When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is...When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.展开更多
This paper deals with the experimental study on the correlation betweeninsulation resistance(R)and direct current(DC)component(i_(de))and corresponding aging degreeof insulation in the course of the aging within cross...This paper deals with the experimental study on the correlation betweeninsulation resistance(R)and direct current(DC)component(i_(de))and corresponding aging degreeof insulation in the course of the aging within cross linked polyethylene(XLPE)insulation.Theaging tests were performed on a section of 10 kV transmission XLPE cable by means of water needlemethod,and_R was measured by DC voltage superimposed method,R and i_(de)were found to besignificantly dependent on the correspondingaging degree of insulation in the course of aging ofXLPE,and different kind of aging stage has different characteristics.Beside,there are generallysimilar regularity but different amplitude in the course of aging of XLPE insulation in differentelectrolyte,and the various electrochemical tree were found on the surface of aging XLPE cableimmersed in CuSO_(4),solution.Therefore,according to the changing regularity of the DCcharacteristic parameters i.e.R and i_(de)within XLPE insulation judging the aging degree of XLPEinsulation will be an effective method.展开更多
Under complex grid conditions,the grid voltage usually has an imbalance,low order harmonics,and a small of DC bias.When the grid voltage contains low order harmonics and a small amount of DC bias component,the inverte...Under complex grid conditions,the grid voltage usually has an imbalance,low order harmonics,and a small of DC bias.When the grid voltage contains low order harmonics and a small amount of DC bias component,the inverter’s output current cannot meet the grid connection requirements,and there is a three-phase current imbalance in the control strategy of common VSG under unbalanced voltage.A theoretical analysis of non-ideal power grids is carried out,and a VSG control strategy under complex operating conditions is proposed.Firstly,the third-order generalized integrator(TOGI)is used to eliminate the influence of the DC component of grid voltage.An improved delay signal cancellation(DSC)method is proposed to control the balance current and power fluctuation under unbalanced voltage based on the method of common VSG positive and negative sequence separation,It also eliminates the harmonic of command current.Then,the improved quasi proportional resonant controller(QPR)cascaded PI is used to suppress the harmonic current further so that the harmonic content of grid-connected current can meet the grid-connected requirements and achieve the three-phase current balance.Finally,the proposed strategy is verified by simulation under the control objectives of the current balance,active power,and reactive power constant.展开更多
Purpose For improving a beam quality of the linear accelerator and decreasing the influence of failure recovery on the accelerator available time,a high-voltage pulse modulator system is required to enhance the stabil...Purpose For improving a beam quality of the linear accelerator and decreasing the influence of failure recovery on the accelerator available time,a high-voltage pulse modulator system is required to enhance the stability of high-voltage pulses and maintain a low failure rate as well as a low failure recovery time,in order to implement a high-performance and stable operation.Methods This paper systematically analyzes the current status and operating conditions of the modulator equipment of BEPCII linear accelerator and simulates the typical parameters of the modulator considering the high-voltage DC charging power supply,DC charging cables and components and pulsed hydrogen thyratron.The technical route and retrofit scheme are proposed to decrease the failure rate and its recovery time.Results The stability of the high-voltage pulse modulator has increased by 1000 ppm,the failure rate has been decreased by two orders of magnitude,and the averaged recovery time from failures has been reduced by 94%as compared to the last operation period via implementing technical transformation with repeated exploration and experimental verification.展开更多
文摘When single phase earth fault occurs in the arc suppression coil grounding system, the amplitude of the transient capacitance current is high and decays fast, but the attenuation of the transient inductance current is much slower. This paper analyses the DC component of fault branch, and has found it is much bigger than that of the normal branches in transient state. All the simulation results obtained from three compensation types, different fault time and different wave cycles show that the DC component of fault branch is much higher than that of those normal branches. These results verify the effectiveness of taking the DC component as the method of fault line selection in the arc suppression coil grounding system.
基金Supported by the National Natural Science Foundation of China(59677018)
文摘This paper deals with the experimental study on the correlation betweeninsulation resistance(R)and direct current(DC)component(i_(de))and corresponding aging degreeof insulation in the course of the aging within cross linked polyethylene(XLPE)insulation.Theaging tests were performed on a section of 10 kV transmission XLPE cable by means of water needlemethod,and_R was measured by DC voltage superimposed method,R and i_(de)were found to besignificantly dependent on the correspondingaging degree of insulation in the course of aging ofXLPE,and different kind of aging stage has different characteristics.Beside,there are generallysimilar regularity but different amplitude in the course of aging of XLPE insulation in differentelectrolyte,and the various electrochemical tree were found on the surface of aging XLPE cableimmersed in CuSO_(4),solution.Therefore,according to the changing regularity of the DCcharacteristic parameters i.e.R and i_(de)within XLPE insulation judging the aging degree of XLPEinsulation will be an effective method.
基金National Natural Science Foundation of China(61863023).
文摘Under complex grid conditions,the grid voltage usually has an imbalance,low order harmonics,and a small of DC bias.When the grid voltage contains low order harmonics and a small amount of DC bias component,the inverter’s output current cannot meet the grid connection requirements,and there is a three-phase current imbalance in the control strategy of common VSG under unbalanced voltage.A theoretical analysis of non-ideal power grids is carried out,and a VSG control strategy under complex operating conditions is proposed.Firstly,the third-order generalized integrator(TOGI)is used to eliminate the influence of the DC component of grid voltage.An improved delay signal cancellation(DSC)method is proposed to control the balance current and power fluctuation under unbalanced voltage based on the method of common VSG positive and negative sequence separation,It also eliminates the harmonic of command current.Then,the improved quasi proportional resonant controller(QPR)cascaded PI is used to suppress the harmonic current further so that the harmonic content of grid-connected current can meet the grid-connected requirements and achieve the three-phase current balance.Finally,the proposed strategy is verified by simulation under the control objectives of the current balance,active power,and reactive power constant.
文摘Purpose For improving a beam quality of the linear accelerator and decreasing the influence of failure recovery on the accelerator available time,a high-voltage pulse modulator system is required to enhance the stability of high-voltage pulses and maintain a low failure rate as well as a low failure recovery time,in order to implement a high-performance and stable operation.Methods This paper systematically analyzes the current status and operating conditions of the modulator equipment of BEPCII linear accelerator and simulates the typical parameters of the modulator considering the high-voltage DC charging power supply,DC charging cables and components and pulsed hydrogen thyratron.The technical route and retrofit scheme are proposed to decrease the failure rate and its recovery time.Results The stability of the high-voltage pulse modulator has increased by 1000 ppm,the failure rate has been decreased by two orders of magnitude,and the averaged recovery time from failures has been reduced by 94%as compared to the last operation period via implementing technical transformation with repeated exploration and experimental verification.
