发电厂内强迫共振型低频振荡源的定位方法

强迫共振型低频振荡严重危害了电网的安全稳定运行,快速查找并切除扰动源对消除振荡恢复系统稳定意义重大。利用低频扰动电压的衰减特性,提出一种发电厂内强迫共振型低频振荡源定位的新方法。首先利用三次Hermite插值函数提取各个测点的低频振荡扰动变量;然后通过比较各个测点扰动电压的幅值大小定位低频振荡源机组;最后通过理论分析、六机无穷大系统的仿真分析以及某发电厂的实际相量测量单元测量数据的分析,对该方法的正确性进行了验证。     

非连续供电模式下感应电机低频振荡机理分析

采用对称分量法,排除变频器一侧电感和电容影响,对感应电机在最简单的不连续供电模式下(晶闸管供电)的振荡现象进行研究。通过分析电机在三相及两相导通模式下的换相瞬态过程,考虑转速改变时电机方程各量的变化,推导电机在不同过渡过程时其定转子电流的空间向量表达式,并给出其时域形式解,找到感应电机在不连续供电时产生振荡的原因,从电机本体方面对振荡现象进行解释。应用上述分析方法对一台三相感应电机进行计算,计算结果与实验吻合较好。分析方法可作为进一步研究变频器供电的感应电机的过渡过程的基础。     

移相全桥变换器中RC缓冲电路对系统影响机理与优化研究

移相全桥ZVS变换器副边整流二极管电压应力较高,需要设计缓冲电路来保证系统性能。然而,加入RC缓冲电路的变换器在某种工作模式下近似为LCL三阶谐振系统,导致接近开关频率的谐振甚至在整流二极管两侧产生更高的电压应力。通过建立移相全桥ZVS变换器在能量传输模式期间的等效电路模型,揭示RC缓冲电路对系统稳定性产生影响机理及电路参数对振荡的影响规律,通过分析选取合理的RC缓冲电路参数,不仅有效降低整流二极管电压应力,同时抑制由缓冲电路带来的振荡问题,进而提高系统的效率。设计了一个3.2 k W(10 A,320 V)的实验样机,验证了理论分析的正确性。     

Analysis of weld pool vibration characteristics in pulsed gas metal arc welding

Using highspeed camera image measuring and processing, the contour of the weld pool was extracted accurately in pulsed metal inert gas (P-MIG) welding. Based on this extraction method, time and frequency domain characteristics at different points along the contour of the weld pool were analyzed for one pulse one droplet and one pulse two droplets, respectively. The results show that, because of the wave super position that was created by the pulsed arc and droplet impacting the weld pool, the oscillation amplitude along the weld pool fluctuated and decreased with an increase in distance from the point to the arc center. The oscillation near the arc center was complex and intense for one pulse two droplets, and the amplitude were relatively small because the oscillation caused by the pulsed arc could be offset by the molten droplet impact. The weld pool oscillation that was caused by the pulsed arc was stronger than that caused by the droplet.     

基于摄动法的多股簧冲击载荷改进模型

在多股簧冲击载荷原有模型的基础上引入非线性刚度,建立冲击载荷改进模型;基于强非线性振动求解原理提出一种改进多尺度法,并推导了该模型的非线性响应摄动解;结合冲击试验数据对两种模型进行比较。结果表明,改进模型体现了多股簧刚度非线性及振动频率非线性特性,提高了试验数据拟合精度,对描述多股簧动态运动规律更精确,尤其对受冲击载荷及大振幅工况下的多股簧非线性特性研究具有重要意义。该研究也为课题组正在研究的多股簧动态响应特性提供理论基础。     

An input–output linearization algorithm‐based control for optimization of DFIG

This paper proposes an input–output linearization‐based active power control strategy to maximize the energy production of a doubly fed induction generator (DFIG)‐based wind energy conversion system (WECS). The DFIG‐based wind turbine is a nonlinear system, and the nonlinear behavior will result in tracking errors. The proposed control strategy utilizing state feedback successfully deals with the nonlinear behavior existing in the WECS. Such a control will linearize the system input and output first. Then, the control loop and parameters can be designed by the linear system control algorithm. The simulations carried in MATLAB/Simulink demonstrate that the proposed control strategy is effective and promising. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于不完全S变换的低频振荡在线辨识方法

针对传统的低频振荡辨识方法无法确定低频振荡的起振时间点,不利于调度员分析振荡的起因,提出采用不完全S变换方法进行低频振荡的在线辨识,以提高算法的计算效率。仿真测试以及实例分析的结果表明基于不完全S变换的低频振荡在线辨识方法的辨识结果准确、抗噪能力强,能够有效地识别振荡模式个数以及振荡的起振时间点,具有很好的实用价值。     

A Model-trajectory-based Method for Analyzing the Time-varying Oscillation Characteristics of a Fault System

Due to the impossibility for the equilibrium-point eigenvalue method to reflect the oscillation characteristic of the fault system correctly, and the difficulty in choosing the window length using a trajectory eigenvalue method, a model-trajectory method is proposed to analyze the eigenvalue of a fault system. First, the system is equated by the mutual factor after fault clearance. Then the branch current and power of the post-fault system is calculated by the branch current of the original and the fault component network, respectively. Furthermore, the equivalent model of the system is built and linearized at each measuring point. By combining the linearized model with the actual disturbed trajectory, the time series of the eigenvalue of the fault system is calculated. Simulation results of 2-generator system and a 16-generator system illustrate that the model-trajectory method is able to describe the time-varying oscillation characteristic of a fault system effectively and accurately.     

电位模式对碳毡电极上SO_2脱除的影响

用碳毡制备脱除SO2的立体化电极并进行电化学脱硫测试,探索施加的电位模式对电极上SO2脱除的影响。研究表明,SO2从电极表面氧化脱除的过程与电位和施加电位的模式有关。相同条件下恒定部分电位越高脱硫效果越好;高低电位交替振荡脱硫模式比单一恒电位氧化脱硫模式电极活性恢复效果好,所用时间短;恒电位-SO2非氧化循环伏安脱硫模式比高低电位交替振荡模式和单一恒电位模式脱硫效果都好,该过程可以实现电极活性完全恢复且耗时显著减少。     

基于等效电路法的负阻尼能量机理及振荡源定位方法探讨

为解释自由振荡中产生振荡源的机理,在能量法基础之上提出了等效电路法。对电力系统各元件分别建立了其等效电路并组合得到系统的等效电路。根据电路理论,将积分形式的振荡源定位判据转化为相量判据。对于励磁系统,提出了3种振荡源定位判据。将这3种判据转化为相量形式并组合,分析了励磁系统产生振荡源的机理。算例仿真证明了该分析方法的正确性和有效性。该方法可用于在线定位励磁系统振荡源,并分析由于励磁参数设定不当而形成振荡源的机理。