Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunne...Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunneling diodes(FTDs)with tunneling distances of 10 and 5 nm are fabricated,which demonstrate remarkable characteristics,including ultrahigh asymmetry(1.6×10^(4)for 10 nm device and 1.6×10^(3) for 5 nm device),high responsivity(25.3 V^(-1) for 10 nm device and 28.3 V^(-1) for 5 nm device)at zero bias,surpassing the thermal voltage limit of conventional Schottky diodes,and low turn-on voltage(V_(on))of approximately 100 mV for both devices,making them ideal for power conversion applications.Using technology computer-aided design(TCAD)simulations,the observed asymmetry in electronic transport is attributed to the transition between Fowler-Nordheim tunneling(FNT)and trap-assisted tunneling(TAT)under different biasing conditions,as illustrated by the corresponding energy band profiles.Furthermore,by integrating the FTDs,a rectifier bridge circuit is designed and exhibits full-wave rectification behavior,validated through SPICE simulations for THz-band operations.This advancement offers a highly efficient solution for THz-band energy conversion and effective detection applications.展开更多
A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated chara...A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated characteristics.Under SUV light illumination,the rectifier has the excellent full-wave rectification characteristics for the AC input signals of 5,12,and 24 V with different frequencies.Further,experimental results confirmed the feasibility of continuously tuning the rectified output through SUV light-encoding.This work provides valuable insights for the development of optically programmable Ga_(2)O_(3)ACDC converters.展开更多
An ultra low voltage rectifier with high power conversion efficiency （PCE） for PE energy harvesting ap- plications is presented in this paper. This is achieved by utilizing the DTMOS which the body terminal is conne...An ultra low voltage rectifier with high power conversion efficiency （PCE） for PE energy harvesting ap- plications is presented in this paper. This is achieved by utilizing the DTMOS which the body terminal is connected to the gate terminal in a diode connected transistor. This implementation facilitates the rectifier with dynamic con- trol over the threshold voltage. Moreover, we use input powered to take the place of output powered to reduce the power loss and thereby increasing the power conversion efficiency. Based on standard SMIC 0.18 μm CMOS tech- nology, the simulation results show that the voltage conversion efficiency and the power conversion efficiency can reach up to 90.5% and 95.5% respectively, when the input voltage equals to 0.2 V @ 100 Hz with load resistance 50 kW. Input voltages with frequencies in the range of 10 Hz-1 kHz can be rectified.展开更多
A novel structure of low-voltage trigger silicon-controlled rectifiers(LVTSCRs) with low trigger voltage and high holding voltage is proposed for electrostatic discharge(ESD) protection. The proposed ESD protection de...A novel structure of low-voltage trigger silicon-controlled rectifiers(LVTSCRs) with low trigger voltage and high holding voltage is proposed for electrostatic discharge(ESD) protection. The proposed ESD protection device possesses an ESD implant and a floating structure. This improvement enhances the current discharge capability of the gate-grounded NMOS and weakens the current gain of the silicon-controlled rectifier current path. According to the simulation results, the proposed device retains a low trigger voltage characteristic of LVTSCRs and simultaneously increases the holding voltage to 5.53 V, providing an effective way to meet the ESD protection requirement of the 5 V CMOS process.展开更多
The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leadi...The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leading to current zero-crossing distortion and compromised dynamic response.This paper investigates the causes of these distortions,identifying a phase shift between the input current and the grid voltage as a primary factor,and proposes an effective distortion phase identification strategy.Furthermore,the dynamic performance is enhanced through improved current reference calculations and a refined power feedforward strategy.This approach optimizes the system's response to load changes and maintains output voltage stability under unbalanced conditions.Simulation results validate the effectiveness of the proposed methods in reducing current distortion and improving overall performance.展开更多
To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common r...To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common reservoir.First,some operation modes of mPSS are analyzed,which include the separated reservoir mode(SRM)and common reservoir mode(CRM).Then,based on the SRM,and CRM,an energy mutual assistance control model between LVSs has been built to optimize energy loss.Finally,in the simulation,compared to the model without pumped storage in the LVS,the SRMand CLRMcan decrease the total energy loss by 294.377 and 432.578 kWh,respectively.The configuration of mPSS can improve the utilization rate of the new energy source generation system,and relieve the pressure of transformer capacity in the LVS.Compared with the SRM,the proposed CRM has reduced the total energy loss by 138.201 kWh,increased the new energy consumption by 161.642 kWh,and decreased the line loss by 7.271 kWh.With the efficiency of the mPSS improving,the total energy loss reduction of CRM will be 3.5 times that of SRM.Further,the CRMcan significantly reduce the reservoir capacity construction of mPSS and ismore suitable for scenarios where the capacity configuration of mPSS is limited.展开更多
In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the instal...In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the installation height of the first catalyst layer,on the flow field and the overall denitration efficiency of a cement kiln’s SCR(Selective catalytic reduction)denitrification reactor.It is shown that accurate numerical results can be obtained by fitting the particle size distribution function to the actual cement kiln fly ash and implementing a non-uniform particle inlet boundary condition.The relative error between denitration efficiency derived from experimental data,numerical simulation,and real-time system pressure drop ranges from 4%to 9%.Optimization of the SCR reactor is achieved when the rectifier grid thickness ratio k/H≥0.030,the rectifier grid height ratio h/H=0.04,and the spacing between the rectifier grid and the first catalyst layer l/H=0.10.Under these conditions,airflow distribution and particle dispersion upstream of the catalyst result in increased denitration efficiencies of 3.21%,3.43%,and 3.27%,respectively,compared to the least favorable operating conditions.展开更多
The face velocities of the high efficiency particulate air filters and the ultra low penetration airfilters in fan filter units (FFUs) have large relative standard deviation and turbulivity. It seriously affects the ...The face velocities of the high efficiency particulate air filters and the ultra low penetration airfilters in fan filter units (FFUs) have large relative standard deviation and turbulivity. It seriously affects the unidirectivity of the flow in the unidirectional flow clean zone and cleanroom. The cross contamination in this kind of unidirectional flow area is hardly controlled. It is significant to find optional method for keeping the face velocity uniformity of FFU and reducing the face velocity turbulivity of FFU, furthermore, to keep the cleanliness level under FFUs. The normal and easy method is to add flow rectifiers under filters. FFUs with various flow rectifiers have been tested. The uniformity and turbulivity of facevelocity under the FFU are presented in this paper. The influence of the facevelocity uniformity and turbulivity on the contamination boundary of the unidirectional flow is studiedas well.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
A novel, highly linear sampling switch suitable for low-voltage operation is proposed. This switch not only eliminates the nonlinearity introduced by gate-source voltage variation, but also reduces the nonlinearity re...A novel, highly linear sampling switch suitable for low-voltage operation is proposed. This switch not only eliminates the nonlinearity introduced by gate-source voltage variation, but also reduces the nonlinearity resuiting from threshold voltage variation, which has not been accomplished in earlier low-voltage sampling switches. This is achieved by adopting a replica transistor with the same threshold voltage as the sampling transistor. The effectiveness of this technique is demonstrated by a prototype design of a sampling switch in 0. 35μm. The proposed sampling switch achieves a spurious free dynamic range of 111dB for a 0. 2MHz, 1.2Vp-p input signal, sampled at a rate of 2MS/s,about 18dB over the Bootstrapped switch. Also, the on-resistance variation is reduced by 90%. This method is especially useful for low-voltage, high resolution ADCs, which is a hot topic today.展开更多
A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulatio...A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulation shows that this method can boost the input-referred 3rd-order intercept point with much less power dissipation than that of traditional power/linearity tradeoff solution which pays at least 1dB power for 1dB linearity improvement.It is also shown that the size of the common-gate PMOS transistor needs to be optimized to reduce its loaded input impedance so as not to degrade the linearity due to high voltage gain at its source terminal.The simulation is carried out with TSMC 0.18μm RF CMOS technology and SpectreRF.展开更多
Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the ap...Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the application of conventional control strategies for stability operation face several challenges due to the uncontrollability of the DR.In this paper,a coordinated control strategy of offshore wind farms using the DR-HVDC transmission technology to connect with the onshore grid,is investigated.A novel coordinated control strategy for DR-HVDC is proposed based on the analysis of the DC current control ability of the full-bridge-based modular multilevel converter(FB-MMC)at the onshore station and the input and output characteristics of the diode rectifier at the offshore.Considering the characteristics of operation stability and decoupling between reactive power and active power,a simplified design based on double-loop droop control for offshore AC voltage is proposed after power flow and voltage–current(I–V)characteristics of the offshore wind farm being analyzed.Furthermore,the impact of onshore AC fault to offshore wind farm is analyzed,and a fast fault detection and protection strategy without relying on communication is proposed.Case studies carried out by PSCAD/EMTDC verify the effectiveness of the proposed control strategy for the start up,power fluctuation,and onshore and offshore fault conditions.展开更多
The Auto-Transformer Rectifier Unit（ATRU） is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, t...The Auto-Transformer Rectifier Unit（ATRU） is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.展开更多
The increasing proportion of distributed photovoltaics(DPVs)and electric vehicle charging stations in low-voltage distribution networks(LVDNs)has resulted in challenges such as distribution transformer overloads and v...The increasing proportion of distributed photovoltaics(DPVs)and electric vehicle charging stations in low-voltage distribution networks(LVDNs)has resulted in challenges such as distribution transformer overloads and voltage violations.To address these problems,we propose a coordinated planning method for flexible interconnections and energy storage systems(ESSs)to improve the accommodation capacity of DPVs.First,the power-transfer characteristics of flexible interconnection and ESSs are analyzed.The equipment costs of the voltage source converters(VSCs)and ESSs are also analyzed comprehensively,considering the differences in installation and maintenance costs for different installation locations.Second,a bilevel programming model is established to minimize the annual comprehensive cost and yearly total PV curtailment capacity.Within this framework,the upper-level model optimizes the installation locations and capacities of the VSCs and ESSs,whereas the lower-level model optimizes the operating power of the VSCs and ESSs.The proposed model is solved using a non-dominated sorting genetic algorithm with an elite strategy(NSGA-II).The effectiveness of the proposed planning method is validated through an actual LVDN scenario,which demonstrates its advantages in enhancing PV accommodation capacity.In addition,the economic benefits of various planning schemes with different flexible interconnection topologies and different PV grid-connected forms are quantitatively analyzed,demonstrating the adaptability of the proposed coordinated planning method.展开更多
This paper describes the successful fabrication of 4H-SiC junction barrier Schottky （JBS） rectifiers with a linearly graded field limiting ring （LG-FLR）. Linearly variable ring spacings for the FLR termination are...This paper describes the successful fabrication of 4H-SiC junction barrier Schottky （JBS） rectifiers with a linearly graded field limiting ring （LG-FLR）. Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2 （about 80% of the theoretical value）. Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termi- nation, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length.展开更多
The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the t...The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the two conversion techniques is discovered. It is characteristic of the switch functiion to follow mains voltage distortion and mains frequency drift. By utilizing the merit, unidirectional switch duty rations of the inverter follow the variation of DC link voltage automatically, thus the size of DC link electrolytic capacitor can be reduced considerably, bringing about improved mains side power factor. Corresponding topologies and theoretical and theoretical derivations are given, and so are the simulation results, based on which it is confirmed that the single to single phase matrix conversion technique is potentially useful in large scale production, and the introduction of switch function can yield good economic returns.展开更多
An improved structure of Schottky rectifier, called a trapezoid mesa trench metal oxide semiconductor （MOS） barrier Schottky rectifier （TM-TMBS）, is proposed and studied by two-dimensional numerical simulations. B...An improved structure of Schottky rectifier, called a trapezoid mesa trench metal oxide semiconductor （MOS） barrier Schottky rectifier （TM-TMBS）, is proposed and studied by two-dimensional numerical simulations. Both forward and especially better reverse I-V characteristics, including lower leakage current and higher breakdown voltage, are demonstrated by comparing our proposed TM-TMBS with a regular trench MOS barrier Schottky rectifier （TMBS） as well as a conventional planar Schottky barrier diode rectifier. Optimized device parameters corresponding to the requirement for high breakdown voltage are given. With optimized parameters, TM-TMBS attains a breakdown voltage of 186 V, which is 6.3% larger than that of the optimized TMBS, and a leakage current of 4.3×10^-6 A/cm2, which is 26% smaller than that of the optimized TMBS. The relationship between optimized breakdown voltage and some device parameters is studied. Explanations and design rules are given according to this relationship.展开更多
The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and ...The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and mesa bottom corner,are investigated by numerical simulation.The simulation results show that a deep mesa height,a small mesa angle and a smooth mesa bottom（without sub-trench） could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution.Moreover,an optimized mesa structure without sub-trench（mesa height of 2.2 μm and mesa angle of 20°） is experimentally demonstrated.A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm^2 are obtained from the fabricated diode with a 30-μm thick N^- epi-layer,corresponding to 85% of the ideal parallel-plane value.The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge.展开更多
The Vienna rectifier with unbalanced input voltage and load transient is analyzed.A nonlinear control strategy for Vienna rectifier under unbalanced input is proposed.From the view of positive and negative sequence co...The Vienna rectifier with unbalanced input voltage and load transient is analyzed.A nonlinear control strategy for Vienna rectifier under unbalanced input is proposed.From the view of positive and negative sequence components,the proposed nonlinear control strategy suppresses the twice frequency ripple and guarantees the dynamic response characteristic at the same time.Thanks to the proposed nonlinear control strategy,the DC bus capacitor can be reduced a lot since the voltage ripple and drop can be suppressed.A 10 kW Vienna rectifier is built to verify the proposed control strategy.After applying the proposed nonlinear control strategy,the voltage ripple is only7 V and decreases over 75%over the traditional PI control when the unbalanced degree is 20%.The voltage drop can be reduced about 80%than former control strategy which is helpful to reduce the DC bus capacitor and achieve higher power density.The volume of the capacitor can be reduced by 83.3%with the new control method.展开更多
基金National Key Research and Development Program of China(2024YFA1410700,2021YFA1200700)National Natural Science Foundation of China(62474065,T2222025,62174053)+3 种基金Natural Science Foundation of Chongqing(CSTB2024NSCQ-JQX0005)Shanghai Science and Technology Innovation Action Plan(24QA2702300,24YF2710400)National Postdoctoral Program(GZB20240225)Fundamental Research Funds for the Central Universities。
文摘Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunneling diodes(FTDs)with tunneling distances of 10 and 5 nm are fabricated,which demonstrate remarkable characteristics,including ultrahigh asymmetry(1.6×10^(4)for 10 nm device and 1.6×10^(3) for 5 nm device),high responsivity(25.3 V^(-1) for 10 nm device and 28.3 V^(-1) for 5 nm device)at zero bias,surpassing the thermal voltage limit of conventional Schottky diodes,and low turn-on voltage(V_(on))of approximately 100 mV for both devices,making them ideal for power conversion applications.Using technology computer-aided design(TCAD)simulations,the observed asymmetry in electronic transport is attributed to the transition between Fowler-Nordheim tunneling(FNT)and trap-assisted tunneling(TAT)under different biasing conditions,as illustrated by the corresponding energy band profiles.Furthermore,by integrating the FTDs,a rectifier bridge circuit is designed and exhibits full-wave rectification behavior,validated through SPICE simulations for THz-band operations.This advancement offers a highly efficient solution for THz-band energy conversion and effective detection applications.
基金supported by Natural Science Basic Research Program of Shaanxi Province of China(Grant No.2023JCYB574)National Natural Science Foundation of China(Grant No.62204203)。
文摘A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated characteristics.Under SUV light illumination,the rectifier has the excellent full-wave rectification characteristics for the AC input signals of 5,12,and 24 V with different frequencies.Further,experimental results confirmed the feasibility of continuously tuning the rectified output through SUV light-encoding.This work provides valuable insights for the development of optically programmable Ga_(2)O_(3)ACDC converters.
基金supported by the National Natural Science Foundation of China(Nos.61234002,61322405,61306044,61376033)the National High-Tech Program of China(No.2013AA014103)
文摘An ultra low voltage rectifier with high power conversion efficiency （PCE） for PE energy harvesting ap- plications is presented in this paper. This is achieved by utilizing the DTMOS which the body terminal is connected to the gate terminal in a diode connected transistor. This implementation facilitates the rectifier with dynamic con- trol over the threshold voltage. Moreover, we use input powered to take the place of output powered to reduce the power loss and thereby increasing the power conversion efficiency. Based on standard SMIC 0.18 μm CMOS tech- nology, the simulation results show that the voltage conversion efficiency and the power conversion efficiency can reach up to 90.5% and 95.5% respectively, when the input voltage equals to 0.2 V @ 100 Hz with load resistance 50 kW. Input voltages with frequencies in the range of 10 Hz-1 kHz can be rectified.
基金supported by the National Natural Science Foundation of China (Grant No. 61904110)。
文摘A novel structure of low-voltage trigger silicon-controlled rectifiers(LVTSCRs) with low trigger voltage and high holding voltage is proposed for electrostatic discharge(ESD) protection. The proposed ESD protection device possesses an ESD implant and a floating structure. This improvement enhances the current discharge capability of the gate-grounded NMOS and weakens the current gain of the silicon-controlled rectifier current path. According to the simulation results, the proposed device retains a low trigger voltage characteristic of LVTSCRs and simultaneously increases the holding voltage to 5.53 V, providing an effective way to meet the ESD protection requirement of the 5 V CMOS process.
文摘The Vienna rectifier is a widely adopted solution for high-power rectification due to its efficiency and straightforward design.However,its performance can degrade under unbalanced three phase voltage conditions,leading to current zero-crossing distortion and compromised dynamic response.This paper investigates the causes of these distortions,identifying a phase shift between the input current and the grid voltage as a primary factor,and proposes an effective distortion phase identification strategy.Furthermore,the dynamic performance is enhanced through improved current reference calculations and a refined power feedforward strategy.This approach optimizes the system's response to load changes and maintains output voltage stability under unbalanced conditions.Simulation results validate the effectiveness of the proposed methods in reducing current distortion and improving overall performance.
基金sponsored by the State Grid Corporation of China Technology Project(Research on Key Technologies and Equipment Development of Micro Pumped Storage for Distributed New Energy Consumption in Distribution Networks,5400-202324196A-1-1-ZN).
文摘To enhance energy interaction among low-voltage stations(LVSs)and reduce the line loss of the distribution network,a novel operation mode of the micro-pumped storage system(mPSS)has been proposed based on the common reservoir.First,some operation modes of mPSS are analyzed,which include the separated reservoir mode(SRM)and common reservoir mode(CRM).Then,based on the SRM,and CRM,an energy mutual assistance control model between LVSs has been built to optimize energy loss.Finally,in the simulation,compared to the model without pumped storage in the LVS,the SRMand CLRMcan decrease the total energy loss by 294.377 and 432.578 kWh,respectively.The configuration of mPSS can improve the utilization rate of the new energy source generation system,and relieve the pressure of transformer capacity in the LVS.Compared with the SRM,the proposed CRM has reduced the total energy loss by 138.201 kWh,increased the new energy consumption by 161.642 kWh,and decreased the line loss by 7.271 kWh.With the efficiency of the mPSS improving,the total energy loss reduction of CRM will be 3.5 times that of SRM.Further,the CRMcan significantly reduce the reservoir capacity construction of mPSS and ismore suitable for scenarios where the capacity configuration of mPSS is limited.
基金Anhui Province Key Research and Development Plan of the Ecological Environment Project(No.202104i07020016).
文摘In this study,Computational Fluid Dynamics(CFD)together with a component transport model are exploited to investigate the influence of dimensionless parameters,involving the height of the rectifier grid and the installation height of the first catalyst layer,on the flow field and the overall denitration efficiency of a cement kiln’s SCR(Selective catalytic reduction)denitrification reactor.It is shown that accurate numerical results can be obtained by fitting the particle size distribution function to the actual cement kiln fly ash and implementing a non-uniform particle inlet boundary condition.The relative error between denitration efficiency derived from experimental data,numerical simulation,and real-time system pressure drop ranges from 4%to 9%.Optimization of the SCR reactor is achieved when the rectifier grid thickness ratio k/H≥0.030,the rectifier grid height ratio h/H=0.04,and the spacing between the rectifier grid and the first catalyst layer l/H=0.10.Under these conditions,airflow distribution and particle dispersion upstream of the catalyst result in increased denitration efficiencies of 3.21%,3.43%,and 3.27%,respectively,compared to the least favorable operating conditions.
文摘The face velocities of the high efficiency particulate air filters and the ultra low penetration airfilters in fan filter units (FFUs) have large relative standard deviation and turbulivity. It seriously affects the unidirectivity of the flow in the unidirectional flow clean zone and cleanroom. The cross contamination in this kind of unidirectional flow area is hardly controlled. It is significant to find optional method for keeping the face velocity uniformity of FFU and reducing the face velocity turbulivity of FFU, furthermore, to keep the cleanliness level under FFUs. The normal and easy method is to add flow rectifiers under filters. FFUs with various flow rectifiers have been tested. The uniformity and turbulivity of facevelocity under the FFU are presented in this paper. The influence of the facevelocity uniformity and turbulivity on the contamination boundary of the unidirectional flow is studiedas well.
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.
文摘A novel, highly linear sampling switch suitable for low-voltage operation is proposed. This switch not only eliminates the nonlinearity introduced by gate-source voltage variation, but also reduces the nonlinearity resuiting from threshold voltage variation, which has not been accomplished in earlier low-voltage sampling switches. This is achieved by adopting a replica transistor with the same threshold voltage as the sampling transistor. The effectiveness of this technique is demonstrated by a prototype design of a sampling switch in 0. 35μm. The proposed sampling switch achieves a spurious free dynamic range of 111dB for a 0. 2MHz, 1.2Vp-p input signal, sampled at a rate of 2MS/s,about 18dB over the Bootstrapped switch. Also, the on-resistance variation is reduced by 90%. This method is especially useful for low-voltage, high resolution ADCs, which is a hot topic today.
文摘A CMOS radio frequency low noise amplifier with high linearity and low operation voltage of less than 1.0V is presented.In this circuit,an auxiliary MOSFET in the triode region is used to boost the linearity.Simulation shows that this method can boost the input-referred 3rd-order intercept point with much less power dissipation than that of traditional power/linearity tradeoff solution which pays at least 1dB power for 1dB linearity improvement.It is also shown that the size of the common-gate PMOS transistor needs to be optimized to reduce its loaded input impedance so as not to degrade the linearity due to high voltage gain at its source terminal.The simulation is carried out with TSMC 0.18μm RF CMOS technology and SpectreRF.
基金supported by State Grid Science and Technology Project“Study on Key Technologies of Large Scale Offshore Wind Power Integrating with Onshore Grid”(4000-202055045A-0-0-00)
文摘Due to low investment cost and high reliability,a new scheme called DR-HVDC(Diode Rectifier based HVDC)transmission was recently proposed for grid integration of large offshore wind farms.However,in this scheme,the application of conventional control strategies for stability operation face several challenges due to the uncontrollability of the DR.In this paper,a coordinated control strategy of offshore wind farms using the DR-HVDC transmission technology to connect with the onshore grid,is investigated.A novel coordinated control strategy for DR-HVDC is proposed based on the analysis of the DC current control ability of the full-bridge-based modular multilevel converter(FB-MMC)at the onshore station and the input and output characteristics of the diode rectifier at the offshore.Considering the characteristics of operation stability and decoupling between reactive power and active power,a simplified design based on double-loop droop control for offshore AC voltage is proposed after power flow and voltage–current(I–V)characteristics of the offshore wind farm being analyzed.Furthermore,the impact of onshore AC fault to offshore wind farm is analyzed,and a fast fault detection and protection strategy without relying on communication is proposed.Case studies carried out by PSCAD/EMTDC verify the effectiveness of the proposed control strategy for the start up,power fluctuation,and onshore and offshore fault conditions.
文摘The Auto-Transformer Rectifier Unit（ATRU） is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced k VA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.
基金supported by the Science and Technology Support Program of Guizhou Province([2022]General 012)the Key Science and Technology Project of China Southern Power Grid Corporation(GZKJXM20220043)。
文摘The increasing proportion of distributed photovoltaics(DPVs)and electric vehicle charging stations in low-voltage distribution networks(LVDNs)has resulted in challenges such as distribution transformer overloads and voltage violations.To address these problems,we propose a coordinated planning method for flexible interconnections and energy storage systems(ESSs)to improve the accommodation capacity of DPVs.First,the power-transfer characteristics of flexible interconnection and ESSs are analyzed.The equipment costs of the voltage source converters(VSCs)and ESSs are also analyzed comprehensively,considering the differences in installation and maintenance costs for different installation locations.Second,a bilevel programming model is established to minimize the annual comprehensive cost and yearly total PV curtailment capacity.Within this framework,the upper-level model optimizes the installation locations and capacities of the VSCs and ESSs,whereas the lower-level model optimizes the operating power of the VSCs and ESSs.The proposed model is solved using a non-dominated sorting genetic algorithm with an elite strategy(NSGA-II).The effectiveness of the proposed planning method is validated through an actual LVDN scenario,which demonstrates its advantages in enhancing PV accommodation capacity.In addition,the economic benefits of various planning schemes with different flexible interconnection topologies and different PV grid-connected forms are quantitatively analyzed,demonstrating the adaptability of the proposed coordinated planning method.
基金Project supported by the State Key Program of the National Natural Science Foundation of China(Grant No.61234006)
文摘This paper describes the successful fabrication of 4H-SiC junction barrier Schottky （JBS） rectifiers with a linearly graded field limiting ring （LG-FLR）. Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2 （about 80% of the theoretical value）. Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termi- nation, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length.
文摘The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the two conversion techniques is discovered. It is characteristic of the switch functiion to follow mains voltage distortion and mains frequency drift. By utilizing the merit, unidirectional switch duty rations of the inverter follow the variation of DC link voltage automatically, thus the size of DC link electrolytic capacitor can be reduced considerably, bringing about improved mains side power factor. Corresponding topologies and theoretical and theoretical derivations are given, and so are the simulation results, based on which it is confirmed that the single to single phase matrix conversion technique is potentially useful in large scale production, and the introduction of switch function can yield good economic returns.
基金Project supported by the International Research Training Group "Materials and Concepts for Interconnects and Nanosystems"
文摘An improved structure of Schottky rectifier, called a trapezoid mesa trench metal oxide semiconductor （MOS） barrier Schottky rectifier （TM-TMBS）, is proposed and studied by two-dimensional numerical simulations. Both forward and especially better reverse I-V characteristics, including lower leakage current and higher breakdown voltage, are demonstrated by comparing our proposed TM-TMBS with a regular trench MOS barrier Schottky rectifier （TMBS） as well as a conventional planar Schottky barrier diode rectifier. Optimized device parameters corresponding to the requirement for high breakdown voltage are given. With optimized parameters, TM-TMBS attains a breakdown voltage of 186 V, which is 6.3% larger than that of the optimized TMBS, and a leakage current of 4.3×10^-6 A/cm2, which is 26% smaller than that of the optimized TMBS. The relationship between optimized breakdown voltage and some device parameters is studied. Explanations and design rules are given according to this relationship.
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant No.61234006)the Open Foundation of the State Key Laboratory of Electronic Thin Films and Integrated Devices,China(Grant No.KFJJ201301)the National Science and Technology Major Project of the Ministry of Science and Technology,China(Grant No.2013ZX02305-003)
文摘The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and mesa bottom corner,are investigated by numerical simulation.The simulation results show that a deep mesa height,a small mesa angle and a smooth mesa bottom（without sub-trench） could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution.Moreover,an optimized mesa structure without sub-trench（mesa height of 2.2 μm and mesa angle of 20°） is experimentally demonstrated.A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm^2 are obtained from the fabricated diode with a 30-μm thick N^- epi-layer,corresponding to 85% of the ideal parallel-plane value.The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge.
基金supported in part by the National Natural Science Foundation of China (Nos. 51777093 ,51722702)
文摘The Vienna rectifier with unbalanced input voltage and load transient is analyzed.A nonlinear control strategy for Vienna rectifier under unbalanced input is proposed.From the view of positive and negative sequence components,the proposed nonlinear control strategy suppresses the twice frequency ripple and guarantees the dynamic response characteristic at the same time.Thanks to the proposed nonlinear control strategy,the DC bus capacitor can be reduced a lot since the voltage ripple and drop can be suppressed.A 10 kW Vienna rectifier is built to verify the proposed control strategy.After applying the proposed nonlinear control strategy,the voltage ripple is only7 V and decreases over 75%over the traditional PI control when the unbalanced degree is 20%.The voltage drop can be reduced about 80%than former control strategy which is helpful to reduce the DC bus capacitor and achieve higher power density.The volume of the capacitor can be reduced by 83.3%with the new control method.
