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
Because of its controlled power factor and no commutation failure,current source converter(CSC)made up of reverse-blocking IGCTs(RB-IGCTs)offers broad application prospects in the field of HVDC system.Valve voltage an...Because of its controlled power factor and no commutation failure,current source converter(CSC)made up of reverse-blocking IGCTs(RB-IGCTs)offers broad application prospects in the field of HVDC system.Valve voltage and power operating range as the most important operating characteristics should be paid attention to but they are always contradictory.First,the relationship between valve voltage and modulation index is obtained.In particular,valve voltage of converter under the three typical modulation methods is compared,analyzed,and verified.Second,with the help of the independent control strategy and coordinated control strategy of both ends,power operating ranges of the three modulation methods are comprehensively analyzed and compared.Third,in order to solve power coupling at a low active power,the improved coordination control strategy at both ends in this paper is proposed and the relationships among active power,reactive power,DC current and phase angle difference are given in detail.Finally,a 500 kV/3 kA simulation system was built in PSCAD/EMTDC to obtain comparison results of the key operating characteristics of CSC under different modulation methods and the converter can realize unity power operation under random active power after adopting the improved coordinated control strategy,and DC current does not decrease to zero,verifying effectiveness of the coordinated control strategy.展开更多
相比于电荷流的高功耗,自旋流可以高效地传输能量与信息的同时避免焦耳热的产生,因此基于自旋流的电子器件成为未来电子信息器件研发的重要方向之一.自旋流及其输运现象的相关研究是自旋电子学器件的开发基础.本文着眼于铁磁金属镍(Ni)...相比于电荷流的高功耗,自旋流可以高效地传输能量与信息的同时避免焦耳热的产生,因此基于自旋流的电子器件成为未来电子信息器件研发的重要方向之一.自旋流及其输运现象的相关研究是自旋电子学器件的开发基础.本文着眼于铁磁金属镍(Ni)与非磁重金属(Pt)构建的异质结结构,研究了异质结界面的自旋输运特性,发现其对扩散自旋流的全阻塞效应.本工作以基于钇铁石榴石(yttrium iron garnet,YIG)的YIG/Ni/Pt三层器件开展,采用自旋泵浦技术激发扩散自旋流注入到镍中,同时检测与分析器件中的逆自旋霍尔电压,并与YIG/Ni双层器件中的信号进行对比分析.结果证明YIG/Ni/Pt三层器件中的铂金属层仅起分流作用而对逆自旋霍尔电流无贡献,即镍层中的扩散自旋流被阻塞于Ni/Pt异质结界面.本工作加深了对界面处自旋流输运的认识,铁磁性金属/非磁重金属自旋流阻塞界面的发现也为自旋电子器件的设计及新功能开发提供了新的思路与手段.展开更多
The tundish induction heating power supply(TIHPS)is one of the most important equipment in the continuous casting process for metallurgical manufacturing.Specially,the constant temperature control is greatly significa...The tundish induction heating power supply(TIHPS)is one of the most important equipment in the continuous casting process for metallurgical manufacturing.Specially,the constant temperature control is greatly significant for metallurgical manufacturing.In terms of the relationship between TIH load temperature and output power of TIHPS,the constant temperature control can be realized by power control.In this paper,a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed.Besides,an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control.To meet the requirement of the system,controller parameters are designed properly.Experiments are con?ducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.展开更多
The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC gr...The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC grid.Although the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC breakers.The latter can extinguish DC faults by the fault-blocking converters.Without using DC breakers,there is no bottleneck in its technical feasibility.Nevertheless,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main drawback.The aim of this paper is to minimize its power interruption time,by optimizing protection coordination strategies.To cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are considered.In this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are analyzed.Based on this,a control function is designed to reduce the air-deionization time.To minimize the influence of the DC faults,a separation methodology for restarting the system is proposed.The effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.展开更多
In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking su...In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking submodules(QRBSMs)and current limit modules(CLMs)are employed to improve the DC fault handling capability for HVDC applications.This paper analyzes such a new converter configuration and operation principles.Then the DC pole-to-pole short circuit fault is taken into consideration for further study,as well as the fault current blocking mechanism and quantitative relationship between system electrical stress and key parameters.To validate the feasibility of the proposed topology and fault protection theory,extensive simulation results are demonstrated.It is concluded that the QRB-MMC can effectively block the fault current under DC fault condition.In addition,CLMs play an important role in further accelerating fault current attenuation.Moreover,QRB-MMC employs the original control and modulation strategies under normal operation conditions;thus,it further reduces the complexity of industry design.展开更多
Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction in patients with respiratory failure due to cervical spinal c...Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction in patients with respiratory failure due to cervical spinal cord injury. This paper presents an eigth-channel stimulator circuit with an output stage (electrode driving circuit) that doesn’t need off-chip blocking-capacitors and is used for phrenic nerve stimulation. This stimulator circuit utilizes only 1 output stage for 8 channels. The proposed current generator circuit in this stimulator reducing to a single step the translation of the digital input bits into the stimulus current, thus minimizing silicon area and power consumption. An 8 bit implementation is utilized for this current generator circuit. The average pulse width for this eight- channel stimulator with 1 mA current, 20 Hz frequency and 8 bits resolution, is 150 - 300 μs. The average power consumption for a single-channel stimulation is 38 mW from a 1.2 V power supply. This implantable stimulator system was simulated in HSPICE using 90 nm CMOS technology.展开更多
A novel 4 μm thickness drift region lateral insulated gate bipolar transistor with a floating n-region （NR- LIGBT） in p-substrate is proposed. Due to the field modulation from the n-region, the vertical blocking ca...A novel 4 μm thickness drift region lateral insulated gate bipolar transistor with a floating n-region （NR- LIGBT） in p-substrate is proposed. Due to the field modulation from the n-region, the vertical blocking capability is enhanced and the breakdown voltage is improved significantly. Low area cost, high current capability and short turn-off time are achieved because of the high average electric field per micron. Simulation results show that the blocking capability of the new LIGBT increases by about 58% when compared with the conventional LIGBT （C-LIGBT） for the same 100 μm drift region length. Furthermore, the turn-off time is shorter than that of the conventional LIGBT for nearly same blocking capability.展开更多
为提高原子荧光仪中激发光源的瞬间激发强度及其光谱稳定性,提出一种基于VMOS管稳流原理的双通道脉冲高压稳流电路设计方法,即采用由VMOS管和放大器组成的电流闭环负反馈电路来维持峰值电流稳定,从而实现激发光源激发强度的稳定。设计...为提高原子荧光仪中激发光源的瞬间激发强度及其光谱稳定性,提出一种基于VMOS管稳流原理的双通道脉冲高压稳流电路设计方法,即采用由VMOS管和放大器组成的电流闭环负反馈电路来维持峰值电流稳定,从而实现激发光源激发强度的稳定。设计稳流控制信号处理电路、闭环稳流电路、稳流闭锁电路及高压供电电路。在驱动不同阻抗元素灯及供电电压在150~250 V波动时,工作电流波动幅度均在±0.4%以内;输出电流可在0~160 m A数字设置,与设置电流线性相关度为0.998 7。测试结果表明:该设计的电流稳流效果较好,能满足不同元素灯及不同强度工作电流的驱动要求。展开更多
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.
基金supported in part by Science and Technology Project of State Grid Corporation of China.(5500202058059A0000).
文摘Because of its controlled power factor and no commutation failure,current source converter(CSC)made up of reverse-blocking IGCTs(RB-IGCTs)offers broad application prospects in the field of HVDC system.Valve voltage and power operating range as the most important operating characteristics should be paid attention to but they are always contradictory.First,the relationship between valve voltage and modulation index is obtained.In particular,valve voltage of converter under the three typical modulation methods is compared,analyzed,and verified.Second,with the help of the independent control strategy and coordinated control strategy of both ends,power operating ranges of the three modulation methods are comprehensively analyzed and compared.Third,in order to solve power coupling at a low active power,the improved coordination control strategy at both ends in this paper is proposed and the relationships among active power,reactive power,DC current and phase angle difference are given in detail.Finally,a 500 kV/3 kA simulation system was built in PSCAD/EMTDC to obtain comparison results of the key operating characteristics of CSC under different modulation methods and the converter can realize unity power operation under random active power after adopting the improved coordinated control strategy,and DC current does not decrease to zero,verifying effectiveness of the coordinated control strategy.
文摘相比于电荷流的高功耗,自旋流可以高效地传输能量与信息的同时避免焦耳热的产生,因此基于自旋流的电子器件成为未来电子信息器件研发的重要方向之一.自旋流及其输运现象的相关研究是自旋电子学器件的开发基础.本文着眼于铁磁金属镍(Ni)与非磁重金属(Pt)构建的异质结结构,研究了异质结界面的自旋输运特性,发现其对扩散自旋流的全阻塞效应.本工作以基于钇铁石榴石(yttrium iron garnet,YIG)的YIG/Ni/Pt三层器件开展,采用自旋泵浦技术激发扩散自旋流注入到镍中,同时检测与分析器件中的逆自旋霍尔电压,并与YIG/Ni双层器件中的信号进行对比分析.结果证明YIG/Ni/Pt三层器件中的铂金属层仅起分流作用而对逆自旋霍尔电流无贡献,即镍层中的扩散自旋流被阻塞于Ni/Pt异质结界面.本工作加深了对界面处自旋流输运的认识,铁磁性金属/非磁重金属自旋流阻塞界面的发现也为自旋电子器件的设计及新功能开发提供了新的思路与手段.
文摘The tundish induction heating power supply(TIHPS)is one of the most important equipment in the continuous casting process for metallurgical manufacturing.Specially,the constant temperature control is greatly significant for metallurgical manufacturing.In terms of the relationship between TIH load temperature and output power of TIHPS,the constant temperature control can be realized by power control.In this paper,a TIHPS structure with three-phase PWM rectifiers and full-bridge cascaded inverter is proposed.Besides,an input harmonic current blocking strategy and a load voltage feedforward control are also proposed to realize constant temperature control.To meet the requirement of the system,controller parameters are designed properly.Experiments are con?ducted to validate the feasibility and effectiveness of the proposed TIHPS topology and the control methods.
文摘The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy integration.Currently,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC grid.Although the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC breakers.The latter can extinguish DC faults by the fault-blocking converters.Without using DC breakers,there is no bottleneck in its technical feasibility.Nevertheless,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main drawback.The aim of this paper is to minimize its power interruption time,by optimizing protection coordination strategies.To cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are considered.In this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are analyzed.Based on this,a control function is designed to reduce the air-deionization time.To minimize the influence of the DC faults,a separation methodology for restarting the system is proposed.The effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.
基金supported in part by the State Key Laboratory of Large Electric Drive System and Equipment Technology(No.SKLLDJ042016005)in part by Open Fund of State Key Laboratory of Operation and Control of Renewable Energy&Storage Systemsin part by the National Key Research and Development Program of China(2016YFE0131700).
文摘In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking submodules(QRBSMs)and current limit modules(CLMs)are employed to improve the DC fault handling capability for HVDC applications.This paper analyzes such a new converter configuration and operation principles.Then the DC pole-to-pole short circuit fault is taken into consideration for further study,as well as the fault current blocking mechanism and quantitative relationship between system electrical stress and key parameters.To validate the feasibility of the proposed topology and fault protection theory,extensive simulation results are demonstrated.It is concluded that the QRB-MMC can effectively block the fault current under DC fault condition.In addition,CLMs play an important role in further accelerating fault current attenuation.Moreover,QRB-MMC employs the original control and modulation strategies under normal operation conditions;thus,it further reduces the complexity of industry design.
文摘Phrenic nerve stimulation is a technique whereby a nerve stimulator provides electrical stimulation of the phrenic nerve to cause diaphragmatic contraction in patients with respiratory failure due to cervical spinal cord injury. This paper presents an eigth-channel stimulator circuit with an output stage (electrode driving circuit) that doesn’t need off-chip blocking-capacitors and is used for phrenic nerve stimulation. This stimulator circuit utilizes only 1 output stage for 8 channels. The proposed current generator circuit in this stimulator reducing to a single step the translation of the digital input bits into the stimulus current, thus minimizing silicon area and power consumption. An 8 bit implementation is utilized for this current generator circuit. The average pulse width for this eight- channel stimulator with 1 mA current, 20 Hz frequency and 8 bits resolution, is 150 - 300 μs. The average power consumption for a single-channel stimulation is 38 mW from a 1.2 V power supply. This implantable stimulator system was simulated in HSPICE using 90 nm CMOS technology.
基金supported by the National Natural Science Foundation of China(No.61076082)
文摘A novel 4 μm thickness drift region lateral insulated gate bipolar transistor with a floating n-region （NR- LIGBT） in p-substrate is proposed. Due to the field modulation from the n-region, the vertical blocking capability is enhanced and the breakdown voltage is improved significantly. Low area cost, high current capability and short turn-off time are achieved because of the high average electric field per micron. Simulation results show that the blocking capability of the new LIGBT increases by about 58% when compared with the conventional LIGBT （C-LIGBT） for the same 100 μm drift region length. Furthermore, the turn-off time is shorter than that of the conventional LIGBT for nearly same blocking capability.
文摘为提高原子荧光仪中激发光源的瞬间激发强度及其光谱稳定性,提出一种基于VMOS管稳流原理的双通道脉冲高压稳流电路设计方法,即采用由VMOS管和放大器组成的电流闭环负反馈电路来维持峰值电流稳定,从而实现激发光源激发强度的稳定。设计稳流控制信号处理电路、闭环稳流电路、稳流闭锁电路及高压供电电路。在驱动不同阻抗元素灯及供电电压在150~250 V波动时,工作电流波动幅度均在±0.4%以内;输出电流可在0~160 m A数字设置,与设置电流线性相关度为0.998 7。测试结果表明:该设计的电流稳流效果较好,能满足不同元素灯及不同强度工作电流的驱动要求。
