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
We propose a continuously tunable method of sub-half-wavelength localization via the coherent control of the spontaneous emission of a four-level Y-type atomic system, which is coupled to three strong coupling fields ...We propose a continuously tunable method of sub-half-wavelength localization via the coherent control of the spontaneous emission of a four-level Y-type atomic system, which is coupled to three strong coupling fields including a standing-wave field together with a weak probe field. It is shown that the sub-half-wavelength atomic localization is realized for both resonance and off-resonance cases. Furthermore, by varying the probe detuning in succession, the positions of the two localization peaks are tuned continuously within a wide range of probe field frequencies, which provides convenience for the realization of sub-half-wavelength atomic localization experimentally.展开更多
This paper presents the main results on the use of conventional protection hardware to protect a Half Wavelength Transmission Line, or shortly AC-Link, for possible occurrence of three-phase and single-phase fault dur...This paper presents the main results on the use of conventional protection hardware to protect a Half Wavelength Transmission Line, or shortly AC-Link, for possible occurrence of three-phase and single-phase fault during energization maneuver. Lines of these dimensions do not exist today, but in countries of continental size they could be an interesting alternative to HVDC transmission, since the AC-Link has less dependence on Power Electronics technology. The studies on performance and relay settings were implemented using the RTDS real-time simulator. It is important to note that the AC-Link protection for the energization maneuver can be performed with existing hardware on conventional relays.展开更多
面向“碳达峰、碳中和”目标,发展半波长输电技术可为构建以新能源为主体的新型电力系统提供能源保障。半波长技术因其输电距离远、经济性好等独特优势,在“西电东送”能源战略中有较好的应用前景。针对输电线路自然长度不足工频半波长...面向“碳达峰、碳中和”目标,发展半波长输电技术可为构建以新能源为主体的新型电力系统提供能源保障。半波长技术因其输电距离远、经济性好等独特优势,在“西电东送”能源战略中有较好的应用前景。针对输电线路自然长度不足工频半波长现象以及固定调谐的不足,文章提出一种变阻抗型可控调谐方法,基于可控串补(thyristor controlled series compensator,TCSC)阻抗控制策略构造可微调的调谐电感,基于电容三级投切策略构造可分级的调谐电容。对可控调谐可行性、故障过电压特征以及串补过压抑制进行仿真分析。结果表明,可控调谐能够消除电气长度误差,使线路保持半波长特性,线路补偿效果与可控调谐长度相关。展开更多
The voltage characteristics of a half-wavelength transmission(HWLT)system lack mechanism explanation and systematic summary.In this paper,both the steady-state and fault voltage characteristics are analyzed and explai...The voltage characteristics of a half-wavelength transmission(HWLT)system lack mechanism explanation and systematic summary.In this paper,both the steady-state and fault voltage characteristics are analyzed and explained based on the wave process method.An analysis model is established for HWLT lines and wave propagation equations with different terminal conditions are deduced.For steady-state conditions,voltage profiles along HWLT lines are depicted and partial overvoltage occurs when there is an overload or low-power factor.In addition,fault voltage characteristics are analyzed under load-rejection or short-circuit conditions.The series resonance overvoltage will happen when short-circuit faults occur at certain positions and its peak value is influenced by grid strength or fault type.Furthermore,a refined transmission line model is presented to consider non-ideal factors and simulation results demonstrate that geomorphic conditions and electromagnetic environments influence line voltage characteristics to a certain extent.展开更多
With the proposed concept of global energy interconnection, half-wavelength alternating current transmission(HWACT) technology becomes of more interest.HWACT lines can be adopted to establish a pointto-grid system, in...With the proposed concept of global energy interconnection, half-wavelength alternating current transmission(HWACT) technology becomes of more interest.HWACT lines can be adopted to establish a pointto-grid system, in which the penetrating power(PP) is produced between receiving terminals, having a significant effect on the power flow distribution.In order to investigate this phenomenon, the PP characteristics of the HWACT system are researched in this paper.First, the mathematical relationship between the transmission power and terminal bus voltages of a single HWACT line is derived using the equations of a distributed parameter model.The research indicates that the relationship between power and terminal voltages shows ‘‘reverse characteristics"opposite to those of regular short transmission lines.Then, the concept and definition of PP in a point-to-grid system with two receiving terminals are proposed, and the corresponding relationship between PP and the terminal bus voltages is derived.Simulations are carried out to validate the theory under different conditions, so that the accuracy and adaptiveness of the theoretical analysis can be proved.In addition, the results demonstrate that selecting the location for a HWACT system has demanding requirements in order to control the value of PP.展开更多
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.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11104163 and 11047011)the Science Foundation of Hubei Province,China (Grant No. 2010CDZ055)
文摘We propose a continuously tunable method of sub-half-wavelength localization via the coherent control of the spontaneous emission of a four-level Y-type atomic system, which is coupled to three strong coupling fields including a standing-wave field together with a weak probe field. It is shown that the sub-half-wavelength atomic localization is realized for both resonance and off-resonance cases. Furthermore, by varying the probe detuning in succession, the positions of the two localization peaks are tuned continuously within a wide range of probe field frequencies, which provides convenience for the realization of sub-half-wavelength atomic localization experimentally.
文摘This paper presents the main results on the use of conventional protection hardware to protect a Half Wavelength Transmission Line, or shortly AC-Link, for possible occurrence of three-phase and single-phase fault during energization maneuver. Lines of these dimensions do not exist today, but in countries of continental size they could be an interesting alternative to HVDC transmission, since the AC-Link has less dependence on Power Electronics technology. The studies on performance and relay settings were implemented using the RTDS real-time simulator. It is important to note that the AC-Link protection for the energization maneuver can be performed with existing hardware on conventional relays.
文摘面向“碳达峰、碳中和”目标,发展半波长输电技术可为构建以新能源为主体的新型电力系统提供能源保障。半波长技术因其输电距离远、经济性好等独特优势,在“西电东送”能源战略中有较好的应用前景。针对输电线路自然长度不足工频半波长现象以及固定调谐的不足,文章提出一种变阻抗型可控调谐方法,基于可控串补(thyristor controlled series compensator,TCSC)阻抗控制策略构造可微调的调谐电感,基于电容三级投切策略构造可分级的调谐电容。对可控调谐可行性、故障过电压特征以及串补过压抑制进行仿真分析。结果表明,可控调谐能够消除电气长度误差,使线路保持半波长特性,线路补偿效果与可控调谐长度相关。
基金supported by the State Grid Corporation of China(No.SGSDDK00KJJS1600149).
文摘The voltage characteristics of a half-wavelength transmission(HWLT)system lack mechanism explanation and systematic summary.In this paper,both the steady-state and fault voltage characteristics are analyzed and explained based on the wave process method.An analysis model is established for HWLT lines and wave propagation equations with different terminal conditions are deduced.For steady-state conditions,voltage profiles along HWLT lines are depicted and partial overvoltage occurs when there is an overload or low-power factor.In addition,fault voltage characteristics are analyzed under load-rejection or short-circuit conditions.The series resonance overvoltage will happen when short-circuit faults occur at certain positions and its peak value is influenced by grid strength or fault type.Furthermore,a refined transmission line model is presented to consider non-ideal factors and simulation results demonstrate that geomorphic conditions and electromagnetic environments influence line voltage characteristics to a certain extent.
基金supported by National Natural Science Foundation of China (No.51307109)State Grid Corporation of China (No.XT71-16-001)
文摘With the proposed concept of global energy interconnection, half-wavelength alternating current transmission(HWACT) technology becomes of more interest.HWACT lines can be adopted to establish a pointto-grid system, in which the penetrating power(PP) is produced between receiving terminals, having a significant effect on the power flow distribution.In order to investigate this phenomenon, the PP characteristics of the HWACT system are researched in this paper.First, the mathematical relationship between the transmission power and terminal bus voltages of a single HWACT line is derived using the equations of a distributed parameter model.The research indicates that the relationship between power and terminal voltages shows ‘‘reverse characteristics"opposite to those of regular short transmission lines.Then, the concept and definition of PP in a point-to-grid system with two receiving terminals are proposed, and the corresponding relationship between PP and the terminal bus voltages is derived.Simulations are carried out to validate the theory under different conditions, so that the accuracy and adaptiveness of the theoretical analysis can be proved.In addition, the results demonstrate that selecting the location for a HWACT system has demanding requirements in order to control the value of PP.
