本文收集了北京地区一个典型220 k V变电站厂界处220 k V地下电缆的工频磁场自动监测系统3年的数据,通过工频磁感应强度与电流强度相关性分析及监测数据长期、短期、瞬时变化规律分析,发现工频磁感应强度与电流强度具有强相关性;且工频...本文收集了北京地区一个典型220 k V变电站厂界处220 k V地下电缆的工频磁场自动监测系统3年的数据,通过工频磁感应强度与电流强度相关性分析及监测数据长期、短期、瞬时变化规律分析,发现工频磁感应强度与电流强度具有强相关性;且工频磁感应强度冬季高于夏季,工作日高于周末,一天中峰值出现在9~10点与18~22点;针对变化规律得出的结论可为相关的实际监测工作提供借鉴。展开更多
给出注入功率空间中满足输电线路热稳定性约束的电力系统安全域的快速计算方法。该热稳定安全域综合考虑了输电线路电流的有功和无功分量。通过有功静态安全域的数学表达式来描述输电线路有功电流与节点有功注入功率之间的数学关系;对...给出注入功率空间中满足输电线路热稳定性约束的电力系统安全域的快速计算方法。该热稳定安全域综合考虑了输电线路电流的有功和无功分量。通过有功静态安全域的数学表达式来描述输电线路有功电流与节点有功注入功率之间的数学关系;对于输电线路的无功电流与节点无功注入功率之间的数学关系,则由"修正的关联矩阵"和基本回路矩阵描述。计算所需的全部状态变量均采用广域测量系统(wide area measurement system,WAMS)实测获得。以新英格兰39节点系统为例对该方法所确定的热稳定安全域进行校验,结果表明:由该方法所确定的热稳定安全域边界相比基于直流潮流模型的结果更精确;其计算量较采用交流潮流模型的逐点法更低。展开更多
为解决交流系统大扰动下电流源型直流输电(line commutate converter based HVDC,LCC-HVDC)系统电磁暂态精度响应实时求取困难的问题,该文基于动态相量法仿真框架,详细讨论了大扰动下LCC-HVDC直流输电系统的建模方案,并针对工程现场的...为解决交流系统大扰动下电流源型直流输电(line commutate converter based HVDC,LCC-HVDC)系统电磁暂态精度响应实时求取困难的问题,该文基于动态相量法仿真框架,详细讨论了大扰动下LCC-HVDC直流输电系统的建模方案,并针对工程现场的计算精度与计算复杂度要求和逆变侧容易发生的换相失败现象,重构了易于拓展的仿真模型计算框架。多故障场景的仿真对比实验表明,与传统的动态相量仿真方案相比,所提出的框架能够准确反映直流系统在逆变侧交流系统受扰下的暂态响应特征,同时提高了计算速度,实现了LCC-HVDC系统暂态响应的高精度、实时化计算。展开更多
Organic light emitting diodes (OLEDs) incorporating an n-doping transport layer comprised of 8-hydroxy-quin- olinato lithium (Liq) doped into 4' 7- diphyenyl-1,10-phenanthroline (BPhen) as ETL and a p-doping tr...Organic light emitting diodes (OLEDs) incorporating an n-doping transport layer comprised of 8-hydroxy-quin- olinato lithium (Liq) doped into 4' 7- diphyenyl-1,10-phenanthroline (BPhen) as ETL and a p-doping transport layer that includes tetrafluro-tetracyano-quinodimethane (F4- TCNQ) doped into 4,4′, 4″-tris (3-methylphenylphenylamono) triphe- nylamine (m-MTDATA) are demonstrated. In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency Of organic light-emitting diodes are improved significantly after introducing an n-doping (BPhen:33wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4- TCNQ as a hole transport layer (HTL). Compared with the control device (without doping) , the current efficiency and power efficiency of the most efficient device (device C) are enhanced by approximately 51% and 89% ,respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to efficient charge balance in the emission zone.展开更多
In this paper the growing process of China power grid from formation of local power grids to nationwide interconnection is reviewed. The scale and structure of power grid construction in the near future, especially th...In this paper the growing process of China power grid from formation of local power grids to nationwide interconnection is reviewed. The scale and structure of power grid construction in the near future, especially the planning on sending power from west to east, North-South supplementation and nationwide interconnection are introduced. In addition, the technologies to be extended in future grid development are briefed, such as HVDC, FACTS and compact transmission line, etc.展开更多
This paper describes the planned power transmission from west to east through three channels. It presents the main characteristics of these three channels and the problems need to be solved.
This paper introduces the current situation of China power industry and interconnection, the necessity to develop interconnection, the principle of nationwide interconnection and the key technologies to be studiedincl...This paper introduces the current situation of China power industry and interconnection, the necessity to develop interconnection, the principle of nationwide interconnection and the key technologies to be studiedinclude HVDC and FACTS. The paper also discusses thefeasibility of 750 kV to be used in the northwest.regionand to speed up research and development of nighervoltage level in other regions of China, as well as scl-ence and technical innovation for transmission and dis-tribution projects.展开更多
The modern travelling wave based fault location principles for transmission lines are analyzed.In order to apply the travelling wave principles to HVDC transmission lines,the special technical problems are studied.Bas...The modern travelling wave based fault location principles for transmission lines are analyzed.In order to apply the travelling wave principles to HVDC transmission lines,the special technical problems are studied.Based on this,a fault locating system for HVDC transmission lines is developed.The system can support modern double ended and single ended travelling wave princi- ples simultaneously,and it is composed of three different parts:travelling wave data acquisition and processing system,communication network and PC based master station.In the system,the fault generated transients are induced from the ground leads of the over-voltage suppression capacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 kV Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China.Some field operation experiences are summarized,showing that the system has very high reliability and accuracy,and the maximum location error is about 3 km(not more than 0.3%of the total line length). Obviously,the application of the system is successful,and the fault location problem has finally been solved completely since the line operation.展开更多
The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous...The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.展开更多
On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UP...On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems (FACTS) controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.展开更多
Thyristor control phase shifter (TCPS) is one of the new facilities implemented in power network, leading to the development of economically efficient and technically reliable system. This paper introduces the functio...Thyristor control phase shifter (TCPS) is one of the new facilities implemented in power network, leading to the development of economically efficient and technically reliable system. This paper introduces the function of TCPS in power system, describes its working principle and structure, and suggests some simple models used in its study and briefly presents the comparison between different types of TCPSs and their applications.展开更多
With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net w...With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.展开更多
Motivated by the recent advances of transition-metal-nitrogen-carbon (TM-N-C) materials in catalysis, we investigate the electronic structure and transport properties of FeN3-embedded armchair and zigzag graphene nano...Motivated by the recent advances of transition-metal-nitrogen-carbon (TM-N-C) materials in catalysis, we investigate the electronic structure and transport properties of FeN3-embedded armchair and zigzag graphene nanoribbons (FeN3@AGNRs, FeN3@ZGNRs) with different widths. The first-principles results indicate that the FeN3 induces significant changes on the band structures of both ZGNRs and AGNRs, making the resultant systems quite different from the pristine ones and own room-temperature stable ferromagnetic (FM) ground states. While only FeN3@AGNRs possess a significant spin-dependent negative differential resistance (NDR) and a striking current polarization (nearly 100%) behaviors, due to that FeN3 introduces two isolated spin-down states, which contribute current with different performances when they couple with different frontier orbits. It is suggested that by embedding FeN3 complexes, AGNRs can be used to build spin devices in spintronics.展开更多
Most of the hydropower projects in Southwest China and the adjacent foreign regions will be put into operation between 2015 and 2020, which will bring some difficulties for reasonable accommodation and delivery of ele...Most of the hydropower projects in Southwest China and the adjacent foreign regions will be put into operation between 2015 and 2020, which will bring some difficulties for reasonable accommodation and delivery of electric energy. In this paper the author studies the development scale, development schedule, accommodation and transmission schemes of the cascade hydropower stations along the Lancang River basin, one of the five large basins in China, based on the load characteristics of grids at both the sending end and the receiving end, the strategy of complementary utilization of thermal power and hydropower, the advanced transmission technologies, and the optimal economic performance. The study results show that, the cascade hydropower stations on the upper reaches of the Lancang River in Yunnan should mainly serve Guangdong Province, with proper planning of partly serving Yunnan Province during dry seasons. The transmission schemes should adopt UHVDC, UHVAC, and single-tower double-circuited HVDC transmission scheme according to the transmission capacity and distance.展开更多
This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze...This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze effects of the shared loop ground DC transmission system electrode on the operation of HVDC system size under different operation modes, and compare with the independent ground electrode, ground electrode impact on environment under different operation mode, and the paper finally puts forward some solving measures for the influence of the shared ground electrode on the environment and public ground electrode effects on DC system operation problems.展开更多
The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microele...The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.展开更多
文摘本文收集了北京地区一个典型220 k V变电站厂界处220 k V地下电缆的工频磁场自动监测系统3年的数据,通过工频磁感应强度与电流强度相关性分析及监测数据长期、短期、瞬时变化规律分析,发现工频磁感应强度与电流强度具有强相关性;且工频磁感应强度冬季高于夏季,工作日高于周末,一天中峰值出现在9~10点与18~22点;针对变化规律得出的结论可为相关的实际监测工作提供借鉴。
文摘给出注入功率空间中满足输电线路热稳定性约束的电力系统安全域的快速计算方法。该热稳定安全域综合考虑了输电线路电流的有功和无功分量。通过有功静态安全域的数学表达式来描述输电线路有功电流与节点有功注入功率之间的数学关系;对于输电线路的无功电流与节点无功注入功率之间的数学关系,则由"修正的关联矩阵"和基本回路矩阵描述。计算所需的全部状态变量均采用广域测量系统(wide area measurement system,WAMS)实测获得。以新英格兰39节点系统为例对该方法所确定的热稳定安全域进行校验,结果表明:由该方法所确定的热稳定安全域边界相比基于直流潮流模型的结果更精确;其计算量较采用交流潮流模型的逐点法更低。
文摘为解决交流系统大扰动下电流源型直流输电(line commutate converter based HVDC,LCC-HVDC)系统电磁暂态精度响应实时求取困难的问题,该文基于动态相量法仿真框架,详细讨论了大扰动下LCC-HVDC直流输电系统的建模方案,并针对工程现场的计算精度与计算复杂度要求和逆变侧容易发生的换相失败现象,重构了易于拓展的仿真模型计算框架。多故障场景的仿真对比实验表明,与传统的动态相量仿真方案相比,所提出的框架能够准确反映直流系统在逆变侧交流系统受扰下的暂态响应特征,同时提高了计算速度,实现了LCC-HVDC系统暂态响应的高精度、实时化计算。
文摘Organic light emitting diodes (OLEDs) incorporating an n-doping transport layer comprised of 8-hydroxy-quin- olinato lithium (Liq) doped into 4' 7- diphyenyl-1,10-phenanthroline (BPhen) as ETL and a p-doping transport layer that includes tetrafluro-tetracyano-quinodimethane (F4- TCNQ) doped into 4,4′, 4″-tris (3-methylphenylphenylamono) triphe- nylamine (m-MTDATA) are demonstrated. In order to examine the improvement in the conductivity of transport layers, hole-only and electron-only devices are fabricated. The current and power efficiency Of organic light-emitting diodes are improved significantly after introducing an n-doping (BPhen:33wt% Liq) layer as an electron transport layer (ETL) and a p-doping layer composed of m-MTDATA and F4- TCNQ as a hole transport layer (HTL). Compared with the control device (without doping) , the current efficiency and power efficiency of the most efficient device (device C) are enhanced by approximately 51% and 89% ,respectively, while driving voltage is reduced by 29%. This improvement is attributed to the improved conductivity of the transport layers that leads to efficient charge balance in the emission zone.
文摘In this paper the growing process of China power grid from formation of local power grids to nationwide interconnection is reviewed. The scale and structure of power grid construction in the near future, especially the planning on sending power from west to east, North-South supplementation and nationwide interconnection are introduced. In addition, the technologies to be extended in future grid development are briefed, such as HVDC, FACTS and compact transmission line, etc.
文摘This paper describes the planned power transmission from west to east through three channels. It presents the main characteristics of these three channels and the problems need to be solved.
文摘This paper introduces the current situation of China power industry and interconnection, the necessity to develop interconnection, the principle of nationwide interconnection and the key technologies to be studiedinclude HVDC and FACTS. The paper also discusses thefeasibility of 750 kV to be used in the northwest.regionand to speed up research and development of nighervoltage level in other regions of China, as well as scl-ence and technical innovation for transmission and dis-tribution projects.
文摘The modern travelling wave based fault location principles for transmission lines are analyzed.In order to apply the travelling wave principles to HVDC transmission lines,the special technical problems are studied.Based on this,a fault locating system for HVDC transmission lines is developed.The system can support modern double ended and single ended travelling wave princi- ples simultaneously,and it is composed of three different parts:travelling wave data acquisition and processing system,communication network and PC based master station.In the system,the fault generated transients are induced from the ground leads of the over-voltage suppression capacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 kV Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China.Some field operation experiences are summarized,showing that the system has very high reliability and accuracy,and the maximum location error is about 3 km(not more than 0.3%of the total line length). Obviously,the application of the system is successful,and the fault location problem has finally been solved completely since the line operation.
文摘The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.
文摘On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems (FACTS) controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.
文摘Thyristor control phase shifter (TCPS) is one of the new facilities implemented in power network, leading to the development of economically efficient and technically reliable system. This paper introduces the function of TCPS in power system, describes its working principle and structure, and suggests some simple models used in its study and briefly presents the comparison between different types of TCPSs and their applications.
基金Sponsored by the Ph.D. Programs Foundation of Ministry of Education of China(Grant No.20070286047)the Scientific Innovation Foundation forYoungster of CSEE
文摘With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.
基金supported by the National Natural Science Foundation of China(No.21643011)the Fundamental Research Foundations for the Central Universities(No.ZYGX2016J067)
文摘Motivated by the recent advances of transition-metal-nitrogen-carbon (TM-N-C) materials in catalysis, we investigate the electronic structure and transport properties of FeN3-embedded armchair and zigzag graphene nanoribbons (FeN3@AGNRs, FeN3@ZGNRs) with different widths. The first-principles results indicate that the FeN3 induces significant changes on the band structures of both ZGNRs and AGNRs, making the resultant systems quite different from the pristine ones and own room-temperature stable ferromagnetic (FM) ground states. While only FeN3@AGNRs possess a significant spin-dependent negative differential resistance (NDR) and a striking current polarization (nearly 100%) behaviors, due to that FeN3 introduces two isolated spin-down states, which contribute current with different performances when they couple with different frontier orbits. It is suggested that by embedding FeN3 complexes, AGNRs can be used to build spin devices in spintronics.
文摘Most of the hydropower projects in Southwest China and the adjacent foreign regions will be put into operation between 2015 and 2020, which will bring some difficulties for reasonable accommodation and delivery of electric energy. In this paper the author studies the development scale, development schedule, accommodation and transmission schemes of the cascade hydropower stations along the Lancang River basin, one of the five large basins in China, based on the load characteristics of grids at both the sending end and the receiving end, the strategy of complementary utilization of thermal power and hydropower, the advanced transmission technologies, and the optimal economic performance. The study results show that, the cascade hydropower stations on the upper reaches of the Lancang River in Yunnan should mainly serve Guangdong Province, with proper planning of partly serving Yunnan Province during dry seasons. The transmission schemes should adopt UHVDC, UHVAC, and single-tower double-circuited HVDC transmission scheme according to the transmission capacity and distance.
文摘This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze effects of the shared loop ground DC transmission system electrode on the operation of HVDC system size under different operation modes, and compare with the independent ground electrode, ground electrode impact on environment under different operation mode, and the paper finally puts forward some solving measures for the influence of the shared ground electrode on the environment and public ground electrode effects on DC system operation problems.
文摘The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.