In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power ...In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.展开更多
This paper analyses the performance request of arc welding power source used in intelligent control of weld pool shape in pulsed GTAW, and develops a sample power source. The main circuit of the power source takes the...This paper analyses the performance request of arc welding power source used in intelligent control of weld pool shape in pulsed GTAW, and develops a sample power source. The main circuit of the power source takes the structure of single ended inverter with two switches, and takes IGBTs as power switches. The working frequency of the inverter is set at 20 kHz. The control circuit takes PWM circuit as center, and uses single chip computer to complete the manage functions such as the control of working sequence, setting and changing of the welding parameters, sensing of the welding states and communication with outside computer etc. The dynamic reacting time of the whole power is 1 ms, the range of the output current is 5～250 A, the precision of the output current reaches to 1 A. The power strikes arc by contacting workpiece under 5 A, and have convenient interface with system computer. All above shows this power source is one with high performance.展开更多
风电机组的大规模接入导致电力系统惯量明显下降,并对系统频率安全稳定造成威胁。针对风电高渗透电力系统区域惯量辨识中频率最优测点选择困难和惯量估计误差较大等问题,提出了一种基于组合模型的风电高渗透电力系统区域惯量辨识方法。...风电机组的大规模接入导致电力系统惯量明显下降,并对系统频率安全稳定造成威胁。针对风电高渗透电力系统区域惯量辨识中频率最优测点选择困难和惯量估计误差较大等问题,提出了一种基于组合模型的风电高渗透电力系统区域惯量辨识方法。首先,采用基于形状距离(shape-based distance,SBD)指标的K-shape聚类算法对频率响应曲线进行聚类,并确定各区域内频率动态响应曲线的最优测量路径。其次,结合最小二乘支持向量机(least squares support vector machine,LSSVM)和受控自回归滑动平均模型(autoregressive moving average with exogenous input,ARMAX)对不同风电渗透率下各区域惯量水平进行辨识,并与传统ARMAX模型的惯量辨识结果进行对比分析。最后,通过改进的IEEE10机39节点系统对所提方法的有效性进行仿真验证。结果表明,所提方法有效提高了区域和全系统惯量辨识精度。展开更多
基金supported by the National Basic Research Programof China (2011CB711102)the National Natural Science Foundation of China (10672017,11002045)
文摘In this paper,wave and vibratory power transmission in a finite L-shaped Mindlin plate with two simply supported opposite edges are investigated using the wave approach.The dynamic responses,active and reactive power flow in the finite plate are calculated by the Mindlin plate theory （MPT） and classic plate theory （CPT）.To satisfy the boundary conditions and continuous conditions at the coupled junction of the finite L-shaped plate,the near-field and far-field waves are entirely contained in the wave approach.The in-plane longitudinal and shear waves are also considered.The results indicate that the vibratory power flow based on the MPT is different from that based on the CPT not only at high frequencies but also at low and medium frequencies.The influence of the plate thickness on the vibrational power flow is investigated.From the results it is seen that the shear and rotary inertia correction of the MPT can influence the active and reactive power at the junction of the L-shaped plate not only at high frequencies but also at low and medium frequencies.Furthermore,the effects of structural damping on the active and reactive power flow at the junction are also analyzed.
文摘This paper analyses the performance request of arc welding power source used in intelligent control of weld pool shape in pulsed GTAW, and develops a sample power source. The main circuit of the power source takes the structure of single ended inverter with two switches, and takes IGBTs as power switches. The working frequency of the inverter is set at 20 kHz. The control circuit takes PWM circuit as center, and uses single chip computer to complete the manage functions such as the control of working sequence, setting and changing of the welding parameters, sensing of the welding states and communication with outside computer etc. The dynamic reacting time of the whole power is 1 ms, the range of the output current is 5～250 A, the precision of the output current reaches to 1 A. The power strikes arc by contacting workpiece under 5 A, and have convenient interface with system computer. All above shows this power source is one with high performance.
文摘风电机组的大规模接入导致电力系统惯量明显下降,并对系统频率安全稳定造成威胁。针对风电高渗透电力系统区域惯量辨识中频率最优测点选择困难和惯量估计误差较大等问题,提出了一种基于组合模型的风电高渗透电力系统区域惯量辨识方法。首先,采用基于形状距离(shape-based distance,SBD)指标的K-shape聚类算法对频率响应曲线进行聚类,并确定各区域内频率动态响应曲线的最优测量路径。其次,结合最小二乘支持向量机(least squares support vector machine,LSSVM)和受控自回归滑动平均模型(autoregressive moving average with exogenous input,ARMAX)对不同风电渗透率下各区域惯量水平进行辨识,并与传统ARMAX模型的惯量辨识结果进行对比分析。最后,通过改进的IEEE10机39节点系统对所提方法的有效性进行仿真验证。结果表明,所提方法有效提高了区域和全系统惯量辨识精度。
