This paper presents two schemes of high performance CMOS current mirror, one of them is used for operational tran-sconductance amplifier (OTA) in analog VLSI systems. The linearity, output impedance, bandwidth and acc...This paper presents two schemes of high performance CMOS current mirror, one of them is used for operational tran-sconductance amplifier (OTA) in analog VLSI systems. The linearity, output impedance, bandwidth and accuracy are the most parameters to determine the performance of the current mirror. Here a comparison of two architectures based on same architecture of the amplifier is presented. This comparison includes: linearity, output impedance, bandwidth and accuracy. These two circuits are validated with simulation in technology AMS 0.35 μm. An operational amplifier based on the adapted current mirror is proposed. Its frequency analysis with large bandwidth is validated with the same technology.展开更多
In this study it is demonstrated that oxygen-plasma-generated CuOx can enhance the holes injection from ITO anode into polymer layer in single-layer polymer EL devices. The possible reason for this enhancement is beca...In this study it is demonstrated that oxygen-plasma-generated CuOx can enhance the holes injection from ITO anode into polymer layer in single-layer polymer EL devices. The possible reason for this enhancement is because the ITO anode modified with CuOx possesses much higher work function than pure ITO anode, which reduces the barrier for hole-injection and further lowers the operational voltage of the polymer EL devices. The work function shift is probable due to the oxygen-plasma-generated CuOx can store more releasable oxygen, and the releasable oxygen in turn changes the oxygen concentration just near ITO surface, which will shift the work function of ITO anode.展开更多
A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxi...A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxidesemiconductor field-effect transistor (MOSFET)-BJT hybrid operation mode. Further, it has multiple emitter dots linked to each other in parallel to improve ionic sensitivity. Using hydrogen ionic solutions as reference solutions, we conduct experiments in which we compare the sensitivity and threshold voltage of the multi-emitter-dot gated lateral BJT with that of the single-emitter-dot gated lateral BJT. The multi-emitter-dot gated lateral BJT not only shows increased sensitivity but, more importantly, the proposed device can be operated under very low gate voltage, whereas the conventional ion-sensitive field-effect transistors cannot. This special characteristic is significant for low power devices and for function devices in which the provision of a gate voltage is difficult.展开更多
Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal...Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal grounding method in urban MV network.展开更多
Summary: The efficiency of cold storage red blood cells (CSRBC) or whole blood at -80 ℃ used in 27 Rh(D) negative patients during surgical operation was reported. The Rh(D) negative patients received the transfusion...Summary: The efficiency of cold storage red blood cells (CSRBC) or whole blood at -80 ℃ used in 27 Rh(D) negative patients during surgical operation was reported. The Rh(D) negative patients received the transfusion of CSRBC or whole blood stored at -80 ℃ for 180 to 360 days. The changes in the indexes, such as blood TB, DB, K +, Na +, BUN, Cr, urine protein (URPO), UOB, Hb, HCT, serum total protein, relative to hemolytic reaction and blood volume before and after transfusion were observed. The results showed that after transfusion of CSRBC or whole blood 27 cases were negative for urine protein and UOB, and the levels of BUN and Cr were normal (P>0.05). Blood TB, DB, Hb, and HCT were increased, while pH, blood K + and blood Na + was normal with the difference being not significant before and after operation (P>0.05). Plasma protein was decreased, but there was no significant difference before and after operation (P>0.05). It was suggested that CSRBC or whole blood at -80 ℃ could be safely infused to the Rh(D) negative patients without side effects during the surgical operation.展开更多
In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψ...In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψf/Ld during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system.Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5 kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.展开更多
Lithium metal batteries(LMBs) promise energy density over 400 Wh kg^(-1).However,they suffer severe electrochemical performance deterioration at sub-zero temperatures.Such failure behavior highly correlates to inferio...Lithium metal batteries(LMBs) promise energy density over 400 Wh kg^(-1).However,they suffer severe electrochemical performance deterioration at sub-zero temperatures.Such failure behavior highly correlates to inferior lithium metal anode(LMA) compatibility and sluggish Li^(+) desolvation.Here,we demonstrate that cyclopentylmethyl ether(CPME) based diluted high-concentration electrolyte(DHCE)enables-60℃ LMBs operation.By leveraging the loose coordination between Li^(+) and CPME,such developed electrolyte boosts the formation of ion clusters to derive anion-dominant interfacial chemistry for enhancing LMA compatibility and greatly accelerates Li^(+) desolvation kinetics.The resulting electrolyte demonstrates high Coulombic efficiencies(CE),providing over 99.5%,99.1%,98.5% and 95% at 25,-20,-40,and-60℃respectively.The assembled Li-S battery exhibits remarkable cyclic stability in-20,and-40℃ at 0.2 C charging and 0.5 C discharging.Even at-60℃,Li-S cell with this designed electrolyte retains> 70% of the initial capacity over 170 cycles.Besides,lithium metal coin cell and pouch cell with10 mg cm^(-2) high S cathode loading exhibit cycling stability at-20℃.This work offers an opportunity for rational designing electrolytes toward low temperature LMBs.展开更多
To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a ...To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.展开更多
With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor b...With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor banks will bear large numbers of over-voltage inevitably.If the over-voltage exceeds certain amplitude,the capacitor will be damaged.This paper aims at the capacitor banks in the 35 kV side of Shanghai Xu-xing 500 kV substation,and applies ATP-EMTP to simulate the over-voltages generated by operating the switches under different angles of the source.Finally,according to the results of simulation and theoretical analysis,a best choice(i.e.angles of the source) to switch on capacitor banks is proposed.In this case the over-voltage on the capacitor will be limited to lowest.展开更多
This paper reports that the transverse laser induced thermoelectric voltages (LITV) axe observed for the first time in the step flow growth (1- x)PD(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin fi...This paper reports that the transverse laser induced thermoelectric voltages (LITV) axe observed for the first time in the step flow growth (1- x)PD(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength, the largest induced voltage is observed in the 0.50Pb(Mg1/3Nb2/3)O3-0.50 PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.展开更多
This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed...This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed‐loop coils are promising for many easily‐quenching direct‐current(DC)applications,where their performance is determined by magnetomotive forces,total number of turns,and dimensions.As the primary interface parameter in an application system,the operational current must be accurately and rapidly measured.Generally,this is achieved by dividing the measured magnetic field by the coil constant.However,even if the influence of the screening current induced field(SCIF)is not considered,existing methods for the coil constant may be disturbed by the performance and location of Hall sensors,or experience a long measuring period.Therefore,a relatively accurate and fast method is proposed in this study,which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator.The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method(FEM)model,and its current accuracy can be equivalent to the resolution of the employed power supply.It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location,and has a more reliable accuracy in contrast to the simulation method.Compared to the experimentally conventional method,the proposed method presents a significantly faster speed.The impact of the SCIF was considered and proven to be negligible for the tested pancake coils.Even for coils whose coil constant vibrates owing to the SCIF,this method can be adapted to directly measure various operational currents.Furthermore,it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM,and a procedure for reducing this error was proposed.展开更多
Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operati...Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.展开更多
This paper studies the reactive power and voltage coordinated control scheme. According to the characteristics of Hunan power grid, the coordinated schemes about Hunan power grid with Central China Power Grid, as well...This paper studies the reactive power and voltage coordinated control scheme. According to the characteristics of Hunan power grid, the coordinated schemes about Hunan power grid with Central China Power Grid, as well as Changsha power grid are proposed. At the same time, this paper builds a two-way interactive and multiple dispatching reactive power and voltage coordinated control mode, and can be successfully applied in Hunan power grid. The operation results show that this control scheme fulfills the ability of large power grids in optimal allocating of resources, effectively integrates the reactive power resources of the entire grid, achieves the purpose of reducing power grid loss, improving voltage quality, reducing the operating numbers of the reactive power equipment.展开更多
This paper presents a new first order all pass filter configurations. The proposed all pass filter configuration employs two configurations namely VDVTA and OTAs based first order all pass filter configuration. The fi...This paper presents a new first order all pass filter configurations. The proposed all pass filter configuration employs two configurations namely VDVTA and OTAs based first order all pass filter configuration. The first proposed configuration employs a single VDVTA and one grounded capacitor whereas the second proposed configuration employs two OTAs and one grounded capacitor. Both types of proposed configurations are fully electronically tunable and their quality factors do not depend on tunable pole frequency range. The reported configurations yield low active and passive sensitivities and also have low power consumption with very low supply voltage ± 0.85 V with Bias Voltage ± 0.50 V. The PSPICE simulation of the proposed VDVTA and two OTAs based first order all pass filter configurations are verified using 0.18 μm CMOS Technology Process Parameters.展开更多
A configuration using current feedback amplifiers AD844 and multiplier AD534 has been presented, which is capable of realizing Voltage Controlled Floating Inductance (proportional and in-verse proportional). The appli...A configuration using current feedback amplifiers AD844 and multiplier AD534 has been presented, which is capable of realizing Voltage Controlled Floating Inductance (proportional and in-verse proportional). The application of band pass filter in Figure 4(a), notch filter in Figure 5(a) and Hartley oscillator in Figure 6(a) and simulation result in Figures 4(b)-(d), Figures 5(b)-(d), Figures 6(b)-(d) shows the workability of proposed configuration.展开更多
文摘This paper presents two schemes of high performance CMOS current mirror, one of them is used for operational tran-sconductance amplifier (OTA) in analog VLSI systems. The linearity, output impedance, bandwidth and accuracy are the most parameters to determine the performance of the current mirror. Here a comparison of two architectures based on same architecture of the amplifier is presented. This comparison includes: linearity, output impedance, bandwidth and accuracy. These two circuits are validated with simulation in technology AMS 0.35 μm. An operational amplifier based on the adapted current mirror is proposed. Its frequency analysis with large bandwidth is validated with the same technology.
文摘In this study it is demonstrated that oxygen-plasma-generated CuOx can enhance the holes injection from ITO anode into polymer layer in single-layer polymer EL devices. The possible reason for this enhancement is because the ITO anode modified with CuOx possesses much higher work function than pure ITO anode, which reduces the barrier for hole-injection and further lowers the operational voltage of the polymer EL devices. The work function shift is probable due to the oxygen-plasma-generated CuOx can store more releasable oxygen, and the releasable oxygen in turn changes the oxygen concentration just near ITO surface, which will shift the work function of ITO anode.
基金Supported by the National Natural Science Foundation of China under Grant No 61403014
文摘A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxidesemiconductor field-effect transistor (MOSFET)-BJT hybrid operation mode. Further, it has multiple emitter dots linked to each other in parallel to improve ionic sensitivity. Using hydrogen ionic solutions as reference solutions, we conduct experiments in which we compare the sensitivity and threshold voltage of the multi-emitter-dot gated lateral BJT with that of the single-emitter-dot gated lateral BJT. The multi-emitter-dot gated lateral BJT not only shows increased sensitivity but, more importantly, the proposed device can be operated under very low gate voltage, whereas the conventional ion-sensitive field-effect transistors cannot. This special characteristic is significant for low power devices and for function devices in which the provision of a gate voltage is difficult.
文摘Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal grounding method in urban MV network.
文摘Summary: The efficiency of cold storage red blood cells (CSRBC) or whole blood at -80 ℃ used in 27 Rh(D) negative patients during surgical operation was reported. The Rh(D) negative patients received the transfusion of CSRBC or whole blood stored at -80 ℃ for 180 to 360 days. The changes in the indexes, such as blood TB, DB, K +, Na +, BUN, Cr, urine protein (URPO), UOB, Hb, HCT, serum total protein, relative to hemolytic reaction and blood volume before and after transfusion were observed. The results showed that after transfusion of CSRBC or whole blood 27 cases were negative for urine protein and UOB, and the levels of BUN and Cr were normal (P>0.05). Blood TB, DB, Hb, and HCT were increased, while pH, blood K + and blood Na + was normal with the difference being not significant before and after operation (P>0.05). Plasma protein was decreased, but there was no significant difference before and after operation (P>0.05). It was suggested that CSRBC or whole blood at -80 ℃ could be safely infused to the Rh(D) negative patients without side effects during the surgical operation.
基金supported in part by the Research Fund for the National Natural Science Foundation of China under Grant 52125701, 52007039, 51877054in part by the Key areas R&D Program of Guangdong Province China under Grant 2021B0101310001。
文摘In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψf/Ld during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system.Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5 kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.
基金supported by the National Natural Science Foundation of China(Nos.21975087,22008082)。
文摘Lithium metal batteries(LMBs) promise energy density over 400 Wh kg^(-1).However,they suffer severe electrochemical performance deterioration at sub-zero temperatures.Such failure behavior highly correlates to inferior lithium metal anode(LMA) compatibility and sluggish Li^(+) desolvation.Here,we demonstrate that cyclopentylmethyl ether(CPME) based diluted high-concentration electrolyte(DHCE)enables-60℃ LMBs operation.By leveraging the loose coordination between Li^(+) and CPME,such developed electrolyte boosts the formation of ion clusters to derive anion-dominant interfacial chemistry for enhancing LMA compatibility and greatly accelerates Li^(+) desolvation kinetics.The resulting electrolyte demonstrates high Coulombic efficiencies(CE),providing over 99.5%,99.1%,98.5% and 95% at 25,-20,-40,and-60℃respectively.The assembled Li-S battery exhibits remarkable cyclic stability in-20,and-40℃ at 0.2 C charging and 0.5 C discharging.Even at-60℃,Li-S cell with this designed electrolyte retains> 70% of the initial capacity over 170 cycles.Besides,lithium metal coin cell and pouch cell with10 mg cm^(-2) high S cathode loading exhibit cycling stability at-20℃.This work offers an opportunity for rational designing electrolytes toward low temperature LMBs.
文摘To realize effective utilization of renewable energy sources,a novel polymorphic topology with hybrid control strategy based LLC resonant converter was analyzed and designed in this paper.By combining the merits of a full bridge LLC resonant converter,three-level half bridge LLC resonant converter,and variable frequency control mode,the converter realizes an intelligent estimation of input voltage by automatically changing its internal cir-cuit topology.Under this control strategy,different input voltages determine different operation modes.This is achieved in full bridge LLC mode when the input voltage is low.If the input voltage rises to a certain level,it operates in three-level half bridge LLC mode.These switches are digital and entirely carried out by the DSP(Digi-tal Signal Processor),which means that an auxiliary circuit is unnecessary,where a simple strategy of software modification can be utilized.Experimental results of a 500W prototype with 100V~600V input voltage and full load efficiency of up to 92%are developed to verify feasibility and practicability.This type of converter is suitable for applications with an ultra-wide input voltage range,such as wind turbines,photovoltaic generators,bioenergy,and other renewable energy sources.
基金supported of the Fundamental Research Founds for the Central Universities
文摘With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor banks will bear large numbers of over-voltage inevitably.If the over-voltage exceeds certain amplitude,the capacitor will be damaged.This paper aims at the capacitor banks in the 35 kV side of Shanghai Xu-xing 500 kV substation,and applies ATP-EMTP to simulate the over-voltages generated by operating the switches under different angles of the source.Finally,according to the results of simulation and theoretical analysis,a best choice(i.e.angles of the source) to switch on capacitor banks is proposed.In this case the over-voltage on the capacitor will be limited to lowest.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10274026)
文摘This paper reports that the transverse laser induced thermoelectric voltages (LITV) axe observed for the first time in the step flow growth (1- x)PD(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT, x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength, the largest induced voltage is observed in the 0.50Pb(Mg1/3Nb2/3)O3-0.50 PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.
基金supported by National Natural Science Foundation of China(NSFC)under project 51977130.
文摘This study proposes a method for measuring the operational current of high temperature superconducting(HTS)non‐insulation(NI)closed‐loop coils,which operate in the steady persistent‐current‐mode(PCM).HTS NI closed‐loop coils are promising for many easily‐quenching direct‐current(DC)applications,where their performance is determined by magnetomotive forces,total number of turns,and dimensions.As the primary interface parameter in an application system,the operational current must be accurately and rapidly measured.Generally,this is achieved by dividing the measured magnetic field by the coil constant.However,even if the influence of the screening current induced field(SCIF)is not considered,existing methods for the coil constant may be disturbed by the performance and location of Hall sensors,or experience a long measuring period.Therefore,a relatively accurate and fast method is proposed in this study,which is based on adjusting the output current of the adjustable power supply and monitoring the coil voltage as an indicator.The proposed method was validated through experiments and simulations using an equivalent circuit model coupled with a finite element method(FEM)model,and its current accuracy can be equivalent to the resolution of the employed power supply.It was demonstrated that this method reduced the requirements for Hall sensor’s performance and location,and has a more reliable accuracy in contrast to the simulation method.Compared to the experimentally conventional method,the proposed method presents a significantly faster speed.The impact of the SCIF was considered and proven to be negligible for the tested pancake coils.Even for coils whose coil constant vibrates owing to the SCIF,this method can be adapted to directly measure various operational currents.Furthermore,it was demonstrated that the measurement error can be influenced by the current discrepancy among turns when the coil is not in the steady PCM,and a procedure for reducing this error was proposed.
基金supported by the National Key Rese arch and Development Program of China(2018YFB0904100)Science and Technology Project of State Grid(SGHB0000KXJS1800685)
文摘Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.
文摘This paper studies the reactive power and voltage coordinated control scheme. According to the characteristics of Hunan power grid, the coordinated schemes about Hunan power grid with Central China Power Grid, as well as Changsha power grid are proposed. At the same time, this paper builds a two-way interactive and multiple dispatching reactive power and voltage coordinated control mode, and can be successfully applied in Hunan power grid. The operation results show that this control scheme fulfills the ability of large power grids in optimal allocating of resources, effectively integrates the reactive power resources of the entire grid, achieves the purpose of reducing power grid loss, improving voltage quality, reducing the operating numbers of the reactive power equipment.
文摘This paper presents a new first order all pass filter configurations. The proposed all pass filter configuration employs two configurations namely VDVTA and OTAs based first order all pass filter configuration. The first proposed configuration employs a single VDVTA and one grounded capacitor whereas the second proposed configuration employs two OTAs and one grounded capacitor. Both types of proposed configurations are fully electronically tunable and their quality factors do not depend on tunable pole frequency range. The reported configurations yield low active and passive sensitivities and also have low power consumption with very low supply voltage ± 0.85 V with Bias Voltage ± 0.50 V. The PSPICE simulation of the proposed VDVTA and two OTAs based first order all pass filter configurations are verified using 0.18 μm CMOS Technology Process Parameters.
文摘A configuration using current feedback amplifiers AD844 and multiplier AD534 has been presented, which is capable of realizing Voltage Controlled Floating Inductance (proportional and in-verse proportional). The application of band pass filter in Figure 4(a), notch filter in Figure 5(a) and Hartley oscillator in Figure 6(a) and simulation result in Figures 4(b)-(d), Figures 5(b)-(d), Figures 6(b)-(d) shows the workability of proposed configuration.