Monovalent anions,with relatively low charge density,exhibit weak bond energy with Zn^(2+)ions,which facilitates the solubility of Zn salts and the regulation of solvation structures.In this study,zinc bis(aminosulfat...Monovalent anions,with relatively low charge density,exhibit weak bond energy with Zn^(2+)ions,which facilitates the solubility of Zn salts and the regulation of solvation structures.In this study,zinc bis(aminosulfate)(Zn(NH_(2)SO_(3))_(2))with a monovalent anion,NH_(2)SO_(3)^(-),was synthesized and dissolved in different ratios of dimethyl sulfoxide(DMSO)and H_(2)O as electrolytes for Zn-ion batteries(ZIBs).From the perspective of game theory,the influences of DMSO and H_(2)O on the solvation structure and electrochemical performance of the Zn(NH_(2)SO_(3))_(2)based electrolytes has been meticulously discussed.Computations and spectra analysis indicate that DMSO molecules are reluctant to penetrate the primary solvation structure of Zn^(2+)ions.Indeed,increasing DMSO in electrolytes can induce a transition from solvent-separated ion pairs(SSIP)to contact ion pairs(CIP),resulting in an enrichment of anions in the primary solvation structure.This alteration can significantly suppress parasitic reactions,enhance nucleation density,and refine the deposition morphology during the Zn plating process,leading to superior cyclic stability and high coulombic efficiency(CE)of Zn//Cu and Zn//Zn cells.However,the enrichment of anions in the primary solvation structure also inhibits the activity of Zn^(2+)ions,amplifies the polarization effect,and engenders a sluggish ionization dynamics,resulting in the low energy conversion efficiency of the battery.These findings underscore the influence of the anion ratio within the primary solvation structure on electrochemical properties of electrolytes for ZIBs,which may be a pivotal determinant in the Zn deposition process.展开更多
Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheatin...Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.展开更多
The environmental conditions around the first offshore HZ 21- 1 steel wellhead platform in the South China Sea are characterized by deep water, frequent typhoons, rough waves, high water temperature, severely corrosiv...The environmental conditions around the first offshore HZ 21- 1 steel wellhead platform in the South China Sea are characterized by deep water, frequent typhoons, rough waves, high water temperature, severely corrosive seawater, and thick fouling organism attachments. The design and effectiveness of galvanic anode protection system are presented, and several methods are described, which are the calculation method of the protective current density considering the variation of water depth, the method of determining protection parameters considering various factors, the arrangement of anodes based on potential distribution and current requirements at different water depths, and the method of anode installation. Finally the effect of the accuracy of selected cathodic protection parameters on the economic benefits of offshore projects is also discussed..展开更多
The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criter...The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criterion is proposed. The first layer of the criterion adopts the adaptive adjustment threshold as the setting value to realize full-line fault monitoring, which is not affected by the system operation mode and fault type. The second layer is used to locate the fault section of the line and improve the selectivity of the protection strategy. Considering the difficulty in accurately identifying high-resistance ground faults using current protection, an identification method based on compound power is proposed by analyzing the zero-sequence network of the system. Simulation results show that the proposed protection strategy can realize full-length line protection and the effective identification of high-resistance ground faults and is not affected by the system load variation and fault type.展开更多
In this paper, a hybrid control strategy for a matrix converter fed wind energy conversion system is presented. Since the wind speed may vary, output parameters like power, frequency and voltage may fluctuate. Hence i...In this paper, a hybrid control strategy for a matrix converter fed wind energy conversion system is presented. Since the wind speed may vary, output parameters like power, frequency and voltage may fluctuate. Hence it is necessary to design a system that regulates output parameters, such as voltage and frequency, and thereby provides a constant voltage and frequency output from the wind energy conversion system. Matrix converter is used in the proposed solution as the main power conditioner as a more efficient alternative when compared to traditional back-back converter structure. To control the output voltage, a vector modulation based refined control structure is used. A power tracker is included to maximize the mechanical output power of the turbine. Over current protection and clamp circuit input protection have been introduced to protect the system from over current. It reduces the spikes generated at the output of the converter. The designed system is capable of supplying an output voltage of constant frequency and amplitude within the expected ranges of input during the operation. The matrix converter control using direct modulation method, modified Venturini modulation method and vector modulation method was simulated, the results were compared and it was inferred that vector modulation method was superior to the other two methods. With the proposed technique, voltage transfer ratio and harmonic profile have been improved compared to the other two modulation techniques. The behaviour of the system is corroborated by MATLAB Simulink, and hardware is realized using an FPGA controller. Experimental results are found to be matching with the simulation results.展开更多
This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation tools....This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation tools.The effectiveness of the proposed controller is assessed with simulations in test systems with high percentage of converter-interfaced generation.The simulations focus on the operation of protection relays that use negative-sequence quantities in their directional elements.This paper also presents and compares two strategies to limit reactive negative-sequence currents,and active and reactive positive-sequence currents.A tutorial test system and a regional system part of the actual Brazilian Interconnected Power System are used to assess the correctness of the proposed controller in three-phase fundamental-frequency RMS dynamic simulations.展开更多
With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme ca...With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme can be severely influenced by the Line Charging Capacitive Current(LCCC)with increased voltage level and Current Transformer(CT)saturation under external close-in faults.This paper presents a new UHV/EHV current-based protection scheme using the ratio of phasor summation of the two-end currents to the local end current,instead of summation of the two-end currents,to discriminate the internal faults.The accuracy and effectiveness of the proposed protection technique are tested on the 110 kV Western System Coordinating Council(WSCC)9-bus system using PSCAD/MATLAB.The simulation results confirm the reliable operation of the proposed scheme during internal/external faults and its independence from fault location,fault resistance,type of fault,and variations in source impedance.Finally,the effectiveness of the proposed scheme is also verified with faults during power swing and in series compensated lines.展开更多
To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically a...To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically adjusted to achieve a maximum driving capability and lower quiescent current of only 300 nA.To increase the loop stability of the proposed LDO,a high impedance transconductance buffer under a micro quiescent current is designed for splitting the pole that exists at the gate of the pass transistor to the dominant pole,and a zero is designed for the purpose of the second pole phase compensation.The proposed LDO is fabricated in a BiCMOS process. The measurement results show that the short-circuit current of the LDO is 190 mA,the constant limit current under a high drop-out voltage is 440 mA,and the maximum load current under a low drop-out voltage is up to 800 mA. In addition,the quiescent current of the LDO is only 7μA,the load regulation is about 0.56%on full scale,the line regulation is about 0.012%/V,the PSRR at 120 Hz is 58 dB and the drop-out voltage is only 70 mV when the load current is 250 mA.展开更多
Pulsed current cathodic protection(PCCP)could be more effective than direct current cathodic protection(DCCP)for mitigating corrosion in buried structures in the oil and gas industries if appropriate pulsed parameters...Pulsed current cathodic protection(PCCP)could be more effective than direct current cathodic protection(DCCP)for mitigating corrosion in buried structures in the oil and gas industries if appropriate pulsed parameters are chosen.The purpose of this research is to present the corrosion prevention mechanism of the PCCP technique by taking into account the effects of duty cycle as well as frequency,modeling the relationships between pulse parameters(frequency and duty cycle)and system outputs(corrosion rate,protective current and pipe-to-soil potential)and finally identifying the most effective protection conditions over a wide range of frequency(2–10 kHz)and duty cycle(25%-75%).For this,pipe-to-soil potential,pH,current and power consumption,corrosion rate,surface deposits and investigation of pitting corrosion were taken into account.To model the input-output relationship in the PCCP method,a data-driven machine learning approach was used by training an artificial neural network(ANN).The results revealed that the PCCP system could yield the best protection conditions at 10 kHz frequency and 50%duty cycle,resulting in the longest protection length with the lowest corrosion rate at a consumption current 0.3 time that of the DCCP method.In the frequency range of 6–10 kHz and duty cycles of 50%-75%,SEM images indicated a uniform distribution of calcite deposits and no pits on cathode surface.展开更多
The multi-terminal VSC-HVDC grid is believed to be widely applied in the future power system. The dc line protection is the key technique for operation security and power supply reliability of the dc grid. In this pap...The multi-terminal VSC-HVDC grid is believed to be widely applied in the future power system. The dc line protection is the key technique for operation security and power supply reliability of the dc grid. In this paper, the single-ended protections, namely, the traveling-wave based protection and transient-variable based protection, as well as the pilot protections, mainly including the directional pilot protection and current differential protection, are discussed in detail. With the analyzed protections, the effective main and back-up protection strategy can be configured for the dc line in multi-terminal VSC-HVDC grid.展开更多
Transformer Differential and overcurrent schemes are traditionally used as main and backup protection respectively. The differential protection relay (SEL487E) has dedicated harmonic restraint function which blocks th...Transformer Differential and overcurrent schemes are traditionally used as main and backup protection respectively. The differential protection relay (SEL487E) has dedicated harmonic restraint function which blocks the relay tripping during the transformer magnetizing inrush conditions. However, the backup overcurrent relay (SEL751A) applied to the transformer protection does not have harmonic restraint element and trip the overcurrent relay during the inrush conditions. Therefore, major contribution of this research work is the developed harmonic blocking scheme for transformer which uses element (87HB) of the transformer differential relay (SEL487E) to send an IEC61850 GOOSE-based harmonic blocking signal to the backup overcurrent relay (SEL751A) to inhibit from tripping during the transformer magnetizing inrush current conditions. The simulation results proved that IEC61850 standard-based protection scheme is faster than the hardwired signals. Therefore, the speed and reliability of the transformer scheme are improved using the IEC61850 standard-based GOOSE applications.展开更多
基金supported by the National Natural Science Foundation of China(51972187 and 22279068)the Natural Science Foundation of Shandong Province(ZR2023ME182)the Fundation of Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal Materials(Anhui University of Technology)(GFST2024KF03)。
文摘Monovalent anions,with relatively low charge density,exhibit weak bond energy with Zn^(2+)ions,which facilitates the solubility of Zn salts and the regulation of solvation structures.In this study,zinc bis(aminosulfate)(Zn(NH_(2)SO_(3))_(2))with a monovalent anion,NH_(2)SO_(3)^(-),was synthesized and dissolved in different ratios of dimethyl sulfoxide(DMSO)and H_(2)O as electrolytes for Zn-ion batteries(ZIBs).From the perspective of game theory,the influences of DMSO and H_(2)O on the solvation structure and electrochemical performance of the Zn(NH_(2)SO_(3))_(2)based electrolytes has been meticulously discussed.Computations and spectra analysis indicate that DMSO molecules are reluctant to penetrate the primary solvation structure of Zn^(2+)ions.Indeed,increasing DMSO in electrolytes can induce a transition from solvent-separated ion pairs(SSIP)to contact ion pairs(CIP),resulting in an enrichment of anions in the primary solvation structure.This alteration can significantly suppress parasitic reactions,enhance nucleation density,and refine the deposition morphology during the Zn plating process,leading to superior cyclic stability and high coulombic efficiency(CE)of Zn//Cu and Zn//Zn cells.However,the enrichment of anions in the primary solvation structure also inhibits the activity of Zn^(2+)ions,amplifies the polarization effect,and engenders a sluggish ionization dynamics,resulting in the low energy conversion efficiency of the battery.These findings underscore the influence of the anion ratio within the primary solvation structure on electrochemical properties of electrolytes for ZIBs,which may be a pivotal determinant in the Zn deposition process.
基金supported by National Natural Science Foundation of China(No.11575240)Key Program of Research and Development of Hefei Science Center,CAS(grant 2016HSC-KPRD002)
文摘Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.
文摘The environmental conditions around the first offshore HZ 21- 1 steel wellhead platform in the South China Sea are characterized by deep water, frequent typhoons, rough waves, high water temperature, severely corrosive seawater, and thick fouling organism attachments. The design and effectiveness of galvanic anode protection system are presented, and several methods are described, which are the calculation method of the protective current density considering the variation of water depth, the method of determining protection parameters considering various factors, the arrangement of anodes based on potential distribution and current requirements at different water depths, and the method of anode installation. Finally the effect of the accuracy of selected cathodic protection parameters on the economic benefits of offshore projects is also discussed..
基金Supported by the National Natural Science Foundation of China(U22B20106)the State Grid Power Company of Hunan Province Science and Technology Project(5216A5220022).
文摘The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criterion is proposed. The first layer of the criterion adopts the adaptive adjustment threshold as the setting value to realize full-line fault monitoring, which is not affected by the system operation mode and fault type. The second layer is used to locate the fault section of the line and improve the selectivity of the protection strategy. Considering the difficulty in accurately identifying high-resistance ground faults using current protection, an identification method based on compound power is proposed by analyzing the zero-sequence network of the system. Simulation results show that the proposed protection strategy can realize full-length line protection and the effective identification of high-resistance ground faults and is not affected by the system load variation and fault type.
文摘In this paper, a hybrid control strategy for a matrix converter fed wind energy conversion system is presented. Since the wind speed may vary, output parameters like power, frequency and voltage may fluctuate. Hence it is necessary to design a system that regulates output parameters, such as voltage and frequency, and thereby provides a constant voltage and frequency output from the wind energy conversion system. Matrix converter is used in the proposed solution as the main power conditioner as a more efficient alternative when compared to traditional back-back converter structure. To control the output voltage, a vector modulation based refined control structure is used. A power tracker is included to maximize the mechanical output power of the turbine. Over current protection and clamp circuit input protection have been introduced to protect the system from over current. It reduces the spikes generated at the output of the converter. The designed system is capable of supplying an output voltage of constant frequency and amplitude within the expected ranges of input during the operation. The matrix converter control using direct modulation method, modified Venturini modulation method and vector modulation method was simulated, the results were compared and it was inferred that vector modulation method was superior to the other two methods. With the proposed technique, voltage transfer ratio and harmonic profile have been improved compared to the other two modulation techniques. The behaviour of the system is corroborated by MATLAB Simulink, and hardware is realized using an FPGA controller. Experimental results are found to be matching with the simulation results.
基金supported by CNPQ,FAPERJ and Coordenacao de Aperfeicoamento de Pessoal de Nível Superior–Brasil(CAPES)Finance Code 001。
文摘This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation tools.The effectiveness of the proposed controller is assessed with simulations in test systems with high percentage of converter-interfaced generation.The simulations focus on the operation of protection relays that use negative-sequence quantities in their directional elements.This paper also presents and compares two strategies to limit reactive negative-sequence currents,and active and reactive positive-sequence currents.A tutorial test system and a regional system part of the actual Brazilian Interconnected Power System are used to assess the correctness of the proposed controller in three-phase fundamental-frequency RMS dynamic simulations.
文摘With respect to sensitivity,selectivity and speed of operation,the current differential scheme is a better way to protect transmission lines than overcurrent and distance-based schemes.However,the protection scheme can be severely influenced by the Line Charging Capacitive Current(LCCC)with increased voltage level and Current Transformer(CT)saturation under external close-in faults.This paper presents a new UHV/EHV current-based protection scheme using the ratio of phasor summation of the two-end currents to the local end current,instead of summation of the two-end currents,to discriminate the internal faults.The accuracy and effectiveness of the proposed protection technique are tested on the 110 kV Western System Coordinating Council(WSCC)9-bus system using PSCAD/MATLAB.The simulation results confirm the reliable operation of the proposed scheme during internal/external faults and its independence from fault location,fault resistance,type of fault,and variations in source impedance.Finally,the effectiveness of the proposed scheme is also verified with faults during power swing and in series compensated lines.
基金supported by the Ministerial "12th Five-Year" Pre-Research Fund of China(No.413080203)
文摘To achieve a constant current limit,low power consumption and high driving capability,a micro-power LDO with a piecewise voltage-foldback current-limit circuit is presented.The current-limit threshold is dynamically adjusted to achieve a maximum driving capability and lower quiescent current of only 300 nA.To increase the loop stability of the proposed LDO,a high impedance transconductance buffer under a micro quiescent current is designed for splitting the pole that exists at the gate of the pass transistor to the dominant pole,and a zero is designed for the purpose of the second pole phase compensation.The proposed LDO is fabricated in a BiCMOS process. The measurement results show that the short-circuit current of the LDO is 190 mA,the constant limit current under a high drop-out voltage is 440 mA,and the maximum load current under a low drop-out voltage is up to 800 mA. In addition,the quiescent current of the LDO is only 7μA,the load regulation is about 0.56%on full scale,the line regulation is about 0.012%/V,the PSRR at 120 Hz is 58 dB and the drop-out voltage is only 70 mV when the load current is 250 mA.
文摘Pulsed current cathodic protection(PCCP)could be more effective than direct current cathodic protection(DCCP)for mitigating corrosion in buried structures in the oil and gas industries if appropriate pulsed parameters are chosen.The purpose of this research is to present the corrosion prevention mechanism of the PCCP technique by taking into account the effects of duty cycle as well as frequency,modeling the relationships between pulse parameters(frequency and duty cycle)and system outputs(corrosion rate,protective current and pipe-to-soil potential)and finally identifying the most effective protection conditions over a wide range of frequency(2–10 kHz)and duty cycle(25%-75%).For this,pipe-to-soil potential,pH,current and power consumption,corrosion rate,surface deposits and investigation of pitting corrosion were taken into account.To model the input-output relationship in the PCCP method,a data-driven machine learning approach was used by training an artificial neural network(ANN).The results revealed that the PCCP system could yield the best protection conditions at 10 kHz frequency and 50%duty cycle,resulting in the longest protection length with the lowest corrosion rate at a consumption current 0.3 time that of the DCCP method.In the frequency range of 6–10 kHz and duty cycles of 50%-75%,SEM images indicated a uniform distribution of calcite deposits and no pits on cathode surface.
基金supported by the National Natural Science Foundation of China(No.U1866205).
文摘The multi-terminal VSC-HVDC grid is believed to be widely applied in the future power system. The dc line protection is the key technique for operation security and power supply reliability of the dc grid. In this paper, the single-ended protections, namely, the traveling-wave based protection and transient-variable based protection, as well as the pilot protections, mainly including the directional pilot protection and current differential protection, are discussed in detail. With the analyzed protections, the effective main and back-up protection strategy can be configured for the dc line in multi-terminal VSC-HVDC grid.
基金funded by the National Research Foundation(NRF)THRIP grant TP2011061100004,ESKOM TESP(Capacitor Banks Placement)ESKOM Academy of Learning,ESKOM Power Plants Energy Institute(EPPEI)and CPUT(Prestigious Project)grant for the Centre of Substation Automation and Energy Management Systems(CSAEMS)development and growth.
文摘Transformer Differential and overcurrent schemes are traditionally used as main and backup protection respectively. The differential protection relay (SEL487E) has dedicated harmonic restraint function which blocks the relay tripping during the transformer magnetizing inrush conditions. However, the backup overcurrent relay (SEL751A) applied to the transformer protection does not have harmonic restraint element and trip the overcurrent relay during the inrush conditions. Therefore, major contribution of this research work is the developed harmonic blocking scheme for transformer which uses element (87HB) of the transformer differential relay (SEL487E) to send an IEC61850 GOOSE-based harmonic blocking signal to the backup overcurrent relay (SEL751A) to inhibit from tripping during the transformer magnetizing inrush current conditions. The simulation results proved that IEC61850 standard-based protection scheme is faster than the hardwired signals. Therefore, the speed and reliability of the transformer scheme are improved using the IEC61850 standard-based GOOSE applications.
