Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the...Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the internet of things(IoT)sensor nodes and energy harvesting[2].Mean-while,considering that capacitor has a much higher energy density than inductor,high-power applications.展开更多
Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique wa...Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.展开更多
Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challeng...Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.展开更多
In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effec...In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.展开更多
In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To ...In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.展开更多
随着宽禁带功率半导体器件的广泛使用,更高开关频率的双有源桥(dual active bridge,DAB)变换器带来了更大的开关损耗,对于软开关技术提出更高要求。为了进一步拓展零电压开通(zero-voltage switching,ZVS)范围,文中对ZVS精确模型和传统...随着宽禁带功率半导体器件的广泛使用,更高开关频率的双有源桥(dual active bridge,DAB)变换器带来了更大的开关损耗,对于软开关技术提出更高要求。为了进一步拓展零电压开通(zero-voltage switching,ZVS)范围,文中对ZVS精确模型和传统电感电流全局最优条件方法进行分析,提出一种结合励磁电流运行的移相调制策略,该策略可实现DAB变换器全功率范围内所有开关管的ZVS运行(8-ZVS运行)。在考虑开关管非线性特性和死区时间限制基础上得到更精确的ZVS模型,并推导引入励磁电流的ZVS模型。此外,所提出的控制方案具有无缝模式转换的特点,电感电流的有效值也可以达到准最佳状态。最后,搭建6kW/150kHz的高频DAB变换器样机以验证模型有效性。实验结果表明,该控制算法可以在任意模式和工况下实现8-ZVS运行,从而提升系统在轻载和中载工况下运行效率。展开更多
A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching (ZVS) PWM converter based on phase and amplitude control (PAC), w...A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching (ZVS) PWM converter based on phase and amplitude control (PAC), when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes.展开更多
零电压开通变频控制(variable frequency controlled zero-voltage-switching,VF-ZVS)可在无辅助电路条件下实现零电压开通(zero-voltage-switching,ZVS),进一步提升碳化硅MOSFET逆变器的功率密度。但在三相有源中点钳位逆变器(active-n...零电压开通变频控制(variable frequency controlled zero-voltage-switching,VF-ZVS)可在无辅助电路条件下实现零电压开通(zero-voltage-switching,ZVS),进一步提升碳化硅MOSFET逆变器的功率密度。但在三相有源中点钳位逆变器(active-neural-point-converter,ANPC)中,全功率器件ZVS会大幅增加输出电感电流纹波,改变ANPC逆变器的电流续流路径,影响SiC器件损耗分布特征。论文建立电流纹波关于矢量作用时间的分段数学表达式,提出计及电流纹波的SiC器件损耗建模方法,表征VF-ZVS控制下电流纹波对开关管损耗特性的影响规律。进一步,分析VF-ZVS控制下2SiC、4SiC I和4SiC II 3种典型混合ANPC拓扑的新增工作模态特性;利用所提出的损耗模型,评估在不同调制度、全功率等级下上述3种混合拓扑的开关损耗、通态损耗和损耗分布均衡度,并通过6kW SiC实验平台,在不同功率等级下实验验证了SiC器件损耗模型和3种混合拓扑损耗评估结果的正确性。展开更多
With the increasing awareness of environmental protection, people’s concern of pollution issues arising. Vehicles, as the most important means of transportation, its exhaust emission has received considerable attenti...With the increasing awareness of environmental protection, people’s concern of pollution issues arising. Vehicles, as the most important means of transportation, its exhaust emission has received considerable attention. The catalytic converter is able to purify harmful substances in exhaust gas. The absolute content of precious metals in the catalytic converter dominates the exhaust gas purification effect. Accurate detection of precious metal content is of great significance for controlling the cost of catalysts, ensuring catalytic performance and recovering precious metals from spent catalysts. We herein summarized several instruments for precious metals content exploration, such as X-ray fluorescence spectrometer (XRF), atomic absorption spectrometer (AAS), inductively coupled plasma emission spectrometer (ICP) and spectrophotometer. In this thesis, the feasibility of using various devices for characterizing precious metal content in catalytic converters is analyzed and their strengths or weaknesses are elaborated.展开更多
In the modern wireless communication system,the manipulation for polarization of electromagnetic wave plays a important role in improving the capacity and reliability of communication.In this paper,a multifunctional p...In the modern wireless communication system,the manipulation for polarization of electromagnetic wave plays a important role in improving the capacity and reliability of communication.In this paper,a multifunctional polarization converter(MFPC)based on the multilayer reconfigurable metasurface is proposed,which can assist the source antenna to transmit and receive multiple polarization signals.The MFPC consists of a grating which can filter out the undesired polarization and four layers of metasurfaces incorporated with PIN diodes.The functions of the MFPC include LTC and LTL polarization conversions,co-polarization transmission and reflection for arbitrary polarization.By changing the states of PIN diodes,the functions of MFPC can be dynamically switched.Loaded on the aperture of source antenna,the proposed MFPC can serve as a transmissive array with multiple polarization channels,and can also provide EM protection for source antenna by reflecting the incoming interference waves.Cascading of the metasurfaces produces Fabry-Perot resonance in the MFPC,and it contributes to the realization of LTC and LTL polarization conversions.To verify the performance of the proposed MFPC,the prototype is fabricated and tested.The measured results show that the fractional bandwidths of four functions are all higher than 31.9% with transmission or reflection coefficients higher than-2 d B.The frequency band of each function is mainly concentrated in S-band.The measured data are in agreement with the simulated results.展开更多
We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward cur...We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward current of 8 A with a forward volt-age of 5 V,and has a reverse breakdown voltage of 612 V.The forward turn-on voltage(VF)and the on-resistance(Ron)are 1.17 V and 0.46Ω,respectively.The conversion efficiency of theβ-Ga_(2)O_(3)SBD-based DC-DC converter is 95.81%.This work indicates the great potential of Ga_(2)O_(3)SBDs and relevant circuits in power electronic applications.展开更多
In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on out...In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.展开更多
This work focuses on the fuzzy controller for the proposed three-phase interleaved Step-up converter(ISC).The fuzzy controller for the proposed ISC converters for electric vehicles has been discussed in detail.The pro...This work focuses on the fuzzy controller for the proposed three-phase interleaved Step-up converter(ISC).The fuzzy controller for the proposed ISC converters for electric vehicles has been discussed in detail.The proposed ISC direct current(DC-DC)converter could also be used in automobiles,satellites,industries,and propulsion.To enhance voltage gain,the proposed ISC Converter combines boost converter and interleaved converter(IC).This design also reduces the number of switches.As a result,ISC converter switching losses are reduced.The proposed ISC Converter topology can produce a 143 V output voltage and 1 kW of power.Due to the high voltage gain of this converter design,it is suitable for medium and high-power systems.The proposed ISC Converter topology is simulated in MATLAB/Simulink.The simulated output displays a high output voltage.But the output voltage contains maximum ripples.Fuzzy proposes an ISC Converter which makes closed loop responsiveness and reduces the output voltage ripple.The proposed ISC converter has the lowest ripple output voltage,which is less than 2%,because the duty cycle is regulated using the fuzzy logic controller.It offers high voltage gain,minimal ripple,and low switching loss.The performance of the proposed converter is compared to that of the fuzzy and Pro-portional Integral(PI)controllers implemented in MATLAB.展开更多
双有源桥(Dual Active Bridge,DAB)在需要高效能量双向流动的工作场景有广泛的应用。在高开关频率工作时,变换器开关器件结电容充放电时间无法忽略,导致扩展移相控制下DAB零电压开通(Zero Voltage Switching,ZVS)范围断续。通过分析扩...双有源桥(Dual Active Bridge,DAB)在需要高效能量双向流动的工作场景有广泛的应用。在高开关频率工作时,变换器开关器件结电容充放电时间无法忽略,导致扩展移相控制下DAB零电压开通(Zero Voltage Switching,ZVS)范围断续。通过分析扩展移相控制下双有源桥DC-DC变换器工作模态,建立高开关频率工况下DAB变换器数学模型,提出一种利用磁化电流扩宽ZVS范围的方法。在此基础上,结合电感电流应力优化算法,提出一种适用于高频工况应用的电流应力优化下的软开关控制策略。采用该控制策略,可以有效减小导通损耗,消除开关损耗,显著提升高开关频率下的变换器效率。搭建400 kHz实验样机,验证控制策略有效性。展开更多
基金This work is supported by the Macao Science and Technology Development Fund(FDCT)under Grant 0041/2022/A1by the Research Committee of University of Macao under Grant MYRG2022-00004-IME.
文摘Switched-capacitor(SC)DC-DC converter[1]is an impor-tant alternative to inductive DC-DC converter,in terms of removing the bulky power inductor.Hence,it is widely used in low-profile,low-power applications,such as the internet of things(IoT)sensor nodes and energy harvesting[2].Mean-while,considering that capacitor has a much higher energy density than inductor,high-power applications.
文摘Code converters are essential in digital nano communication;therefore,a low-complexity optimal QCA layout for a BCD to Excess-3 code converter has been proposed in this paper.A QCA clockphase-based design technique was adopted to investigate integration with other complicated circuits.Using a unique XOR gate,the recommended circuit’s cell complexity has been decreased.The findings produced using the QCADesigner-2.0.3,a reliable simulation tool,prove the effectiveness of the current structure over earlier designs by considering the number of cells deployed,the area occupied,and the latency as design metrics.In addition,the popular tool QCAPro was used to estimate the energy dissipation of the proposed design.The proposed technique reduces the occupied space by∼40%,improves cell complexity by∼20%,and reduces energy dissipation by∼1.8 times(atγ=1.5EK)compared to the current scalable designs.This paper also studied the suggested structure’s energy dissipation and compared it to existing works for a better performance evaluation.
基金Project supported by the National Undergraduate Training Projects for Innovation and Entrepreneurship (Grant No. 5003182007)the National Natural Science Foundation of China (Grant No. 12074137)+1 种基金the National Key Research and Development Project of China (Grant No. 2021YFB2801903)the Natural Science Foundation from the Science,Technology,and Innovation Commission of Shenzhen Municipality (Grant No. JCYJ20220530161010023)。
文摘Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.
基金This work was supported by China Railway Corporation Science and Technology Research and Development Project(P2021J038).
文摘In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.
基金funded by the National Natural Science Foundation of China(52067013),and the Provincial Natural Science Foundation of Gansu(20JR5RA395).
文摘In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.
文摘随着宽禁带功率半导体器件的广泛使用,更高开关频率的双有源桥(dual active bridge,DAB)变换器带来了更大的开关损耗,对于软开关技术提出更高要求。为了进一步拓展零电压开通(zero-voltage switching,ZVS)范围,文中对ZVS精确模型和传统电感电流全局最优条件方法进行分析,提出一种结合励磁电流运行的移相调制策略,该策略可实现DAB变换器全功率范围内所有开关管的ZVS运行(8-ZVS运行)。在考虑开关管非线性特性和死区时间限制基础上得到更精确的ZVS模型,并推导引入励磁电流的ZVS模型。此外,所提出的控制方案具有无缝模式转换的特点,电感电流的有效值也可以达到准最佳状态。最后,搭建6kW/150kHz的高频DAB变换器样机以验证模型有效性。实验结果表明,该控制算法可以在任意模式和工况下实现8-ZVS运行,从而提升系统在轻载和中载工况下运行效率。
基金Project supported by Shanghai Leading Academic DisciplineProject (Grant No .T0103) ,and Shanghai Post Doctoral Scienti-fic Research (Grant No .05R214122)
文摘A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching (ZVS) PWM converter based on phase and amplitude control (PAC), when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes.
文摘零电压开通变频控制(variable frequency controlled zero-voltage-switching,VF-ZVS)可在无辅助电路条件下实现零电压开通(zero-voltage-switching,ZVS),进一步提升碳化硅MOSFET逆变器的功率密度。但在三相有源中点钳位逆变器(active-neural-point-converter,ANPC)中,全功率器件ZVS会大幅增加输出电感电流纹波,改变ANPC逆变器的电流续流路径,影响SiC器件损耗分布特征。论文建立电流纹波关于矢量作用时间的分段数学表达式,提出计及电流纹波的SiC器件损耗建模方法,表征VF-ZVS控制下电流纹波对开关管损耗特性的影响规律。进一步,分析VF-ZVS控制下2SiC、4SiC I和4SiC II 3种典型混合ANPC拓扑的新增工作模态特性;利用所提出的损耗模型,评估在不同调制度、全功率等级下上述3种混合拓扑的开关损耗、通态损耗和损耗分布均衡度,并通过6kW SiC实验平台,在不同功率等级下实验验证了SiC器件损耗模型和3种混合拓扑损耗评估结果的正确性。
文摘With the increasing awareness of environmental protection, people’s concern of pollution issues arising. Vehicles, as the most important means of transportation, its exhaust emission has received considerable attention. The catalytic converter is able to purify harmful substances in exhaust gas. The absolute content of precious metals in the catalytic converter dominates the exhaust gas purification effect. Accurate detection of precious metal content is of great significance for controlling the cost of catalysts, ensuring catalytic performance and recovering precious metals from spent catalysts. We herein summarized several instruments for precious metals content exploration, such as X-ray fluorescence spectrometer (XRF), atomic absorption spectrometer (AAS), inductively coupled plasma emission spectrometer (ICP) and spectrophotometer. In this thesis, the feasibility of using various devices for characterizing precious metal content in catalytic converters is analyzed and their strengths or weaknesses are elaborated.
基金supported in part by the Joint Funds of the National Natural Science Foundation of China(G02)(Grant No.U1834203)in part by of the Science and Technology Department of Sichuan Province(S01)(Grant No.2020JDTD0009)。
文摘In the modern wireless communication system,the manipulation for polarization of electromagnetic wave plays a important role in improving the capacity and reliability of communication.In this paper,a multifunctional polarization converter(MFPC)based on the multilayer reconfigurable metasurface is proposed,which can assist the source antenna to transmit and receive multiple polarization signals.The MFPC consists of a grating which can filter out the undesired polarization and four layers of metasurfaces incorporated with PIN diodes.The functions of the MFPC include LTC and LTL polarization conversions,co-polarization transmission and reflection for arbitrary polarization.By changing the states of PIN diodes,the functions of MFPC can be dynamically switched.Loaded on the aperture of source antenna,the proposed MFPC can serve as a transmissive array with multiple polarization channels,and can also provide EM protection for source antenna by reflecting the incoming interference waves.Cascading of the metasurfaces produces Fabry-Perot resonance in the MFPC,and it contributes to the realization of LTC and LTL polarization conversions.To verify the performance of the proposed MFPC,the prototype is fabricated and tested.The measured results show that the fractional bandwidths of four functions are all higher than 31.9% with transmission or reflection coefficients higher than-2 d B.The frequency band of each function is mainly concentrated in S-band.The measured data are in agreement with the simulated results.
基金supported by the National Natural Science Foundation of China (NSFC) under Grant Nos. 61925110, 61821091, 62004184 and 62234007the Key-Area Research and Development Program of Guangdong Province under Grant No. 2020B010174002
文摘We demonstrate superb large-area verticalβ-Ga_(2)O_(3)SBDs with a Schottky contact area of 1×1 mm^(2)and obtain a high-efficiency DC-DC converter based on the device.Theβ-Ga_(2)O_(3)SBD can obtain a forward current of 8 A with a forward volt-age of 5 V,and has a reverse breakdown voltage of 612 V.The forward turn-on voltage(VF)and the on-resistance(Ron)are 1.17 V and 0.46Ω,respectively.The conversion efficiency of theβ-Ga_(2)O_(3)SBD-based DC-DC converter is 95.81%.This work indicates the great potential of Ga_(2)O_(3)SBDs and relevant circuits in power electronic applications.
文摘In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.
文摘This work focuses on the fuzzy controller for the proposed three-phase interleaved Step-up converter(ISC).The fuzzy controller for the proposed ISC converters for electric vehicles has been discussed in detail.The proposed ISC direct current(DC-DC)converter could also be used in automobiles,satellites,industries,and propulsion.To enhance voltage gain,the proposed ISC Converter combines boost converter and interleaved converter(IC).This design also reduces the number of switches.As a result,ISC converter switching losses are reduced.The proposed ISC Converter topology can produce a 143 V output voltage and 1 kW of power.Due to the high voltage gain of this converter design,it is suitable for medium and high-power systems.The proposed ISC Converter topology is simulated in MATLAB/Simulink.The simulated output displays a high output voltage.But the output voltage contains maximum ripples.Fuzzy proposes an ISC Converter which makes closed loop responsiveness and reduces the output voltage ripple.The proposed ISC converter has the lowest ripple output voltage,which is less than 2%,because the duty cycle is regulated using the fuzzy logic controller.It offers high voltage gain,minimal ripple,and low switching loss.The performance of the proposed converter is compared to that of the fuzzy and Pro-portional Integral(PI)controllers implemented in MATLAB.
文摘双有源桥(Dual Active Bridge,DAB)在需要高效能量双向流动的工作场景有广泛的应用。在高开关频率工作时,变换器开关器件结电容充放电时间无法忽略,导致扩展移相控制下DAB零电压开通(Zero Voltage Switching,ZVS)范围断续。通过分析扩展移相控制下双有源桥DC-DC变换器工作模态,建立高开关频率工况下DAB变换器数学模型,提出一种利用磁化电流扩宽ZVS范围的方法。在此基础上,结合电感电流应力优化算法,提出一种适用于高频工况应用的电流应力优化下的软开关控制策略。采用该控制策略,可以有效减小导通损耗,消除开关损耗,显著提升高开关频率下的变换器效率。搭建400 kHz实验样机,验证控制策略有效性。