This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive p...This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive power injection effect of DFIG on transient overvoltage is firstly analyzed and the reactive power capacity evaluation of DFIG considering its de-loading operation is then conducted. In the proposed strategy, the reactive power limit of DFIG can be flexibly extended during the transient process in coordination with its active power adjustment. As a result, the transient overvoltage caused by DC bipolar block can be effectively suppressed. Moreover, key outer loop parameters such as Q-V control coefficient and deloading coefficient can be determined based on the voltage level of point of common coupling(PCC) and the available power capacity of DFIG. Finally, case studies based on MATLAB/Simulink simulation are used to verify the effectiveness of the proposed control strategy.展开更多
The Li-ion capacitors(LICs)develop rapidly due to their double-high features of high-energy density and high-power density.However,the relative low capacity of cathode and sluggish kinetics of anode seriously impede t...The Li-ion capacitors(LICs)develop rapidly due to their double-high features of high-energy density and high-power density.However,the relative low capacity of cathode and sluggish kinetics of anode seriously impede the development of LICs.Herein,the precisely pore-engineered and heteroatomtailored defective hierarchical porous carbons(DHPCs)as large-capacity cathode and high-rate anode to construct high-performance dual-carbon LICs have been developed.The DHPCs are prepared based on triple-activation mechanisms by direct pyrolysis of sustainable lignin with urea to generate the interconnected hierarchical porous structure and plentiful heteroatominduced defects.Benefiting from these advanced merits,DHPCs show the well-matched high capacity and fast kinetics of both cathode and anode,exhibiting large capacities,superior rate capability and long-term lifespan.Both experimental and computational results demonstrate the strong synergistic effect of pore and dopants for Li storage.Consequently,the assembled dual-carbon LIC exhibits high voltage of 4.5 V,high-energy density of 208 Wh kg^(−1),ultrahigh power density of 53.4 kW kg^(−1)and almost zerodecrement cycling lifetime.Impressively,the full device with high mass loading of 9.4 mg cm^(−2)on cathode still outputs high-energy density of 187 Wh kg^(−1),demonstrative of their potential as electrode materials for high-performance electrochemical devices.展开更多
Mechanochemical reactions at the sliding interface between a single-crystalline silicon(Si)wafer and a silica(SiO2)microsphere were studied in three environmental conditions:humid air,potassium chloride(KCl)solution,a...Mechanochemical reactions at the sliding interface between a single-crystalline silicon(Si)wafer and a silica(SiO2)microsphere were studied in three environmental conditions:humid air,potassium chloride(KCl)solution,and KCl solution with an applied voltage.Compared to that from humid air,mechanochemical material removal from the silicon surface increased substantially in the KCl-immersed condition,and further increased when electrochemistry was introduced into the tribological system.By measuring the load dependence of the material removal rate and analyzing the results using a mechanically assisted Arrhenius-type kinetic model,the activation energy(E_(a))and the mechanical energy(E_(m)),by which this energy is reduced by mechanical activation,were compared qualitatively under different environmental conditions.In the KCl-immersed condition,mechanochemistry may decrease the required effective energy of reactions(E_(eff)=E_(a)−E_(m))and promote material removal mainly through improved catalysis of the mechanochemical reactions facilitated by greater availability of water molecules compared to the humid air condition.Thus,the effectiveness of the mechanochemistry is improved.In the electrochemical condition,electrochemically-accelerated oxidation of the silicon surface was confirmed by the X-ray photoelectron spectroscopy(XPS)characterization.The results strongly suggest that electrochemistry further stimulates mechanochemical reactions primarily by increasing the initial energy state of the surface via the facilitated formation of interfacial bonding bridges,i.e.,a surface oxidation/hydroxylation process.展开更多
基金jointly supported by the National Natural Science Foundation of China (No.51677165,No.51837004)the National Key R&D Program of China (No.2017YFB0902000)。
文摘This paper presents a P-Q coordination based highvoltage ride through(HVRT) control strategy for doubly fed induction generators(DFIGs) based on a combined Q-V control and P-V de-loading control. The active/reactive power injection effect of DFIG on transient overvoltage is firstly analyzed and the reactive power capacity evaluation of DFIG considering its de-loading operation is then conducted. In the proposed strategy, the reactive power limit of DFIG can be flexibly extended during the transient process in coordination with its active power adjustment. As a result, the transient overvoltage caused by DC bipolar block can be effectively suppressed. Moreover, key outer loop parameters such as Q-V control coefficient and deloading coefficient can be determined based on the voltage level of point of common coupling(PCC) and the available power capacity of DFIG. Finally, case studies based on MATLAB/Simulink simulation are used to verify the effectiveness of the proposed control strategy.
基金financialy supported by National Natural Science Foundation of China(Grants 22005298,22125903,51872283,22075279,22279137)Dalian Innovation Support Plan for High Level Talents(2019RT09)+3 种基金Dalian National Laboratory For Clean Energy(DNL),CAS,DNL Cooperation Fund,CAS(DNL201912,DNL201915,DNL202016,DNL202019),DICP(DICP I2020032)The Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLUDNL Fund 2021002,YLU-DNL Fund 2021009)Suzhou University Scientific Research Platform(2021XJPT07)China Postdoctoral Science Foundation(2019 M661141)
文摘The Li-ion capacitors(LICs)develop rapidly due to their double-high features of high-energy density and high-power density.However,the relative low capacity of cathode and sluggish kinetics of anode seriously impede the development of LICs.Herein,the precisely pore-engineered and heteroatomtailored defective hierarchical porous carbons(DHPCs)as large-capacity cathode and high-rate anode to construct high-performance dual-carbon LICs have been developed.The DHPCs are prepared based on triple-activation mechanisms by direct pyrolysis of sustainable lignin with urea to generate the interconnected hierarchical porous structure and plentiful heteroatominduced defects.Benefiting from these advanced merits,DHPCs show the well-matched high capacity and fast kinetics of both cathode and anode,exhibiting large capacities,superior rate capability and long-term lifespan.Both experimental and computational results demonstrate the strong synergistic effect of pore and dopants for Li storage.Consequently,the assembled dual-carbon LIC exhibits high voltage of 4.5 V,high-energy density of 208 Wh kg^(−1),ultrahigh power density of 53.4 kW kg^(−1)and almost zerodecrement cycling lifetime.Impressively,the full device with high mass loading of 9.4 mg cm^(−2)on cathode still outputs high-energy density of 187 Wh kg^(−1),demonstrative of their potential as electrode materials for high-performance electrochemical devices.
基金This work has been carried out at Advanced Research Center for Nanolithography(ARCNL),a public-private partnership of University of Amsterdam(UvA),Vrije University Amsterdam(VU),the Dutch Research Council(NWO),and the semiconductor equipment manufacturer(Advanced Semiconductor Material Lithography(ASML)).Bart WEBER acknowledges funding from the NWO VENI(Grant No.VI.Veni.192.177).
文摘Mechanochemical reactions at the sliding interface between a single-crystalline silicon(Si)wafer and a silica(SiO2)microsphere were studied in three environmental conditions:humid air,potassium chloride(KCl)solution,and KCl solution with an applied voltage.Compared to that from humid air,mechanochemical material removal from the silicon surface increased substantially in the KCl-immersed condition,and further increased when electrochemistry was introduced into the tribological system.By measuring the load dependence of the material removal rate and analyzing the results using a mechanically assisted Arrhenius-type kinetic model,the activation energy(E_(a))and the mechanical energy(E_(m)),by which this energy is reduced by mechanical activation,were compared qualitatively under different environmental conditions.In the KCl-immersed condition,mechanochemistry may decrease the required effective energy of reactions(E_(eff)=E_(a)−E_(m))and promote material removal mainly through improved catalysis of the mechanochemical reactions facilitated by greater availability of water molecules compared to the humid air condition.Thus,the effectiveness of the mechanochemistry is improved.In the electrochemical condition,electrochemically-accelerated oxidation of the silicon surface was confirmed by the X-ray photoelectron spectroscopy(XPS)characterization.The results strongly suggest that electrochemistry further stimulates mechanochemical reactions primarily by increasing the initial energy state of the surface via the facilitated formation of interfacial bonding bridges,i.e.,a surface oxidation/hydroxylation process.
