum worldwide. Consequently, the increased integration of renewable energy sources into power grids has necessitated the inclusion of flexible capacities in the power systems to solve problems of intermittent and fluctuating characteristics associated with renewable generation outputs. In this work, we study the regulating cost of a power system with high renewable penetration using an improved time-series system production simulation analysis method. The operational cost of the system is considered as the objective function. Three different methods to increase regulating capacities, including using interconnection lines, building additional flexible power capacities, and retrofitting existing thermal power plants, are adopted and simulated to compare the costs of accommodating renewable energy in the system in these cases. Our results indicate that increasing the flexibility of thermal power plants and developing crossregional connection lines are cost-effective methods of increasing renewable energy consumption.展开更多
This paper addresses the issues regarding the economics of clean energy transmission channels in Southeast Asia.The research developed an improved comprehensive model for the generation and transmission planning consi...This paper addresses the issues regarding the economics of clean energy transmission channels in Southeast Asia.The research developed an improved comprehensive model for the generation and transmission planning considering variable renewable energy characteristics,and it simulated the hourly resolution operation condition of a cross-regional interconnection grid of Southeast Asia,China,and South Asia.Additionally,we conducted a sensitivity analysis,and the assessment of the channels’economics covered a variety of factors such as clean energy penetration,CO_(2),and pollutant reduction.Conclusions are drawn regarding the influence of different parameters and conditions on the economics of the transmission channel.Subsequently,several recommendations were proposed based on these analyses,which could support the development of the scheme of Southeast Asia power grid and the interconnection of the Belt and Road initiative.展开更多
Although the Combined Cooing,Heating and Power System(hereinafter referred to as“CCHP”)improves the capacity utilization rate and energy utilization efficiency,single use of CCHP system cannot realize dynamic matchi...Although the Combined Cooing,Heating and Power System(hereinafter referred to as“CCHP”)improves the capacity utilization rate and energy utilization efficiency,single use of CCHP system cannot realize dynamic matching between supply and demand loads due to the unbalance features of the user’s cooling and heating loads.On the basis of user convenience and wide applicability of clean air energy,this paper tries to put forward a coupled CCHP system with combustion gas turbine and ASHP ordered power by heat,analyze trends of such parameters as gas consumption and power consumption of heat pump in line with adjustment of heating load proportion of combustion gas turbine,and optimize the system ratio in the method of annual costs and energy environmental benefit assessment.Based on the analysis of the hourly simulation and matching characteristics of the cold and hot load of the 100 thousand square meter building,it is found that the annual cost of the air source heat pump is low,but the energy and environmental benefits are poor.It will lead to 6.35%shortage of cooling load in summer.Combined with the evaluation method of primary energy consumption and zero carbon dioxide emission,the coupling system of CHHP and air source heat pump with 41%gas turbine load ratio is the best configuration.This system structure and optimization method can provide some reference for the development of CCHP coupling system.展开更多
In the process of large-scale,grid-connected wind power operations,it is important to establish an accurate probability distribution model for wind farm fluctuations.In this study,a wind power fluctuation modeling met...In the process of large-scale,grid-connected wind power operations,it is important to establish an accurate probability distribution model for wind farm fluctuations.In this study,a wind power fluctuation modeling method is proposed based on the method of moving average and adaptive nonparametric kernel density estimation(NPKDE)method.Firstly,the method of moving average is used to reduce the fluctuation of the sampling wind power component,and the probability characteristics of the modeling are then determined based on the NPKDE.Secondly,the model is improved adaptively,and is then solved by using constraint-order optimization.The simulation results show that this method has a better accuracy and applicability compared with the modeling method based on traditional parameter estimation,and solves the local adaptation problem of traditional NPKDE.展开更多
Software performance evaluation in multimedia communication systems is typically formulated into a multi-layered client-server queuing network(MLCSQN) problem. However, the existing analytical methods to MLCSQN model ...Software performance evaluation in multimedia communication systems is typically formulated into a multi-layered client-server queuing network(MLCSQN) problem. However, the existing analytical methods to MLCSQN model cannot provide satisfactory solution in terms of accuracy, convergence and consideration of interlocking effects. To this end, this paper proposes a heuristic solving method for MLCSQN model to boost the performance prediction of distributed multimedia software systems. The core concept of this method is referred to as the basic model, which can be further decomposed into two sub-models: client sub-model and server sub-model. The client sub-model calculates think time for server sub-model, and the server sub-model calculates waiting time for client sub-model. Using a breadthfirst traversal from leaf nodes to the root node and vice versa, the basic model is then adapted to MLCSQN, with net sub-models iteratively resolved. Similarly, the interlocking problem is effectively addressed with the help of the basic model. This analytical solver enjoys advantages of fast convergence, independence on specific average value analysis(MVA) methods and eliminating interlocking effects.Numerical experimental results on accuracy and computation efficiency verify its superiority over anchors.展开更多
At present,there are few studies on the comprehensive evaluation of green power grid development in China,and all aspects of green power grid need to be evaluated.Therefore,this paper studies the green development lev...At present,there are few studies on the comprehensive evaluation of green power grid development in China,and all aspects of green power grid need to be evaluated.Therefore,this paper studies the green development level of power distribution network.This paper proposes a multi-level fuzzy comprehensive evaluation method,which first needs to classify the influencing factors.Therefore,this paper constructs an indicator system for the evaluation of green development of power distribution network from three dimensions.In order to avoid the influence of subjective factors,this paper adopts the model combining analytic hierarchy process and entropy weight method to give weight to indexes.Finally,five typical regions are selected for empirical analysis.The results show that the model established in this paper can reflect the green development level of power distribution network in each region and put forward relevant improvement suggestions for each region.展开更多
A modeling method of regional integrated energy system based on bus method and transient simulation is proposed,and the system optimization is based on the dynamic balance of supply and demand in the whole year energy...A modeling method of regional integrated energy system based on bus method and transient simulation is proposed,and the system optimization is based on the dynamic balance of supply and demand in the whole year energy supply cycle.A CCHP systemof gas turbine coupled with ground source heat pump and electric refrigeration unit is constructed.The energy relationship of the systemis described by bus structure,and the transient calculationmodel is built on TRNSYS platform.The weighted sum of annual total cost saving rate,primary energy saving rate and environmental pollutant shadow cost saving rate is taken as the optimized objective function,and on the basis of annual dynamic balance,the Hooke-Jeeves algorithm is used for optimization of the system configuration.A complex commercial area in Beijing is taken as an example,and different weighting coefficients are set for optimization of the system configuration.The results show that,from the perspective of economy,environmental benefit and primary energy consumption,performance of the system increases and then decreases with rise of gas turbine power;under the simulated cooling/heating load,the maximum number of optimum configuration is seen in the combination of 35 kW gas turbine+723 kW GSHP and 1178 kW electric chiller;in comparison with traditional distributed system,the annual cost saving rate,primary energy saving rate and environmental pollutant shadow cost saving rate of the system are 29.4%,49.6%and 58.2%,respectively.展开更多
High-frequency resonance can occur when a modular multilevel converter(MMC)is inserted into an AC grid.Additional damping control is a relatively low-cost resonance suppression strategy compared to passive damping str...High-frequency resonance can occur when a modular multilevel converter(MMC)is inserted into an AC grid.Additional damping control is a relatively low-cost resonance suppression strategy compared to passive damping strategies.This paper analyzes the influences of a feed-forward voltage filter and feedback current filter for the inner controller for the high-frequency impedance characteristics of the MMC based on a model.Moreover,the mechanism,influencing factors,and limitations of the existing strategy including an additional lowpass filter in the voltage feed-forward stage are investigated.Secondly,a resonance suppression strategy for the inclusion of additional cascaded notch filters in the voltage feed-forward stage is proposed,and its parameter design method and applicable scenarios are analyzed.In addition,this paper analyzes the effects of the inclusion of an additional control in other stages for the inner controller of the MMC.Finally,the correctness of the theoretical analysis and the proposed strategy is verified based on the simulation of an actual project on PSCAD/EMTDC.展开更多
As the proportion of electricity in final energy consumption gradually increases,CO_(2) emissions reduction actions in the power system will become the key to achieving China’s carbon-peak and carbon-neutrality goals...As the proportion of electricity in final energy consumption gradually increases,CO_(2) emissions reduction actions in the power system will become the key to achieving China’s carbon-peak and carbon-neutrality goals.It is essential to analyse and quantify the driving forces of CO_(2) emissions from electricity generation in the fossil-rich area in China.This paper aims to identify the characteristics of CO_(2) emissions generated by electricity and provide a basis for formulating CO_(2)-reduction policies in power systems.First,we analyse the current state of CO_(2) emissions from electricity generation in Anhui Province that was dominated by fossil energy during the period 2010-19.Then,we apply the logarithmic mean Divisia index method to find the nature of the factors influencing the changes in CO_(2) emissions.Finally,we analyse the CO_(2)-reduction measures of each side of the source-network-load-storage of the power system in Anhui through a power-system carbon-reduction path analysis model proposed in this study and provide policy suggestions.The results showed the following.(i)CO_(2) emissions in Anhui Province continued to increase from 2010 to 2019 and the trend in the growth rate of CO_(2) emissions presented approximately a u-shaped curve.(ii)Economic activity has always been the dominant factor driving the growth of electricity CO_(2) emis-sions.The increase in the proportion of renewable energy in power generation,the improvement in thermal power-conversion efficiency and the decrease in the intensity of power consumption are the three major driving factors for the reduction in CO_(2) emissions from power generation in Anhui.(iii)The CO_(2)-reduction measures of the power system are provided in each link of the source-network-load-storage,such as developing the photovoltaic industry and building energy storage,upgrading and transforming coal-fired power stations,redu-cing the loss rate of transmission lines on the grid side and improving the efficiency of the utilization of electricity on the user side.展开更多
Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the constructi...Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.展开更多
China will strive to achieve a‘dual carbon’target:‘carbon peak’by 2030 and‘carbon-neutral’by 2060.In this context,improving the efficiency of renewable energy and reducing the use of thermal power are important ...China will strive to achieve a‘dual carbon’target:‘carbon peak’by 2030 and‘carbon-neutral’by 2060.In this context,improving the efficiency of renewable energy and reducing the use of thermal power are important ways to achieve the target.Clean,efficient and large-capacity energy-storage technology is the key to improving the utilization rate of renewable energy.First,this paper proposes to use compressed-air energy-storage technology instead of the old energy-storage technology to build an economical and environmentally friendly comprehensive energy park capacity optimization configuration model.Second,this paper uses the newly proposed improved chicken swarm optimization algorithm to solve the model,which is more accurate and faster.Finally,this paper analyzes a comprehensive energy park in north-west China.Through case analysis,it can be seen that the average utilization rate of renewable energy can reach 73.87%through the model proposed in this paper,while the average power-abandonment rate is only 9.32%.展开更多
With the gradual upgradation of global energy consumption and the associated development of multi-energy sources,the pace of unified energy planning and design has been accelerated and the concept of multi-energy syst...With the gradual upgradation of global energy consumption and the associated development of multi-energy sources,the pace of unified energy planning and design has been accelerated and the concept of multi-energy system(MES)has been formed.The industrial structure of industrial park(IP)consists of production and marketing of multi-energy sources,which makes IP become an ideal application scenario for MES.The coupling between multi-sources raises the complexity level of IP,which requires the demand side analysis in IP as it enables customers to actively participate in energy planning and development.This paper presents the concept and operation strategies of integrated demand response(IDR),and its model classification is analyzed in detail.Optimization model and IDR with varying time period are studied in IP to determine their impacts on the system.A detailed survey of different techniques in both operation strategies and model classification is presented and the classification is based on pros and cons.Finally,key issues and outlooks are discussed.展开更多
In this paper,the dynamic coupling between the wind turbine rotor speed recovery(WTRSR)and inertial response of the conventional virtual synchronous generator(VSG)controlled wind farms(WFs)is analyzed.Three distinguis...In this paper,the dynamic coupling between the wind turbine rotor speed recovery(WTRSR)and inertial response of the conventional virtual synchronous generator(VSG)controlled wind farms(WFs)is analyzed.Three distinguishing features are revealed.Firstly,the inertial response characteristics of VSG controlled WFs(VSG-WFs)are impaired by the dynamic coupling.Secondly,when the influence of WTRSR is dominant,the inertial response characteristics of VSG-WFs are even worse than the condition under which WFs do not participate in the response of grid frequency.Thirdly,this phenomenon cannot be eliminated by only enlarging the inertia parameter of VSG-WFs,because the influence of WTRSR would also increase with the enhancement of inertial response.A decoupling scheme to eliminate the negative influence is then proposed in this paper.By starting the WTRSR process after inertial response period,the dynamic coupling is eliminated and the inertial response characteristics of WFs are improved.Finally,the effectiveness of the analysis and the proposed scheme are verified by simulation results.展开更多
The electricity distribution network is experiencing a profound transformation with the concept of the smart grid,providing possibilities for selfish consumers to interact with the distribution system operator(DSO)and...The electricity distribution network is experiencing a profound transformation with the concept of the smart grid,providing possibilities for selfish consumers to interact with the distribution system operator(DSO)and to maximize their individual energy consumption utilities.However,this profitseeking behavior among consumers may violate the network constraints,such as line flows,transformer capacity and bus voltage magnitude limits.Therefore,a network-constrained energy consumption(NCEC)game among active load aggregators(ALAs)is proposed to guarantee the safety of the distribution network.The temporal and spatial constraints of an ALA are both considered,which leads the formulated model to a generalized Nash equilibrium problem(GNEP).By resorting to a well-developed variational inequality(VI)theory,we study the existence of solutions to the NCEC game problem.Subsequently,a two-level distributed algorithm is proposed to find the variational equilibrium(VE),a fair and stable solution to the formulated game model.Finally,the effectiveness of the proposed game model and the efficiency of the distributed algorithm are tested on an IEEE-33 bus system.展开更多
Based on completely mastering±800 kV transmission technologies,the first±1100 kV direct current(DC)transmission demonstration project is being constructed in China.Combining theoretical analysis and a large ...Based on completely mastering±800 kV transmission technologies,the first±1100 kV direct current(DC)transmission demonstration project is being constructed in China.Combining theoretical analysis and a large number of experiments,the margin of switching overvoltage in converter stations,the configuration scheme and performance of lightning arresters,the shielding angles of ground lines under different geographical conditions,and the maximum air gap of lines have been determined.The switching impulse flashover characteristics of equipotential sphere and typical rod-plane air gaps are also provided.The external insulation is designed differently for light,medium,and heavy pollution areas.For the±1100 kV project,if the 8×1250 mm^(2)conductors are applied,the pole gap is 26 m and the height of the line is 25 m,all the electromagnetic parameters will meet the requirement of international electromagnetic standards.The key design points of±1100 kV converter transformers,smoothing reactors,converter valves,and wall bushings are researched and the 75 mH smoothing reactors,±1100 kV/5000 A converter valves,and±1100 kV/5523 A wall bushings are successfully made.The optimised hierarchical connection modes and coordination control measure of the±1100 kV project are studied and the results can provide sufficient technical support for the demonstration project.展开更多
This paper proposes a novel AC filter system for a line commutated converter high voltage DC(LCC-HVDC)transmission system.Through the coordination of the hybrid active power filters(APF)and the existing reactive compe...This paper proposes a novel AC filter system for a line commutated converter high voltage DC(LCC-HVDC)transmission system.Through the coordination of the hybrid active power filters(APF)and the existing reactive compensation devices,the proposed filter system can not only enhance the suppression performance for LCC-HVDC harmonics,but also optimize the AC yard layout with reduced reactive power subbanks,reducing the cost of HVDC projects.The novel filter system adopts a serial passive resonance topology obtained by careful comparison of different APFs.A proper control scheme is then designed integrating the control strategy of the APF and impedance characteristics of the HVDC system,which is able to realize harmonic suppression and dynamic reactive power support simultaneously.In addition,a novel self-adaption digital low-pass filter algorithm is presented,which is used in the APF harmonic detecting step,enhancing both high precision and fast dynamic response.On the basis of a real HVDC project,the advantages of proposed filter system in harmonic suppression,reactive power regulation,and sub-banks reduction are simulated and demonstrated.展开更多
Increasing the application of renewable energy in the power system is an effective way to achieve the goal of‘Dual Carbon’.At the same time,the high proportion of renewable energy connected to the grid endangers the...Increasing the application of renewable energy in the power system is an effective way to achieve the goal of‘Dual Carbon’.At the same time,the high proportion of renewable energy connected to the grid endangers the safe operation of the power system.To solve this problem,this paper proposes the application of a copula function to describe the correlation between wind power and photovoltaic power,and reduce the uncertainty of power-system operation with a high proportion of renewable energy.In order to increase the robustness of the model,this paper proposes the application of the conditional value-at-risk theory to construct the objective function of the model and effectively control the tail risk of power-system operation costs.Through case analysis,it is found that the model proposed in this paper has strong practicality and economy.展开更多
基金supported by the Science and Technology Project of State Grid Zhejiang Electric Power Co.,Ltd.under Grant B311JY21000A。
文摘In this paper,a model free volt/var control(VVC)algorithm is developed by using deep reinforcement learning(DRL).We transform the VVC problem of distribution networks into the network framework of PPO algorithm,in order to avoid directly solving a large-scale nonlinear optimization problem.We select photovoltaic inverters as agents to adjust system voltage in a distribution network,taking the reactive power output of inverters as action variables.An appropriate reward function is designed to guide the interaction between photovoltaic inverters and the distribution network environment.OPENDSS is used to output system node voltage and network loss.This method realizes the goal of optimal VVC in distribution network.The IEEE 13-bus three phase unbalanced distribution system is used to verify the effectiveness of the proposed algorithm.Simulation results demonstrate that the proposed method has excellent performance in voltage and reactive power regulation of a distribution network.
基金funded by the State Grid Science and Technology Research Program:“Research on coordination development mode and reliability evaluation of source,network,load and storage considering the safety requirements(No.B3440818K005)”
文摘The European power grid is one of the largest regional interconnected power grids in the world.It realizes a multinational grid operation,which is rare.The total installed capacity of the European power grid is the largest throughout the world.In addition,the integration and utilization of renewable energy in this grid is a great benchmark for other countries and can help promote energy transformation and achieve a high proportion of renewable energy consumption.Based on the analysis of the existing status of the European interconnected power grid and the development history of this power grid,this paper summarizes four key development stages of the European power grid.In addition,the characteristics of each stage and the development prospect of the European power grid are analyzed.On this basis,this paper gives suggestions for the development and construction of China’s energy internet;this can provide valuable reference for further studies on China’s energy internet.
基金supported by State Grid Corporation Technology Project (5400-201956447A-0-0-00)。
文摘In a multi-energy collaboration system, cooling, heating, electricity, and other energy components are coupled to complement each other. Through multi-energy coordination and cooperation, they can significantly improve their individual operating efficiency and overall economic benefits. Demand response, as a multi-energy supply and demand balance method, can further improve system flexibility and economy. Therefore, a multi-energy cooperative system optimization model has been proposed, which is driven by price-based demand response to determine the impact of power-demand response on the optimal operating mode of a multi-energy cooperative system. The main components of the multi-energy collaborative system have been analyzed. The multi-energy coupling characteristics have been identified based on the energy hub model. Using market elasticity as a basis, a price-based demand response model has been built. The model has been optimized to minimize daily operating cost of the multi-energy collaborative system. Using data from an actual situation, the model has been verified, and we have shown that the adoption of price-based demand response measures can significantly improve the economy of multi-energy collaborative systems.
基金supported by National Key Research and Development Programe of China (No.2018YFB0904000)the State Grid Science & Technology Project (Title: Northeast Asia Power Grid Interconnection Feasibility Study)
文摘To address the issue of climate change caused by the use of polluting, non-renewable energy sources, the use of renewable energy has gained momentum worldwide. Consequently, the increased integration of renewable energy sources into power grids has necessitated the inclusion of flexible capacities in the power systems to solve problems of intermittent and fluctuating characteristics associated with renewable generation outputs. In this work, we study the regulating cost of a power system with high renewable penetration using an improved time-series system production simulation analysis method. The operational cost of the system is considered as the objective function. Three different methods to increase regulating capacities, including using interconnection lines, building additional flexible power capacities, and retrofitting existing thermal power plants, are adopted and simulated to compare the costs of accommodating renewable energy in the system in these cases. Our results indicate that increasing the flexibility of thermal power plants and developing crossregional connection lines are cost-effective methods of increasing renewable energy consumption.
基金Supported by Science and Technology Foundation of GEIG(52450018000M)National Key R&D Program of China(2016YFB0900500).
文摘This paper addresses the issues regarding the economics of clean energy transmission channels in Southeast Asia.The research developed an improved comprehensive model for the generation and transmission planning considering variable renewable energy characteristics,and it simulated the hourly resolution operation condition of a cross-regional interconnection grid of Southeast Asia,China,and South Asia.Additionally,we conducted a sensitivity analysis,and the assessment of the channels’economics covered a variety of factors such as clean energy penetration,CO_(2),and pollutant reduction.Conclusions are drawn regarding the influence of different parameters and conditions on the economics of the transmission channel.Subsequently,several recommendations were proposed based on these analyses,which could support the development of the scheme of Southeast Asia power grid and the interconnection of the Belt and Road initiative.
基金This research was funded by the research on rapid modeling methods for integrated energy systems,Grant No.SGTYHT/17-JS-204.
文摘Although the Combined Cooing,Heating and Power System(hereinafter referred to as“CCHP”)improves the capacity utilization rate and energy utilization efficiency,single use of CCHP system cannot realize dynamic matching between supply and demand loads due to the unbalance features of the user’s cooling and heating loads.On the basis of user convenience and wide applicability of clean air energy,this paper tries to put forward a coupled CCHP system with combustion gas turbine and ASHP ordered power by heat,analyze trends of such parameters as gas consumption and power consumption of heat pump in line with adjustment of heating load proportion of combustion gas turbine,and optimize the system ratio in the method of annual costs and energy environmental benefit assessment.Based on the analysis of the hourly simulation and matching characteristics of the cold and hot load of the 100 thousand square meter building,it is found that the annual cost of the air source heat pump is low,but the energy and environmental benefits are poor.It will lead to 6.35%shortage of cooling load in summer.Combined with the evaluation method of primary energy consumption and zero carbon dioxide emission,the coupling system of CHHP and air source heat pump with 41%gas turbine load ratio is the best configuration.This system structure and optimization method can provide some reference for the development of CCHP coupling system.
基金supported by Science and Technology project of the State Grid Corporation of China“Research on Active Development Planning Technology and Comprehensive Benefit Analysis Method for Regional Smart Grid Comprehensive Demonstration Zone”National Natural Science Foundation of China(51607104)
文摘In the process of large-scale,grid-connected wind power operations,it is important to establish an accurate probability distribution model for wind farm fluctuations.In this study,a wind power fluctuation modeling method is proposed based on the method of moving average and adaptive nonparametric kernel density estimation(NPKDE)method.Firstly,the method of moving average is used to reduce the fluctuation of the sampling wind power component,and the probability characteristics of the modeling are then determined based on the NPKDE.Secondly,the model is improved adaptively,and is then solved by using constraint-order optimization.The simulation results show that this method has a better accuracy and applicability compared with the modeling method based on traditional parameter estimation,and solves the local adaptation problem of traditional NPKDE.
基金supported by the Application Research of the Remote Sensing Technology on Global Energy Internet(JYYKJXM(2017)011)the National Natural Science Foundation of China(61671332,41701518,41771452,41771454,U1736206)+4 种基金National key R&D Project(2016YFE0202300)Hubei Province Technological Innovation Major Project(2017AAA123)Applied Basic Research Program of Wuhan City(2016010101010025)Basic Research Program of Shenzhen(JCYJ20170306171431656)the Fundamental Research Funds for the Central Universities(2042016gf0033)
文摘Software performance evaluation in multimedia communication systems is typically formulated into a multi-layered client-server queuing network(MLCSQN) problem. However, the existing analytical methods to MLCSQN model cannot provide satisfactory solution in terms of accuracy, convergence and consideration of interlocking effects. To this end, this paper proposes a heuristic solving method for MLCSQN model to boost the performance prediction of distributed multimedia software systems. The core concept of this method is referred to as the basic model, which can be further decomposed into two sub-models: client sub-model and server sub-model. The client sub-model calculates think time for server sub-model, and the server sub-model calculates waiting time for client sub-model. Using a breadthfirst traversal from leaf nodes to the root node and vice versa, the basic model is then adapted to MLCSQN, with net sub-models iteratively resolved. Similarly, the interlocking problem is effectively addressed with the help of the basic model. This analytical solver enjoys advantages of fast convergence, independence on specific average value analysis(MVA) methods and eliminating interlocking effects.Numerical experimental results on accuracy and computation efficiency verify its superiority over anchors.
基金Project Supported by the 2018 Key Projects of Philosophy and Social Sciences Research,Ministry of Education,China(Grant No.18JZD032).Topic:Research on Policies and Mechanisms of Building a Clean,Low-Carbon,Safe and Efficient Energy System.
文摘At present,there are few studies on the comprehensive evaluation of green power grid development in China,and all aspects of green power grid need to be evaluated.Therefore,this paper studies the green development level of power distribution network.This paper proposes a multi-level fuzzy comprehensive evaluation method,which first needs to classify the influencing factors.Therefore,this paper constructs an indicator system for the evaluation of green development of power distribution network from three dimensions.In order to avoid the influence of subjective factors,this paper adopts the model combining analytic hierarchy process and entropy weight method to give weight to indexes.Finally,five typical regions are selected for empirical analysis.The results show that the model established in this paper can reflect the green development level of power distribution network in each region and put forward relevant improvement suggestions for each region.
基金This research was funded by the Research on Rapid Modeling Methods for Integrated Energy Systems,Grant No.SGTYHT/17-JS-204.
文摘A modeling method of regional integrated energy system based on bus method and transient simulation is proposed,and the system optimization is based on the dynamic balance of supply and demand in the whole year energy supply cycle.A CCHP systemof gas turbine coupled with ground source heat pump and electric refrigeration unit is constructed.The energy relationship of the systemis described by bus structure,and the transient calculationmodel is built on TRNSYS platform.The weighted sum of annual total cost saving rate,primary energy saving rate and environmental pollutant shadow cost saving rate is taken as the optimized objective function,and on the basis of annual dynamic balance,the Hooke-Jeeves algorithm is used for optimization of the system configuration.A complex commercial area in Beijing is taken as an example,and different weighting coefficients are set for optimization of the system configuration.The results show that,from the perspective of economy,environmental benefit and primary energy consumption,performance of the system increases and then decreases with rise of gas turbine power;under the simulated cooling/heating load,the maximum number of optimum configuration is seen in the combination of 35 kW gas turbine+723 kW GSHP and 1178 kW electric chiller;in comparison with traditional distributed system,the annual cost saving rate,primary energy saving rate and environmental pollutant shadow cost saving rate of the system are 29.4%,49.6%and 58.2%,respectively.
基金supported in part by Science and Technology Project of State Grid Corporation of China,“Research on Harmonic Oscillation ProblemsSuppression Strategies of Flexible DC Connected to AC Grid”,(No.SGTYHT/17-JS-199).
文摘High-frequency resonance can occur when a modular multilevel converter(MMC)is inserted into an AC grid.Additional damping control is a relatively low-cost resonance suppression strategy compared to passive damping strategies.This paper analyzes the influences of a feed-forward voltage filter and feedback current filter for the inner controller for the high-frequency impedance characteristics of the MMC based on a model.Moreover,the mechanism,influencing factors,and limitations of the existing strategy including an additional lowpass filter in the voltage feed-forward stage are investigated.Secondly,a resonance suppression strategy for the inclusion of additional cascaded notch filters in the voltage feed-forward stage is proposed,and its parameter design method and applicable scenarios are analyzed.In addition,this paper analyzes the effects of the inclusion of an additional control in other stages for the inner controller of the MMC.Finally,the correctness of the theoretical analysis and the proposed strategy is verified based on the simulation of an actual project on PSCAD/EMTDC.
基金support from the State Grid Economic and Technological Research Institute,and financial support from the State Grid Corporation of China Headquarters Technology Project‘Research on Electricity Carbon Emission Accounting Methods and Key Technologies in New Type of Power System’(Project Number:52182021N006).
文摘As the proportion of electricity in final energy consumption gradually increases,CO_(2) emissions reduction actions in the power system will become the key to achieving China’s carbon-peak and carbon-neutrality goals.It is essential to analyse and quantify the driving forces of CO_(2) emissions from electricity generation in the fossil-rich area in China.This paper aims to identify the characteristics of CO_(2) emissions generated by electricity and provide a basis for formulating CO_(2)-reduction policies in power systems.First,we analyse the current state of CO_(2) emissions from electricity generation in Anhui Province that was dominated by fossil energy during the period 2010-19.Then,we apply the logarithmic mean Divisia index method to find the nature of the factors influencing the changes in CO_(2) emissions.Finally,we analyse the CO_(2)-reduction measures of each side of the source-network-load-storage of the power system in Anhui through a power-system carbon-reduction path analysis model proposed in this study and provide policy suggestions.The results showed the following.(i)CO_(2) emissions in Anhui Province continued to increase from 2010 to 2019 and the trend in the growth rate of CO_(2) emissions presented approximately a u-shaped curve.(ii)Economic activity has always been the dominant factor driving the growth of electricity CO_(2) emis-sions.The increase in the proportion of renewable energy in power generation,the improvement in thermal power-conversion efficiency and the decrease in the intensity of power consumption are the three major driving factors for the reduction in CO_(2) emissions from power generation in Anhui.(iii)The CO_(2)-reduction measures of the power system are provided in each link of the source-network-load-storage,such as developing the photovoltaic industry and building energy storage,upgrading and transforming coal-fired power stations,redu-cing the loss rate of transmission lines on the grid side and improving the efficiency of the utilization of electricity on the user side.
基金supported by National Key Research and Development Program of China(2016YFB0900100)
文摘Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.
文摘China will strive to achieve a‘dual carbon’target:‘carbon peak’by 2030 and‘carbon-neutral’by 2060.In this context,improving the efficiency of renewable energy and reducing the use of thermal power are important ways to achieve the target.Clean,efficient and large-capacity energy-storage technology is the key to improving the utilization rate of renewable energy.First,this paper proposes to use compressed-air energy-storage technology instead of the old energy-storage technology to build an economical and environmentally friendly comprehensive energy park capacity optimization configuration model.Second,this paper uses the newly proposed improved chicken swarm optimization algorithm to solve the model,which is more accurate and faster.Finally,this paper analyzes a comprehensive energy park in north-west China.Through case analysis,it can be seen that the average utilization rate of renewable energy can reach 73.87%through the model proposed in this paper,while the average power-abandonment rate is only 9.32%.
基金supported by National Key R&D Program of China(No.2017YFB0903300)National Science Foundation of China(No.51777065)Beijing Natural Science Foundation(No.3182037).
文摘With the gradual upgradation of global energy consumption and the associated development of multi-energy sources,the pace of unified energy planning and design has been accelerated and the concept of multi-energy system(MES)has been formed.The industrial structure of industrial park(IP)consists of production and marketing of multi-energy sources,which makes IP become an ideal application scenario for MES.The coupling between multi-sources raises the complexity level of IP,which requires the demand side analysis in IP as it enables customers to actively participate in energy planning and development.This paper presents the concept and operation strategies of integrated demand response(IDR),and its model classification is analyzed in detail.Optimization model and IDR with varying time period are studied in IP to determine their impacts on the system.A detailed survey of different techniques in both operation strategies and model classification is presented and the classification is based on pros and cons.Finally,key issues and outlooks are discussed.
基金supported by Science and Technology Project of State Grid Corporation of China(No.5102-201956300A-0-0-00)。
文摘In this paper,the dynamic coupling between the wind turbine rotor speed recovery(WTRSR)and inertial response of the conventional virtual synchronous generator(VSG)controlled wind farms(WFs)is analyzed.Three distinguishing features are revealed.Firstly,the inertial response characteristics of VSG controlled WFs(VSG-WFs)are impaired by the dynamic coupling.Secondly,when the influence of WTRSR is dominant,the inertial response characteristics of VSG-WFs are even worse than the condition under which WFs do not participate in the response of grid frequency.Thirdly,this phenomenon cannot be eliminated by only enlarging the inertia parameter of VSG-WFs,because the influence of WTRSR would also increase with the enhancement of inertial response.A decoupling scheme to eliminate the negative influence is then proposed in this paper.By starting the WTRSR process after inertial response period,the dynamic coupling is eliminated and the inertial response characteristics of WFs are improved.Finally,the effectiveness of the analysis and the proposed scheme are verified by simulation results.
基金This work was supported in part by the Science and Technology Project of SGCC“Research on Morphologies and Pathways of Future Power System”。
文摘The electricity distribution network is experiencing a profound transformation with the concept of the smart grid,providing possibilities for selfish consumers to interact with the distribution system operator(DSO)and to maximize their individual energy consumption utilities.However,this profitseeking behavior among consumers may violate the network constraints,such as line flows,transformer capacity and bus voltage magnitude limits.Therefore,a network-constrained energy consumption(NCEC)game among active load aggregators(ALAs)is proposed to guarantee the safety of the distribution network.The temporal and spatial constraints of an ALA are both considered,which leads the formulated model to a generalized Nash equilibrium problem(GNEP).By resorting to a well-developed variational inequality(VI)theory,we study the existence of solutions to the NCEC game problem.Subsequently,a two-level distributed algorithm is proposed to find the variational equilibrium(VE),a fair and stable solution to the formulated game model.Finally,the effectiveness of the proposed game model and the efficiency of the distributed algorithm are tested on an IEEE-33 bus system.
文摘Based on completely mastering±800 kV transmission technologies,the first±1100 kV direct current(DC)transmission demonstration project is being constructed in China.Combining theoretical analysis and a large number of experiments,the margin of switching overvoltage in converter stations,the configuration scheme and performance of lightning arresters,the shielding angles of ground lines under different geographical conditions,and the maximum air gap of lines have been determined.The switching impulse flashover characteristics of equipotential sphere and typical rod-plane air gaps are also provided.The external insulation is designed differently for light,medium,and heavy pollution areas.For the±1100 kV project,if the 8×1250 mm^(2)conductors are applied,the pole gap is 26 m and the height of the line is 25 m,all the electromagnetic parameters will meet the requirement of international electromagnetic standards.The key design points of±1100 kV converter transformers,smoothing reactors,converter valves,and wall bushings are researched and the 75 mH smoothing reactors,±1100 kV/5000 A converter valves,and±1100 kV/5523 A wall bushings are successfully made.The optimised hierarchical connection modes and coordination control measure of the±1100 kV project are studied and the results can provide sufficient technical support for the demonstration project.
基金This work was supported in part by the National Natural Science Foundation of China(U1766210,51625702)Science and Technology Program of SGCC.
文摘This paper proposes a novel AC filter system for a line commutated converter high voltage DC(LCC-HVDC)transmission system.Through the coordination of the hybrid active power filters(APF)and the existing reactive compensation devices,the proposed filter system can not only enhance the suppression performance for LCC-HVDC harmonics,but also optimize the AC yard layout with reduced reactive power subbanks,reducing the cost of HVDC projects.The novel filter system adopts a serial passive resonance topology obtained by careful comparison of different APFs.A proper control scheme is then designed integrating the control strategy of the APF and impedance characteristics of the HVDC system,which is able to realize harmonic suppression and dynamic reactive power support simultaneously.In addition,a novel self-adaption digital low-pass filter algorithm is presented,which is used in the APF harmonic detecting step,enhancing both high precision and fast dynamic response.On the basis of a real HVDC project,the advantages of proposed filter system in harmonic suppression,reactive power regulation,and sub-banks reduction are simulated and demonstrated.
文摘Increasing the application of renewable energy in the power system is an effective way to achieve the goal of‘Dual Carbon’.At the same time,the high proportion of renewable energy connected to the grid endangers the safe operation of the power system.To solve this problem,this paper proposes the application of a copula function to describe the correlation between wind power and photovoltaic power,and reduce the uncertainty of power-system operation with a high proportion of renewable energy.In order to increase the robustness of the model,this paper proposes the application of the conditional value-at-risk theory to construct the objective function of the model and effectively control the tail risk of power-system operation costs.Through case analysis,it is found that the model proposed in this paper has strong practicality and economy.