考虑到传统二极管钳位型和电容钳位型拓扑应用于6 k V/10 k V高压变频领域时存在的诸多问题,提出了一种有源中点钳位式(ANPC)5电平变流器选择谐波消除脉宽调制(SHE-PWM)控制方法。在分析了ANPC 5电平拓扑各桥臂的基本结构的基础上,建立...考虑到传统二极管钳位型和电容钳位型拓扑应用于6 k V/10 k V高压变频领域时存在的诸多问题,提出了一种有源中点钳位式(ANPC)5电平变流器选择谐波消除脉宽调制(SHE-PWM)控制方法。在分析了ANPC 5电平拓扑各桥臂的基本结构的基础上,建立了ANPC拓扑相关数学模型;分析了5电平SHE-PWM的基本原理,构建了以消除低次谐波为目标的非线性方程组,并基于牛顿迭代法给出N=7时的SHE-PWM相关解域;针对ANPC拓扑存在的飞跨电容稳压问题,分析了飞跨电容的稳压原理,进而给出了冗余电压矢量调度方式。样机实验结果表明,所提ANPC 5电平拓扑SHE-PWM控制方法实现了低开关频率下变流系统的高效控制,在消除系统低次谐波的基础上,保证了直流电容和飞跨电容的稳压效果。展开更多
A CMOS （complementary metal-oxide-semiconductor transistor） low-dropout regulator （LDO） with 3. 3 V output voltage and 100 mA output current for system-on-chip applications to reduce board space and external pins ...A CMOS （complementary metal-oxide-semiconductor transistor） low-dropout regulator （LDO） with 3. 3 V output voltage and 100 mA output current for system-on-chip applications to reduce board space and external pins is presented. By utilizing a dynamic slew-rate enhancement（SRE） circuit and nested Miller compensation （NMC） on the LDO structure, the proposed LDO provides high stability during line and load regulation without off-chip load capacitors. The overshot voltage is limited within 550 mV and the settling time is less than 50 μs when the load current decreases from 100 mA to 1 mA. By using a 30 nA reference current, the quiescent current is 3.3 μA. The proposed design is implemented by CSMC 0. 5 μm mixed-signal process. The experimental results agree with the simulation results.展开更多
A comparison of the effectiveness of installing reactive power compensators,such as shunt capacitors,static var compensators(SVCs),and static synchronous compensators(STATCOMs),was presented in large-scale power netwo...A comparison of the effectiveness of installing reactive power compensators,such as shunt capacitors,static var compensators(SVCs),and static synchronous compensators(STATCOMs),was presented in large-scale power networks.A suitable bus was first identified using modal analysis method.The single shunt capacitor,single SVC,and single STATCOM were installed separately on the most critical bus.The effects of the installation of different devices on power loss reduction,voltage profile improvement,and voltage stability margin enhancement were examined and compared for 57-and 118-bus transmission systems.The comparative study results show that SVC,and STATCOM are expensive compared to shunt capacitor,yet the effect of installing STATCOM is better than SVC and the effect of installing SVC is better than that of shunt capacitor in achieving power loss reduction,voltage profile improvement and voltage stability margin enhancement.展开更多
The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high...The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high working voltage is an appealing cathode candidate for PIBs,while the poor cycling performance and low electronic conductivity dramatically hinder the application.Herein,a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite(KVPO4F@3DC)is successfully designed in this study to tackle these problems.In the composite,KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by crosslinked large area carbon sheets.As the cathode for PIBs,the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g^-1 at 20 mA g^-1.An excellent long cycle stability with a capacity retention of 85.4%over 550 cycles at 500 mA g^-1 is achieved.In addition,it maintains 83.6%of its initial capacity at 50 mA g^-1 after 100 cycles at 55℃.The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode,successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.展开更多
The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(Ni-rich NCM)cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transiti...The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(Ni-rich NCM)cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transition when operating at a high voltage(≥4.5 V).Herein,a traditional carbonate electrolyte with lithium difluoro(oxalato)borate(Li DFOB)and tris(trimethylsilyl)phosphate(TMSP)as dual additives that can preferentially oxidize and decompose to form a stable F,B and Si-rich cathode-electrolyte interphase(CEI)that effectively inhibits continual electrolyte decomposition,transition metal dissolves,surface phase transition and gas generation.In addition,TMSP also removes trace H_(2)O/HF in the electrolyte to increase the electrolyte stability.Owing to the synergistic effect of Li DFOB and TMSP,the Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) half cells exhibit the capacity retention 76.3%after 500 cycles at a super high voltage of 4.7 V,the graphite/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)full cells exhibit high capacity retention of 82.8%after 500 cycles at 4.5 V,and Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)pouch cells exhibit high capacity retention 94%after 200 cycles at 4.5 V.This work is expected to provide an effective electrolyte optimizing strategy compatible with high energy density lithium-ion battery manufacturing systems.展开更多
文摘考虑到传统二极管钳位型和电容钳位型拓扑应用于6 k V/10 k V高压变频领域时存在的诸多问题,提出了一种有源中点钳位式(ANPC)5电平变流器选择谐波消除脉宽调制(SHE-PWM)控制方法。在分析了ANPC 5电平拓扑各桥臂的基本结构的基础上,建立了ANPC拓扑相关数学模型;分析了5电平SHE-PWM的基本原理,构建了以消除低次谐波为目标的非线性方程组,并基于牛顿迭代法给出N=7时的SHE-PWM相关解域;针对ANPC拓扑存在的飞跨电容稳压问题,分析了飞跨电容的稳压原理,进而给出了冗余电压矢量调度方式。样机实验结果表明,所提ANPC 5电平拓扑SHE-PWM控制方法实现了低开关频率下变流系统的高效控制,在消除系统低次谐波的基础上,保证了直流电容和飞跨电容的稳压效果。
基金The Key Science and Technology Project of Zhejiang Province(No.2007C21021)
文摘A CMOS （complementary metal-oxide-semiconductor transistor） low-dropout regulator （LDO） with 3. 3 V output voltage and 100 mA output current for system-on-chip applications to reduce board space and external pins is presented. By utilizing a dynamic slew-rate enhancement（SRE） circuit and nested Miller compensation （NMC） on the LDO structure, the proposed LDO provides high stability during line and load regulation without off-chip load capacitors. The overshot voltage is limited within 550 mV and the settling time is less than 50 μs when the load current decreases from 100 mA to 1 mA. By using a 30 nA reference current, the quiescent current is 3.3 μA. The proposed design is implemented by CSMC 0. 5 μm mixed-signal process. The experimental results agree with the simulation results.
文摘A comparison of the effectiveness of installing reactive power compensators,such as shunt capacitors,static var compensators(SVCs),and static synchronous compensators(STATCOMs),was presented in large-scale power networks.A suitable bus was first identified using modal analysis method.The single shunt capacitor,single SVC,and single STATCOM were installed separately on the most critical bus.The effects of the installation of different devices on power loss reduction,voltage profile improvement,and voltage stability margin enhancement were examined and compared for 57-and 118-bus transmission systems.The comparative study results show that SVC,and STATCOM are expensive compared to shunt capacitor,yet the effect of installing STATCOM is better than SVC and the effect of installing SVC is better than that of shunt capacitor in achieving power loss reduction,voltage profile improvement and voltage stability margin enhancement.
基金financially supported by the National Natural Science Foundation of China(51672078 and 21473052)Hunan University State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Independent Research Project(71675004)Hunan Youth Talents(2016RS3025)。
文摘The investigation on the cathode material of potassium ion batteries(PIBs),one of the most promising alternatives to lithium ion batteries,is of great significance.Potassium vanadium fluorophosphate(KVPO4F)with a high working voltage is an appealing cathode candidate for PIBs,while the poor cycling performance and low electronic conductivity dramatically hinder the application.Herein,a plum pudding model inspired three-dimensional amorphous carbon network modified KVPO4F composite(KVPO4F@3DC)is successfully designed in this study to tackle these problems.In the composite,KVPO4F particles are homogeneously wrapped by a layer of amorphous carbon and bridged by crosslinked large area carbon sheets.As the cathode for PIBs,the KVPO4F@3DC composite exhibits a high average operating voltage about 4.10 V with a super-high discharge capacity of 102.96 mAh g^-1 at 20 mA g^-1.An excellent long cycle stability with a capacity retention of 85.4%over 550 cycles at 500 mA g^-1 is achieved.In addition,it maintains 83.6%of its initial capacity at 50 mA g^-1 after 100 cycles at 55℃.The design of KVPO4F@3DC with plum pudding structure provides facilitative electron conductive network and stable electrode/electrode interface for electrode,successfully innovating an ultra-stable and high-performance cathode material for potassium ion batteries.
基金supported by the National Natural Science Foundation of China(52172201,51732005,51902118,and 52102249)China Postdoctoral Science Foundation(2019M662609 and 2020T130217)。
文摘The LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(Ni-rich NCM)cathode materials suffer from electrochemical performance degradation upon cycling due to detrimental cathode interface reactions and irreversible surface phase transition when operating at a high voltage(≥4.5 V).Herein,a traditional carbonate electrolyte with lithium difluoro(oxalato)borate(Li DFOB)and tris(trimethylsilyl)phosphate(TMSP)as dual additives that can preferentially oxidize and decompose to form a stable F,B and Si-rich cathode-electrolyte interphase(CEI)that effectively inhibits continual electrolyte decomposition,transition metal dissolves,surface phase transition and gas generation.In addition,TMSP also removes trace H_(2)O/HF in the electrolyte to increase the electrolyte stability.Owing to the synergistic effect of Li DFOB and TMSP,the Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) half cells exhibit the capacity retention 76.3%after 500 cycles at a super high voltage of 4.7 V,the graphite/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)full cells exhibit high capacity retention of 82.8%after 500 cycles at 4.5 V,and Li/LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)pouch cells exhibit high capacity retention 94%after 200 cycles at 4.5 V.This work is expected to provide an effective electrolyte optimizing strategy compatible with high energy density lithium-ion battery manufacturing systems.
