Solid-state polymer electrolytes are an important factor in the deployment of highsafety and high-energy-density solid-state lithium metal batteries.Nevertheless,use of the traditional polyethylene oxide-based solid-s...Solid-state polymer electrolytes are an important factor in the deployment of highsafety and high-energy-density solid-state lithium metal batteries.Nevertheless,use of the traditional polyethylene oxide-based solid-state polymer electrolyte is limited due to its inherently low ionic conductivity and narrow electrochemical stability window.Herein,for the first time,we specifically designed a cyanoethyl cellulosein-deep eutectic solvent composite eutectogel as a promising candidate for hybrid solid-state polymer electrolytes.It is found that the proposed eutectogel electrolyte achieves high ionic conductivity(1.87×10^(−3) S cm^(−1) at 25℃),superior electrochemical stability(up to 4.8 V),and outstanding lithium plating/striping behavior(low overpotential of 0.04 V at 1mAcm^(−2) and 1mAh cm^(−2) over 300 h).With the eutectogel-based solid-state polymer electrolyte,a 4.45 V LiCoO_(2)/Li metal battery delivers prominent long-term lifespan(capacity retention of 85%after 200 cycles)and high average Coulombic efficiency(99.5%)under ambient conditions,significantly outperforming the traditional carbonate-based liquid electrolyte.Our work demonstrates a promising strategy for designing eutectogel-based solid-state polymer electrolytes to realize high-voltage and high-energy lithium metal batteries.展开更多
In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψ...In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψf/Ld during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system.Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5 kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.展开更多
混合双馈入直流输电系统中电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)子系统对电压源换流器高压直流输电(voltage source converter based high voltage direct current,VSC-HV...混合双馈入直流输电系统中电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)子系统对电压源换流器高压直流输电(voltage source converter based high voltage direct current,VSC-HVDC)子系统运行特性的影响机理有待深入研究。首先建立了基于不同LCC-HVDC子系统控制模式的混合双馈入直流输电系统数学模型,并分析归纳了VSC-HVDC子系统的安全稳定运行约束条件和判据,提出了一种确定混合双馈入直流系统中VSC-HVDC子系统稳态运行区域的计算方法。在此基础上对比分析了VSC-HVDC子系统稳态运行区域与LCC-HVDC子系统控制模式、交流系统短路比、LCC-HVDC与VSC-HVDC容量配比之间的关系。最后,基于PSCAD/EMTDC软件搭建了混合双馈入直流系统仿真模型,仿真验证了VSC-HVDC子系统稳态运行区域计算方法的有效性。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52073298,U1706229,52072195)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21070304)the Youth Innovation Promotion Association of CAS(2020217).
文摘Solid-state polymer electrolytes are an important factor in the deployment of highsafety and high-energy-density solid-state lithium metal batteries.Nevertheless,use of the traditional polyethylene oxide-based solid-state polymer electrolyte is limited due to its inherently low ionic conductivity and narrow electrochemical stability window.Herein,for the first time,we specifically designed a cyanoethyl cellulosein-deep eutectic solvent composite eutectogel as a promising candidate for hybrid solid-state polymer electrolytes.It is found that the proposed eutectogel electrolyte achieves high ionic conductivity(1.87×10^(−3) S cm^(−1) at 25℃),superior electrochemical stability(up to 4.8 V),and outstanding lithium plating/striping behavior(low overpotential of 0.04 V at 1mAcm^(−2) and 1mAh cm^(−2) over 300 h).With the eutectogel-based solid-state polymer electrolyte,a 4.45 V LiCoO_(2)/Li metal battery delivers prominent long-term lifespan(capacity retention of 85%after 200 cycles)and high average Coulombic efficiency(99.5%)under ambient conditions,significantly outperforming the traditional carbonate-based liquid electrolyte.Our work demonstrates a promising strategy for designing eutectogel-based solid-state polymer electrolytes to realize high-voltage and high-energy lithium metal batteries.
基金supported in part by the Research Fund for the National Natural Science Foundation of China under Grant 52125701, 52007039, 51877054in part by the Key areas R&D Program of Guangdong Province China under Grant 2021B0101310001。
文摘In electrolytic capacitorless permanent magnet synchronous motor(PMSM) drives, the DC-link voltage will fluctuate in a wide range due to the use of slim film capacitor. When the flux-weakening current is lower than-ψf/Ld during the high speed operation, the flux-weakening control loop will transform to a positive feedback mode, which means the reduction of flux-weakening current will lead to the acceleration of the voltage saturation, thus the whole system will be unstable. In order to solve this issue, this paper proposes a novel flux-weakening method for electrolytic capacitorless motor drives to maintain a negative feedback characteristic of the control loop during high speed operation. Based on the analysis of the instability mechanism in flux-weakening region, a quadrature voltage constrain mechanism is constructed to stabilize the system.Meanwhile, the parameters of the controller are theoretically designed for easier industrial application. The proposed algorithm is implemented on a 1.5 kW electrolytic capacitorless PMSM drive to verify the effectiveness of the flux-weakening performance.
文摘混合双馈入直流输电系统中电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)子系统对电压源换流器高压直流输电(voltage source converter based high voltage direct current,VSC-HVDC)子系统运行特性的影响机理有待深入研究。首先建立了基于不同LCC-HVDC子系统控制模式的混合双馈入直流输电系统数学模型,并分析归纳了VSC-HVDC子系统的安全稳定运行约束条件和判据,提出了一种确定混合双馈入直流系统中VSC-HVDC子系统稳态运行区域的计算方法。在此基础上对比分析了VSC-HVDC子系统稳态运行区域与LCC-HVDC子系统控制模式、交流系统短路比、LCC-HVDC与VSC-HVDC容量配比之间的关系。最后,基于PSCAD/EMTDC软件搭建了混合双馈入直流系统仿真模型,仿真验证了VSC-HVDC子系统稳态运行区域计算方法的有效性。
