To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector mac...To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.展开更多
A frequency-domain-based sufficient condition is derived to guarantee the globally asymptotic stability of the simplest Takagi-Sugeno （T-S） fuzzy control system by using the circle criterion. The analysis is perform...A frequency-domain-based sufficient condition is derived to guarantee the globally asymptotic stability of the simplest Takagi-Sugeno （T-S） fuzzy control system by using the circle criterion. The analysis is performed in the frequency domain, and hence the condition is of great significance when the frequency-response method, which is widely used in the linear control theory and practice, is employed to synthesize the simplest T-S fuzzy controller. Besides, this sufficient condition is featured by a graphical interpretation, which makes the condition straightforward to be used. Comparisons are drawn between the performance of the simplest T-S fuzzy controller and that of the linear compensator. Two numerical examples are presented to demonstrate how this sufficient condition can be applied to both stable and unstable plants.展开更多
强耦合条件下,复杂系统的有限元分析受到自由度的影响计算成本高昂。虽然模态叠加技术能减少耦合系统的自由度,但基于忽略不同子系统间高阶模态和低阶模态耦合作用的假设,若使用非耦合模态可能导致收敛性差。基于无阻尼声振耦合方程,本...强耦合条件下,复杂系统的有限元分析受到自由度的影响计算成本高昂。虽然模态叠加技术能减少耦合系统的自由度,但基于忽略不同子系统间高阶模态和低阶模态耦合作用的假设,若使用非耦合模态可能导致收敛性差。基于无阻尼声振耦合方程,本文采用分片传递函数法(Patch transfer function method,PTFM)将耦合面处理成一系列独立的分片,每个分片上所属单元节点值的平均值定义为分片传递函数,通过使用连续性关系计算耦合系统的分片传递函数。将耦合矩阵的求逆简化为源点到响应点的传递函数,可以快速计算耦合系统响应值。分别利用直接耦合法(Direct coupling method,DCM)和分片传递函数法计算板和空气声腔耦合模型,验证分片传递函数法的有效性,并讨论了分片传递函数的算法原理和计算误差。展开更多
Winding is one of themost important components in power transformers.Ensuring the health state of the winding is of great importance to the stable operation of the power system.To efficiently and accurately diagnose t...Winding is one of themost important components in power transformers.Ensuring the health state of the winding is of great importance to the stable operation of the power system.To efficiently and accurately diagnose the disc space variation(DSV)fault degree of transformer winding,this paper presents a diagnostic method of winding fault based on the K-Nearest Neighbor(KNN)algorithmand the frequency response analysis(FRA)method.First,a laboratory winding model is used,and DSV faults with four different degrees are achieved by changing disc space of the discs in the winding.Then,a series of FRA tests are conducted to obtain the FRA results and set up the FRA dataset.Second,ten different numerical indices are utilized to obtain features of FRA curves of faulted winding.Third,the 10-fold cross-validation method is employed to determine the optimal k-value of KNN.In addition,to improve the accuracy of the KNN model,a comparative analysis is made between the accuracy of the KNN algorithm and k-value under four distance functions.After getting the most appropriate distance metric and kvalue,the fault classificationmodel based on theKNN and FRA is constructed and it is used to classify the degrees of DSV faults.The identification accuracy rate of the proposed model is up to 98.30%.Finally,the performance of the model is presented by comparing with the support vector machine(SVM),SVM optimized by the particle swarmoptimization(PSO-SVM)method,and randomforest(RF).The results show that the diagnosis accuracy of the proposed model is the highest and the model can be used to accurately diagnose the DSV fault degrees of the winding.展开更多
文中以一种新型变压器绕组检测方法——扫频阻抗法为理论依据,建立了试验室测试系统,并利用该系统对单相双绕组变压器进行了测试。其结果表明:扫频阻抗法能够有效反映变压器绕组分布式参数,且其测试结果在频率大于11.5 k Hz时与频响曲...文中以一种新型变压器绕组检测方法——扫频阻抗法为理论依据,建立了试验室测试系统,并利用该系统对单相双绕组变压器进行了测试。其结果表明:扫频阻抗法能够有效反映变压器绕组分布式参数,且其测试结果在频率大于11.5 k Hz时与频响曲线呈现轴对称关系;短路故障会造成50 Hz处阻抗值与相关系数皆发生变化,且故障越严重,阻抗值与相关系数的变化越明显。展开更多
轴向位移故障是电力变压器常见故障之一,为此结合有限元模型与频率响应法,提出了一种基于“结构参数–电气参数–试验结果”诊断思路的电力变压器轴向位移故障诊断方法。基于实际变压器的结构尺寸及材料特性在Ansoft Maxwell中建立变压...轴向位移故障是电力变压器常见故障之一,为此结合有限元模型与频率响应法,提出了一种基于“结构参数–电气参数–试验结果”诊断思路的电力变压器轴向位移故障诊断方法。基于实际变压器的结构尺寸及材料特性在Ansoft Maxwell中建立变压器有限元模型,计算了变压器主要电气参数（对地电容、饼间电容等）,分析了不同轴向位移故障程度下电气参数的变化。为研究变压器绕组轴向位移故障对变压器频率响应曲线的影响,运用有限元模型中求解得到的电气参数,搭建了变压器等值电路模型。仿真了不同轴向位移程度下变压器的频率响应曲线的变化,结果表明：轴向位移故障会引起频率响应曲线在150 k Hz左右产生幅值变化,同时导致200-250 k Hz频率带及350-450 k Hz频率带上谐振峰的整体右移。仿真结果与现场试验表现出较好的一致性,因此,提出的故障诊断方法可以对现有判据进行补充,以提高变压器轴向位移故障诊断的准确度。展开更多
基金Project(51335003)supported by the National Natural Science Foundation of ChinaProject(20111102110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To ameliorate reliability analysis efficiency for aeroengine components, such as compressor blade, support vector machine response surface method(SRSM) is proposed. SRSM integrates the advantages of support vector machine(SVM) and traditional response surface method(RSM), and utilizes experimental samples to construct a suitable response surface function(RSF) to replace the complicated and abstract finite element model. Moreover, the randomness of material parameters, structural dimension and operating condition are considered during extracting data so that the response surface function is more agreeable to the practical model. The results indicate that based on the same experimental data, SRSM has come closer than RSM reliability to approximating Monte Carlo method(MCM); while SRSM(17.296 s) needs far less running time than MCM(10958 s) and RSM(9840 s). Therefore,under the same simulation conditions, SRSM has the largest analysis efficiency, and can be considered a feasible and valid method to analyze structural reliability.
文摘A frequency-domain-based sufficient condition is derived to guarantee the globally asymptotic stability of the simplest Takagi-Sugeno （T-S） fuzzy control system by using the circle criterion. The analysis is performed in the frequency domain, and hence the condition is of great significance when the frequency-response method, which is widely used in the linear control theory and practice, is employed to synthesize the simplest T-S fuzzy controller. Besides, this sufficient condition is featured by a graphical interpretation, which makes the condition straightforward to be used. Comparisons are drawn between the performance of the simplest T-S fuzzy controller and that of the linear compensator. Two numerical examples are presented to demonstrate how this sufficient condition can be applied to both stable and unstable plants.
文摘强耦合条件下,复杂系统的有限元分析受到自由度的影响计算成本高昂。虽然模态叠加技术能减少耦合系统的自由度,但基于忽略不同子系统间高阶模态和低阶模态耦合作用的假设,若使用非耦合模态可能导致收敛性差。基于无阻尼声振耦合方程,本文采用分片传递函数法(Patch transfer function method,PTFM)将耦合面处理成一系列独立的分片,每个分片上所属单元节点值的平均值定义为分片传递函数,通过使用连续性关系计算耦合系统的分片传递函数。将耦合矩阵的求逆简化为源点到响应点的传递函数,可以快速计算耦合系统响应值。分别利用直接耦合法(Direct coupling method,DCM)和分片传递函数法计算板和空气声腔耦合模型,验证分片传递函数法的有效性,并讨论了分片传递函数的算法原理和计算误差。
基金supported in part by Shaanxi Natural Science Foundation Project (2023-JC-QN-0438)in part by Fundamental Research Funds for the Central Universities (2452021050).
文摘Winding is one of themost important components in power transformers.Ensuring the health state of the winding is of great importance to the stable operation of the power system.To efficiently and accurately diagnose the disc space variation(DSV)fault degree of transformer winding,this paper presents a diagnostic method of winding fault based on the K-Nearest Neighbor(KNN)algorithmand the frequency response analysis(FRA)method.First,a laboratory winding model is used,and DSV faults with four different degrees are achieved by changing disc space of the discs in the winding.Then,a series of FRA tests are conducted to obtain the FRA results and set up the FRA dataset.Second,ten different numerical indices are utilized to obtain features of FRA curves of faulted winding.Third,the 10-fold cross-validation method is employed to determine the optimal k-value of KNN.In addition,to improve the accuracy of the KNN model,a comparative analysis is made between the accuracy of the KNN algorithm and k-value under four distance functions.After getting the most appropriate distance metric and kvalue,the fault classificationmodel based on theKNN and FRA is constructed and it is used to classify the degrees of DSV faults.The identification accuracy rate of the proposed model is up to 98.30%.Finally,the performance of the model is presented by comparing with the support vector machine(SVM),SVM optimized by the particle swarmoptimization(PSO-SVM)method,and randomforest(RF).The results show that the diagnosis accuracy of the proposed model is the highest and the model can be used to accurately diagnose the DSV fault degrees of the winding.
文摘文中以一种新型变压器绕组检测方法——扫频阻抗法为理论依据,建立了试验室测试系统,并利用该系统对单相双绕组变压器进行了测试。其结果表明:扫频阻抗法能够有效反映变压器绕组分布式参数,且其测试结果在频率大于11.5 k Hz时与频响曲线呈现轴对称关系;短路故障会造成50 Hz处阻抗值与相关系数皆发生变化,且故障越严重,阻抗值与相关系数的变化越明显。
文摘轴向位移故障是电力变压器常见故障之一,为此结合有限元模型与频率响应法,提出了一种基于“结构参数–电气参数–试验结果”诊断思路的电力变压器轴向位移故障诊断方法。基于实际变压器的结构尺寸及材料特性在Ansoft Maxwell中建立变压器有限元模型,计算了变压器主要电气参数（对地电容、饼间电容等）,分析了不同轴向位移故障程度下电气参数的变化。为研究变压器绕组轴向位移故障对变压器频率响应曲线的影响,运用有限元模型中求解得到的电气参数,搭建了变压器等值电路模型。仿真了不同轴向位移程度下变压器的频率响应曲线的变化,结果表明：轴向位移故障会引起频率响应曲线在150 k Hz左右产生幅值变化,同时导致200-250 k Hz频率带及350-450 k Hz频率带上谐振峰的整体右移。仿真结果与现场试验表现出较好的一致性,因此,提出的故障诊断方法可以对现有判据进行补充,以提高变压器轴向位移故障诊断的准确度。
