Line-commutated converter-voltage source converter(LCC-VSC)power transmission technology does not have the problem of communication failure very usually.It therefore can support the long-distance,long-capacity transmi...Line-commutated converter-voltage source converter(LCC-VSC)power transmission technology does not have the problem of communication failure very usually.It therefore can support the long-distance,long-capacity transmission of electric energy.However,factors such as topology,control strategy,and short-circuit capacities make the traditional protection principles not fully applicable to LCC-VSC hybrid transmission systems.To enhance the reliability of hybrid DC systems,a single-ended principle based on transmission coefficients is proposed and produced.First,the equivalent circuit of the LCC-VSC hybrid DC system is analyzed and the expression of the first traveling wave is deduced accordingly.Then,the concept of multi-frequency transmission coefficients is proposed by analyzing the amplitude-frequency,and the characteristics of each element.Finally,the LCC-VSCDC system model is built to verify the reliability and superiority of the principle itself.Theoretical analysis and experimental verification show that the principle has strong interference resistance.展开更多
Hybrid high-voltage direct current(HVDC)transmission has the characteristic of long transmission distance,complex corridor environment,and rapid fault evolution of direct current(DC)lines.As high fault current can eas...Hybrid high-voltage direct current(HVDC)transmission has the characteristic of long transmission distance,complex corridor environment,and rapid fault evolution of direct current(DC)lines.As high fault current can easily cause irreversible damage to power devices,rapid and reliable line protection and isolation are necessary to improve the security and reliability of hybrid HVDC transmission system.To address such requirement,this paper proposes a single-ended protection method based on transient voltage frequency band characteristics.First,the frequency characteristics of the smoothing reactor,DC filter,and DC line are analyzed,and the characteristic frequency band is defined.A fault criterion is then constructed based on the voltage characteristic frequency band energy,and faulty pole selection is performed according to the fault voltage characteristic frequency band energy ratio.The proposed protection method is verified by simulation,and the results show that it can rapidly and reliably identify internal and external faults,accurately select faulty poles without data communication synchronization,and has good fault-resist-ance and anti-interference performance.展开更多
With China’s continued development of society and economy, the importance of ecological environmental protection is growing. This protection has become an indispensable part of social development. The use of various ...With China’s continued development of society and economy, the importance of ecological environmental protection is growing. This protection has become an indispensable part of social development. The use of various green environmental protection equipment can effectively promote ecological environmental protection and reduce the adverse effects of human activities on the environment. In the field of sports lighting equipment in China, traditional lighting methods constitute an inherent danger to the environment, leading to a waste of valuable resources and environmental pollution. This study involves a multi-tile-multifunctional-function controller, which effectively solves the control problem of the control light. In the sports lighting group, the high and low-level lighting of the sports lighting group, and adjust the light from the height highly effectively to adjust each height. The low-shot mode reduces the power consumption of the system by about 33% to 60%, which significantly helps energy saving. By optimizing the performance of the lighting system, promoting the preservation of power resources, reducing the adverse effects of pollution caused by equipment utilization and energy waste, and promoting the harmonious cohabitation of human and natural environment. .展开更多
Multi-terminal hybrid high-voltage direct current(HVDC)systems have been developed quickly in recent years in power transmission area.However,for voltage-source converter(VSC)stations in hybrid HVDC systems,no direct ...Multi-terminal hybrid high-voltage direct current(HVDC)systems have been developed quickly in recent years in power transmission area.However,for voltage-source converter(VSC)stations in hybrid HVDC systems,no direct current(DC)filters are required.In addition,the DC reactor is also not installed at the line end because the DC fault can be limited by the converter itself.This means that the boundary element at the line end is absent,and the single-ended protections used in line commutated converter(LCC)based HVDC(LCC-HVDC)systems or VSC-HVDC systems cannot distinguish the fault line in multi-terminal hybrid HVDC systems.This paper proposes a novel singleended DC protection strategy suitable for the multi-terminal hybrid HVDC system,which mainly applies the transient information and active injection concept to detect and distinguish the fault line.Compared with the single-ended protections used in LCC-HVDC and VSC-HVDC systems,the proposed protection strategy is not dependent on the line boundary element and is thus suitable for the multiterminal hybrid HVDC system.The corresponding simulation cases based on power systems computer aided design(PSCAD)/electromagnetic transients including DC(EMTDC)are carried out to verify the superiority of the proposed protection.展开更多
Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies...Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies on the design,analysis,and measurement of differential antennas have been published.This paper presents an overview of the fundamentals and applications of differential antennas.First,it compares differential to bal-anced and single-ended to unbalanced antennas and explains why the new terms(differential and single-ended antennas)should be adopted instead of the old terms(balanced and unbalanced antennas).Second,it addresses the quantitative relationship between a differential antenna and its single-ended counterpart,which is important and useful because the properties of either the differential or single-ended antenna can be determined from the other with a known solution.Third,it describes how differential antennas can be measured,with a special emphasis on the balun method.Fourth,it classifies dif-ferential antennas into wire,slot,microstrip,printed,and dielectric resonator antennas to better present their suitability and functionality.Fifth,it pro-vides application examples of differential antennas from simple discrete wire to sophisticated microstrip designs.Finally,it is argued that the old paradigms of lower gains and bulkier sizes of differential antennas as compared to single-ended antennas do not always hold true;for instance,differen-tial microstrip patch antennas can possess comparable or even smaller sizes and higher gain values than single-ended microstrip patch antennas.展开更多
This paper presents a single-ended input differential output low-noise amplifier intended for GPS applications. We propose a method to reduce the gain/amplitude and phase imbalance of a differential output exploiting ...This paper presents a single-ended input differential output low-noise amplifier intended for GPS applications. We propose a method to reduce the gain/amplitude and phase imbalance of a differential output exploiting the inductive coupling of a transformer or center-tapped differential inductor.A detailed analysis of the theory of imbalance reduction,as well as a discussion on the principle of choosing the dimensions of a transformer,are given.An LNA has been implemented using TSMC 0.18μm technology with ESD-protected.Measurement on board shows a voltage gain of 24.6 dB at 1.575 GHz and a noise figure of 3.2 dB.The gain imbalance is below 0.2 dB and phase imbalance is less than 2 degrees.The LNA consumes 5.2 mA from a 1.8 V supply.展开更多
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘Line-commutated converter-voltage source converter(LCC-VSC)power transmission technology does not have the problem of communication failure very usually.It therefore can support the long-distance,long-capacity transmission of electric energy.However,factors such as topology,control strategy,and short-circuit capacities make the traditional protection principles not fully applicable to LCC-VSC hybrid transmission systems.To enhance the reliability of hybrid DC systems,a single-ended principle based on transmission coefficients is proposed and produced.First,the equivalent circuit of the LCC-VSC hybrid DC system is analyzed and the expression of the first traveling wave is deduced accordingly.Then,the concept of multi-frequency transmission coefficients is proposed by analyzing the amplitude-frequency,and the characteristics of each element.Finally,the LCC-VSCDC system model is built to verify the reliability and superiority of the principle itself.Theoretical analysis and experimental verification show that the principle has strong interference resistance.
基金supported by the National Natural Science Foundation of China(52037003)the Major Special and Technology Project of Yunnan Province(202002AF080001).
文摘Hybrid high-voltage direct current(HVDC)transmission has the characteristic of long transmission distance,complex corridor environment,and rapid fault evolution of direct current(DC)lines.As high fault current can easily cause irreversible damage to power devices,rapid and reliable line protection and isolation are necessary to improve the security and reliability of hybrid HVDC transmission system.To address such requirement,this paper proposes a single-ended protection method based on transient voltage frequency band characteristics.First,the frequency characteristics of the smoothing reactor,DC filter,and DC line are analyzed,and the characteristic frequency band is defined.A fault criterion is then constructed based on the voltage characteristic frequency band energy,and faulty pole selection is performed according to the fault voltage characteristic frequency band energy ratio.The proposed protection method is verified by simulation,and the results show that it can rapidly and reliably identify internal and external faults,accurately select faulty poles without data communication synchronization,and has good fault-resist-ance and anti-interference performance.
文摘With China’s continued development of society and economy, the importance of ecological environmental protection is growing. This protection has become an indispensable part of social development. The use of various green environmental protection equipment can effectively promote ecological environmental protection and reduce the adverse effects of human activities on the environment. In the field of sports lighting equipment in China, traditional lighting methods constitute an inherent danger to the environment, leading to a waste of valuable resources and environmental pollution. This study involves a multi-tile-multifunctional-function controller, which effectively solves the control problem of the control light. In the sports lighting group, the high and low-level lighting of the sports lighting group, and adjust the light from the height highly effectively to adjust each height. The low-shot mode reduces the power consumption of the system by about 33% to 60%, which significantly helps energy saving. By optimizing the performance of the lighting system, promoting the preservation of power resources, reducing the adverse effects of pollution caused by equipment utilization and energy waste, and promoting the harmonious cohabitation of human and natural environment. .
文摘Multi-terminal hybrid high-voltage direct current(HVDC)systems have been developed quickly in recent years in power transmission area.However,for voltage-source converter(VSC)stations in hybrid HVDC systems,no direct current(DC)filters are required.In addition,the DC reactor is also not installed at the line end because the DC fault can be limited by the converter itself.This means that the boundary element at the line end is absent,and the single-ended protections used in line commutated converter(LCC)based HVDC(LCC-HVDC)systems or VSC-HVDC systems cannot distinguish the fault line in multi-terminal hybrid HVDC systems.This paper proposes a novel singleended DC protection strategy suitable for the multi-terminal hybrid HVDC system,which mainly applies the transient information and active injection concept to detect and distinguish the fault line.Compared with the single-ended protections used in LCC-HVDC and VSC-HVDC systems,the proposed protection strategy is not dependent on the line boundary element and is thus suitable for the multiterminal hybrid HVDC system.The corresponding simulation cases based on power systems computer aided design(PSCAD)/electromagnetic transients including DC(EMTDC)are carried out to verify the superiority of the proposed protection.
文摘Driven by the great demand for highly integrated wireless system-on-chip and system-in-package devices,there has recently been increas-ing interest in the research and development of differential antennas.Many studies on the design,analysis,and measurement of differential antennas have been published.This paper presents an overview of the fundamentals and applications of differential antennas.First,it compares differential to bal-anced and single-ended to unbalanced antennas and explains why the new terms(differential and single-ended antennas)should be adopted instead of the old terms(balanced and unbalanced antennas).Second,it addresses the quantitative relationship between a differential antenna and its single-ended counterpart,which is important and useful because the properties of either the differential or single-ended antenna can be determined from the other with a known solution.Third,it describes how differential antennas can be measured,with a special emphasis on the balun method.Fourth,it classifies dif-ferential antennas into wire,slot,microstrip,printed,and dielectric resonator antennas to better present their suitability and functionality.Fifth,it pro-vides application examples of differential antennas from simple discrete wire to sophisticated microstrip designs.Finally,it is argued that the old paradigms of lower gains and bulkier sizes of differential antennas as compared to single-ended antennas do not always hold true;for instance,differen-tial microstrip patch antennas can possess comparable or even smaller sizes and higher gain values than single-ended microstrip patch antennas.
基金Project supported by the Core Electronic Devices,High-End General Chips and Basic Software Products Major Projects.China(No. 2009ZX01031-002-008)
文摘This paper presents a single-ended input differential output low-noise amplifier intended for GPS applications. We propose a method to reduce the gain/amplitude and phase imbalance of a differential output exploiting the inductive coupling of a transformer or center-tapped differential inductor.A detailed analysis of the theory of imbalance reduction,as well as a discussion on the principle of choosing the dimensions of a transformer,are given.An LNA has been implemented using TSMC 0.18μm technology with ESD-protected.Measurement on board shows a voltage gain of 24.6 dB at 1.575 GHz and a noise figure of 3.2 dB.The gain imbalance is below 0.2 dB and phase imbalance is less than 2 degrees.The LNA consumes 5.2 mA from a 1.8 V supply.
