共查询到19条相似文献,搜索用时 323 毫秒
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混沌识别是对非线性时间序列进行混沌预测的前提。针对时间序列风速确定性与随机性相结合的复杂非线性特征,研究了不同的混沌识别方法,并对风速时间序列进行混沌特征识别。应用随机噪声、周期运动及经典混沌系统的时间序列对所选方法进行可靠性验证。对美国国家风能研究中心M2测风塔实测时间序列风速数据进行非线性混沌特征识别。结果表明:风速时间序列具有明显的混沌特征;各风速时间序列表现出不同程度的混沌特征;各混沌识别方法对风速时间序列混沌特征的表达形式不同,互为补充,相互验证。 相似文献
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针对目前月降雨序列混沌特性研究中存在的问题,以广东省西江流域高要站月降雨序列为例,运用功率谱方法、主成分分析法、饱和关联维数法、C-C方法进行了混沌特性的判定及特征参数的求取,同时分析了数据长度和噪声对混沌研究的影响.研究结果表明,利用功率谱方法进行混沌判定时,单纯的根据连续多峰的噪声背景作为判定混沌存在的依据并不可靠;饱和关联维数法仅从能量角度对混沌序列进行判定,此外,对混沌序列进行滤波会导致此法判定结果的稳健性降低,C-C方法证明了其计算结果的可靠性;为计算出相对稳定的饱和关联维D2,计算数据的长度至少应为450个点;递归图及相应的各种定量判定标准验证了改进的双小波空域降噪方法可有效去除混沌序列中噪声的影响. 相似文献
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辨识混沌时间序列中的确定性 总被引:2,自引:1,他引:1
总结了一些分析混沌时间序列的关键技术:相空间重构、吸引子维数、Lyapunov指数、熵等,并综合运用这些方法来判断时间序列是否存在混沌现象。 相似文献
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针对时间序列风速确定性与随机性相结合的复杂非线性特征,基于相空间重构理论和最大Lyapunov指数对其进行混沌与分形特征分析。首先,以经典Lorenz混沌系统及非混沌完全随机白噪声时间序列为验证算例,通过相空间重构和最大Lyapunov指数法判断以上2种非线性时间序列的混沌特征,分别从定性和定量的角度验证了所提方法的可行性;其次,对美国风能研究中心实测风速数据进行相空间重构,计算其最大Lyapunov指数并估算其可预测时间,最后采用G-P算法分析了实测风速时间序列的饱和关联维数。结果表明:相空间重构理论及最大Lyapunov指数法均可作为判断混沌特征的重要方法,时间序列风速具有明显的混沌分形特征及短期可预测性。 相似文献
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混沌相空间的卡尔曼滤波模型及其应用 总被引:1,自引:1,他引:0
针对混沌时间序列,提出将混沌分析方法和卡尔曼滤波实时技术相耦合,建立混沌相空间的卡尔曼滤波模型.以混沌系统的相点为状态变量构成相点的状态空间描述,运用卡尔曼滤波实时预测并校正相点的未来演化规律,据此对四川省电力系统的日负荷时间序列进行短期预测.实例表明,该模型有利于跟踪相空间中相点的非线性演化轨迹,预测精度高、效果好. 相似文献
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应用混沌分形理论,选择合适的滞时,对去噪后车用发动机振动信号时间序列进行了相空间重构,并得出了不同嵌入相空间下去噪后车用发动机振动信号时间序列关联维的变化规律。计算结果表明:经去噪后车用发动机振动信号时间序列具有分形特征,且该时间序列是混沌序列。在车用发动机系统中,影响去噪后车用发动机振动信号的系统内部因素最多可达8个,最小不会小于1个。 相似文献
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针对风能发电及天气预报等领域中一直是难点和重点的风速时间序列预测问题,首先分别通过相图法和最大Lyapunov指数法定性定量确定风速时间序列具有混沌特征;在此基础上,针对风速时间序列混沌特征结合相空间重构理论进行预测,根据C-C算法确定嵌入维数及延迟时间,将混沌理论应用于Volterra自适应模型,建立新的风速预测模型;以Lorenz方程为例验证该预测模型的准确性,并通过预测风速对比实测风速,进行误差分析。结果表明:风速时间序列具有明显的混沌特征;风速时间序列的混沌特征表明其长期预测是不现实的,但其确定性结构表明其具有短期可预测性;以预测Lorenz方程数值解的方式验证了Volterra自适应预测模型的准确性,其预测误差控制在10~(-4)以内;Volterra自适应预测模型可以对实测风速时间序列进行准确的预测,预测误差控制在0.1 m/s内。 相似文献
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Niu Xize Qiu Jiajun 《Energy Conversion, IEEE Transaction on》2002,17(2):164-168
In this paper, the nonlinear phenomenon known as Hopf bifurcation, chaos and asynchronous operation of a simple power system are explored. Firstly, taking into account the nonlinearity of the generator shaft and the interaction of mechanics and electrics in the generator sets, the authors obtain a transient model by combining Park equations and mechanics equations. Then the Hopf bifurcation, period-doubling bifurcation and chaos caused by too large a line resistance are investigated with nonlinear mode and Floquet theory. The bifurcation figure of the system is also given. Further study shows that the chaos attractor breaks up into asynchronous operation when the resistance becomes larger. This way of loss-of-stability is different from that caused by loss-of-excitation 相似文献
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Hiroshi Gotoda Yuta Asano Keng Hoo Chuah Genichiro Kushida 《International Journal of Heat and Mass Transfer》2009,52(23-24):5423-5432
From the viewpoint of nonlinear dynamics, the dynamic behavior of buoyancy-induced flame oscillation has been experimentally investigated under a swirling flow produced by rotating a cylindrical burner tube. As the rotational Reynolds number increases, the dynamic behavior undergoes a significant transition from periodic oscillation to low-dimensional deterministic chaos, through quasi-periodic oscillation. This is clearly demonstrated by nonlinear time series analysis based on chaos theory. The motion of the vortical structure around the burner tube due to the centrifugal instability associated with a rotating Taylor–Couette flow plays an important role in the onset of low-dimensional deterministic chaos. 相似文献
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Dongbin Xiu 《International Journal of Heat and Mass Transfer》2003,46(24):4681-4693
We present a generalized polynomial chaos algorithm for the solution of transient heat conduction subject to uncertain inputs, i.e. random heat conductivity and capacity. The stochastic input and solution are represented spectrally by the orthogonal polynomial functionals from the Askey scheme, as a generalization of the original polynomial chaos idea of Wiener [Am. J. Math. 60 (1938) 897]. A Galerkin projection in random space is applied to derive the equations in the weak form. The resulting set of deterministic equations is subsequently discretized by the spectral/hp element method in physical space and integrated in time. Numerical examples are given and the convergence of the chaos expansion is demonstrated for a model problem. 相似文献
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AGC机组调配问题是一个含连续和离散变量的混合非线性优化问题,提出了一种基于混沌多Agent的双重粒子群算法。该算法以混沌和粒子群优化算法以及多Agent技术为基础,利用混沌映射提高初始种群的质量,引入临界算子增强Agent的多样性。在算法迭代中,每一个Agent通过与其随机配置的邻居竞争、合作,并且吸收了粒子群优化算法的进化机制,可以更稳定、快速地收敛到全局最优解。通过算例仿真结果表明,所提出的算法具有质量高的解、稳定性好的收敛特征和快的寻优速度。 相似文献
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转子-定子系统松动-碰摩耦合故障的动态响应分析 总被引:2,自引:0,他引:2
建立了考虑定子与基础之间的连接刚度和阻尼(包括定子本身运动)的转子-定子系统发生松动-碰摩时的动力学模型和微分方程,对系统在运行过程中的非线性行为进行了数值仿真分析,发现随着转速的变化过程,此类系统响应主要以拟周期或阵发性分岔进入混沌,而由拟周期或倍周期倒分岔离开混沌。在超临界转速区,系统的响应以混沌和周期k的分频运动为主要运动形式。该结果为转子-定子系统的故障诊断提供了依据和参考。 相似文献
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A fast stochastic solution method for the Blade Element Momentum equations for long‐term load assessment 下载免费PDF全文
Unsteady power output and long‐term loads (extreme and fatigue) drive wind turbine design. However, these loads are difficult to include in optimization loops and are typically only assessed in a post‐optimization load analysis or via reduced‐order methods. Both alternatives yield suboptimal results. The reason for this difficulty lays in the deterministic approaches to long‐term loads assessment. To model the statistics of lifetime loads they require the analysis of many unsteady load cases, generated from many different random seeds—a computationally expensive procedure. In this paper, we present an alternative: a stochastic solution for the unsteady aerodynamic loads based on a projection of the unsteady Blade Element Momentum (BEM) equations onto a stochastic space spanned by chaos exponentials. This approach is similar to the increasingly popular polynomial chaos expansion, but with 2 major differences. First, the BEM equations constitute a random process, varying in time, while previous polynomial chaos expansion methods were concerned with random parameters (ie, random but constant in time or initial values). Second, a new, more efficient basis (the exponential chaos) is used. This new stochastic method enables us to obtain unsteady long‐term loads much faster, enabling unsteady loads to become accessible inside wind turbine optimization loops. In this paper we derive the stochastic BEM solution and present the most relevant results showing the accuracy of the new method. 相似文献