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
The single-ended fault location based on travelling waves(TWs)is commonly used for long-distance high-voltage AC transmission lines.However,it relies on high sampling frequency and accurate capturing of the TW head ar...The single-ended fault location based on travelling waves(TWs)is commonly used for long-distance high-voltage AC transmission lines.However,it relies on high sampling frequency and accurate capturing of the TW head arrival time.Accordingly,this study establishes a transient analytical method for fault location based on the similarity between the transient recorded waveform and output waveforms of analytical calculation model.In the proposed method,fuzzy constraints of fault features are constructed through time-distance and waveform-scaling correlations while considering the deviation factors of the frequency-dependent wave velocity and TW head arrival time.Accordingly,the high-dimensional space of the fitting problem is transformed into a one-dimensional implicit function fitting problem containing only the fault distance,thereby enabling the waveform comparison problem to be quickly solved based on fault TW features.Under the fuzzy constraints proposed in this study,the proposed method requires only a relatively vague identification of the TW head,and the requirements for sampling frequency are also more lenient.In addition,a sliding window scheme is adopted for enhancing the TW morphology characteristics.Finally,the proposed method is tested using PSCAD,and the simulations validate the fault location accuracy of the proposed method.展开更多
In a DC grid with dedicated metallic return(DMR),the coupling effects among the positive pole,negative pole,and DMR conductors must be considered,which makes fault identification particularly difficult.In addition,the...In a DC grid with dedicated metallic return(DMR),the coupling effects among the positive pole,negative pole,and DMR conductors must be considered,which makes fault identification particularly difficult.In addition,the identification of high-impedance faults remains a major challenge for DC grid protection.To address these issues,this study proposes an adaptive single-end protection method for DC grid based on the transient mean value of the current limiting reactor(CLR)modal voltage.First,a fault analysis model of the DC grid with DMR is established using the Clarke transformation.The characteristics of CLR modal voltage are then clarified.A fault pole-selection method based on a novel modulus phase plane is next proposed.A threshold scaling factor based on the differential of DC bus voltage is then constructed to enhance the sensitivity and rapidity of the protection,which can adaptively modify the threshold according to the fault severity.Finally,a simulation model of a four-terminal DC grid with DMR is developed in PSCAD/EMTDC.The speed and reliability of the proposed protection method are verified by simulations and experiments.展开更多
This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adop...This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adopted in grounding protection system.Compared with the usual current acquisition,the measurement data is accurate,there is no redundant loop,and the economic benefit is high.In this study,the single-end and double-end grounding fault protections of superconducting magnet coil are analyzed,and the fault voltage and current under different fault conditions are calculated.The simulation model of CSMC magnet grounding fault is established,and the simulation results of the model are basically consistent with the theoretical calculation.Finally,a small capacity experiment platform is used to verify the function of the grounding protection system.The experimental results show that by comparing the neutral fault sampling voltage with the theoretical grounding protection threshold,the grounding protection system can effectively detect different types of grounding faults and transmit signals to the control system to protect the coils of superconducting magnets.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
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
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 direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection sch...Multi-terminal direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection schemes adopted by the MMC-MTDC DC project are not sufficiently sensitive to high-impedance faults.To solve this problem,this paper first analyzes the characteristics of the first traveling wave of the fault on the DC transmission line and derives the expressions of the first traveling wave of the fault when the DC transmission line has an internal and external fault.Subsequently,the line frequency characteristic is used to simplify the traveling wave expression and construct the fault coefficient.Finally,the principle of single-ended traveling wave protection based on the fault coefficient is proposed.Simulation results show that the protection principle has a strong ability to withstand transition resistance and noise interference.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
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
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 Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011035).
文摘The single-ended fault location based on travelling waves(TWs)is commonly used for long-distance high-voltage AC transmission lines.However,it relies on high sampling frequency and accurate capturing of the TW head arrival time.Accordingly,this study establishes a transient analytical method for fault location based on the similarity between the transient recorded waveform and output waveforms of analytical calculation model.In the proposed method,fuzzy constraints of fault features are constructed through time-distance and waveform-scaling correlations while considering the deviation factors of the frequency-dependent wave velocity and TW head arrival time.Accordingly,the high-dimensional space of the fitting problem is transformed into a one-dimensional implicit function fitting problem containing only the fault distance,thereby enabling the waveform comparison problem to be quickly solved based on fault TW features.Under the fuzzy constraints proposed in this study,the proposed method requires only a relatively vague identification of the TW head,and the requirements for sampling frequency are also more lenient.In addition,a sliding window scheme is adopted for enhancing the TW morphology characteristics.Finally,the proposed method is tested using PSCAD,and the simulations validate the fault location accuracy of the proposed method.
基金supported in part by the Joint Funds of the National Natural Science Foundation of China(No.U22B6006)the National Natural Science Foundation of China(No.52207126)Natural Science Foundation of Sichuan Province(No.2023NSFSC0296).
文摘In a DC grid with dedicated metallic return(DMR),the coupling effects among the positive pole,negative pole,and DMR conductors must be considered,which makes fault identification particularly difficult.In addition,the identification of high-impedance faults remains a major challenge for DC grid protection.To address these issues,this study proposes an adaptive single-end protection method for DC grid based on the transient mean value of the current limiting reactor(CLR)modal voltage.First,a fault analysis model of the DC grid with DMR is established using the Clarke transformation.The characteristics of CLR modal voltage are then clarified.A fault pole-selection method based on a novel modulus phase plane is next proposed.A threshold scaling factor based on the differential of DC bus voltage is then constructed to enhance the sensitivity and rapidity of the protection,which can adaptively modify the threshold according to the fault severity.Finally,a simulation model of a four-terminal DC grid with DMR is developed in PSCAD/EMTDC.The speed and reliability of the proposed protection method are verified by simulations and experiments.
文摘This work presents a grounding protection system of the central solenoid model coil(CSMC)of the Comprehensive Research Facility for Fusion Technology(CRAFT).The scheme of neutral point voltage detections has been adopted in grounding protection system.Compared with the usual current acquisition,the measurement data is accurate,there is no redundant loop,and the economic benefit is high.In this study,the single-end and double-end grounding fault protections of superconducting magnet coil are analyzed,and the fault voltage and current under different fault conditions are calculated.The simulation model of CSMC magnet grounding fault is established,and the simulation results of the model are basically consistent with the theoretical calculation.Finally,a small capacity experiment platform is used to verify the function of the grounding protection system.The experimental results show that by comparing the neutral fault sampling voltage with the theoretical grounding protection threshold,the grounding protection system can effectively detect different types of grounding faults and transmit signals to the control system to protect the coils of superconducting magnets.
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. .
基金supported by the National Natural Science Foundation of China-State Grid Joint Fund for Smart Grid(No.U2066210).
文摘Multi-terminal direct current based on a modular multilevel converter(MMC-MTDC)has received more attention due to the advantages of large capacity and high flexibility.However,the current traveling wave protection schemes adopted by the MMC-MTDC DC project are not sufficiently sensitive to high-impedance faults.To solve this problem,this paper first analyzes the characteristics of the first traveling wave of the fault on the DC transmission line and derives the expressions of the first traveling wave of the fault when the DC transmission line has an internal and external fault.Subsequently,the line frequency characteristic is used to simplify the traveling wave expression and construct the fault coefficient.Finally,the principle of single-ended traveling wave protection based on the fault coefficient is proposed.Simulation results show that the protection principle has a strong ability to withstand transition resistance and noise interference.
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.
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.
