一种基于在线建模的自适应有源噪声控制快速算法

针对次级通路时变条件下的快速算法展开研究.首先分析了已有的基于次级通路在线建模的FxLMS算法,同时给出了带策略选择的权系数局布迭代算法;在此基础上,提出了一种针对次级通路在线建模的带策略选择的局布迭代有源控制快速算法.给出了该快速算法的实现步骤;比较了不同算法的运算量;就次级通路为时变与非时变两种情况下对算法进行了计算机仿真.结果表明,本文提出的快速算法能有效地降低原算法的运算量,提高原算法次级通路在线建模部分的性能,并可在稳态时取得较原算法更优的降噪量.     

A narrowband active noise control system with reference synthesis

Most active noise control (ANC) algorithms require a model of the secondary path (SP). If there are large changes in the SP, online SP modeling algorithms may not be able to follow the changes quickly enough to prevent divergence. In this work, the mirror‐MFxLMS (MMFxLMS) is adapted to narrowband ANC, and the resulting algorithm is analyzed. The MMFxLMS is an algorithm similar to the MFxLMS and FxLMS but has online SP modeling; it is stable for any SP estimate and does not require auxiliary noise. In addition, a technique to alternate between MFxLMS and MMFxLMS is proposed, resulting in the M³FxLMS algorithm, which does not sacrifice performance and assures stability. However, the M³FxLMS requires a reference signal that is not available in feedback ANC. Feedback ANC is important in many practical cases, for instance, in ANC headphones. To solve this problem, a technique is proposed to synthesize a reference formed by a sum of sinusoids using measurements from the error sensor signal. This technique uses the fast Fourier transform to obtain estimates of the harmonic frequencies of the periodic noise components, and then refines and tracks these using a phase‐locked loop (PLL). The resulting algorithm enables a stable ANC system, even under large and sudden changes in the SP. The proposed PLL is also new and has a lock‐in range equal to the full band of the system.     

A numerically stable,finite memory,fast array recursive least squares filter for broadband active noise control

For broadband active noise control applications with a rapidly changing primary path, it is desirable to find algorithms with a rapid convergence, a fast tracking performance, and a low computational cost. Recently, a promising algorithm has been presented, called the fast‐array Kalman filter, which uses rotation matrices to calculate the filter parameters. However, when this algorithm is implemented, it can show unstable behavior because of finite precision error propagation. In this paper, a novel algorithm is presented, which exhibits the fast convergence and tracking properties and the linear calculation complexity of the fast‐array Kalman filter but does not suffer from the mentioned numerical problems. This is accomplished by running two finite length growing memory recursive least squares filters in parallel and using a convex combination of the two filters when the control signal is calculated. A reset of the filter parameters with proper re‐initialization is enforced periodically. The mixing parameters will be chosen in such a way that the total available information used for the calculation of the control signal will be approximately equal at every time instance. The performance of the filter is shown in numerical simulations and real‐time lab experiments. The numerical experiments show that the algorithm performs better numerically than the fast‐array sliding window recursive least squares filter, while achieving a comparable convergence rate and tracking performance. The real‐time lab experiments confirm the behavior shown in the simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

ANC系统次级通道背景噪声的处理方法

由于电力变压器ANC系统次级通道背景噪声的影响,使其辨识参数不能反映次级通道本身特性,影响整个降噪系统的降噪效果和收敛性能。论文首先以Fx-LMS算法为例,分析了辨识误差对算法收敛系数的影响。然后提出了一种次级通道背景噪声的去噪新方法,即将分时测量法与信号相关性分析结合,极大限度抑制了与激励信号频段相近的背景噪声影响。最后通过仿真计算证明去除背景噪声的效果明显,次级通道辨识精度显著提高。     

A new indirect adaptive algorithm for feedforward control with application to active noise cancellation

This paper considers the deterministic adaptive feedforward control problem for disturbance rejection. A new indirect adaptive control algorithm is presented as an alternative to the well-known ‘filtered-X LMS’ algorithm when the disturbance is periodic with unknown frequency and the plant, possibly non-minumum phase, is unknown. This new algorithm requires the solution of a Diophantine equation and a simple scheme to recursively solve this type of equation is suggested. the new algorithm is shown to converge without the use of a dither signal for plant modelling. Simulations demonstrate that the proposed algorithm has a substantially better transient response and convergence speed than the filtered-X LMS algorithm. the applicability of the algorithm to the adaptive active-noise-cancelling problem is demonstrated using an identified acoustic model.     

基于遗传算法的有源消声系统设计

建立了基于遗传算法的自适应有源消声模型,介绍有源消声系统原理,自适应控制系统的关键在于其控制算法,用算法来调整滤波器的系数.在消声系统里必须考虑的因素主要有误差、声音的延迟、声音的衰减、在公式中适当的加入相位变化等.该系统结合神经网络算法,遗传算法和BP算法结合并改进提高了精度和准确性,可以用来优化神经网络的结构及其权值.实验分别从单音和复音情况进行,实验结果证明了基于神经网络算法的自适应有源消声系统有良好的消声效果,该系统稳定性较强.     

柴油发电机房主动噪声控制系统的设计

在系统研究主动噪声控制技术和柴油发电机房内噪声来源的基础上,作者提出了一种利用复合主动噪声控制思想,改善柴油发电机房内噪声环境的方案,具体地说,就是采用反馈主动噪声控制系统,抵消发电机房低频噪声的总辐射,还采用前馈主动噪声控制系统,抵消柴油发动机噪声的基频分量及其多次谐波分量,分析表明,该方案具有较好的除噪效果和较高的实用价值。     

Development and convergence analysis of new least‐mean‐square‐based algorithm equipped with exponential‐decay step size and disturbance compensation for active noise control

In real‐world active noise control (ANC) applications, disturbance can be picked up by error sensors and significantly degrade the steady‐state ANC performance. This study proposes two techniques in combination with a least‐mean‐square (LMS) based ANC algorithm, named normalized filtered‐x LMS/commutation error (NFxLMS/CE) algorithm, to deal with the disturbance that is independent of a reference signal. A new stochastic method to analyze convergence properties of the NFxLMS/CE algorithm under influence of the disturbance is first established. Given that the reference signal is persistently exciting of sufficient order, exponential convergence of the algorithm is derived with a step‐size condition. An exponential‐decay step size (EDSS) is then proposed to obtain a new ANC algorithm referred to as EDSS‐NFxLMS/CE algorithm. In addition, a disturbance‐compensation (DC) technique is developed for the EDSS‐NFxLMS/CE algorithm to obtain an EDSS‐NFxLMS/CE_DC algorithm such that the influence of the disturbance can be reduced. It is shown that the EDSS‐NFxLMS/CE_DC algorithm is exponentially convergent. Moreover, computer simulations show that the EDSS‐NFxLMS/CE_DC algorithm can achieve a better ANC performance in terms of convergence rate and level of noise reduction as compared with that using the EDSS‐NFxLMS/CE algorithm without DC and that using NFxLMS/CE_DC algorithm of constant step sizes. These results support the effectiveness of the proposed techniques and EDSS‐NFxLMS/CE_DC algorithm. Copyright © 2012 John Wiley & Sons, Ltd.     

高比例风电对电力系统调频指标影响的定量分析

风电对电力系统现有调频体系的影响是否显著历来存在争议。文中考虑常规电源、负荷等与风电频率特性的交互作用,推导了含不同比例风电的系统总功率波动概率模型,进而得到最大频率偏差、静态频率偏差、一/二次调频调整速度、调频备用需求等关键调频指标随置信区间变化的概率表达式,从而提供了定量分析风电对系统调频体系影响的方法。对电网进行仿真分析提供了参考性结论。     

Behavior of the least mean square algorithm with a periodically time‐varying input power

The paper analyzes the transient and steady‐state performances of a least mean square algorithm in the rarely‐studied situation of a time‐varying input power. A scenario of periodic pulsed variation of the input power is considered. The analysis is carried out in the context of tracking a Markov plant with a white Gaussian input. It is shown that the mean square deviation (MSD) converges to a periodic sequence having the same period as that of the variation of the input power. Expressions are derived for the convergence time and the steady‐state peak MSD. Surprisingly, it is found that neither the transient performance nor the steady‐state performance degrades with rapid variation of the input power. On the other hand, slow input power variation causes degradation in both the transient and steady‐state performances for given amplitude of variation of the input power. In the case of a time‐invariant plant, neither rapid nor slow variation of the input power causes degradation in the steady‐state performance. On the other hand, there is degradation in the transient performance for slow variation of the input power. Copyright © 2012 John Wiley & Sons, Ltd.     

An efficient numerical technique for the implementation of SSLS and cyclostationary noise analysis in physics-based device simulators

The paper introduces a novel numerical technique for the efficient implementation of SSLS and cyclostationary noise analysis in physics-based device simulators calculating the time-varying device working point exploiting the harmonic balance technique. The technique is based on a mixed time-frequency evaluation of the matrix-vector products involved in the iterative solution of linear systems, indispensable for the simulation of realistic 2D or 3D device structures, relevant to the previous analyses. The algorithm, applicable to all PDE systems where the memory part is linear, allows for a significant improvement in the computation time with respect to the direct, frequency-domain implementation.     

STATCOM抑制低频振荡及稳定电压在风电场中的应用研究

连接到电网的大型风电场将影响系统的稳定性,因此,提出了一种结合阻尼支持和电压稳定的STATCOM附加控制方法。首先分析了STATCOM提供阻尼转矩和保持电压稳定二者的相互影响机理并提出基于自抗扰的控制方法,然后通过协调优化算法,对控制器的相关参数进行了优化设计,在保证稳定电压的同时有效抑制了低频振荡。典型的4机2区域系统由Digsilent平台搭建,并进行了仿真研究实现电压控制和阻尼控制的协调,更好地抑制了系统振荡并提高系统稳定性。     

ADF4350低相噪频率合成器在射频无线通信设备中的应用

现代射频和微波电子系统中要求频率源具有高频低相噪,且具有可靠性好、体积小、功耗低的特点。ADF4350频率合成器具有全集成、低相位噪声的优点,内置片上VCO（压控振荡器）与PLL（锁相环）,可以工作在极宽的连续频率范围内,广泛用于无线基础设备及测试设备,无线LAN,CATV和时钟发生器中。本文简要介绍了ADF4350的主要功能,详细给出了基于ADF4350用作直接变换调制器以及和ADuC812,ADSP-21xx的接口连接的设计方案。     

电力变压器有源降噪中次级声源的参数优化分析

为了获得较好的全局有源降噪效果,需合理布置次级声源,次级声源参数优化是电力变压器有源降噪技术研究中的核心问题。在分析有源降噪物理机制的基础上,建立了电力变压器的噪声辐射模型,得到变压器周围声场分布与噪声源、次级声源的关系。考虑实际工程需要,将次级声源参数分为2大类,并结合噪声辐射模型,从数目、位置、源强3方面对次级声源进行参数优化。鉴于位置和源强等参数间的交互影响关系,提出对固定参数和灵活参数进行交替优选,形成基于遗传算法的渐次搜索逼近策略。通过将具体算例与基于COMSOL软件的仿真结果相比较,表明该优化策略可获得较好的全局有源降噪效果。     

功率同步控制的模块化多电平换流器阻抗建模及谐振稳定性分析

为了研究模块化多电平换流器(MMC)采用功率同步控制时的阻抗特性和其接入后系统的宽频谐振稳定性,通过谐波状态空间方法,考虑MMC的内部动态特性和完整的控制回路,建立了MMC采用功率同步控制时的等效阻抗模型。分析了功率同步控制中新引入的功率同步环、无功-电压控制及其他主要控制环节对阻抗特性的影响。研究表明采用功率同步控制的MMC在次同步频段和高频段均可能出现负阻尼效应,因而存在引发谐振不稳定的风险。基于PSCAD/EMTDC进行了阻抗扫描和电磁暂态仿真,其仿真结果分别验证了所建立模型和稳定性分析结果的准确性。     

计及数字控制延时影响的含PMSG电力系统的宽频振荡z域阻抗判据研究

随着大量数字控制被应用于永磁直驱风电机组,受数字控制延时影响,含永磁直驱风电机组电力系统的宽频振荡问题日益突出。为了深入分析宽频振荡失稳机理以及快速准确地评估系统稳定性,提出了一种新的阻抗建模方法和稳定性判据。首先,基于精确离散化方法将含有延时环节的永磁直驱风电机组以及受端交流电网中的系统元件分别建模成锁相环坐标系下的z域阻抗模型。根据电路原理,将所有系统元件聚合成z域聚合阻抗模型,以此作为后续理论发展的模型基础。然后,基于盖尔圆定理,提出广义禁区判据来分析系统稳定性。最后,在Matlab/Simulink中搭建含永磁直驱风电机组的改进IEEE 3机9节点模型验证所提方法的有效性。     

单周控制三相四线制有源电力滤波器的补偿性能研究

单周控制三相四线制有源电力滤波器具有检测量少、控制器结构简单以及鲁棒性强等优点。分析了系统的全局稳定条件和补偿后电流中直流分量的产生机理,研究了系统带不平衡负载和动、稳态补偿性能以及稳定性。结果表明,当系统参数满足全局稳定条件时,单周控制三相四线制有源电力滤波器具有较好的动、稳态补偿性能,并能抑制三相负载的不平衡。单周控制以峰值电流检测的调制方式导致补偿后电流中含有的直流分量是影响系统补偿性能的主导因素。     

电网电压前馈控制VSG的阻抗建模与并网稳定性分析

针对电网电压谐波背景下虚拟同步发电机（VSG）并网电流畸变及并网稳定性下降问题,文中提出了一种基于电流环的电网电压前馈控制策略。从入网电流传递函数出发,设计电压前馈控制模块以消除背景谐波的影响,并基于谐波线性化方法分别建立加入前馈控制前后的VSG序阻抗模型,对其在各频段阻抗特性及并网稳定性上的影响进行对比分析。结果表明,引入该前馈控制等同于在VSG输出端并联虚拟阻抗,输出阻抗的高频段幅频曲线上移,可以改善非理想电网条件下的并网电流质量。同时,中高频段相频特性由容性矫正为感性,可以消除并网条件下的谐波振荡风险,提高交互系统稳定性。最后,基于实时仿真实验平台（RT-LAB）硬件在环实验验证了文中控制策略及理论分析的正确性。     

A three‐dimensional mesh refinement algorithm with low boundary reflections for the finite‐difference time‐domain simulation of metallic structures

We present a method for including areas of high grid density into a general grid for the finite‐difference time‐domain method in three dimensions. Reflections occurring at the boundaries separating domains of different grid size are reduced significantly by introducing appropriate interpolation methods for missing boundary points. Several levels of refinement can be included into one calculation using a hierarchical refinement architecture. The algorithm is implemented with an auxiliary differential equation technique that allows for the simulation of metallic structures. We illustrate the performance of the algorithm through the simulation of metal nano‐particles included in a coarser grid and by investigating gold optical antennas. Copyright © 2009 John Wiley & Sons, Ltd.