The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system sta...The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.展开更多
Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circui...Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circuit response;moreover it is convenient for controller design purpose. Due to simple and effective methodology, average state space is the most common method among the modelling methods. In this paper a bidirectional full bridge converter is modelled by average state space and for each mode of operations a controller is designed. Attained mathematical model results are in a close agreement with detailed circuit simulation.展开更多
Reliability analysis based on equipment's performance degradation characteristics is one of the significant research areas in reliability research. Nowadays, many researches are carried on multi-sample analysis. B...Reliability analysis based on equipment's performance degradation characteristics is one of the significant research areas in reliability research. Nowadays, many researches are carried on multi-sample analysis. But it is limited for a single equipment reliability prediction. Therefore, the method of reliability prediction based on state space model(SSM) is proposed in this research. Feature energy of the monitored signals is extracted with the wavelet packet analysis and the associated frequency band energy with online monitored data. Then,degradation feature is improved by moving average filtering processing taken as input pair model parameter of SSM to be estimated. In the end, state space predicting model of degradation index is established. The probability density distribution of the degradation index is predicted, and the degree of reliability is calculated. A real testing example of bearing is used to demonstrate the rationality and effectiveness of this method. It is a useful method for single sample reliability prediction.展开更多
The state space average model and the large signal models of Pulse Skip Modulation （PSM） mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of t...The state space average model and the large signal models of Pulse Skip Modulation （PSM） mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of the characteristics of PSM converter is described in this paper, of which include efficiency, frequency spectrum analysis, output voltage ripple, response speed and interference rejection capability. Compared with PWM control mode, PSM converter has high efficiency, especially with fight loads, quick response, good interference rejection and good EMC characteristic. Improved PSM slightly, it could be a kind of good independent regulating mode during the whole operating process for a DC-DC converter. Finally, some experimental results are also presented in this paper.展开更多
Within the approximations of spherical lattice cell, central-field, and relativistic Fermi statis- tics, an algorithm with average atom model is presented to calculate the electronic energy levels and equation of stat...Within the approximations of spherical lattice cell, central-field, and relativistic Fermi statis- tics, an algorithm with average atom model is presented to calculate the electronic energy levels and equation of state for hot and dense matter at arbitrary densities and temperatures. Choosing Zink's analytical potential as initial potential, we have solved the Dirac-Slater equation which satisfies the Weigner-Seitz boundary condition. The electronic energy bands are not taken into account. Tak- ing energy level degeneracy as a continuous function of density, we have considered the pressure ionization effects for highly dense matter. Results for ^(13)Al atom are shown.展开更多
Ion population fraction（IPF） calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation intera...Ion population fraction（IPF） calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation interactions between the electrons of an ion which are present in a plasma environment. The average atom models, e.g., screened hydrogenic model with l-splitting（SHML）, now have the capabilities for such calculations and are becoming more popular for in line plasma calculations. In our previous work [Ali A, Shabbir Naz G, Shahzad M S, Kouser R, Rehman A and Nasim M H 2018 High Energy Density Phys. 26 48], we have improved the continuum lowering model and included the exchange and correlation effects in SHML. This study presents the calculation of IPF using classical theory of fluctuation for our improved screened hydrogenic model with l-splitting（I-SHML） under local thermodynamic equilibrium conditions for iron and aluminum plasma over a wide range of densities and temperatures. We have compared our results with other models and have found a very good agreement among them.展开更多
The error of single step-ahead output prediction is the information traditionally used to correct the state estimate while exploiting the new measurement of the system output.However,its dynamics and statistical prope...The error of single step-ahead output prediction is the information traditionally used to correct the state estimate while exploiting the new measurement of the system output.However,its dynamics and statistical properties can be further studied and exploited in other ways.It is known that in the case of suboptimal state estimation,this output prediction error forms a correlated sequence,hence it can be effectively predicted in real time.Such a suboptimal scenario is typical in applications where the process noise model is not known or it is uncertain.Therefore,the paper deals with the problems of analytical and empirical modeling,identification,and prediction of the output error of the suboptimal state estimator for the sake of improving the output prediction accuracy and ultimately the performance of the model predictive control.The improvements are validated on an empirical model of type 1 diabetes within an in-silico experiment focused on glycemia prediction and implementation of the MPC-based artificial pancreas.展开更多
The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model ...The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model the DAB,calculate its input impedance,and analyze the system stability.In this study,two continuous-time impedance models of the DAB,i.e.,a reduced-order model named the power-based impedance model(PBIM)and a full-order model named the generalized state-space average impedance model(GSSAM),are proposed and used to calculate the input impedance in a single-phase modulation mode.The modeling errors are analyzed,the participation factors and residuals are calculated,and a Bode diagram is constructed to illustrate the change in the input impedance with increasing leakage inductance.Simulations are conducted using various circuit parameters to verify the results.The results show that the PBIM exhibits simplicity and accuracy in the low-frequency domain,whereas the GSSAM performs better in the high-frequency domain.展开更多
新型电力系统的频率动态过程受到新能源机组故障穿越行为的显著影响,目前只能通过机电暂态仿真进行精准的暂态频率安全评估,在线应用困难。为此,该文提出一种基于关键准稳态计算的暂态频率安全定量评估方法,通过直接计算故障过程中的若...新型电力系统的频率动态过程受到新能源机组故障穿越行为的显著影响,目前只能通过机电暂态仿真进行精准的暂态频率安全评估,在线应用困难。为此,该文提出一种基于关键准稳态计算的暂态频率安全定量评估方法,通过直接计算故障过程中的若干个关键准稳态断面从而有效判断各新能源机组运行状态,进而实现暂态过程中频率安全指标的准确快速计算。具体而言,首先提出一种故障过程中关键准稳态计算方法,并据此评估系统最大频率变化率。其次,通过引入系统频率变量,提出一种直接计算故障后稳态频率的通用方法。最后,结合新能源机组各状态下的功率缺额,建立了基于关键准稳态的平均系统频率(average system frequency based on quasi-steady-state,QSS-ASF)模型,利用该模型仿真能够快速预测出故障发生后的频率最低点。仿真结果表明,所提方法在不同扰动及电源结构下均可准确判断新能源机组状态,各项频率安全指标评估误差均低于2%,兼具准确性与高效性。展开更多
文摘The high potentiality of integrating renewable energies,such as photovoltaic,into a modern electrical microgrid system,using DC-to-DC converters,raises some issues associated with controller loop design and system stability.The generalized state space average model(GSSAM)concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies.This paper presents a GSSAM for parallel DC-to-DC converters,namely:buck,boost,and buck-boost converters.The rationale of this study is that modern electrical systems,such as DC networks,hybrid microgrids,and electric ships,are formed by parallel DC-to-DC converters with separate DC input sources.Therefore,this paper proposes a GSSAM for any number of parallel DC-to-DC converters.The proposed GSSAM is validated and investigated in a time-domain simulation environment,namely a MATLAB/SIMULINK.The study compares the steady-state,transient,and oscillatory performance of the state-space average model with a fully detailed switching model.
文摘Modelling of bidirectional full bridge DC-DC converter as one of the most applicable converters has received significant attention. Mathematical modelling reduces the simulation time in comparison with detailed circuit response;moreover it is convenient for controller design purpose. Due to simple and effective methodology, average state space is the most common method among the modelling methods. In this paper a bidirectional full bridge converter is modelled by average state space and for each mode of operations a controller is designed. Attained mathematical model results are in a close agreement with detailed circuit simulation.
基金the National Science and Technology Major Project of China(No.2013ZX04012071)the National Natural Science Foundation of China(No.51175057)
文摘Reliability analysis based on equipment's performance degradation characteristics is one of the significant research areas in reliability research. Nowadays, many researches are carried on multi-sample analysis. But it is limited for a single equipment reliability prediction. Therefore, the method of reliability prediction based on state space model(SSM) is proposed in this research. Feature energy of the monitored signals is extracted with the wavelet packet analysis and the associated frequency band energy with online monitored data. Then,degradation feature is improved by moving average filtering processing taken as input pair model parameter of SSM to be estimated. In the end, state space predicting model of degradation index is established. The probability density distribution of the degradation index is predicted, and the degree of reliability is calculated. A real testing example of bearing is used to demonstrate the rationality and effectiveness of this method. It is a useful method for single sample reliability prediction.
基金Supported by the National Natural Science Foundation of China (No.60436030)
文摘The state space average model and the large signal models of Pulse Skip Modulation （PSM） mode are given in this paper. Farther more, based on these models and simulations of PSM converter circuits, the analysis of the characteristics of PSM converter is described in this paper, of which include efficiency, frequency spectrum analysis, output voltage ripple, response speed and interference rejection capability. Compared with PWM control mode, PSM converter has high efficiency, especially with fight loads, quick response, good interference rejection and good EMC characteristic. Improved PSM slightly, it could be a kind of good independent regulating mode during the whole operating process for a DC-DC converter. Finally, some experimental results are also presented in this paper.
文摘Within the approximations of spherical lattice cell, central-field, and relativistic Fermi statis- tics, an algorithm with average atom model is presented to calculate the electronic energy levels and equation of state for hot and dense matter at arbitrary densities and temperatures. Choosing Zink's analytical potential as initial potential, we have solved the Dirac-Slater equation which satisfies the Weigner-Seitz boundary condition. The electronic energy bands are not taken into account. Tak- ing energy level degeneracy as a continuous function of density, we have considered the pressure ionization effects for highly dense matter. Results for ^(13)Al atom are shown.
文摘Ion population fraction（IPF） calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation interactions between the electrons of an ion which are present in a plasma environment. The average atom models, e.g., screened hydrogenic model with l-splitting（SHML）, now have the capabilities for such calculations and are becoming more popular for in line plasma calculations. In our previous work [Ali A, Shabbir Naz G, Shahzad M S, Kouser R, Rehman A and Nasim M H 2018 High Energy Density Phys. 26 48], we have improved the continuum lowering model and included the exchange and correlation effects in SHML. This study presents the calculation of IPF using classical theory of fluctuation for our improved screened hydrogenic model with l-splitting（I-SHML） under local thermodynamic equilibrium conditions for iron and aluminum plasma over a wide range of densities and temperatures. We have compared our results with other models and have found a very good agreement among them.
基金supported by the grant VEGA 1/0049/20—Modelling and Control of Biosystems,the Ministry of Education,Science,Development and Sport of the Slovak Republic.
文摘The error of single step-ahead output prediction is the information traditionally used to correct the state estimate while exploiting the new measurement of the system output.However,its dynamics and statistical properties can be further studied and exploited in other ways.It is known that in the case of suboptimal state estimation,this output prediction error forms a correlated sequence,hence it can be effectively predicted in real time.Such a suboptimal scenario is typical in applications where the process noise model is not known or it is uncertain.Therefore,the paper deals with the problems of analytical and empirical modeling,identification,and prediction of the output error of the suboptimal state estimator for the sake of improving the output prediction accuracy and ultimately the performance of the model predictive control.The improvements are validated on an empirical model of type 1 diabetes within an in-silico experiment focused on glycemia prediction and implementation of the MPC-based artificial pancreas.
基金Supported by the National Natural Science Foundation of China(52005436).
文摘The dual active bridge(DAB)is a widely used DC-DC topology owing to its ease of control and ability to achieve various control objectives.When designing a DAB-based system under broadband perturbations,one must model the DAB,calculate its input impedance,and analyze the system stability.In this study,two continuous-time impedance models of the DAB,i.e.,a reduced-order model named the power-based impedance model(PBIM)and a full-order model named the generalized state-space average impedance model(GSSAM),are proposed and used to calculate the input impedance in a single-phase modulation mode.The modeling errors are analyzed,the participation factors and residuals are calculated,and a Bode diagram is constructed to illustrate the change in the input impedance with increasing leakage inductance.Simulations are conducted using various circuit parameters to verify the results.The results show that the PBIM exhibits simplicity and accuracy in the low-frequency domain,whereas the GSSAM performs better in the high-frequency domain.
文摘新型电力系统的频率动态过程受到新能源机组故障穿越行为的显著影响,目前只能通过机电暂态仿真进行精准的暂态频率安全评估,在线应用困难。为此,该文提出一种基于关键准稳态计算的暂态频率安全定量评估方法,通过直接计算故障过程中的若干个关键准稳态断面从而有效判断各新能源机组运行状态,进而实现暂态过程中频率安全指标的准确快速计算。具体而言,首先提出一种故障过程中关键准稳态计算方法,并据此评估系统最大频率变化率。其次,通过引入系统频率变量,提出一种直接计算故障后稳态频率的通用方法。最后,结合新能源机组各状态下的功率缺额,建立了基于关键准稳态的平均系统频率(average system frequency based on quasi-steady-state,QSS-ASF)模型,利用该模型仿真能够快速预测出故障发生后的频率最低点。仿真结果表明,所提方法在不同扰动及电源结构下均可准确判断新能源机组状态,各项频率安全指标评估误差均低于2%,兼具准确性与高效性。
