基于扰动功率法的短期电能质量扰动源判定

采用扰动功率法对电压骤升、电压骤降、短时停电等短期电能质量扰动进行扰动源的判定,对公共连接点的各个支路,其扰动功率初始峰值极性作为扰动方向判定的依据,极性不同的支路为扰动源所在的支路。仿真结果表明,该方法对判定电压骤升、电压骤降、短时停电等短期电能质量扰动的扰动源有较好的效果。     

基于扰动功率法的短期电能质量扰动源判定

采用扰动功率法对电压骤升、电压骤降、短时停电等短期电能质量扰动进行扰动源的判定,对公共连接点的各个支路,其扰动功率初始峰值极性作为扰动方向判定的依据,极性不同的支路为扰动源所在的支路。仿真结果表明,该方法对判定电压骤升、电压骤降、短时停电等短期电能质量扰动的扰动源有较好的效果。     

基于扰动功率法的短期电能质量扰动源判定

文中采用扰动功率法对电压骤升、电压骤降、短时停电等短期电能质量扰动进行扰动源的判定,对公共连接点的各个支路,其扰动功率初始峰值极性作为扰动方向判定的依据,极性不同的支路为扰动源所在的支路.仿真结果表明,该方法对判定电压骤升、电压骤降、短时停电等短期电能质量扰动的扰动源有较好的效果.     

基于时域特征分析的电能质量扰动分类

在分析电能质量扰动信号的时域特征的基础上,提取了4个用于分类电能质量扰动的特征量,并且提出了一种电能质量扰动分类方法。所提取的扰动分类特征量具有较为明确的物理意义,因此,有利于对各种电能质量扰动进行估值;某一特征量或某几个特征量能唯一确定一种扰动,使扰动判断不再具有或然性;任一扰动的特征量不因其他扰动的存在而改变其值,因此,可以准确辨别出混合扰动。MATLAB仿真和分析表明,该方法能有效地分类更多的单一和混合电能质量扰动,并且计算耗时更少。     

基于扰动观测器的双馈风电机组最优复合反馈控制研究

双馈风电机组的转子通过变流器连接到电网,由于在转子侧的硬件电路中含有开关模块,使系统在运行过程中极易产生谐波扰动,该谐波会增加风机的损耗,使风机运行不稳定,减低电能质量。针对这些问题,首先设计了一种最优复合反馈控制器,使无扰动风机系统工作在稳定状态;然后,对含谐波扰动的风机系统,设计扰动观测器,观测出谐波扰动并在输入端进行抵消,使含谐波扰动的风机系统能够快速到达稳态;最后,通过仿真验证了设计的扰动观测器能够准确观测出谐波扰动,控制策略能够使双馈风电机组系统快速到达稳定状态。     

一种新的电能质量扰动分类识别算法

通过分析电能质量扰动信号的时域特征,提出一种电能质量扰动分类方法.所提取的扰动分类特征量具有明确的物理意义,有利于对各种电能质量扰动进行估值.某一特征量或某几个特征量能唯一确定一种扰动,使扰动判断不再具有或然性.任一扰动的特征量不因其他扰动的存在而改变.因此,可以准确辨别出混合扰动.MATLAB仿真结果表明,该方法能有...     

电能质量扰动发生器控制策略及其实现

为了测试电力变压器、CVT、电力电容器、无功与谐波补偿装置等试验设备在电能质量扰动下的工况,设计了一种电能质量扰动发生器,能模拟实际电网输出各种形式电压与电流扰动。采用电压外环与电流内环的PWM整流控制实现了直流电压的稳定;利用电压前馈与重复学习相结合的控制策略实现了发生器较高精度输出;利用DSP+FPGA构建控制系统具有较好的实时性与可靠性。通过10 kV、2 MVA工业样机实验,证明了设计的正确性。     

二次扰动信息及其在继电保护中的应用

故障后的电力系统经常伴随着断路器开断操作或转换性故障等二次扰动，二次扰动会引起继电保护装置的不正确动作，甚至造成大面积停电或稳定性破坏事故。论文定义并分析了二次扰动和二次扰动信息，提出了根据叠加原理计算二次扰动信息的计算方法，分析了二次扰动对继电保护的影响并探讨了利用二次扰动信息构造继电保护的可能性。     

基于改进扰动功率和能量法的暂态扰动定位

功率和能量法是一种定位电能质量扰动问题的常用方法,但它在定位向系统注入能量的扰动类型时,会发生原理性错误。文中对此进行了改进,提出一种基于改进功率和能量法的暂态扰动定位方法。改进法结合了扰动初始能量的极值和扰动初始电压的极值,使其可以同时处理向系统注入能量的扰动和系统释放能量的扰动。改进方法不需要在定位前对暂态扰动进行分类,就可以对2类暂态扰动进行准确的定位。对比仿真分析表明,改进方法达到了准确定位2类暂态扰动的目的。     

用小波变换和瞬时功率定位电能质量扰动源

为经济合理地精确定位电能质量扰动,根据监测点的电压电流波形,基于小波多分辨率,提出了一种扰动源定位新方法。该法首先对电压电流波形进行小波变换确定扰动的起止时刻,然后基于瞬时功率计算扰动功率和扰动能量,最后通过分析确定扰动源在监测设备的位置。针对电压暂降和电容器投切造成的扰动,运用此法分别依据ATP仿真数据和实际监测数据进行了分析,准确判断了扰动源在监测点的位置。结果表明,只要电网中的监测设备足够多,依据对扰动源定位的方法可实现扰动源的精确定位。     

电能质量复合扰动分类的研究进展

针对电能质量复合扰动的识别问题,通过举例分析复合扰动信号,讨论了复合扰动的特点。详细综述国内外电能质量复合扰动分类的研究现状,将其研究方法分为单标签分类和多标签分类两大方面,分别对这两个方面中目前采用的思想和方法进行讨论。在单标签分类中,分别从直接分类、S变换+分类器、小波变换+神经网络、支持向量机和其它方法五个方面进行复合扰动分类讨论。在多标签分类中,分别从分类思路、分类策略和标签相关性等方面对该方法进行了讨论。最后,分析了电能质量复合扰动识别目前存在的问题,对其研究进行了展望。     

基于S变换和扩张神经网络的电能质量扰动分类

提出了一种基于S变换和扩张神经网络的电能质量扰动分类方法。首先使用S变换对扰动信号进行时频分析,研究了在有多种扰动同时发生的情况下,从S变换的结果中提取扰动特征量的方法,得到了由基频特征矢量、高频特征矢量、相位特征矢量组成的特征矢量组。最后,将提取出来的扰动特征矢量组送入由扩张神经网络构建的分类器中,完成对扰动的分类。扩张神经网络以扩张距离代替欧氏距离来衡量测试数据与聚类中心的相似度,分类正确率高、结构简单、训练快速。仿真结果表明,该方法能准确地对扰动进行分类,对噪声不敏感。     

Adaptive IDA‐PBC for underactuated mechanical systems with constant disturbances

This work investigates the control of nonlinear underactuated mechanical systems with matched and unmatched constant disturbances. To this end, a new control strategy is proposed, which builds upon the interconnection‐and‐damping‐assignment passivity‐based control, augmenting it with an additional term for the purpose of disturbance compensation. In particular, the disturbances are estimated adaptively and then accounted for in the control law employing a new matching condition of algebraic nature. Stability conditions are discussed, and for comparison purposes, an alternative controller based on partial feedback linearization is presented. The effectiveness of the proposed approach is demonstrated with numerical simulations for three motivating examples: the inertia wheel pendulum, the disk‐on‐disk system, and the pendulum‐on‐cart system.     

Rejection of narrow‐band disturbances subject to uncertain time delays

In this work, the problem of designing feedback contollers for the rejection of narrow‐band disturbances is considered. The design technique proposed herein is based on the overparametrization of a nominal minimum‐variance controller, which is designed by means of an ARMA model of a sinusoid in noise. The extra degrees of freedom so introduced are used to improve the robustness of the nominal controller, when the time delay of the plant is subject to uncertainties, by minimizing a minimum‐variance performance index along a one‐dimensional line. Copyright © 2000 John Wiley & Sons, Ltd.     

Rejection of unknown periodic disturbances for continuous‐time MIMO systems with dynamic uncertainties

Rejection of unknown periodic disturbances in multi‐channel systems has several industrial applications that include aerospace, consumer electronics, and many other industries. This paper presents a design and analysis of an output‐feedback robust adaptive controller for multi‐input multi‐output continuous‐time systems in the presence of modeling errors and broadband output noise. The trade‐off between robust stability and performance improvement as well as practical design considerations for performance improvements are presented. It is demonstrated that proper shaping of the open‐loop plant singular values as well as over‐parameterizing the controller parametric model can significantly improve performance. Numerical simulations are performed to demonstrate the effectiveness of the proposed scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

The internal model principle for periodic disturbances with rapidly time‐varying frequencies

In this paper, we study the limitations of scheduling an internal model to reject disturbances with a time‐varying frequency. Hence, any adaptive method that uses scheduling and frequency estimation is also limited in the same manner. The limitations of scheduling are to investigate by posing and solving the problem of rejecting periodic disturbances from a multichannel system when the frequencies of the periodic disturbances are changing rapidly in time by designing an scheduled controller that satisfies the internal model principle. The periodic disturbances are modeled by a sum of sinusoids and the frequencies of the disturbances are used for scheduling the controller. It is shown that a controller that regulates input additive disturbances may not regulate the same disturbances added to the output of the system. This is in contrast to the classical case where the frequency of the disturbances is constant. Copyright © 2011 John Wiley & Sons, Ltd.     

基于自定义阈值函数的小波去噪算法

基于硬阈函数和软阈函数的小波去噪算法处理的信号分别存在偏差和方差过大的缺点,为有效解决这一问题,提出基于自定义阈值函数的小波去噪算法。研究给出了一种改进型的自定义阈值函数,建立了该函数的数学模型,对基于该函数的小波去噪算法的去噪效果进行了仿真,并将该算法应用于实际的电能质量暂态信号检测之中。仿真和实验结果进一步表明了自定义阈值函数的优越性和基于自定义阈值函数小波去噪算法的有效性。     

Bounded‐error state and parameter estimation of tip‐tilt disturbances in adaptive optics systems

The main objective of this paper was to estimate tip‐tilt disturbances in adaptive optics systems. In a bounded‐error context, set inversion methods based on interval analysis are used to guarantee both state and parameter estimation of tip‐tilt disturbances. Consequently, two methods are performed. The first method is based on contraction–bisection, and the second one is based only on contraction. Both methods are thus compared, and results are discussed according to computational time and pessimism introduced on each estimated parameter. Copyright © 2013 John Wiley & Sons, Ltd.     

Adaptive finite‐time control for high‐order nonlinear systems with mismatched disturbances

In this paper, adaptive finite‐time control is addressed for a class of high‐order nonlinear systems with mismatched disturbances. An adaptive finite‐time controller is designed in which variable gains are adjusted to ensure finite‐time stabilization for the closed‐loop system. Chattering is reduced by a designed adaptive sliding mode observer which is also used to deal with the mismatched disturbances in finite time. The proposed adaptive finite‐time control method avoids calculating derivative repeatedly of traditional backstepping methods and reduces computational burden effectively. Three numerical examples are given to illustrate the effectiveness of the proposed method.     

Robust space vector modulation technique for unbalance voltage disturbances

Space vector modulation (SVM) is one of the most popular PWM techniques used in multilevel inverters. The calculation of reference vector location is very important for SVM technique to obtain exact switching times and to determine correct space vectors. Balanced/unbalanced voltage disturbance occurred in a three-phase system affects the switching times and output voltage of the multilevel inverter. In this study, effects of the disturbances such as line–line faults, balanced and unbalanced voltage sags/swells to SVM technique are investigated and a new technique derived from Clarke transformation is proposed. The effects of disturbances are minimized with this new method. Power System Computer-Aided Design is used to simulate the proposed test system.