Frequency support capability of variable speed wind turbine based on electromagnetic coupler

In the variable speed wind turbine based on electromagnetic coupler (WT-EMC), a synchronous generator is directly coupled with grid. So like conventional power plants WT-EMC is able to support grid frequency inherently. But due to the reduced inertia of synchronous generator, its frequency support capability has to be enhanced. In this paper, the frequency support capability of WT-EMC is studied at three typical wind conditions and with two control strategies—droop control and inertial control to enhance its frequency support capability. The synchronous generator speed, more stable than the grid frequency which is the input signal for Type 3 and Type 4 wind turbine frequency support controller, is used for the calculation of WT-EMC supplementary torque command. The integrated simulation environment based on the aeroelastic code HAWC2 and software Matlab/Simulink is used to build a 2 MW WT-EMC model and study the frequency support capability of a wind farm consisting of WT-EMC.     

同步带传动失效及疲劳寿命研究

通过实验及理论分析，探讨了带的张力、带及带轮的节距差、齿形等对同步带传动的失效形式及疲劳寿命的影响，并分析了同步带产生疲劳破坏的机理．     

综合单元验前信息的系统可靠度Bayes评估

针对目前可靠性评估方法的不足,提出了综合单元验前信息的系统可靠度Bayes评估方法。该方法根据验前信息确定各单元的验前分布,将寿命型单元等效为成败型单元,将混联系统等效为串联系统,从而将复杂系统转化为成败型单元串联系统,在此基础上利用各单元的验后前两阶矩进行系统可靠度综合,能够较好地解决传统方法对数据依赖性过强、不能有效综合验前信息等缺陷。最后通过仿真示例验证了该方法的合理性与有效性。     

仪表设备故障原因的分析与查寻

本文系统阐述了对仪表故障的类型及原因,在仪器仪表与现场运行环境越来越融为一体的今天,它不仅适合指导仪器仪表的故障查寻,也适合施工安装线路故障的查寻。     

THEORY OF MUM FOR METAL SPHERICAL ROTOR WITH CONTACTLESS SUSPENSION

Based on the motion equations of an unbalanced spherical rotor with contactless suspension,three methods of MUM (mass unbalance measurement) are put forward to measure the total massunbalance, radical mass unbalance and radical mass unbalance of the rotor. Total mass unbalance isobtained when the unbalanced rotor plays as a simple pendulum in static situation. The pendulant pe-riod and pendulant midpoint indicate magnitude and direction of total mass unbalance of the rotorrespectively Analysis of the motion equations by using the averaging method yields that the rotor willdo a special side oscillation when an auxiliary system maks the rotor spin about its pole axis which isorientating toward the local vertical. The radical mass unbalance can be obtained by building a properdisplacement sensor to sense the amplitude of the side oscillation. Necessary analysis of the motionequaions also shows that when the rotor spins at a small angular velocity and the rotary axis is per-pendicular to the vertical, the p     

电力系统谐波分析的近似同步法

提出了一种谐波分析的新方法——近似同步法。近似同步法采用了不严格相等的采样间隔，从而使每个采样点都尽量靠近同步采样点。近似同步法根据信号频率的变化实时地调整采样间隔，并且只需一个信号周期就可完成一次采样过程。近似同步法还提供了一个用基于系统辨识的矩阵反演定理导出的误差校正公式，它能消除近似同步采样造成的原始误差。Matlab仿真表明，近似同步法用于电力系统谐波分析不仅实时性好，而且精度也很高。     

轻型臂关节力矩传感器的设计

介绍了轻型臂智能关节力矩传感器的弹性体及信号调理电路设计，进行了传感器静态标定试验的研究，为改善传感器的动态响应特性，根据“逆模型”思想，采用最小二乘法、基于函数联接型神经网络法以及辅助变量法设计了力矩传感器的动态补偿器。实验结果表明，辅助变量法具有更好的补偿作用，设计的力矩传感器满足轻型臂系统的要求。     

基于永磁同步交流伺服电动机的转矩控制系统研究

介绍了一种基于永磁同步伺服电动机（PMSM）的转矩控制系统，该系统由转矩控制电路和泵升电压逆变回馈电路两部分构成，详细讨论了这种复合结构的工作原理和控制方法，并阐述了相应的矢量解耦控制策略。最后，给出了实际运行的实验结果数据，可以满足恒定转矩控制的要求。     

A bulk-flow analysis of static and dynamic characteristics of floating ring seals

The bulk-flow model was used to calculate the static and the dynamic characteristics of floating ring seals because the solutions based on the numerical integration of the complete Navier–Stokes equations can be very time consuming. A steepest-descent method is used to find the seal's equilibrium position efficiently. The bulk-flow model is governed by three partial differential equations on eccentric working conditions. A finite-difference scheme has been used to solve the nonlinear governing equations. Compared to Nelson and Nguyen's fast fourier transform method, this scheme has better consistency. Perturbation analysis of the flow variables yields a set of zeroth and first-order equations. The SIMPLE algorithm is used to integrate the system of bulk-flow equations. Comparisons of the numerical predictions (lock-up eccentricity ratio, leakage flow rate and rotordynamic coefficients) with Ha's results, which were formulated using the Fourier series, and experimental data are presented subsequently.     

FINITE DIFFERENCE METHOD-BASED SIMULATION OF TEMPERATURE FIELDS FOR APPLICATION TO ORTHOGONAL CUTTING WITH COATED TOOLS

A finite difference method was proposed to model the effect of a variety of tool coatings on the magnitude and distribution of temperatures through the tool-chip contact region and the coating/substrate boundaries. For each workpiece-tool pair tested the intensity of uniformly distributed heat flux and relevant analytically obtained values of the heat partition coefficient were assumed to change with variations of cutting speed and the corresponding friction. In this case the simulation of an orthogonal machining of AISI 1045 steel was performed using special computing algorithm with elementary balances of induced energies (MBE). It is concluded that the temperature contours obtained reflect favorable the specific contact conditions existing at the tool-chip interface and substantial differences can arise from coating effects.