An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aero...An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.展开更多
Implicit-explicit （IMEX） linear multistep methods are popular techniques for solving partial differential equations （PDEs） with terms of different types. While fixed timestep versions of such schemes have been dev...Implicit-explicit （IMEX） linear multistep methods are popular techniques for solving partial differential equations （PDEs） with terms of different types. While fixed timestep versions of such schemes have been developed and studied, implicit-explicit schemes also naturally arise in general situations where the temporal smoothness of the solution changes. In this paper we consider easily implementable variable step-size implicit-explicit （VSIMEX） linear multistep methods for time-dependent PDEs. Families of order-p, pstep VSIMEX schemes are constructed and analyzed, where p ranges from 1 to 4. The corresponding schemes are simple to implement and have the property that they reduce to the classical IMEX schemes whenever constant time step-sizes are imposed. The methods are validated on the Burgers＇ equation. These results demonstrate that by varying the time step-size, VSIMEX methods can outperform their fixed time step counterparts while still maintaining good numerical behavior.展开更多
According to the relationship between truncation error and step size of two implicit second-order-derivative multistep formulas based on Hermite interpolation polynomial,a variable-order and variable-step-size numeric...According to the relationship between truncation error and step size of two implicit second-order-derivative multistep formulas based on Hermite interpolation polynomial,a variable-order and variable-step-size numerical method for solving differential equations is designed.The stability properties of the formulas are discussed and the stability regions are analyzed.The deduced methods are applied to a simulation problem.The results show that the numerical method can satisfy calculation accuracy,reduce the number of calculation steps and accelerate calculation speed.展开更多
光伏发电系统效率优化关键在于最大功率点跟踪(maximum power point tracking,MPPT)控制技术,传统算法在环境变化及部分阴影下存在局限。对此,设计了模糊逻辑控制策略与改进型变步长扰动观察法,后者通过自适应步长调节和双层搜索结构,...光伏发电系统效率优化关键在于最大功率点跟踪(maximum power point tracking,MPPT)控制技术,传统算法在环境变化及部分阴影下存在局限。对此,设计了模糊逻辑控制策略与改进型变步长扰动观察法,后者通过自适应步长调节和双层搜索结构,标准测试条件下效率达99.3%。实验表明,该算法具备优越的动态响应、稳态精度和环境适应性,可为光伏系统高效运行提供技术支撑。展开更多
为减小光伏电池因环境变化造成的功率损失,提高系统的光电转换效率及跟踪响应速度,在传统电导增量法的基础上结合自适应变步长最小均方差LMS(least mean squre)算法,提出了一种自适应变步长最大功率跟踪算法,并在Matlab环境下利用SimPow...为减小光伏电池因环境变化造成的功率损失,提高系统的光电转换效率及跟踪响应速度,在传统电导增量法的基础上结合自适应变步长最小均方差LMS(least mean squre)算法,提出了一种自适应变步长最大功率跟踪算法,并在Matlab环境下利用SimPowerSystem功能模块建立了光伏电池的数学模型及自适应变步长算法的控制器模型。仿真结果表明,该算法在光照、温度等系统参数扰动的情况下都能快速找到新的工作点,表现出良好的动态及稳态特性,证实了算法的正确性和有效性。展开更多
太阳能光伏阵列的输出功率随外界环境因素的变化而变化,为了能高效利用太阳能电池,需要进行光伏阵列的最大功率点跟踪(Maximum Power Point Tracking,简称MPPT)。扰动观察法以其简单有效而得到了广泛应用。提出了一种新颖的变步长扰动...太阳能光伏阵列的输出功率随外界环境因素的变化而变化,为了能高效利用太阳能电池,需要进行光伏阵列的最大功率点跟踪(Maximum Power Point Tracking,简称MPPT)。扰动观察法以其简单有效而得到了广泛应用。提出了一种新颖的变步长扰动观察法,对传统方法的动态特性进行优化。在Matlab/Simulink下进行了系统的建模与仿真,并进行了实验研究。结果表明,该方法能快速准确地跟踪外部环境变化,并能保证系统的稳定性。展开更多
由于现今光伏系统使用场所的环境因素变化较大,需要有更高的转换效率和适应度,为了改善定步长电导增量法控制能力的局限性,使其适应在多变环境下的最大功率点跟踪控制。因此在定步长电导增量法的基础上,结合自适应最小均方差LMS(Least M...由于现今光伏系统使用场所的环境因素变化较大,需要有更高的转换效率和适应度,为了改善定步长电导增量法控制能力的局限性,使其适应在多变环境下的最大功率点跟踪控制。因此在定步长电导增量法的基础上,结合自适应最小均方差LMS(Least Mean Squre)算法,提出了一种改进的自适应变步长最大功率跟踪算法,并在Matlab环境下利用Simulink平台搭建光伏电池仿真模块及自适应变步长算法的S函数控制模块。仿真结果表明,该算法能够快速准确地跟踪最大功率点,并能保持系统的稳定性。展开更多
基金The National Natural Science Foundation of China(No50475073,50775036)the High Technology Research Program of Jiangsu Province(NoBG2006035)
文摘An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.
基金supported by an NSERC Canada Postgraduate Scholarshipsupported by a grant from NSERC Canada
文摘Implicit-explicit （IMEX） linear multistep methods are popular techniques for solving partial differential equations （PDEs） with terms of different types. While fixed timestep versions of such schemes have been developed and studied, implicit-explicit schemes also naturally arise in general situations where the temporal smoothness of the solution changes. In this paper we consider easily implementable variable step-size implicit-explicit （VSIMEX） linear multistep methods for time-dependent PDEs. Families of order-p, pstep VSIMEX schemes are constructed and analyzed, where p ranges from 1 to 4. The corresponding schemes are simple to implement and have the property that they reduce to the classical IMEX schemes whenever constant time step-sizes are imposed. The methods are validated on the Burgers＇ equation. These results demonstrate that by varying the time step-size, VSIMEX methods can outperform their fixed time step counterparts while still maintaining good numerical behavior.
基金supported by the National Natural Science Foundation of China Under Grant No.61773008.
文摘According to the relationship between truncation error and step size of two implicit second-order-derivative multistep formulas based on Hermite interpolation polynomial,a variable-order and variable-step-size numerical method for solving differential equations is designed.The stability properties of the formulas are discussed and the stability regions are analyzed.The deduced methods are applied to a simulation problem.The results show that the numerical method can satisfy calculation accuracy,reduce the number of calculation steps and accelerate calculation speed.
文摘光伏发电系统效率优化关键在于最大功率点跟踪(maximum power point tracking,MPPT)控制技术,传统算法在环境变化及部分阴影下存在局限。对此,设计了模糊逻辑控制策略与改进型变步长扰动观察法,后者通过自适应步长调节和双层搜索结构,标准测试条件下效率达99.3%。实验表明,该算法具备优越的动态响应、稳态精度和环境适应性,可为光伏系统高效运行提供技术支撑。
文摘为减小光伏电池因环境变化造成的功率损失,提高系统的光电转换效率及跟踪响应速度,在传统电导增量法的基础上结合自适应变步长最小均方差LMS(least mean squre)算法,提出了一种自适应变步长最大功率跟踪算法,并在Matlab环境下利用SimPowerSystem功能模块建立了光伏电池的数学模型及自适应变步长算法的控制器模型。仿真结果表明,该算法在光照、温度等系统参数扰动的情况下都能快速找到新的工作点,表现出良好的动态及稳态特性,证实了算法的正确性和有效性。
文摘太阳能光伏阵列的输出功率随外界环境因素的变化而变化,为了能高效利用太阳能电池,需要进行光伏阵列的最大功率点跟踪(Maximum Power Point Tracking,简称MPPT)。扰动观察法以其简单有效而得到了广泛应用。提出了一种新颖的变步长扰动观察法,对传统方法的动态特性进行优化。在Matlab/Simulink下进行了系统的建模与仿真,并进行了实验研究。结果表明,该方法能快速准确地跟踪外部环境变化,并能保证系统的稳定性。
文摘由于现今光伏系统使用场所的环境因素变化较大,需要有更高的转换效率和适应度,为了改善定步长电导增量法控制能力的局限性,使其适应在多变环境下的最大功率点跟踪控制。因此在定步长电导增量法的基础上,结合自适应最小均方差LMS(Least Mean Squre)算法,提出了一种改进的自适应变步长最大功率跟踪算法,并在Matlab环境下利用Simulink平台搭建光伏电池仿真模块及自适应变步长算法的S函数控制模块。仿真结果表明,该算法能够快速准确地跟踪最大功率点,并能保持系统的稳定性。
