The correct rate of detection for fabric defect is affected by low contrast of images. Aiming at the problem,frequencytuned salient map is used to detect the fabric defect. Firstly,the images of fabric defect are divi...The correct rate of detection for fabric defect is affected by low contrast of images. Aiming at the problem,frequencytuned salient map is used to detect the fabric defect. Firstly,the images of fabric defect are divided into blocks. Then,the blocks are highlighted by frequency-tuned salient algorithm. Simultaneously,gray-level co-occurrence matrix is used to extract the characteristic value of each rectangular patch. Finally,PNN is used to detect the defect on the fabric image. The performance of proposed algorithm is estimated off-line by two sets of fabric defect images. The theoretical argument is supported by experimental results.展开更多
This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial re...This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial response and damping power via power injection from/to the energy storage system. The effect of a VSG with constant parameters(CP-VSG) on the system frequency is analyzed. Based on the case study, self-tuning algorithms are used to search for optimal parameters during the operation of the VSG in order to minimize the amplitude and rate of change of the frequency variations. The performances of the proposed self-tuning(ST)-VSG, the frequency droop method, and the CP-VSG are evaluated by comparing their effects on attenuating frequency variationsunder load variations. For both simulated and experimental cases, the ST-VSG was found to be more efficient than the other two methods in improving frequency stability.展开更多
利用直流输电线路的直流功率调制可以有效地抑制交直流互联电网区域间的低频振荡,而如何确定合适的直流调制控制器参数是一个研究难点。在传统的Prony分析方法中引入多信号到基于奇异值-总体最小二乘法(Singular Value Decomposed-total...利用直流输电线路的直流功率调制可以有效地抑制交直流互联电网区域间的低频振荡,而如何确定合适的直流调制控制器参数是一个研究难点。在传统的Prony分析方法中引入多信号到基于奇异值-总体最小二乘法(Singular Value Decomposed-total Least Square,SVD-TLS)确定信号阶数的改进Prony算法中,并在考虑系统初始状态的条件下辨识系统降阶传递函数,给出了不依赖电力系统的数学模型而辨识出系统降阶模型的实用步骤,有效的避开了控制器参数在以往设计中的困难。依据辨识所得结果结合极点配置法整定控制器参数。通过理论分析和IEEE四机系统验证了改进多信号Prony算法提高了辨识精度;仿真结果表明互联系统附加参数经过改进算法整定的直流调制控制器可以明显增加交直流互联系统的振荡阻尼,提高系统运行稳定性。展开更多
文摘The correct rate of detection for fabric defect is affected by low contrast of images. Aiming at the problem,frequencytuned salient map is used to detect the fabric defect. Firstly,the images of fabric defect are divided into blocks. Then,the blocks are highlighted by frequency-tuned salient algorithm. Simultaneously,gray-level co-occurrence matrix is used to extract the characteristic value of each rectangular patch. Finally,PNN is used to detect the defect on the fabric image. The performance of proposed algorithm is estimated off-line by two sets of fabric defect images. The theoretical argument is supported by experimental results.
基金supported by National High Technology Research and Development Program of China(863Program)(No.2015AA050607)the National key Research and Development Program of China(No.2016YFB0900300)the Science and Technology project of SGCC(No.NYB17201700151)
文摘This paper investigates the use of a virtual synchronous generator(VSG) to improve frequency stability in an autonomous photovoltaic-diesel microgrid with energy storage. VSG control is designed to emulate inertial response and damping power via power injection from/to the energy storage system. The effect of a VSG with constant parameters(CP-VSG) on the system frequency is analyzed. Based on the case study, self-tuning algorithms are used to search for optimal parameters during the operation of the VSG in order to minimize the amplitude and rate of change of the frequency variations. The performances of the proposed self-tuning(ST)-VSG, the frequency droop method, and the CP-VSG are evaluated by comparing their effects on attenuating frequency variationsunder load variations. For both simulated and experimental cases, the ST-VSG was found to be more efficient than the other two methods in improving frequency stability.
文摘利用直流输电线路的直流功率调制可以有效地抑制交直流互联电网区域间的低频振荡,而如何确定合适的直流调制控制器参数是一个研究难点。在传统的Prony分析方法中引入多信号到基于奇异值-总体最小二乘法(Singular Value Decomposed-total Least Square,SVD-TLS)确定信号阶数的改进Prony算法中,并在考虑系统初始状态的条件下辨识系统降阶传递函数,给出了不依赖电力系统的数学模型而辨识出系统降阶模型的实用步骤,有效的避开了控制器参数在以往设计中的困难。依据辨识所得结果结合极点配置法整定控制器参数。通过理论分析和IEEE四机系统验证了改进多信号Prony算法提高了辨识精度;仿真结果表明互联系统附加参数经过改进算法整定的直流调制控制器可以明显增加交直流互联系统的振荡阻尼,提高系统运行稳定性。
