The existing LCC-HVDC transmission project adopts the fixed-time delay restarting method.This method has disadvantages such as non-selectivity,long restart process,and high probability of restart failure.These issues ...The existing LCC-HVDC transmission project adopts the fixed-time delay restarting method.This method has disadvantages such as non-selectivity,long restart process,and high probability of restart failure.These issues cause a secondary impact on equipment and system power fluctuation.To solve this problem,an adaptive restarting method based on the principle of fault location by current injection is proposed.First,an additional control strategy is proposed to inject a current detection signal.Second,the propagation law of the current signal in the line is analyzed based on the distributed parameter model of transmission line.Finally,a method for identifying fault properties based on the principle of fault location is proposed.The method fully considers the influence of the long-distance transmission line with earth capacitance and overcomes the influence of the increasing effect of the opposite terminal.Simulation results show that the proposed method can accurately identify the fault properties under various complex fault conditions and subsequently realize the adaptive restarting process.展开更多
This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transforma...This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.展开更多
To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on...To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on directional couplers is proposed.Two cascaded symmetrical directional couplers compose a coupling device to inject the DM currents.When the coupling device is used,two devices are necessary to achieve the equivalence between radiation and injection,i.e.the equivalence between the injected voltages and the field strength,which is linear,regardless of the characteristics of the equipment under test(EUT).The results are verified by experiments using typical coaxial cables and nonlinear devices,where the equivalence between the nonlinear EUT responses induced by radiation and injection at both ends is achieved by using two coupling devices.At a frequency up to 1.75 GHz,the maximal experimental error is only 3.39%.The experimental results confirm the accuracy of the proposed method even both the EUTs work in the nonlinear region.The proposed method is applicable for radiated susceptibility(RS) testing of interconnected systems in the microwave frequency band.展开更多
To deal with the invalidation of commonly employed series model and parallel model in capacitance-voltage(C-V)characterization of organic thin films when current injection is significant,a three-element equivalent cir...To deal with the invalidation of commonly employed series model and parallel model in capacitance-voltage(C-V)characterization of organic thin films when current injection is significant,a three-element equivalent circuit model is proposed.On this basis,the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method.The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor,a diode,and a resistor.Moreover,the accurate C-V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result,and the real capacitance is 35.7%higher than the directly measured capacitance at 5-V bias in the parallel mode.This work strongly demonstrates the necessity to consider current injection in C-V measurement and provides a strategy for accurate C-V characterization experimentally.展开更多
There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cab...There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.展开更多
The Magneto-acoustic Tomography with Current Injection (MAT-CI) is a new biological electrical impedance imaging technique that combines Electrical Impedance Tomography (EIT) with Ultrasonic Imaging (UI), which posses...The Magneto-acoustic Tomography with Current Injection (MAT-CI) is a new biological electrical impedance imaging technique that combines Electrical Impedance Tomography (EIT) with Ultrasonic Imaging (UI), which possesses the non-invasive and high-contrast of the EIT and the high-resolution of the UI. The MAT-CI is expected to acquire high quality image and embraces a wide application. Its principle is to put the conductive sample in the Static Magnetic Field(SMF) and inject a time-varying current, during which the SMF and the current interact and generate the Lorentz Force that inspire ultrasonic signal received by the ultrasonic transducers positioned around the sample. And then according to related reconstruction algorithm and ultrasonic signal, electrical conductivity image is obtained. In this paper, a forward problem mathematical model of the MAT-CI has been set up to deduce the theoretical equation of the electromagnetic field and solve the sound source distribution by Green’s function. Secondly, a sound field restoration by Wiener filtering and reconstruction of current density by time-rotating method have deduced the Laplace’s equation that caters to the current density to further acquire the electrical conductivity distribution image of the sample through iteration method. In the end, double-loop coils experiments have been conducted to verify its feasibility.展开更多
La_(0.8)Te_(0.2)MnO_3/YBa_2Cu_3O_(7-δ)(F/S)bilayers were fabricated by electrophoretic technique. The thickness of La_(0.8)Te_(0.2)MnO_3 is ~70 μm, the dimensions of YBa_2Cu_3O_(7-δ) superconductor are 5 mm×10...La_(0.8)Te_(0.2)MnO_3/YBa_2Cu_3O_(7-δ)(F/S)bilayers were fabricated by electrophoretic technique. The thickness of La_(0.8)Te_(0.2)MnO_3 is ~70 μm, the dimensions of YBa_2Cu_3O_(7-δ) superconductor are 5 mm×10 mm×0.5 mm. The image of cross-sectional profile was measured by scanning electron microscopy (SEM). Standard four-probe method was used for YBa_2Cu_3O_(7-δ) superconducting resistance measurements. Either 1 mA current is injected from S layer to F layer ((+I_(inj))) or from F layer to S layer (-I_(inj)),the normal resistance is lower than that without current injection. The critical transition temperature is higher than that without current injection.展开更多
On the basis of detailed analysis of a novel harmonic counteracting method which can be used to effectively compensate the supply line harmonic currents of a passive single phase diode bridge rectifier, this paper pr...On the basis of detailed analysis of a novel harmonic counteracting method which can be used to effectively compensate the supply line harmonic currents of a passive single phase diode bridge rectifier, this paper presents two simpler single phase diode bridge rectifier configurations and their alternatives which can achieve low supply line current THD(total harmonic distortion) too. Moreover, this paper also proposes a few passive hamonic counteracting networks for multi single phase rectifiers which are connected in parallel.展开更多
Plasma in a typically elongated cross-section tokamak （for example, EAST） is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading t...Plasma in a typically elongated cross-section tokamak （for example, EAST） is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading to disruption, and a large halo current is generated helically in EAST typically in the scrape-off layer. When flowing into the vacuum vessel through in-vessel components, the halo current will give rise to a large J × B force acting on the vessel and the in-vessel components. In EAST VDE experiment, part of the eddy current is measured in halo sensors, due to the large loop voltage. Primary experimental data demonstrate that the halo current first lands on the outer plate and then flows clockwise, and the analysis of the information indicates that the maximum halo current estimated in EAST is about 0.4 times the plasma current and the maximum value of TPF × Ih/Ip0 is 0.65, furthermore Ih/Ipo and TPF × Ih/Ipo tend to increase with the increase of Ip0. The test of the strong gas injection system shows good success in increasing the radiated power, which may be effective in reducing the halo current.展开更多
The degradation of transconductance （G） of a gate-modulated generation current IGD in a LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress （EIS）. The trapped elect...The degradation of transconductance （G） of a gate-modulated generation current IGD in a LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress （EIS）. The trapped electrons located in the gate oxide over the LDD region （QL） makes the effective drain voltage diminish. Accordingly, the G peak in depletion （GMD） and that in weak inversion （GMw） decrease. It is found that △GMD and △GMw each have a linear relationship with the n-th power of stress time （tn） in a dual-log coordinate： △GMD octn, AGMD octn （n = 0.25）. During the alternate stress, the injected holes neutralize QL induced by the previous EIS. This neutralization makes the effective VD restore to the initial value and then the IGD peak recovers completely. Yet the threshold voltage recovery is incomplete due to the trapped electron located over the channel （Qc）. As a result, GMW only recovers to circa 50% of the initial value after the hole-injection-stress （HIS）. Instead, GMD almost recovers. The relevant mechanisms are given in detail.展开更多
We investigate the effect of Rashba spin-orbit coupling(RSOC)on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential.The system shows that the photoconductivitie...We investigate the effect of Rashba spin-orbit coupling(RSOC)on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential.The system shows that the photoconductivities of resonant shift and injection current contributions are nonzero,while the photoconductivities of non-resonant shift current contribution are zero.We find that the RSOC induces a warping term,which leads to the nonzero rectified currents.Moreover,the photoconductivities of resonant injection(shift)current contribution are(not)related to the relaxation rate.The similar behavior can be found in other Dirac materials,and our findings provide a way to tune the nonlinear transport properties of Dirac materials.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
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
基金supported by Science and Technology Project of State Grid Corporation of China(52094020006U)National Natural Science Foundation of China(NSFC)(52061635105)China Postdoctoral Science Foundation(2021M692525).
文摘The existing LCC-HVDC transmission project adopts the fixed-time delay restarting method.This method has disadvantages such as non-selectivity,long restart process,and high probability of restart failure.These issues cause a secondary impact on equipment and system power fluctuation.To solve this problem,an adaptive restarting method based on the principle of fault location by current injection is proposed.First,an additional control strategy is proposed to inject a current detection signal.Second,the propagation law of the current signal in the line is analyzed based on the distributed parameter model of transmission line.Finally,a method for identifying fault properties based on the principle of fault location is proposed.The method fully considers the influence of the long-distance transmission line with earth capacitance and overcomes the influence of the increasing effect of the opposite terminal.Simulation results show that the proposed method can accurately identify the fault properties under various complex fault conditions and subsequently realize the adaptive restarting process.
基金supported by the National Natural Science Foundation of China under Grant 61603263。
文摘This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.
基金supported by National Basic Research Program of China(973 Program)
文摘To achieve the electric field strength and the induced currents in equivalence in susceptibility tests with the high-level field radiation above 400 MHz,a double differential-mode(DM) current injection method based on directional couplers is proposed.Two cascaded symmetrical directional couplers compose a coupling device to inject the DM currents.When the coupling device is used,two devices are necessary to achieve the equivalence between radiation and injection,i.e.the equivalence between the injected voltages and the field strength,which is linear,regardless of the characteristics of the equipment under test(EUT).The results are verified by experiments using typical coaxial cables and nonlinear devices,where the equivalence between the nonlinear EUT responses induced by radiation and injection at both ends is achieved by using two coupling devices.At a frequency up to 1.75 GHz,the maximal experimental error is only 3.39%.The experimental results confirm the accuracy of the proposed method even both the EUTs work in the nonlinear region.The proposed method is applicable for radiated susceptibility(RS) testing of interconnected systems in the microwave frequency band.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874007 and 12074076).
文摘To deal with the invalidation of commonly employed series model and parallel model in capacitance-voltage(C-V)characterization of organic thin films when current injection is significant,a three-element equivalent circuit model is proposed.On this basis,the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method.The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor,a diode,and a resistor.Moreover,the accurate C-V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result,and the real capacitance is 35.7%higher than the directly measured capacitance at 5-V bias in the parallel mode.This work strongly demonstrates the necessity to consider current injection in C-V measurement and provides a strategy for accurate C-V characterization experimentally.
基金Project supported by Arm Pre-research Program （51333040101）, National Defense 973 Program （6131380301 ）, National Natural Science Foundation of China （61040003）.
文摘There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.
文摘The Magneto-acoustic Tomography with Current Injection (MAT-CI) is a new biological electrical impedance imaging technique that combines Electrical Impedance Tomography (EIT) with Ultrasonic Imaging (UI), which possesses the non-invasive and high-contrast of the EIT and the high-resolution of the UI. The MAT-CI is expected to acquire high quality image and embraces a wide application. Its principle is to put the conductive sample in the Static Magnetic Field(SMF) and inject a time-varying current, during which the SMF and the current interact and generate the Lorentz Force that inspire ultrasonic signal received by the ultrasonic transducers positioned around the sample. And then according to related reconstruction algorithm and ultrasonic signal, electrical conductivity image is obtained. In this paper, a forward problem mathematical model of the MAT-CI has been set up to deduce the theoretical equation of the electromagnetic field and solve the sound source distribution by Green’s function. Secondly, a sound field restoration by Wiener filtering and reconstruction of current density by time-rotating method have deduced the Laplace’s equation that caters to the current density to further acquire the electrical conductivity distribution image of the sample through iteration method. In the end, double-loop coils experiments have been conducted to verify its feasibility.
文摘La_(0.8)Te_(0.2)MnO_3/YBa_2Cu_3O_(7-δ)(F/S)bilayers were fabricated by electrophoretic technique. The thickness of La_(0.8)Te_(0.2)MnO_3 is ~70 μm, the dimensions of YBa_2Cu_3O_(7-δ) superconductor are 5 mm×10 mm×0.5 mm. The image of cross-sectional profile was measured by scanning electron microscopy (SEM). Standard four-probe method was used for YBa_2Cu_3O_(7-δ) superconducting resistance measurements. Either 1 mA current is injected from S layer to F layer ((+I_(inj))) or from F layer to S layer (-I_(inj)),the normal resistance is lower than that without current injection. The critical transition temperature is higher than that without current injection.
文摘On the basis of detailed analysis of a novel harmonic counteracting method which can be used to effectively compensate the supply line harmonic currents of a passive single phase diode bridge rectifier, this paper presents two simpler single phase diode bridge rectifier configurations and their alternatives which can achieve low supply line current THD(total harmonic distortion) too. Moreover, this paper also proposes a few passive hamonic counteracting networks for multi single phase rectifiers which are connected in parallel.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Grant Nos.2014GB103000 and 2013GB102000)the National Natural Science Foundation of China(Grant No.11205199)
文摘Plasma in a typically elongated cross-section tokamak （for example, EAST） is inherently unstable against vertical displacement. When plasma loses the vertical position control, it moves downward or upward, leading to disruption, and a large halo current is generated helically in EAST typically in the scrape-off layer. When flowing into the vacuum vessel through in-vessel components, the halo current will give rise to a large J × B force acting on the vessel and the in-vessel components. In EAST VDE experiment, part of the eddy current is measured in halo sensors, due to the large loop voltage. Primary experimental data demonstrate that the halo current first lands on the outer plate and then flows clockwise, and the analysis of the information indicates that the maximum halo current estimated in EAST is about 0.4 times the plasma current and the maximum value of TPF × Ih/Ip0 is 0.65, furthermore Ih/Ipo and TPF × Ih/Ipo tend to increase with the increase of Ip0. The test of the strong gas injection system shows good success in increasing the radiated power, which may be effective in reducing the halo current.
基金Project supported by the Shaanxi Provincial Research Project of Education Department,China (Grant No. 11JK0902)the Xi’an Municipal Applied Materials Innovation Fund,China (Grant No. XA-AM-201012)
文摘The degradation of transconductance （G） of a gate-modulated generation current IGD in a LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress （EIS）. The trapped electrons located in the gate oxide over the LDD region （QL） makes the effective drain voltage diminish. Accordingly, the G peak in depletion （GMD） and that in weak inversion （GMw） decrease. It is found that △GMD and △GMw each have a linear relationship with the n-th power of stress time （tn） in a dual-log coordinate： △GMD octn, AGMD octn （n = 0.25）. During the alternate stress, the injected holes neutralize QL induced by the previous EIS. This neutralization makes the effective VD restore to the initial value and then the IGD peak recovers completely. Yet the threshold voltage recovery is incomplete due to the trapped electron located over the channel （Qc）. As a result, GMW only recovers to circa 50% of the initial value after the hole-injection-stress （HIS）. Instead, GMD almost recovers. The relevant mechanisms are given in detail.
基金Project supported by the Shandong Province Natural Science Foundation(Grant No.ZR2021MF077)。
文摘We investigate the effect of Rashba spin-orbit coupling(RSOC)on photoconductivities of rectified currents in monolayer graphene with exchange field and sublattice potential.The system shows that the photoconductivities of resonant shift and injection current contributions are nonzero,while the photoconductivities of non-resonant shift current contribution are zero.We find that the RSOC induces a warping term,which leads to the nonzero rectified currents.Moreover,the photoconductivities of resonant injection(shift)current contribution are(not)related to the relaxation rate.The similar behavior can be found in other Dirac materials,and our findings provide a way to tune the nonlinear transport properties of Dirac materials.
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.
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.
