PCIM China, international conference and exhibition for power electronics, was held in Shanghai on March 21, 2006. PCIM is one of the most authoritative organizations and has won good reputation overseas for a long time.
We are at dawn of a new era−an era where multiple strong market and technological transformations have called for reexamination of our current electric grid.It has opened the door for new thinking about the existing g...We are at dawn of a new era−an era where multiple strong market and technological transformations have called for reexamination of our current electric grid.It has opened the door for new thinking about the existing grid.People have been talking about the“grid of the future”for a few years now.What should this grid look like?What should be in it and why[1]?And how do we get there?展开更多
There is currently great optimism within the electronics community that gallium oxide(Ga_(2)O_(3)) ultra-wide bandgap semiconductors have unprecedented prospects for eventually revolutionizing a rich variety of power ...There is currently great optimism within the electronics community that gallium oxide(Ga_(2)O_(3)) ultra-wide bandgap semiconductors have unprecedented prospects for eventually revolutionizing a rich variety of power electronic applications. Specially, benefiting from its ultra-high bandgap of around 4.8 eV, it is expected that the emerging Ga_(2)O_(3) technology would offer an exciting platform to deliver massively enhanced device performance for power electronics and even completely new applications.展开更多
Gallium oxide(Ga_(2)O_(3))has garnered world-wide atten-tion as an ultrawide-bandgap semiconductor material from the area of power electronics and DUV optical devices benefit-ing from its outstanding electronic and op...Gallium oxide(Ga_(2)O_(3))has garnered world-wide atten-tion as an ultrawide-bandgap semiconductor material from the area of power electronics and DUV optical devices benefit-ing from its outstanding electronic and optoelectronic proper-ties.For one thing,since Ga_(2)O_(3)features high critical break-down field of 8 MV/cm and Baliga’s figure of merit(BFOM)of 3444,it is a promising candidate for advanced high-power applications.For another thing,due to the bandgap directly corresponding to the deep-ultraviolet(DUV)region,Ga_(2)O_(3)is widely used in DUV optoelectronic devices.展开更多
The research in Power Electronics and Dives at The Hong Kong Polytechnic University has been undertaking for many years. Recently, a Power Electronics Research Centre (PERC) has been developed that is contributed towa...The research in Power Electronics and Dives at The Hong Kong Polytechnic University has been undertaking for many years. Recently, a Power Electronics Research Centre (PERC) has been developed that is contributed towards the research anddevelopment in the area. It encompasses the high frequency power supplies, chaos and bifurcation, soft-switching power converters, electrical machines, high precision motion control, traction and traffic control,alternative energy and electrical building services.展开更多
The growing use of lithium-ion batteries in electric transportation and grid-scale storage systems has intensified the need for accurate and highly generalizable state-of-health(SOH)estimation.Conventional approaches ...The growing use of lithium-ion batteries in electric transportation and grid-scale storage systems has intensified the need for accurate and highly generalizable state-of-health(SOH)estimation.Conventional approaches often suffer from reduced accuracy under dynamically uncertain state-of-charge(SOC)operating ranges and heterogeneous aging stresses.This study presents a unified SOH estimation framework that integrates physics-informed modeling,subspace identification,and Transformer-based learning.A reduced-order model is derived from simplified electrochemical dynamics,providing an interpretable and computationally efficient representation of battery behavior.Subspace identification across a wide SOC and SOH range yields degradation-sensitive features,which the Transformer uses to capture long-range aging dynamics via multi-head self-attention.Experiments on LiFePO4 cells under joint-cell training show consistently accurate SOH estimation,with a maximum error of 1.39%,demonstrating the framework’s effectiveness in decoupling SOC and SOH effects.In cross-cell validation,where training and validation are performed on different cells,the model maintains a maximum error of 2.06%,confirming strong generalization to unseen aging trajectories.Comparative experiments on LiFePO_(4)and public LiCoO_(2)datasets confirm the framework’s cross-chemistry applicability.By extracting low-dimensional,physically interpretable features via subspace identification,the framework significantly reduces training cost while maintaining high SOH estimation accuracy,outperforming conventional data-driven models lacking physical guidance.展开更多
Traffic sign detection is an important part of autonomous driving,and its recognition accuracy and speed are directly related to road traffic safety.Although convolutional neural networks(CNNs)have made certain breakt...Traffic sign detection is an important part of autonomous driving,and its recognition accuracy and speed are directly related to road traffic safety.Although convolutional neural networks(CNNs)have made certain breakthroughs in this field,in the face of complex scenes,such as image blur and target occlusion,the traffic sign detection continues to exhibit limited accuracy,accompanied by false positives and missed detections.To address the above problems,a traffic sign detection algorithm,You Only Look Once-based Skip Dynamic Way(YOLO-SDW)based on You Only Look Once version 8 small(YOLOv8s),is proposed.Firstly,a Skip Connection Reconstruction(SCR)module is introduced to efficiently integrate fine-grained feature information and enhance the detection accuracy of the algorithm in complex scenes.Secondly,a C2f module based on Dynamic Snake Convolution(C2f-DySnake)is proposed to dynamically adjust the receptive field information,improve the algorithm’s feature extraction ability for blurred or occluded targets,and reduce the occurrence of false detections and missed detections.Finally,the Wise Powerful IoU v2(WPIoUv2)loss function is proposed to further improve the detection accuracy of the algorithm.Experimental results show that the average precision mAP@0.5 of YOLO-SDW on the TT100K dataset is 89.2%,and mAP@0.5:0.95 is 68.5%,which is 4%and 3.3%higher than the YOLOv8s baseline,respectively.YOLO-SDW ensures real-time performance while having higher accuracy.展开更多
Electric vehicle power battery consistency is the key factor affecting the performance of power batteries. it is not scientific to evaluate the consistency of the battery depending on voltage or capacity. In this pape...Electric vehicle power battery consistency is the key factor affecting the performance of power batteries. it is not scientific to evaluate the consistency of the battery depending on voltage or capacity. In this paper, multi- parameter evaluation method for battery consistency based on principal component analysis is proposed. Firstly, the characteristic parameters of battery consistency are analyzed, the principal component score can be used as the basis for evaluating the consistency of the battery. Then, the function that multi-parameter evaluation of battery consistency is established. Finally, battery balancing strategy based on fuzzy control is developed. The basic principle of fuzzy control is to fuzzy the input quantity based on expert knowledge, and the fuzzy control auantitv is obtained bv fuzzy control rule_ Th~ re.~nlt.~ ~ro v^rlfiocl hv t,~t展开更多
Over the last decade,practical digital control of high-frequency switched-mode power converters has moved from proof-of-concept demonstrations to controller chips commercially available from multiple vendors,with appl...Over the last decade,practical digital control of high-frequency switched-mode power converters has moved from proof-of-concept demonstrations to controller chips commercially available from multiple vendors,with applica-tions to point-of-load and isolated DC/DC converters,microprocessor power supplies,power-factor-correction rectifiers,and others.This paper summarizes some of the advances in the area,including approaches to realizations of high-per-formance,high-frequency digital pulse-width modulated(DPWM) controllers,related analysis,modeling and design techniques,as well as performance gains enabled by digital control such as dynamic response and efficiency improve-ments.Examples of experimentally demonstrated results are presented,together with pointers to areas of current and future research and development.展开更多
A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm^2 and breakdown voltage exceeding 1.5 kV is designed and fabricated.Numerical simulations are carried out to optimize the electric field strength in...A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm^2 and breakdown voltage exceeding 1.5 kV is designed and fabricated.Numerical simulations are carried out to optimize the electric field strength in gate oxide and at the surface of the semiconductor material in the edge termination region.Additional n-type implantation in JFET region is implemented to reduce the specific on-resistance.The typical leakage current is less than 1μA at VDS=1.4 kV.Drain–source current reaches 50 A at VDS=0.75 V and VGS=20 V corresponding to an on-resistance of 15 mΩ.The typical gate threshold voltage is 2.6 V.展开更多
The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs....The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs. Firstly, in this paper we make use of an accelerated life test and a statistical analysis method to establish the capacity accelerated degradation model under three constant stress parameters according to the degradation data, which are charge rate, discharge rate, and operating temperature, and then we propose a capacity degradation model according to the current residual capacity of a Li-ion cell under dynamic stress parameters. Secondly, we analyze the charge and discharge process of a series power battery pack and interpret the correlation between the capacity degradations of the battery pack and its charge/discharge rate. According to this cycling condition, we establish a capacity degradation model of a series power battery pack under inconsistent capacity of cells, and analyze the degradation mechanism with capacity variance and operating temperature difference. The comparative analysis of test results shows that the inconsistent operating temperatures of cells in the series power battery pack are the main cause of its degradation; when the difference between inconsistent temperatures is narrowed by 5 ℃, the cycle life can be improved by more than 50%. Therefore, it effectively improves the cycle life of the series battery pack to reasonably assemble the batteries according to their capacities and to narrow the differences in operating temperature among cells.展开更多
In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transform...In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transformer(ST)-based Medium Voltage(MV)grid support by means of active power control in the ST-fed Low Voltage(LV)grid.The aim of the proposed strategy is to improve the voltage profile in MV grids before the operation of On-Load Tap Changer in the primary substation transformer,which needs tens of seconds.This is realized through reactive power injection by the AC/DC MV converter and simultaneous decrease of the active power consumption of voltage-dependent loads in ST-fed LV grid,controlling the ST output voltage.The last feature has two main effects:the first is to reduce the active power withdrawn from MV grid,and consequently the MV voltage drop caused by the active current component.At the same time,higher reactive power injection capability in the MV converter is unlocked,due to the lower active power demand.As result,the ST increases the voltage support in MV grid.The analysis and simulation results carried out in this paper show improvements compared to similar solutions,i.e.the only reactive power compensation.The impact of the proposed solution has been finally evaluated under different voltage-dependence of the loads in the LV grid.展开更多
A review of three-phase PWM converter topologies which do show a low complexity/high reliability and high efficiency and power density and are therefore of main interest for a future industrial application is presente...A review of three-phase PWM converter topologies which do show a low complexity/high reliability and high efficiency and power density and are therefore of main interest for a future industrial application is presented.A three-switch/level Boost-type PWM rectifier(VIENNA Rectifier),a Buck+Boost-type PWM rectifier with wide output voltage range and the AC/AC Sparse Matrix Converter concept are discussed in detail and topics to be treated in the course of further research are identified.Finally,it is shown how the aspects being relevant for the realization of highly compact converter systems could be integrated into education in the field.展开更多
Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effec...Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effective in DC-DC converters and DC-AC converters. Controller models are set up, and the over-current limit operation principles of analogy and digital control are analyzed too. An 800VA aeronautical power supply bas been constructed to verify the performance of the proposed control strategy in various cases such as the sudden load change and the constant load. The analysis and experiments confirm the advantages of the proposed over-current limit strategies as follows： simple,effective and reliable.展开更多
Traditional power supply method for moving electric railway vehicles is based on contact type power collection technology.This sometimes cannot meet the requirements of modern rail transportation.A new wireless power ...Traditional power supply method for moving electric railway vehicles is based on contact type power collection technology.This sometimes cannot meet the requirements of modern rail transportation.A new wireless power transfer(WPT)technology can offer significant benefits in modern rail transportation particularly in some stringent environments.This paper reviews the status and the development of rail transit power supply technology,and introduces a new challenging technology--inductive power transfer(IPT)technology for rail transit.Tesla established the underpinning of IPT technology and creatively and significantly demonstrated power transfer by using highly resonant tuned coils long time ago.However,only in recent years the IPT technology has been significantly improved including the transfer air-gap length,transfer efficiency,coupling factor,power transfer capability and so on.This is mainly due to innovative semiconductor switches,higher control frequency,better coil designs and high performance material,new track and vehicle construction techniques.Recent advances in IPT for rail transit and major milestones of the developments are summarized in this paper.Some important technical issues such as coupling coil structures,power supply schemes,segmentation switching techniques for long-distance power supply,and bidirectional IPT systems for braking energy feedback are discussed.展开更多
This paper presents a PFCVF (Power Factor Correction) rectifier that uses a variable frequency source for alternators for electric and hybrid vehicles application. In such application, the frequency of the signal in t...This paper presents a PFCVF (Power Factor Correction) rectifier that uses a variable frequency source for alternators for electric and hybrid vehicles application. In such application, the frequency of the signal in the alternator changes according to the vehicle speed, more over the loading effect on the alternator introduces harmonic currents and increases the alternator apparent power requirements. To overcome these problems and aiming more stability and better design of the alternator, a new third harmonic injection technique is proposed. This technique allows to preserve a good THD (Total Harmonic Distortion) of the input source at any frequency and to decrease losses in semiconductors switches, thereby allowing more stability and reducing the apparent power requirements. A comparative study between the standard and the new technique is made and highlights the effectiveness of the new design. A detailed analysis of the proposed topology is presented and simulations as well as experimental results are shown.展开更多
Along with the rapid growth in electric vehicle(EV)market,higher power density and more efficient motor drive inverters are required.It is well known that silicon carbide(SiC)has advantages of high temperature,high ef...Along with the rapid growth in electric vehicle(EV)market,higher power density and more efficient motor drive inverters are required.It is well known that silicon carbide(SiC)has advantages of high temperature,high efficiency and high switching frequency.It is believed that the appropriate utilization of these merits can pave the way to ultra-high power density inverters.This paper presents issues about SiC chip’s current-carrying capability enhancement which is crucial for a compact inverter of tens and hundreds of kilowatts.Technical approaches towards ultra-high power density EV inverter including SiC module packaging,dc-link capacitor function analysis and system level integration are discussed.Different PWM algorithms which may improve efficiency and help to reduce the inverter volume are also studied.展开更多
Simultaneously imposed challenges of highvoltage insulation,high dv/dt,highswitching frequency,fast protection,and thermal management associated with the adoption of 10 kV SiC MOSFET,often pose nearly insurmountable b...Simultaneously imposed challenges of highvoltage insulation,high dv/dt,highswitching frequency,fast protection,and thermal management associated with the adoption of 10 kV SiC MOSFET,often pose nearly insurmountable barriers to potential users,undoubtedly hindering their penetration in mediumvoltage(MV)power conversion.Key novel technologies such as enhanced gatedriver,auxiliary power supply network,PCB planar dcbus,and highdensity inductor are presented,enabling the SiCbased designs in modular MV converters,overcoming aforementioned challenges.However,purely substituting SiC design instead of Sibased ones in modular MV converters,would expectedly yield only limited gains.Therefore,to further elevate SiCbased designs,novel highbandwidth control strategies such as switchingcycle control(SCC)and integrated capacitorblocked transistor(ICBT),as well as highperformance/highbandwidth communication network are developed.All these technologies combined,overcome barriers posed by stateoftheart Si designs and unlock system level benefits such as very high power density,highefficiency,fast dynamic response,unrestricted line frequency operation,and improved power quality,all demonstrated throughout this paper.展开更多
In this paper, a mathematical analysis of the EMI (Electromagnetic Interference) for a 20 kHz/10 kV capacitor charging power supply in frequency-domain is presented, and a related circuit model considering the transie...In this paper, a mathematical analysis of the EMI (Electromagnetic Interference) for a 20 kHz/10 kV capacitor charging power supply in frequency-domain is presented, and a related circuit model considering the transient switching interference is proposed. Due to the high working frequency and the device-switching transitions, the conducted EMI caused by the charging circuit which includes the harmonics of grid frequency, working frequency and device-switching transition frequencies. Thus under certain working situations or loads parallel power supply, the interference may cause charging failure. To solve this problem, a high frequency transformer modeled with stray capacitances and an approximation of the device-switching transition is applied in the Spice-based simulation model, and a mathematical analysis in frequency-domain is presented.展开更多
文摘PCIM China, international conference and exhibition for power electronics, was held in Shanghai on March 21, 2006. PCIM is one of the most authoritative organizations and has won good reputation overseas for a long time.
文摘We are at dawn of a new era−an era where multiple strong market and technological transformations have called for reexamination of our current electric grid.It has opened the door for new thinking about the existing grid.People have been talking about the“grid of the future”for a few years now.What should this grid look like?What should be in it and why[1]?And how do we get there?
文摘There is currently great optimism within the electronics community that gallium oxide(Ga_(2)O_(3)) ultra-wide bandgap semiconductors have unprecedented prospects for eventually revolutionizing a rich variety of power electronic applications. Specially, benefiting from its ultra-high bandgap of around 4.8 eV, it is expected that the emerging Ga_(2)O_(3) technology would offer an exciting platform to deliver massively enhanced device performance for power electronics and even completely new applications.
文摘Gallium oxide(Ga_(2)O_(3))has garnered world-wide atten-tion as an ultrawide-bandgap semiconductor material from the area of power electronics and DUV optical devices benefit-ing from its outstanding electronic and optoelectronic proper-ties.For one thing,since Ga_(2)O_(3)features high critical break-down field of 8 MV/cm and Baliga’s figure of merit(BFOM)of 3444,it is a promising candidate for advanced high-power applications.For another thing,due to the bandgap directly corresponding to the deep-ultraviolet(DUV)region,Ga_(2)O_(3)is widely used in DUV optoelectronic devices.
文摘The research in Power Electronics and Dives at The Hong Kong Polytechnic University has been undertaking for many years. Recently, a Power Electronics Research Centre (PERC) has been developed that is contributed towards the research anddevelopment in the area. It encompasses the high frequency power supplies, chaos and bifurcation, soft-switching power converters, electrical machines, high precision motion control, traction and traffic control,alternative energy and electrical building services.
基金supported by the National Natural Science Foundation of China(No.52207228)the Beijing Natural Science Foundation,China(No.3224070)the National Natural Science Foundation of China(No.52077208).
文摘The growing use of lithium-ion batteries in electric transportation and grid-scale storage systems has intensified the need for accurate and highly generalizable state-of-health(SOH)estimation.Conventional approaches often suffer from reduced accuracy under dynamically uncertain state-of-charge(SOC)operating ranges and heterogeneous aging stresses.This study presents a unified SOH estimation framework that integrates physics-informed modeling,subspace identification,and Transformer-based learning.A reduced-order model is derived from simplified electrochemical dynamics,providing an interpretable and computationally efficient representation of battery behavior.Subspace identification across a wide SOC and SOH range yields degradation-sensitive features,which the Transformer uses to capture long-range aging dynamics via multi-head self-attention.Experiments on LiFePO4 cells under joint-cell training show consistently accurate SOH estimation,with a maximum error of 1.39%,demonstrating the framework’s effectiveness in decoupling SOC and SOH effects.In cross-cell validation,where training and validation are performed on different cells,the model maintains a maximum error of 2.06%,confirming strong generalization to unseen aging trajectories.Comparative experiments on LiFePO_(4)and public LiCoO_(2)datasets confirm the framework’s cross-chemistry applicability.By extracting low-dimensional,physically interpretable features via subspace identification,the framework significantly reduces training cost while maintaining high SOH estimation accuracy,outperforming conventional data-driven models lacking physical guidance.
基金funded by Key research and development Program of Henan Province(No.251111211200)National Natural Science Foundation of China(Grant No.U2004163).
文摘Traffic sign detection is an important part of autonomous driving,and its recognition accuracy and speed are directly related to road traffic safety.Although convolutional neural networks(CNNs)have made certain breakthroughs in this field,in the face of complex scenes,such as image blur and target occlusion,the traffic sign detection continues to exhibit limited accuracy,accompanied by false positives and missed detections.To address the above problems,a traffic sign detection algorithm,You Only Look Once-based Skip Dynamic Way(YOLO-SDW)based on You Only Look Once version 8 small(YOLOv8s),is proposed.Firstly,a Skip Connection Reconstruction(SCR)module is introduced to efficiently integrate fine-grained feature information and enhance the detection accuracy of the algorithm in complex scenes.Secondly,a C2f module based on Dynamic Snake Convolution(C2f-DySnake)is proposed to dynamically adjust the receptive field information,improve the algorithm’s feature extraction ability for blurred or occluded targets,and reduce the occurrence of false detections and missed detections.Finally,the Wise Powerful IoU v2(WPIoUv2)loss function is proposed to further improve the detection accuracy of the algorithm.Experimental results show that the average precision mAP@0.5 of YOLO-SDW on the TT100K dataset is 89.2%,and mAP@0.5:0.95 is 68.5%,which is 4%and 3.3%higher than the YOLOv8s baseline,respectively.YOLO-SDW ensures real-time performance while having higher accuracy.
基金the Special Research Fund for the National Key Research and Development Program of China(No.2016YFB0100107)the National Natural Science Foundation of China(No.51677183)
文摘Electric vehicle power battery consistency is the key factor affecting the performance of power batteries. it is not scientific to evaluate the consistency of the battery depending on voltage or capacity. In this paper, multi- parameter evaluation method for battery consistency based on principal component analysis is proposed. Firstly, the characteristic parameters of battery consistency are analyzed, the principal component score can be used as the basis for evaluating the consistency of the battery. Then, the function that multi-parameter evaluation of battery consistency is established. Finally, battery balancing strategy based on fuzzy control is developed. The basic principle of fuzzy control is to fuzzy the input quantity based on expert knowledge, and the fuzzy control auantitv is obtained bv fuzzy control rule_ Th~ re.~nlt.~ ~ro v^rlfiocl hv t,~t
基金The work presented in this paper has been supported by industrial sponsors of the Colorado Power Electronics Center(CoPEC).The authors would like to acknowledge CoPEC graduate students for significant contributions to the results reported in this paper.
文摘Over the last decade,practical digital control of high-frequency switched-mode power converters has moved from proof-of-concept demonstrations to controller chips commercially available from multiple vendors,with applica-tions to point-of-load and isolated DC/DC converters,microprocessor power supplies,power-factor-correction rectifiers,and others.This paper summarizes some of the advances in the area,including approaches to realizations of high-per-formance,high-frequency digital pulse-width modulated(DPWM) controllers,related analysis,modeling and design techniques,as well as performance gains enabled by digital control such as dynamic response and efficiency improve-ments.Examples of experimentally demonstrated results are presented,together with pointers to areas of current and future research and development.
基金supported by the National Science and Technology Major Project(No.2017YFB0102302)。
文摘A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm^2 and breakdown voltage exceeding 1.5 kV is designed and fabricated.Numerical simulations are carried out to optimize the electric field strength in gate oxide and at the surface of the semiconductor material in the edge termination region.Additional n-type implantation in JFET region is implemented to reduce the specific on-resistance.The typical leakage current is less than 1μA at VDS=1.4 kV.Drain–source current reaches 50 A at VDS=0.75 V and VGS=20 V corresponding to an on-resistance of 15 mΩ.The typical gate threshold voltage is 2.6 V.
基金supported by the National Natural Science Foundation of China(Grant Nos.61004092 and 51007088)the National High Technology Research and Development Program of China(Grant Nos.2011AA11A251 and 2011AA11A262)+1 种基金the International Science&Technology Cooperation Program of China(Grant Nos.2010DFA72760 and 2011DFA70570)the Research Foundation of National Engineering Laboratory for Electric Vehicles,China(GrantNo.2012-NELEV-03)
文摘The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs. Firstly, in this paper we make use of an accelerated life test and a statistical analysis method to establish the capacity accelerated degradation model under three constant stress parameters according to the degradation data, which are charge rate, discharge rate, and operating temperature, and then we propose a capacity degradation model according to the current residual capacity of a Li-ion cell under dynamic stress parameters. Secondly, we analyze the charge and discharge process of a series power battery pack and interpret the correlation between the capacity degradations of the battery pack and its charge/discharge rate. According to this cycling condition, we establish a capacity degradation model of a series power battery pack under inconsistent capacity of cells, and analyze the degradation mechanism with capacity variance and operating temperature difference. The comparative analysis of test results shows that the inconsistent operating temperatures of cells in the series power battery pack are the main cause of its degradation; when the difference between inconsistent temperatures is narrowed by 5 ℃, the cycle life can be improved by more than 50%. Therefore, it effectively improves the cycle life of the series battery pack to reasonably assemble the batteries according to their capacities and to narrow the differences in operating temperature among cells.
基金the German Federal Ministry of Education and Research(BMBF)within the Kopernikus Project ENSURE“New ENergy grid StructURes for the German Energiewende”(03SFK1I0 and 03SFK1I0-2)the Ministry of Science,Research and the Arts of the State of Baden-Württemberg Nr.33−7533−30−10/67/1.
文摘In the last decades the voltage regulation has been challenged by the increase of power variability in the electric grid,due to the spread of non-dispatchable generation sources.This paper introduces a Smart Transformer(ST)-based Medium Voltage(MV)grid support by means of active power control in the ST-fed Low Voltage(LV)grid.The aim of the proposed strategy is to improve the voltage profile in MV grids before the operation of On-Load Tap Changer in the primary substation transformer,which needs tens of seconds.This is realized through reactive power injection by the AC/DC MV converter and simultaneous decrease of the active power consumption of voltage-dependent loads in ST-fed LV grid,controlling the ST output voltage.The last feature has two main effects:the first is to reduce the active power withdrawn from MV grid,and consequently the MV voltage drop caused by the active current component.At the same time,higher reactive power injection capability in the MV converter is unlocked,due to the lower active power demand.As result,the ST increases the voltage support in MV grid.The analysis and simulation results carried out in this paper show improvements compared to similar solutions,i.e.the only reactive power compensation.The impact of the proposed solution has been finally evaluated under different voltage-dependence of the loads in the LV grid.
文摘A review of three-phase PWM converter topologies which do show a low complexity/high reliability and high efficiency and power density and are therefore of main interest for a future industrial application is presented.A three-switch/level Boost-type PWM rectifier(VIENNA Rectifier),a Buck+Boost-type PWM rectifier with wide output voltage range and the AC/AC Sparse Matrix Converter concept are discussed in detail and topics to be treated in the course of further research are identified.Finally,it is shown how the aspects being relevant for the realization of highly compact converter systems could be integrated into education in the field.
基金the National Natural Science Foundation of China (Grant No.50237030).
文摘Some Over-Current Limit Control strategies are analyzed and designed to meet the demands of high reliability and rapid dynamic response in the aeronautical power supply applications. The control schemes are both effective in DC-DC converters and DC-AC converters. Controller models are set up, and the over-current limit operation principles of analogy and digital control are analyzed too. An 800VA aeronautical power supply bas been constructed to verify the performance of the proposed control strategy in various cases such as the sudden load change and the constant load. The analysis and experiments confirm the advantages of the proposed over-current limit strategies as follows： simple,effective and reliable.
基金This work was supported in part by the National Key R&D Program of China under Grant 2017YFB1201003.
文摘Traditional power supply method for moving electric railway vehicles is based on contact type power collection technology.This sometimes cannot meet the requirements of modern rail transportation.A new wireless power transfer(WPT)technology can offer significant benefits in modern rail transportation particularly in some stringent environments.This paper reviews the status and the development of rail transit power supply technology,and introduces a new challenging technology--inductive power transfer(IPT)technology for rail transit.Tesla established the underpinning of IPT technology and creatively and significantly demonstrated power transfer by using highly resonant tuned coils long time ago.However,only in recent years the IPT technology has been significantly improved including the transfer air-gap length,transfer efficiency,coupling factor,power transfer capability and so on.This is mainly due to innovative semiconductor switches,higher control frequency,better coil designs and high performance material,new track and vehicle construction techniques.Recent advances in IPT for rail transit and major milestones of the developments are summarized in this paper.Some important technical issues such as coupling coil structures,power supply schemes,segmentation switching techniques for long-distance power supply,and bidirectional IPT systems for braking energy feedback are discussed.
文摘This paper presents a PFCVF (Power Factor Correction) rectifier that uses a variable frequency source for alternators for electric and hybrid vehicles application. In such application, the frequency of the signal in the alternator changes according to the vehicle speed, more over the loading effect on the alternator introduces harmonic currents and increases the alternator apparent power requirements. To overcome these problems and aiming more stability and better design of the alternator, a new third harmonic injection technique is proposed. This technique allows to preserve a good THD (Total Harmonic Distortion) of the input source at any frequency and to decrease losses in semiconductors switches, thereby allowing more stability and reducing the apparent power requirements. A comparative study between the standard and the new technique is made and highlights the effectiveness of the new design. A detailed analysis of the proposed topology is presented and simulations as well as experimental results are shown.
基金This work was supported by National Key R&D Program of China(No.2016YFB0100600)。
文摘Along with the rapid growth in electric vehicle(EV)market,higher power density and more efficient motor drive inverters are required.It is well known that silicon carbide(SiC)has advantages of high temperature,high efficiency and high switching frequency.It is believed that the appropriate utilization of these merits can pave the way to ultra-high power density inverters.This paper presents issues about SiC chip’s current-carrying capability enhancement which is crucial for a compact inverter of tens and hundreds of kilowatts.Technical approaches towards ultra-high power density EV inverter including SiC module packaging,dc-link capacitor function analysis and system level integration are discussed.Different PWM algorithms which may improve efficiency and help to reduce the inverter volume are also studied.
基金conducted under ARPA-e from DOE with the award number DE-AR0000892.
文摘Simultaneously imposed challenges of highvoltage insulation,high dv/dt,highswitching frequency,fast protection,and thermal management associated with the adoption of 10 kV SiC MOSFET,often pose nearly insurmountable barriers to potential users,undoubtedly hindering their penetration in mediumvoltage(MV)power conversion.Key novel technologies such as enhanced gatedriver,auxiliary power supply network,PCB planar dcbus,and highdensity inductor are presented,enabling the SiCbased designs in modular MV converters,overcoming aforementioned challenges.However,purely substituting SiC design instead of Sibased ones in modular MV converters,would expectedly yield only limited gains.Therefore,to further elevate SiCbased designs,novel highbandwidth control strategies such as switchingcycle control(SCC)and integrated capacitorblocked transistor(ICBT),as well as highperformance/highbandwidth communication network are developed.All these technologies combined,overcome barriers posed by stateoftheart Si designs and unlock system level benefits such as very high power density,highefficiency,fast dynamic response,unrestricted line frequency operation,and improved power quality,all demonstrated throughout this paper.
文摘In this paper, a mathematical analysis of the EMI (Electromagnetic Interference) for a 20 kHz/10 kV capacitor charging power supply in frequency-domain is presented, and a related circuit model considering the transient switching interference is proposed. Due to the high working frequency and the device-switching transitions, the conducted EMI caused by the charging circuit which includes the harmonics of grid frequency, working frequency and device-switching transition frequencies. Thus under certain working situations or loads parallel power supply, the interference may cause charging failure. To solve this problem, a high frequency transformer modeled with stray capacitances and an approximation of the device-switching transition is applied in the Spice-based simulation model, and a mathematical analysis in frequency-domain is presented.
