最大功率点跟踪技术(Maximum Power Point Tracking, MPPT)是光伏发电系统中关键技术研究的热点之一。针对传统扰动观察法跟踪速度和精度无法兼顾的问题,文中提出了一种以功率变化量为步长控制量的自适应变步长扰动观察法,通过判断功率...最大功率点跟踪技术(Maximum Power Point Tracking, MPPT)是光伏发电系统中关键技术研究的热点之一。针对传统扰动观察法跟踪速度和精度无法兼顾的问题,文中提出了一种以功率变化量为步长控制量的自适应变步长扰动观察法,通过判断功率变化趋势,对远离最大功率点,采用大步长逼近;靠近最大功率点,采用小步长逼近。建立太阳能光伏电池数学模型得到其输出特性曲线,再利用MATLAB/Simulink搭建基于Boost电路的MPPT仿真模型,最后经仿真验证了所提出算法的稳定性、快速性和准确性,它比传统算法具有更好的MPPT暂态性能。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
为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化...为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。展开更多
针对人工势场(Artificial Potential Field,APF)法对机械手进行路径规划时存在的问题,提出了关节空间APF自适应变步长和目标偏置的快速扩展随机树(Rapidly-exploring Random Tree,RRT)相结合的方法。在关节空间中进行APF法路径规划,减...针对人工势场(Artificial Potential Field,APF)法对机械手进行路径规划时存在的问题,提出了关节空间APF自适应变步长和目标偏置的快速扩展随机树(Rapidly-exploring Random Tree,RRT)相结合的方法。在关节空间中进行APF法路径规划,减少逆向运动学次数和关节角突变;通过改进斥力和引力势场函数,解决APF法中碰撞和目标不可达问题;采用柯西概率分布,根据末端点与障碍物的距离来改变关节角步长;通过调节RRT算法的目标偏置值,产生合适临时目标点,从而解决APF法局部极小值问题。在APF法存在局部极小值情况下进行机械臂避障仿真,结果表明,自适应变步长路径规划能够生成平滑轨迹并能提高搜索效率,目标偏置RRT选取临时目标点后整体路径长度变短。捡拾机械手在该改进算法下能够有效实现避障拾取任务需求。展开更多
Dynamic simulation plays a fundamental role in security evaluation of distribution networks(DNs).However,the strong stiffness and non-linearity of distributed generation(DG)models in DNs bring about burdensome computa...Dynamic simulation plays a fundamental role in security evaluation of distribution networks(DNs).However,the strong stiffness and non-linearity of distributed generation(DG)models in DNs bring about burdensome computation and noteworthy instability on traditional methods which hampers the rapid response of simulation tool.Thus,a novel L-stable approximate analytical method with high accuracy is proposed to handle these problems.The method referred to as multistage discontinuous Galerkin method(MDGM),first derives approximate analytical solutions(AASs)of state variables which are explicit symbolic expressions concerning system states.Then,in each time window,it substitutes values for symbolic variables and trajectories of state variables are obtained subsequently.This paper applies MDGM to DG models to derive AASs.Local-truncation-error-based variable step size strategy is also developed to further improve simulation efficiency.In addition,this paper establishes detailed MDGM-based dynamic simulation procedure.From case studies on a numerical problem,a modified 33-bus system and a practical large-scale DN,it can be seen that proposed method demonstrates fast and dependable performance compared with the traditional trapezoidal method.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
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
文摘最大功率点跟踪技术(Maximum Power Point Tracking, MPPT)是光伏发电系统中关键技术研究的热点之一。针对传统扰动观察法跟踪速度和精度无法兼顾的问题,文中提出了一种以功率变化量为步长控制量的自适应变步长扰动观察法,通过判断功率变化趋势,对远离最大功率点,采用大步长逼近;靠近最大功率点,采用小步长逼近。建立太阳能光伏电池数学模型得到其输出特性曲线,再利用MATLAB/Simulink搭建基于Boost电路的MPPT仿真模型,最后经仿真验证了所提出算法的稳定性、快速性和准确性,它比传统算法具有更好的MPPT暂态性能。
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.
文摘为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。
文摘针对人工势场(Artificial Potential Field,APF)法对机械手进行路径规划时存在的问题,提出了关节空间APF自适应变步长和目标偏置的快速扩展随机树(Rapidly-exploring Random Tree,RRT)相结合的方法。在关节空间中进行APF法路径规划,减少逆向运动学次数和关节角突变;通过改进斥力和引力势场函数,解决APF法中碰撞和目标不可达问题;采用柯西概率分布,根据末端点与障碍物的距离来改变关节角步长;通过调节RRT算法的目标偏置值,产生合适临时目标点,从而解决APF法局部极小值问题。在APF法存在局部极小值情况下进行机械臂避障仿真,结果表明,自适应变步长路径规划能够生成平滑轨迹并能提高搜索效率,目标偏置RRT选取临时目标点后整体路径长度变短。捡拾机械手在该改进算法下能够有效实现避障拾取任务需求。
文摘Dynamic simulation plays a fundamental role in security evaluation of distribution networks(DNs).However,the strong stiffness and non-linearity of distributed generation(DG)models in DNs bring about burdensome computation and noteworthy instability on traditional methods which hampers the rapid response of simulation tool.Thus,a novel L-stable approximate analytical method with high accuracy is proposed to handle these problems.The method referred to as multistage discontinuous Galerkin method(MDGM),first derives approximate analytical solutions(AASs)of state variables which are explicit symbolic expressions concerning system states.Then,in each time window,it substitutes values for symbolic variables and trajectories of state variables are obtained subsequently.This paper applies MDGM to DG models to derive AASs.Local-truncation-error-based variable step size strategy is also developed to further improve simulation efficiency.In addition,this paper establishes detailed MDGM-based dynamic simulation procedure.From case studies on a numerical problem,a modified 33-bus system and a practical large-scale DN,it can be seen that proposed method demonstrates fast and dependable performance compared with the traditional trapezoidal method.
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。