In this paper, the extremum of second-order directional derivatives, i.e. the gradient of first-order derivatives is discussed. Given second-order directional derivatives in three nonparallel directions, or given seco...In this paper, the extremum of second-order directional derivatives, i.e. the gradient of first-order derivatives is discussed. Given second-order directional derivatives in three nonparallel directions, or given second-order directional derivatives and mixed directional derivatives in two nonparallel directions, the formulae for the extremum of second-order directional derivatives are derived, and the directions corresponding to maximum and minimum are perpendicular to each other.展开更多
The energy conversion optimization control strategy is presented for a family of horizontal-axis variablespeed fixed-pitch wind energy conversion systems,working in the partial load region.The system uses a variablesp...The energy conversion optimization control strategy is presented for a family of horizontal-axis variablespeed fixed-pitch wind energy conversion systems,working in the partial load region.The system uses a variablespeed wind turbine(VSWT)driving a squirrel-cage induction generator(SCIG)connected to a grid.A new maximum power point tracking(MPPT)approach is proposed based on the extremum seeking control principles under the assumption that the wind turbine model and its parameters are poorly known.The aim is to drive the average position of the operation point close to optimality.Here the wind turbulence is used as search disturbance instead of inducing new sinusoidal search signals.The discrete Fourier transform(DFT)process of some available measures estimates the distance of operation point to optimality.The effectiveness of the proposed MPPT approach is validated under different operation conditions by numerical simulations in MATLAB/SIMULINK.The simulation results prove that the new approach can effectively suppress the vibration of system and enhance the dynamic performance of system.展开更多
Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of tw...Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of two-mass drive train, a Squirrel Cage Induction Generator (SCIG), and voltage source converter control by Space Vector Pulse Width Modulation (SPVWM). To achieve Maximum Power Point Tracking (MPPT), the reference speed to the generator is searched via Extremum Seeking Control (ESC). ESC was designed for wind turbine region II operation based on dither-modulation scheme. ESC is a model-free method that has the ability to increase the captured power in real time under turbulent wind without any requirement for wind measurements. The controller is designed in two loops. In the outer loop, ESC is used to set a desired reference speed to PI controller to regulate the speed of the generator and extract the maximum electrical power. The inner control loop is based on Indirect Field Orientation Control (IFOC) to decouple the currents. Finally, Particle Swarm Optimization (PSO) is used to obtain the optimal PI parameters. Simulation and control of the system have been accomplished using MATLAB/Simulink 2014.展开更多
Turbo码是一种常用的信道编码方式,正确识别Turbo码首先要正确识别其子递归系统卷积(recursive system convolutional,RSC)码,由于信道噪声与干扰引发误码,这就要求识别算法具有良好的抗误码性能以及识别能力。利用解调软判决序列,通过...Turbo码是一种常用的信道编码方式,正确识别Turbo码首先要正确识别其子递归系统卷积(recursive system convolutional,RSC)码,由于信道噪声与干扰引发误码,这就要求识别算法具有良好的抗误码性能以及识别能力。利用解调软判决序列,通过编码码元约束方程,构建指数形式的代价函数模型,将识别RSC码的生成矩阵问题转化为求解代价函数全域极值的最优化问题,最后在共轭梯度法的基础上,采用新的PRP步长因子来寻找全域极值点。仿真结果表明,所提算法与现有算法相比,收敛速度更快,在低信噪比下也有良好的识别能力。展开更多
在铁路建设及运营阶段,侵入限界的异物对既有线的安全行车构成极大威胁。将复杂的空间侵限检测转换为简单的平面内异物检测,研究利用二维激光测距传感器构建三维幕墙的侵限检测方法。在异物检测过程中,正常通过的列车不能认作异物,必须...在铁路建设及运营阶段,侵入限界的异物对既有线的安全行车构成极大威胁。将复杂的空间侵限检测转换为简单的平面内异物检测,研究利用二维激光测距传感器构建三维幕墙的侵限检测方法。在异物检测过程中,正常通过的列车不能认作异物,必须设计合理的算法检测并予以剔除。由于列车主要体现在轨道平面的检测结果中,重点研究通过分析扫描点云的分布特征对轨道平面内侵限物体进行分类的算法,提出了利用测量序列极值点作为核心对象的快速DBSCAN(density-based spatial clustering of applications with noise)聚类方法,并利用点簇的运动及分布特征判断是否为正常通过列车。现场试验表明,该方法能够有效区分侵限异物和正常通过的列车。展开更多
分析了单相单级光伏逆变器的模型特点及其对最大功率点跟踪(maximum power point tracking,MPPT)控制的特殊要求,提出了适用于这种类型光伏逆变器的MPPT方法。该方法利用极值搜索算法实现MPPT控制,通过高通滤波器提取逆变器直流电压中...分析了单相单级光伏逆变器的模型特点及其对最大功率点跟踪(maximum power point tracking,MPPT)控制的特殊要求,提出了适用于这种类型光伏逆变器的MPPT方法。该方法利用极值搜索算法实现MPPT控制,通过高通滤波器提取逆变器直流电压中的纹波电压,以该纹波电压为极值搜索算法的扰动信号;在极值搜索算法中引入优化补偿环节,通过该环节提高算法的收敛速度,进一步优化MPPT控制的稳态和动态性能。仿真和实验结果表明该方法可以充分利用单相单级逆变器的固有纹波,在无需额外注入扰动信号的前提下,该MPPT方法能够快速准确地搜索到最大功率点。展开更多
基金Supported by the National Natural Science Foundation of China (10871029,11071025)the Foundation of CAEP (2010A0202010)the Foundation of National Key Laboratory of Science and Technology on Computational Physics
文摘In this paper, the extremum of second-order directional derivatives, i.e. the gradient of first-order derivatives is discussed. Given second-order directional derivatives in three nonparallel directions, or given second-order directional derivatives and mixed directional derivatives in two nonparallel directions, the formulae for the extremum of second-order directional derivatives are derived, and the directions corresponding to maximum and minimum are perpendicular to each other.
基金Supported by the National Basic Research Program("973" Program)(2007CB210303)the Research Funding of Nanjing University of Aeronautics and Astronautrics(NP2011011)
文摘The energy conversion optimization control strategy is presented for a family of horizontal-axis variablespeed fixed-pitch wind energy conversion systems,working in the partial load region.The system uses a variablespeed wind turbine(VSWT)driving a squirrel-cage induction generator(SCIG)connected to a grid.A new maximum power point tracking(MPPT)approach is proposed based on the extremum seeking control principles under the assumption that the wind turbine model and its parameters are poorly known.The aim is to drive the average position of the operation point close to optimality.Here the wind turbulence is used as search disturbance instead of inducing new sinusoidal search signals.The discrete Fourier transform(DFT)process of some available measures estimates the distance of operation point to optimality.The effectiveness of the proposed MPPT approach is validated under different operation conditions by numerical simulations in MATLAB/SIMULINK.The simulation results prove that the new approach can effectively suppress the vibration of system and enhance the dynamic performance of system.
文摘Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of two-mass drive train, a Squirrel Cage Induction Generator (SCIG), and voltage source converter control by Space Vector Pulse Width Modulation (SPVWM). To achieve Maximum Power Point Tracking (MPPT), the reference speed to the generator is searched via Extremum Seeking Control (ESC). ESC was designed for wind turbine region II operation based on dither-modulation scheme. ESC is a model-free method that has the ability to increase the captured power in real time under turbulent wind without any requirement for wind measurements. The controller is designed in two loops. In the outer loop, ESC is used to set a desired reference speed to PI controller to regulate the speed of the generator and extract the maximum electrical power. The inner control loop is based on Indirect Field Orientation Control (IFOC) to decouple the currents. Finally, Particle Swarm Optimization (PSO) is used to obtain the optimal PI parameters. Simulation and control of the system have been accomplished using MATLAB/Simulink 2014.
文摘Turbo码是一种常用的信道编码方式,正确识别Turbo码首先要正确识别其子递归系统卷积(recursive system convolutional,RSC)码,由于信道噪声与干扰引发误码,这就要求识别算法具有良好的抗误码性能以及识别能力。利用解调软判决序列,通过编码码元约束方程,构建指数形式的代价函数模型,将识别RSC码的生成矩阵问题转化为求解代价函数全域极值的最优化问题,最后在共轭梯度法的基础上,采用新的PRP步长因子来寻找全域极值点。仿真结果表明,所提算法与现有算法相比,收敛速度更快,在低信噪比下也有良好的识别能力。
文摘在铁路建设及运营阶段,侵入限界的异物对既有线的安全行车构成极大威胁。将复杂的空间侵限检测转换为简单的平面内异物检测,研究利用二维激光测距传感器构建三维幕墙的侵限检测方法。在异物检测过程中,正常通过的列车不能认作异物,必须设计合理的算法检测并予以剔除。由于列车主要体现在轨道平面的检测结果中,重点研究通过分析扫描点云的分布特征对轨道平面内侵限物体进行分类的算法,提出了利用测量序列极值点作为核心对象的快速DBSCAN(density-based spatial clustering of applications with noise)聚类方法,并利用点簇的运动及分布特征判断是否为正常通过列车。现场试验表明,该方法能够有效区分侵限异物和正常通过的列车。
文摘分析了单相单级光伏逆变器的模型特点及其对最大功率点跟踪(maximum power point tracking,MPPT)控制的特殊要求,提出了适用于这种类型光伏逆变器的MPPT方法。该方法利用极值搜索算法实现MPPT控制,通过高通滤波器提取逆变器直流电压中的纹波电压,以该纹波电压为极值搜索算法的扰动信号;在极值搜索算法中引入优化补偿环节,通过该环节提高算法的收敛速度,进一步优化MPPT控制的稳态和动态性能。仿真和实验结果表明该方法可以充分利用单相单级逆变器的固有纹波,在无需额外注入扰动信号的前提下,该MPPT方法能够快速准确地搜索到最大功率点。
