An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization p...An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization process. The parameters of the model are identified using combined experimental and extended Kalman filter (EKF) recursive methods. The open-circuit voltage and ohmic resistance of the battery are directly measured and calculated from experimental measurements, respectively. The rest of the coupled dynamic parameters, i.e. the RC network parameters, are estimated using the EKF method. Experimental and simulation results are presented to demonstrate the efficacy of the proposed circuit model and parameter identification techniques for simulating battery dynamics.展开更多
The adaptive H_∞ control problem of multi-machine power system in the case of disturbances and uncertain parameters is discussed,based on a Hamiltonian model.Considered the effect of time delay during control and tra...The adaptive H_∞ control problem of multi-machine power system in the case of disturbances and uncertain parameters is discussed,based on a Hamiltonian model.Considered the effect of time delay during control and transmission,a Hamilton model with control time delay is established.Lyapunov-Krasovskii function is selected,and a controller which makes the system asymptotically stable is got.The controller not only achieves the stability control for nonlinear systems with time delay,but also has the ability to suppress the external disturbances and adaptive ability to system parameter perturbation.The simulation results show the effect of the controller.展开更多
Kdesorption from soils in a constant electric field(field strength:44.5Vcm-1) by means of electro-ultrafil-tration (EUF) followed second-order kinetics and could be described by the equation dd/dt = k(D-d)2. From thee...Kdesorption from soils in a constant electric field(field strength:44.5Vcm-1) by means of electro-ultrafil-tration (EUF) followed second-order kinetics and could be described by the equation dd/dt = k(D-d)2. From theequation, such kinetic parameters relating to K desorption from soils as the maximum desorbable quantity D, quantity of K desorbed within 40 minutes d40, initial desorption rate Vo, desorption rate constant k and half-time t1/2 could be calculated. An expression which describes the relationships between the kinetic parameters on the one hand and the responses of barley to fertilizer-K in the field experiments in different sites and the potassium-supplying power of soils on the other was established. Vo, D and d40 were significantly correlated with barley relative yield, K uptake by barley and the content of soil available potassium. The rate constants of K desorption varied between 4.42 × 10-4-1.80 × 10-3kg mg-1 min-1 and highly correlated with the relative yield of barley. The kinetic parameters including Vo, D, d40 and k were successfully used to estimate the K-supplying power of soils.展开更多
There is a certain coupling relationship among the main circuit parameters of a single-phase shunt active power filter(SAPF),which has a great influence on the reasonable selection of various parameter values.By analy...There is a certain coupling relationship among the main circuit parameters of a single-phase shunt active power filter(SAPF),which has a great influence on the reasonable selection of various parameter values.By analyzing the calculation methods of the inductance of alternating current(AC)side and the voltage and capacitance values of direct current(DC)side in the existing single/three-phase SAPF main circuit,a specific single-phase SAPF circuit parameter analytical expression was obtained.Aiming at the coupling relationship among the variables in the resulting expression,the model was optimized and analyzed in MATLAB,and a complete set of parameters design scheme was obtained,which ensure the comprehensive optimization target of the post-harmonic content below 2% is compensated under a specific load.The simulation and experimental procedures verify the correctness of the selected parameters.展开更多
The main objective of electricity regulators when establishing electricity markets is to decrease the cost of electricity through competition. However, this scenario cannot be achieved without a full participation of ...The main objective of electricity regulators when establishing electricity markets is to decrease the cost of electricity through competition. However, this scenario cannot be achieved without a full participation of the electricity demand by reacting against electricity prices. The aim of this research is to develop tools for helping customers and aggregators to join price and demand response programs, while helping them to hedge against the risk of short-term price volatility. In this way, the capacity of and hybrid methodology (Self-Organizing Maps and Statistical Ward's Linkage) to classify high electricity market prices is analysed. Besides, with the help of Non-Parametric Estimation, some price-patterns were found in the abovementioned clusters. The contained knowledge within these patterns supplies customer market-based information on which to base its energy use decisions. The interest for this participation of customers in markets is growing in developed countries to obtain a higher elasticity in demand. Results show the capability of this approach to improve data management and select coherent policies to accomplish cleared demand offers amongst different price scenarios in a more flexible way.展开更多
We investigate the in-medium interparticle potential of hot gauge system with bound states by employing the QED and scalar QED coupling. At the finite temperature an oscillatory behavior of the potential has been foun...We investigate the in-medium interparticle potential of hot gauge system with bound states by employing the QED and scalar QED coupling. At the finite temperature an oscillatory behavior of the potential has been found as well as its variation in terms of different free parameters. We expect the competition among the parameters will lead to an appropriate interparticle potential, which could be extended to discuss the fluid properties of QGP with scalar bound states.展开更多
In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we ...In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.展开更多
Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driv...Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driveline gear ratio and battery parameters are determined. And then a two-level optimization problem is formulated based on analytical target cascading (ATC). At the system level, the optimization of the whole vehicle fuel economy is carried out, while the tractive performance is defined as the constraints. The optimized parameters are cascaded to the subsystem as the optimization targets. At the subsystem level, the final drive and transmission design are optimized to make the ratios as close to the targets as possible. The optimization result shows that the fuel economy had improved significantly, while the tractive performance maintains the former level.展开更多
Nonlinear vibration can cause serious problems in long span cable-stayed bridges.When the internal resonance threshold is reached between the excitation frequency and natural frequency,large amplitudes occur in the ca...Nonlinear vibration can cause serious problems in long span cable-stayed bridges.When the internal resonance threshold is reached between the excitation frequency and natural frequency,large amplitudes occur in the cable.Based on the current situation of lacking corresponding constraint criteria,a model was presented for analyzing the dynamic reliability of coupling oscillation between the cable and tower in a cable-stayed bridge.First of all,in the case of cable sag,the d'Alembert principle is applied to studying the nonlinear dynamic behavior of the structure,and resonance failure interval of parametric oscillation is calculated accordingly.Then the dynamic reliability model is set up using the JC method.An application of this model has been developed for the preliminary design of one cable-stayed bridge located on Hai River in Tianjin,and time histories analysis as well as reliability indexes have been obtained.When frequency ratio between the cable and tower is approaching 1∶2,the reliability index is 0.98,indicating high failure probability.And this is consistent with theoretical derivation and experimental results in reference.This model,which is capable of computing the reliability index of resonance failure,provides theoretical basis for the establishment of corresponding rule.展开更多
Destructions at Fukushima Daiichi NPP (nuclear power plant) caused by earthquake have shown that design level of seismic influences on the equipment has been exceeded. The accident demonstrated the need for stricter...Destructions at Fukushima Daiichi NPP (nuclear power plant) caused by earthquake have shown that design level of seismic influences on the equipment has been exceeded. The accident demonstrated the need for stricter regulations to ensure the seismic resistance of NPP and the need to develop and implement additional anti-seismic procedures in the course of their operation. To proof seismic reliability of NPP systems and components must be made special studies of logarithmic decrement of systems NPP and components. The correct definition of coolant thermodynamics parameters and acoustic parameters are necessary to evaluate logarithmic decrement of coolant systems NPP and their components and consequently for providing of NPP seismic reliability. The proof of presence of a gas phase in the coolant inside reactor is of great importance for practice because of its influence on coolant acoustical parameters and consequently on range of frequency of seismic-acoustical resonance type interaction. Results are obtained by using of known methods in oscillation theory, general acoustics, thermodynamic, electro-mechanical analogies. As well as using experimental data obtained from the vibration dynamical controls reactor WWER-1000.展开更多
Interaction of Aristolochic acid (AA) and guanine (G) was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased...Interaction of Aristolochic acid (AA) and guanine (G) was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased, while the peak potential and the electrochemical kinetic parameters remained the same as when AA was absent, except that the electrode process of guanine that involved two protons and two electrons changed from adsorption controlled to diffusion controlled. It is suggested that an electrochemical inactive supramolecular adduct AA-Gua (1:1) was formed in the system. The adduct cannot be oxidized on the glassy carbon electrode, which indirectly results in the decrease of the free concentration of guanine in the reaction solution and the decrease of peak currents. The binding constant (13) of this adduct is calculated as 7.14× 10^3 mol/L. The possible mechanism for the interaction of Aristolochic acid and DNA was proposed, that may provide a possible pathway for the nosogenesis research of aristolochic acid.展开更多
Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various tempera...Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various temperatures.Electrochemical reaction kinetic parameters were also studied with proper electrochemical techniques.The influence of the secondary corrosion reaction on the anodic linear polarization measurement was also analyzed by theoretical simulation.The results show that,proper ball-milling with nickel powders is beneficial to electrochemical performance.The theoretical simulation proves that,the existence of the side reaction can disturb the measurement of electrochemical reaction kinetic parameters.展开更多
This work deals with a description of a parametric tool for elastic analysis of wind turbine tower, incorporating all analysis steps (preprocessing, processing and post-processing). The tower geometry is approximate...This work deals with a description of a parametric tool for elastic analysis of wind turbine tower, incorporating all analysis steps (preprocessing, processing and post-processing). The tower geometry is approximated by fiat elements in which the membrane effects are evaluated using the FF (free formulation) finite element and the flexure effects are calculated using DKT (discrete shear triangle) finite element. The user-friendly system is implemented using OpenGL library to provide the graphical construction for geometry, mesh orientation, and other requirements of the finite element model. For the processing stage is built a specific dll library implemented in C++ language for the analysis using the FF and DKT finite elements. The post-processing stage is build using specific dialogs box to present all results. The displacement results are visualized in the graphic interface to show the static and dynamic deformations of the tower. Some examples are presented to show all the tasks of the parametric tool.展开更多
The effect of line voltage drop is considered larger on loads, especially on asynchronous motor, transformers and other non-linear load parameters in power system of large ships. A novel power flow method based on imp...The effect of line voltage drop is considered larger on loads, especially on asynchronous motor, transformers and other non-linear load parameters in power system of large ships. A novel power flow method based on improved node voltage method is proposed, and a typical ship power system, which has 2 power stations and 10 nodes, with closed-loop design but open-loop operation, is taken as an example. Simulation results show that the improved power flow calculation method has achieved higher accuracy and better convergence.展开更多
This paper presents the model of a SVC (Static VAR Compensator) which is controlled externally by a PI (Proportional Integral) & PD (Proportional Differential) controllers for the improvements of voltage stabil...This paper presents the model of a SVC (Static VAR Compensator) which is controlled externally by a PI (Proportional Integral) & PD (Proportional Differential) controllers for the improvements of voltage stability and damping effect of an on line power system. Both controller parameters has been optimized by using Ziegler-Nichols close loop tuning method. Both single phase and three phase (L-L) faults have been considered in the research. In this paper, a power system network is considered which is simulated in the phasor simulation method & the network is simulated in four steps; without SVC, With SVC but no externally controlled, SVC with PI controller & SVC with PD controller. Simulation result shows that without SVC, the system parameters become unstable during faults. When SVC is imposed in the network, then system parameters become stable. Again, when SVC is controlled externally by PI & PD controllers, then system parameters becomes stable in faster way then without controller. It has been observed that the SVC ratings are only 50 MVA with controllers and 200 MVA without controllers. So, SVC with PI & PD controllers are more effective to enhance the voltage stability and increases power transmission capacity of a power system. The power system oscillations are also reduced with controllers in compared to that of without controllers. So with both controllers the system performance is greatly enhanced.展开更多
The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (...The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (power system stabilizer) is the main goal of this article. The possibility of application of the new combined approach for the optimal excitation's settings search is presented. MC (Monte Carlo) method, in order to search and select the optimal combination of excitation system, was applied. The proposed method has been researched with a mathematical model of the power system. This model has been built using Matlab/Simulink software. Paper shows advantages and disadvantages of the proposed methods.展开更多
Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is cau...Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is caused by technological progress. However, not all elements of the power system are developing simultaneously. The old type of elements sometimes is sufficient to adapt old system to the new operational conditions. The work developed and proposed in this paper deals with analysis of possible optimization of synchronous generator's excitation system. Authors examined influence of excitation system's parameters to the dynamics of transient processes in the power system. Authors investigated optimal parameters of excitation system of the Kegums hydro power plant. For optimization of parameters objective functions were used. The problem of the mutual influence of excitation systems of neighbor power plants was investigated. Investigation of transient processes using developed model proved that optimization of excitation parameters improves efficiency of regulation of excitation system, damping of active power oscillation and in some cases can prevent out-of-step condition.展开更多
This paper presented PSS (Power system stabilizer) design based on Genetic Algorithm - Fuzzy PID (Proportional Integral and derivative) or GAFPID. GAFPID based PSS design is considered for multimachine power syste...This paper presented PSS (Power system stabilizer) design based on Genetic Algorithm - Fuzzy PID (Proportional Integral and derivative) or GAFPID. GAFPID based PSS design is considered for multimachine power system. The main motivation for this design is to stabilize or to control low-fi'equency oscillation and terminal voltage of power systems. Genetic Algorithm (GA) is employed for the optimization of the parameter of stabilizer. By minimizing an objective function in which the oscillatory speed deviation of the generator, small signal and large signal performance of the system is improved. The effectiveness of the proposed PSS in increasing the damping of system electromechanical oscillation is demonstrated in a simple two-area power system.展开更多
The dynamic reactive power compensation equipment in Jiuquan Wind Power Base of above 10 GW consists of three different types of compensation devices, including: static var generator (SVG), thyristor controlled com...The dynamic reactive power compensation equipment in Jiuquan Wind Power Base of above 10 GW consists of three different types of compensation devices, including: static var generator (SVG), thyristor controlled compensator (TGR) and magnetically controlled reactor (MGR). The lack of experimental verification of performance is not conducive to voltage/var management or full utilization of device capaci- ties. In order to solve the above problems, the compensation device performance test was performed. The test items and procedures were selected based on related national standards with the consideration for different grid structures and wind farm operation modes. The testing contents included dynamic regulating range, active power loss, dynamic response time, and harmonic voltage level. Three types of compensation devices installed in different wind farms, namely SVG, TCR and MCR, were chosen and tested. The performances were compared and analyzed according to the field test results.展开更多
文摘An electrical equivalent circuit model for lithium-ion batteries used for hybrid electric vehicles (HEV) is presented. The model has two RC networks characterizing battery activation and concentration polarization process. The parameters of the model are identified using combined experimental and extended Kalman filter (EKF) recursive methods. The open-circuit voltage and ohmic resistance of the battery are directly measured and calculated from experimental measurements, respectively. The rest of the coupled dynamic parameters, i.e. the RC network parameters, are estimated using the EKF method. Experimental and simulation results are presented to demonstrate the efficacy of the proposed circuit model and parameter identification techniques for simulating battery dynamics.
基金Sponsored by the Natural Science Foundation of Hebei Province,China(Grant No.F2016203006)
文摘The adaptive H_∞ control problem of multi-machine power system in the case of disturbances and uncertain parameters is discussed,based on a Hamiltonian model.Considered the effect of time delay during control and transmission,a Hamilton model with control time delay is established.Lyapunov-Krasovskii function is selected,and a controller which makes the system asymptotically stable is got.The controller not only achieves the stability control for nonlinear systems with time delay,but also has the ability to suppress the external disturbances and adaptive ability to system parameter perturbation.The simulation results show the effect of the controller.
文摘Kdesorption from soils in a constant electric field(field strength:44.5Vcm-1) by means of electro-ultrafil-tration (EUF) followed second-order kinetics and could be described by the equation dd/dt = k(D-d)2. From theequation, such kinetic parameters relating to K desorption from soils as the maximum desorbable quantity D, quantity of K desorbed within 40 minutes d40, initial desorption rate Vo, desorption rate constant k and half-time t1/2 could be calculated. An expression which describes the relationships between the kinetic parameters on the one hand and the responses of barley to fertilizer-K in the field experiments in different sites and the potassium-supplying power of soils on the other was established. Vo, D and d40 were significantly correlated with barley relative yield, K uptake by barley and the content of soil available potassium. The rate constants of K desorption varied between 4.42 × 10-4-1.80 × 10-3kg mg-1 min-1 and highly correlated with the relative yield of barley. The kinetic parameters including Vo, D, d40 and k were successfully used to estimate the K-supplying power of soils.
基金National Natural Science Foundation of China(No.51367010)Science and Technology Program of Gansu Province(No.17JR5RA083)+2 种基金Natural Science Foundation of Gansu Province(No.1610RJZA042)Program for Excellent Team of Scientific Research in Lanzhou Jiaotong University(No.201701)Scientific Research Program of Colleges and Universities in Gansu Province(No.2016B-032)。
文摘There is a certain coupling relationship among the main circuit parameters of a single-phase shunt active power filter(SAPF),which has a great influence on the reasonable selection of various parameter values.By analyzing the calculation methods of the inductance of alternating current(AC)side and the voltage and capacitance values of direct current(DC)side in the existing single/three-phase SAPF main circuit,a specific single-phase SAPF circuit parameter analytical expression was obtained.Aiming at the coupling relationship among the variables in the resulting expression,the model was optimized and analyzed in MATLAB,and a complete set of parameters design scheme was obtained,which ensure the comprehensive optimization target of the post-harmonic content below 2% is compensated under a specific load.The simulation and experimental procedures verify the correctness of the selected parameters.
文摘The main objective of electricity regulators when establishing electricity markets is to decrease the cost of electricity through competition. However, this scenario cannot be achieved without a full participation of the electricity demand by reacting against electricity prices. The aim of this research is to develop tools for helping customers and aggregators to join price and demand response programs, while helping them to hedge against the risk of short-term price volatility. In this way, the capacity of and hybrid methodology (Self-Organizing Maps and Statistical Ward's Linkage) to classify high electricity market prices is analysed. Besides, with the help of Non-Parametric Estimation, some price-patterns were found in the abovementioned clusters. The contained knowledge within these patterns supplies customer market-based information on which to base its energy use decisions. The interest for this participation of customers in markets is growing in developed countries to obtain a higher elasticity in demand. Results show the capability of this approach to improve data management and select coherent policies to accomplish cleared demand offers amongst different price scenarios in a more flexible way.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10747135, 10675052 and 10875050
文摘We investigate the in-medium interparticle potential of hot gauge system with bound states by employing the QED and scalar QED coupling. At the finite temperature an oscillatory behavior of the potential has been found as well as its variation in terms of different free parameters. We expect the competition among the parameters will lead to an appropriate interparticle potential, which could be extended to discuss the fluid properties of QGP with scalar bound states.
文摘In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.
文摘Aiming at the development of parallel hybrid electric vehicle (PHEV) powertrain, parameter matching and optimization are presented, According to the performance of PHEV, the optimization range of engine, motor, driveline gear ratio and battery parameters are determined. And then a two-level optimization problem is formulated based on analytical target cascading (ATC). At the system level, the optimization of the whole vehicle fuel economy is carried out, while the tractive performance is defined as the constraints. The optimized parameters are cascaded to the subsystem as the optimization targets. At the subsystem level, the final drive and transmission design are optimized to make the ratios as close to the targets as possible. The optimization result shows that the fuel economy had improved significantly, while the tractive performance maintains the former level.
基金Supported by National Natural Science Foundation of China(No.50579047).
文摘Nonlinear vibration can cause serious problems in long span cable-stayed bridges.When the internal resonance threshold is reached between the excitation frequency and natural frequency,large amplitudes occur in the cable.Based on the current situation of lacking corresponding constraint criteria,a model was presented for analyzing the dynamic reliability of coupling oscillation between the cable and tower in a cable-stayed bridge.First of all,in the case of cable sag,the d'Alembert principle is applied to studying the nonlinear dynamic behavior of the structure,and resonance failure interval of parametric oscillation is calculated accordingly.Then the dynamic reliability model is set up using the JC method.An application of this model has been developed for the preliminary design of one cable-stayed bridge located on Hai River in Tianjin,and time histories analysis as well as reliability indexes have been obtained.When frequency ratio between the cable and tower is approaching 1∶2,the reliability index is 0.98,indicating high failure probability.And this is consistent with theoretical derivation and experimental results in reference.This model,which is capable of computing the reliability index of resonance failure,provides theoretical basis for the establishment of corresponding rule.
文摘Destructions at Fukushima Daiichi NPP (nuclear power plant) caused by earthquake have shown that design level of seismic influences on the equipment has been exceeded. The accident demonstrated the need for stricter regulations to ensure the seismic resistance of NPP and the need to develop and implement additional anti-seismic procedures in the course of their operation. To proof seismic reliability of NPP systems and components must be made special studies of logarithmic decrement of systems NPP and components. The correct definition of coolant thermodynamics parameters and acoustic parameters are necessary to evaluate logarithmic decrement of coolant systems NPP and their components and consequently for providing of NPP seismic reliability. The proof of presence of a gas phase in the coolant inside reactor is of great importance for practice because of its influence on coolant acoustical parameters and consequently on range of frequency of seismic-acoustical resonance type interaction. Results are obtained by using of known methods in oscillation theory, general acoustics, thermodynamic, electro-mechanical analogies. As well as using experimental data obtained from the vibration dynamical controls reactor WWER-1000.
基金Acknowledgements: Financial support from the National Natural Science Foundation of China (No. 20305004), Program for New Century Excellent Talents in University (No, NCET-05-0572) of China, the Key Science and Technology project of Fujian Province (No. 2005Y015) and the National Natural Science Foundation of Fujian Province (No. D0510006).
文摘Interaction of Aristolochic acid (AA) and guanine (G) was studied by electrochemical techniques in this paper. When AA was added into the guanine solution, the oxidation peak currents of mixture solution decreased, while the peak potential and the electrochemical kinetic parameters remained the same as when AA was absent, except that the electrode process of guanine that involved two protons and two electrons changed from adsorption controlled to diffusion controlled. It is suggested that an electrochemical inactive supramolecular adduct AA-Gua (1:1) was formed in the system. The adduct cannot be oxidized on the glassy carbon electrode, which indirectly results in the decrease of the free concentration of guanine in the reaction solution and the decrease of peak currents. The binding constant (13) of this adduct is calculated as 7.14× 10^3 mol/L. The possible mechanism for the interaction of Aristolochic acid and DNA was proposed, that may provide a possible pathway for the nosogenesis research of aristolochic acid.
文摘Ti0.5Al0.25Ni0.25 alloy prepared by vacuum induction melting was studied.The phase composition was analyzed with X-ray technique and EDS analysis,and its electrochemical properties were investigated at various temperatures.Electrochemical reaction kinetic parameters were also studied with proper electrochemical techniques.The influence of the secondary corrosion reaction on the anodic linear polarization measurement was also analyzed by theoretical simulation.The results show that,proper ball-milling with nickel powders is beneficial to electrochemical performance.The theoretical simulation proves that,the existence of the side reaction can disturb the measurement of electrochemical reaction kinetic parameters.
文摘This work deals with a description of a parametric tool for elastic analysis of wind turbine tower, incorporating all analysis steps (preprocessing, processing and post-processing). The tower geometry is approximated by fiat elements in which the membrane effects are evaluated using the FF (free formulation) finite element and the flexure effects are calculated using DKT (discrete shear triangle) finite element. The user-friendly system is implemented using OpenGL library to provide the graphical construction for geometry, mesh orientation, and other requirements of the finite element model. For the processing stage is built a specific dll library implemented in C++ language for the analysis using the FF and DKT finite elements. The post-processing stage is build using specific dialogs box to present all results. The displacement results are visualized in the graphic interface to show the static and dynamic deformations of the tower. Some examples are presented to show all the tasks of the parametric tool.
基金Supported by the National Natural Science Foundation under Grant No. 60704004
文摘The effect of line voltage drop is considered larger on loads, especially on asynchronous motor, transformers and other non-linear load parameters in power system of large ships. A novel power flow method based on improved node voltage method is proposed, and a typical ship power system, which has 2 power stations and 10 nodes, with closed-loop design but open-loop operation, is taken as an example. Simulation results show that the improved power flow calculation method has achieved higher accuracy and better convergence.
文摘This paper presents the model of a SVC (Static VAR Compensator) which is controlled externally by a PI (Proportional Integral) & PD (Proportional Differential) controllers for the improvements of voltage stability and damping effect of an on line power system. Both controller parameters has been optimized by using Ziegler-Nichols close loop tuning method. Both single phase and three phase (L-L) faults have been considered in the research. In this paper, a power system network is considered which is simulated in the phasor simulation method & the network is simulated in four steps; without SVC, With SVC but no externally controlled, SVC with PI controller & SVC with PD controller. Simulation result shows that without SVC, the system parameters become unstable during faults. When SVC is imposed in the network, then system parameters become stable. Again, when SVC is controlled externally by PI & PD controllers, then system parameters becomes stable in faster way then without controller. It has been observed that the SVC ratings are only 50 MVA with controllers and 200 MVA without controllers. So, SVC with PI & PD controllers are more effective to enhance the voltage stability and increases power transmission capacity of a power system. The power system oscillations are also reduced with controllers in compared to that of without controllers. So with both controllers the system performance is greatly enhanced.
文摘The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (power system stabilizer) is the main goal of this article. The possibility of application of the new combined approach for the optimal excitation's settings search is presented. MC (Monte Carlo) method, in order to search and select the optimal combination of excitation system, was applied. The proposed method has been researched with a mathematical model of the power system. This model has been built using Matlab/Simulink software. Paper shows advantages and disadvantages of the proposed methods.
文摘Excitation system is one of the significant elements affecting the dynamic performance of electric power systems. The power engineering as area of science and industry is subjected to rapid modernization, which is caused by technological progress. However, not all elements of the power system are developing simultaneously. The old type of elements sometimes is sufficient to adapt old system to the new operational conditions. The work developed and proposed in this paper deals with analysis of possible optimization of synchronous generator's excitation system. Authors examined influence of excitation system's parameters to the dynamics of transient processes in the power system. Authors investigated optimal parameters of excitation system of the Kegums hydro power plant. For optimization of parameters objective functions were used. The problem of the mutual influence of excitation systems of neighbor power plants was investigated. Investigation of transient processes using developed model proved that optimization of excitation parameters improves efficiency of regulation of excitation system, damping of active power oscillation and in some cases can prevent out-of-step condition.
文摘This paper presented PSS (Power system stabilizer) design based on Genetic Algorithm - Fuzzy PID (Proportional Integral and derivative) or GAFPID. GAFPID based PSS design is considered for multimachine power system. The main motivation for this design is to stabilize or to control low-fi'equency oscillation and terminal voltage of power systems. Genetic Algorithm (GA) is employed for the optimization of the parameter of stabilizer. By minimizing an objective function in which the oscillatory speed deviation of the generator, small signal and large signal performance of the system is improved. The effectiveness of the proposed PSS in increasing the damping of system electromechanical oscillation is demonstrated in a simple two-area power system.
文摘The dynamic reactive power compensation equipment in Jiuquan Wind Power Base of above 10 GW consists of three different types of compensation devices, including: static var generator (SVG), thyristor controlled compensator (TGR) and magnetically controlled reactor (MGR). The lack of experimental verification of performance is not conducive to voltage/var management or full utilization of device capaci- ties. In order to solve the above problems, the compensation device performance test was performed. The test items and procedures were selected based on related national standards with the consideration for different grid structures and wind farm operation modes. The testing contents included dynamic regulating range, active power loss, dynamic response time, and harmonic voltage level. Three types of compensation devices installed in different wind farms, namely SVG, TCR and MCR, were chosen and tested. The performances were compared and analyzed according to the field test results.