To achieve the goal of carbon neutrality,renewable energy integration through a voltage source converter based multi-terminal direct current(VSC-MTDC)system has been identified as a promising solution.To tackle the si...To achieve the goal of carbon neutrality,renewable energy integration through a voltage source converter based multi-terminal direct current(VSC-MTDC)system has been identified as a promising solution.To tackle the significant DC voltage over-limit problem in a VSC-MTDC system during disturbances,this paper proposes a mode-switching strategy of droop control considering maximum DC voltage regulation capability.The close relationship between node injection powers and node DC voltages in the MTDC system is elaborated,and the most effective regulation approach of local injection power for limiting DC voltage deviation is presented.The operating point trajectories of different droop control explains that the DC voltage deviation can be minimized by fully utilizing the capacity of converters.Therefore,the mode-switching strategy with the maximum DC voltage regulation capability is realized by the switching between the voltage droop control and the constant maximum power control.In addition,a mode recovery process and a smooth switching method are developed to make converters regain the capability of maintaining DC voltage and reduce power fluctuation during mode switching,respectively.Furthermore,three cases are investigated to verify the effectiveness of the proposed mode-switching strategy.Compared with simulation results of the conventional droop control and the DC voltage deviation-dependent droop control,better performance of transient and steady-state DC voltage deviation is achieved through the proposed strategy.展开更多
Although room temperature ionic liquids(ILs)have emerged as potential next-generation electrolytes for their wide electrochemical stability window(ESW),the trade-off between this window and viscosity has hindered thei...Although room temperature ionic liquids(ILs)have emerged as potential next-generation electrolytes for their wide electrochemical stability window(ESW),the trade-off between this window and viscosity has hindered their widespread use in energy storage devices.Here,we present for the first time that such a trade-off can be balanced by mixing two ILs with the common anion([NTf_(2)]^(-))but different cations([EMIM]^(+) and[N1114]^(+))together.The[EMIM]cation-based IL possesses low viscosity while the[N1114]cation-based IL exhibits wide ESW.Since the concentrations of each IL in the mixtures can result in different electrolyte properties,we demonstrate a systematic approach by exploring the properties of various concentration combinations.In addition,the corresponding cell voltage of their resulting graphene supercapacitors(SCs)accompanied based on the interaction between the binary ionic liquid and the electrodes,and the associated electrochemical performance were studied to determine the optimum electrolyte system for the highest SC energy density.The well-balanced viscosity/ESW trade-off is achieved in binary IL consisting 50 vol%[EMIM][NTf_(2)]and 50 vol%[N1114][NTf_(2)]as evident from the extraordinary electrode specific capacitance of 293.1 F g^(-1) and the ultrahigh SC energy density of 177 Wh kg^(-1),which approaches that of a lithium-ion battery.展开更多
In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors (HEMTs) each with a gate-width of 2×50 μm are designed and fabricated. Their excellent DC and RF c...In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors (HEMTs) each with a gate-width of 2×50 μm are designed and fabricated. Their excellent DC and RF characterizations are demonstrated. Their full channel currents and extrinsic maximum transconductance (gm,max) values are measured to be 681 mA/mm and 952 mS/mm, respectively. The off-state gate-to-drain breakdown voltage (BVGD) defined at a gate current of-1 mA/mm is 2.85 V. Additionally, a current-gain cut-off frequency (fT) of 164 GHz and a maximum oscillation frequency (fmax) of 390 GHz are successfully obtained; moreover, the fmax of our device is one of the highest values in the reported 0.15-μm gate-length lattice-matched InP-based HEMTs operating in a millimeter wave frequency range. The high gm,max, BVGD, fmax, and channel current collectively make this device a good candidate for high frequency power applications.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 52377119 and U22B20109.
文摘To achieve the goal of carbon neutrality,renewable energy integration through a voltage source converter based multi-terminal direct current(VSC-MTDC)system has been identified as a promising solution.To tackle the significant DC voltage over-limit problem in a VSC-MTDC system during disturbances,this paper proposes a mode-switching strategy of droop control considering maximum DC voltage regulation capability.The close relationship between node injection powers and node DC voltages in the MTDC system is elaborated,and the most effective regulation approach of local injection power for limiting DC voltage deviation is presented.The operating point trajectories of different droop control explains that the DC voltage deviation can be minimized by fully utilizing the capacity of converters.Therefore,the mode-switching strategy with the maximum DC voltage regulation capability is realized by the switching between the voltage droop control and the constant maximum power control.In addition,a mode recovery process and a smooth switching method are developed to make converters regain the capability of maintaining DC voltage and reduce power fluctuation during mode switching,respectively.Furthermore,three cases are investigated to verify the effectiveness of the proposed mode-switching strategy.Compared with simulation results of the conventional droop control and the DC voltage deviation-dependent droop control,better performance of transient and steady-state DC voltage deviation is achieved through the proposed strategy.
基金Baohua Jia and Han Lin acknowledges the Australia Research Council through the Discovery Project Scheme(DP190103186,DP220100603,FT210100806)the Industrial Transformation Training Centre Scheme(Grant No.IC180100005)The authors wish to express gratitude to the Swinburne Melbourne and Swinburne Sarawak for funding this project under the‘Melbourne-Sarawak Research Collaboration Scheme’(MSRSC)grant.
文摘Although room temperature ionic liquids(ILs)have emerged as potential next-generation electrolytes for their wide electrochemical stability window(ESW),the trade-off between this window and viscosity has hindered their widespread use in energy storage devices.Here,we present for the first time that such a trade-off can be balanced by mixing two ILs with the common anion([NTf_(2)]^(-))but different cations([EMIM]^(+) and[N1114]^(+))together.The[EMIM]cation-based IL possesses low viscosity while the[N1114]cation-based IL exhibits wide ESW.Since the concentrations of each IL in the mixtures can result in different electrolyte properties,we demonstrate a systematic approach by exploring the properties of various concentration combinations.In addition,the corresponding cell voltage of their resulting graphene supercapacitors(SCs)accompanied based on the interaction between the binary ionic liquid and the electrodes,and the associated electrochemical performance were studied to determine the optimum electrolyte system for the highest SC energy density.The well-balanced viscosity/ESW trade-off is achieved in binary IL consisting 50 vol%[EMIM][NTf_(2)]and 50 vol%[N1114][NTf_(2)]as evident from the extraordinary electrode specific capacitance of 293.1 F g^(-1) and the ultrahigh SC energy density of 177 Wh kg^(-1),which approaches that of a lithium-ion battery.
基金Project supported by the National Basic Research Program of China(Grant Nos.2010CB327502 and 2010CB327505)the Advance Research Project(Grant No.5130803XXXX)
文摘In this paper, 0.15-μm gate-length In0.52Al0.48As/In0.53Ga0.47As InP-based high electron mobility transistors (HEMTs) each with a gate-width of 2×50 μm are designed and fabricated. Their excellent DC and RF characterizations are demonstrated. Their full channel currents and extrinsic maximum transconductance (gm,max) values are measured to be 681 mA/mm and 952 mS/mm, respectively. The off-state gate-to-drain breakdown voltage (BVGD) defined at a gate current of-1 mA/mm is 2.85 V. Additionally, a current-gain cut-off frequency (fT) of 164 GHz and a maximum oscillation frequency (fmax) of 390 GHz are successfully obtained; moreover, the fmax of our device is one of the highest values in the reported 0.15-μm gate-length lattice-matched InP-based HEMTs operating in a millimeter wave frequency range. The high gm,max, BVGD, fmax, and channel current collectively make this device a good candidate for high frequency power applications.