基于时滞不等分法T-S模糊时滞系统稳定性准则

提出一种新的时滞分解方法—时滞不等分法,研究了T-S模糊常时滞系统的稳定性准则问题。基于Lyapunov稳定性理论,构造恰当的Lyapunov-Krasovskii泛函,以线性矩阵不等式形式给出一个决策变量少、运算效率高、保守性小的时滞相关稳定性准则。最后给出数例说明该方法的有效性。     

Lyapunov-Krasovskii functional based power system stability analysis in environment of WAMS

In order to analyze power system stability in environment of WAMS (wide area measurement system), a new steady state stability model with time-varying delay was proposed for power system. The factors of exciter and power system stabilizer with delay were introduced into analytical model. To decrease conservativeness of stability analysis, an improved Lyapunov-Krasovskii functional was constructed, and then a new delay-dependent steady state stability criterion for power system, which overcomes the disadvantages of eigenvalue computation method, was derived. The proposed model and criterion were tested on synchronousmachine infinite-bus power system. The test results demonstrate that Lyapunov-Krasovskii functional based power system stability analysis method is applicable and effective in the analysis of time delay power system stability.     

Unified calculation of eigen-solutions in power systems based on matrix perturbation theory

Calculation of eigen-solutions plays an important role in the small signal stability analysis of power systems.In this paper,a novel approach based on matrix perturbation theory is proposed for the calculation of eigen-solutions in a perturbed system.Rigorous theoretical analysis is conducted on the solution of distinct,multiple,and close eigen-solutions,respectively,under perturbations of parameters.The computational flowchart of the unified solution of eigen-solutions is then proposed,aimed toward obtaining eigen-solutions of a perturbed system directly with algebraic formulas without solving an eigenvalue problem repeatedly.Finally,the effectiveness of the matrix perturbation based approach for eigen-solutions’calculation in power systems is verified by numerical examples on a two-area four-machine system.     

考虑传输时滞的电力负荷频率采样控制系统稳定性分析

研究了一类考虑传输时滞的电力负荷频率采样控制系统相关稳定性问题。首先,采用PI型的LFC系统方案,并建立考虑采样和传输时滞的LFC闭环系统模型;其次,根据建立的模型,采用基于双边闭环泛函判据计算系统的时滞稳定裕度,研究系统采样周期与时滞稳定裕度之间的关系,并通过单区域LFC系统对结果进行仿真验证。计算结果表明,与现有文献结果相比,在相同的系统参数条件下,使用提出方法得到的结果保守性降低,且采样周期越大,系统时滞稳定裕度越小,而一定大小的时滞可以增大系统采样周期上界;仿真结果进一步验证了所提出方法的有效性和优势。     

基于深度强化学习的多小区NOMA能效优化功率分配算法

在下行多小区非正交多址接入系统中,功率分配是决定系统性能的关键因素之一。由于多小区系统间的功率优化问题的非凸性,获得最优功率分配在求解上非常困难。为此提出了一种基于深度强化学习最大化能效的功率分配算法,将深度Q网络作为动作?状态值函数,将系统能效直接设置为奖励函数,优化信道功率分配,使系统能量效率最大化。仿真结果表明,该算法比加权最小均方误差、分式规划、最大功率和随机功率算法等能够获得更高的系统能量效率,在算法计算复杂度、收敛速度和稳定性方面也有较好表现。     

时变时滞广域电力系统稳定性分析

针对含有时变时滞的广域电力系统稳定性进行了分析.首先,建立含有时变时滞的广域电力系统模型,构建新型L-K泛函.然后,引入一个关于时变时滞的二次函数,再通过积分不等式得到更低保守性的时变时滞广域电力系统的稳定性判据.最后,采用典型的二阶系统和四机十一节点系统,在Matlab上进行仿真,并将所得结果与其他文献结果进行比较分...     

控制饱和离散时滞线性系统的渐近稳定性

研究了饱和控制多输入离散时滞线性系统的稳定性问题．在满足一定的假设条件下,针对执行器出现饱和控制的情况,通过定义多输入饱和度函数,基于Lyapunov方法给出系统全局渐近稳定的充分性判据,并在系统不满足所给判据时给出其不变吸引域的描述．最后,设计一个算法来实现所得结果,并通过数值算例验证算法的可行性与有效性．     

新的时变时滞Lurie系统的稳定性判据

针对时变时滞Lurie系统的稳定性问题,本文在推导技术上利用积分不等式及交互式凸组合方法,通过构造新的增广Lyapunov-Krasovskii泛函,得到新的基于线性矩阵不等式的时滞相关稳定性准则.数值实例表明,本文方法与文献[12-13]及文献[15-16]相比较,能够获得使系统稳定所容许的更大时滞上界值,说明本文方法具有更低的保守性.     

基于二次函数负定判据的LFC系统稳定性分析

基于改进的二次积分不等式和二次多项式不等式建立的稳定性条件,研究了基于负荷频率控制（LFC）的时滞电力系统稳定性问题。首先,搭建了包含PI参数的负荷频率时滞系统数学模型;然后,通过引入增广的Lyapunov-Krasovskii泛函,利用近年改进的二次积分不等式和二次多项式不等式的充分条件,成功导出了具有时变时滞的系统稳定性判据;最后,通过负荷频率系统模型的实例仿真,验证了所得稳定性判据优于现有的一些计算结果。     

不确定随机多时滞系统鲁棒随机稳定性分析

研究了一类不确定随机多时滞系统的鲁棒随机稳定性问题,其中系统不确定参数满足线性分式结构。首先,将倒数凸方法加以推广,得到一个新的积分不等式引理;然后,充分考虑时滞区间上下限关系,构造了多时滞区间相关的李雅普诺夫函数,并在新的积分不等式方法下,得到具有更小保守性和较少自由变量的时滞相关稳定性条件; 最后,给出一些数值仿真实例,验证了所提方法的有效性。     

Stability switches and bifurcation analysis in a coupled neural system with multiple delays

A coupled neural system with multiple delays has been investigated. The number of equilibrium points is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values of coupling weight by employing the pitchfork bifurcation of the trivial equilibrium point. Further, the local asymptotical stability of the trivial equilibrium point is studied by analyzing the corresponding characteristic equation. Some stability criteria involving multiple delays and coupling weight are obtained. The results show that the neural system exhibits the delay-independent and delay-dependent stability. Increasing delay induces stability switching between resting state and periodic motion in some parameter regions of coupling weight. In addition, the criterion for the global stability of the trivial equilibrium is also derived by constructing a suitable Lyapunov functional. Finally, some numerical simulations are taken to support the theoretical results.     

线性时滞状态反馈下Stuart-Landau系统的多周期解

对一个stuart-landau系统引入时滞状态反馈,研究时滞对非线性系统动力行为的影响。发现时滞可使系统出现周期振动,与无时滞系统不同之处在于有多个周期吸引子共存的现象。从理论上预测由时滞导致的动力学行为,得到周期解的解析形式。随着时滞量的变化,周期解个数及其稳定性发生变化。并通过对比周期解的数值解和解析解,数值验证多周期吸引子共存的现象。这些结果对控制系统的振动和系统同步等有着潜在的应用价值。     

斜拉桥的脉动风荷载数值模拟

风荷载是作用在斜拉桥上的重要动力荷载之一．基于数值模拟方法的风速时程曲线在桥梁结构风振分析中被广泛采用．笔者利用谐波叠加法模拟了风速时程样本．算例表明,计算结果与目标谱吻合良好,模拟精度、速度和计算稳定性均满足实际工程应用要求,证明了所用模拟方法的可靠性．利用足速时程数据,可以进一步对斜拉桥进行动力分析。     

计及DoS攻击和通信时滞的电力系统负荷频率控制

针对开放通信网络中的时滞和DoS攻击,本文建立了基于采样特性的电力系统离散负荷频率控制方案。首先计及电力系统的负荷波动情况,在多区域电力系统负荷频率控制系统(LFC)的状态空间模型的基础上,将通信网络中DoS攻击的危害量化为导致输出采样信号连续丢失数,并分别考虑通信网络中通信时滞和输出信号采样特性,建立包含输出状态反馈控制器的电力系统LFC模型。其次基于此模型,利用含有控制命令更新周期、DoS攻击导致的最大采样信号连续丢失数、通信时滞和 稳定指标的双边闭环Lyapunov泛函和LMI技术,提出LFC系统满足一定 指标的稳定准则,并给出离散状态输出反馈LFC控制器的设计及求解方法。最后以单区域和双区域LFC系统为例,进行仿真验证,与已有结果相比,本文方法在保持系统 渐近稳定前提下,能够容忍更大的通信时滞,结果的保守性更低。并得出本文所设计的控制器保证 稳定性能的基础上,对一定能量限制的DoS攻击具有弹性的防御性能。同时求得系统允许最大采样信号连续丢失数,给出此时DoS攻击情况及控制命令更新周期的情况,可以看出DoS攻击必定导致控制命令更新周期增大,而本文所设计的控制器可以在DoS攻击导致的最大采样信号连续丢失数的情况下,仍然保证系统的 渐近稳定。因此本文方案的有效性和优越性得到了验证。     

A necessary and sufficient stability criterion for networked predictive control systems

Stability of a networked predictive control system subject to network-induced delay and data dropout is investigated in this study. By modeling the closed-loop system as a switched system with an upper-triangular structure, a necessary and sufficient stability criterion is developed. From the criterion, it also can be seen that separation principle holds for networked predictive control systems. A numerical example is provided to confirm the validity and effectiveness of the obtained results.     

改进型Bessel-Legendre不等式在时滞系统稳定性上的应用

改进型Bessel-Legendre不等式具有在时变时滞系统中易于处理的优点,且克服了基于辅助函数的积分不等式与Bessel-Legendre不等式由于在结果的界定上具有逆凸性从而导致这两个不等式在处理时变时滞系统时不易处理的弱点。首先,通过构造合适的Lyapunov-Krasovskii泛函,并应用这种改进型Bessel-Legendre不等式处理泛函导数中的积分项,建立了一个新的时滞系统鲁棒稳定性判据。然后,通过数值实例进行了仿真验证,并将仿真结果与其它已有文献中的仿真结果进行了对比,得知所提方法的系统最大允许时滞上界明显优于其它文献中的结果,可见系统的时滞稳定裕度得到本质上的改善,从而证明了所提方法的有效性与优越性。     

一种多时滞线性系统的稳定性新判据及其镇定控制器设计

研究了具有多时滞的线性系统的稳定性及其镇定问题，利用二次型Lyapunov泛函，给出了一种新的保守性更小的时滞独立稳定性判据，并研究了该判据与控制的关系。在此基础上，研究了这类系统的镇定控制问题，用H∞控制方法设计了保证系统时滞独立渐近稳定的控制器。最后通过两个算例比较了本文所给的判据与文献中已有的判据，并设计了相应的控制器。结果表明，本文所给出的判据确实改进了已有的判据。     

强度折减应用于隧道群整体稳定性分析的判据比较

为了讨论隧道群稳定性问题中判据的适用性,针对采用强度折减理论中塑性区贯通、特征点位移突变与基于力和位移准则判断计算是否收敛3种较为广泛使用的判据加以比较。通过比较表明,计算收敛判据明显偏大,其他两种判据结果较接近。单独使用任何一种判据分析隧道群的稳定性均不合理,也不能较真实地确定安全系数。用基于力和位移准则判断计算是否收敛作为判据不适合隧道群的稳定性分析,而塑性区贯通与特征点突变两判据相结合作为综合判据可以较好地得到隧道群的安全系数。     

Cross-Layer Adaptive Resource Allocation Algorithm with Diverse QoS Requirements for Single-Cell OFDMA Systems

The orthogonal frequency division multiple access( OFDMA) based communication system has been considered as the main trend of next-Generation communication system. But the existing resource allocation algorithm designed for such system is always with high complexity thus hard to be realized. To solve such problem with the constraints of spectrum efficiency and buffer state,a novel cross-layer resource allocation algorithm( RAA) is proposed in this paper. The goal of our RAA is to maximize the system throughput while satisfying several practical constraints,such as fairness among services,head of line( Ho L) delay and diverse quality of service( Qo S) requirements. Due to these constraints,finding the optimal solution becomes a NPhard problem. Therefore in this paper a novel method to solve such problem with acceptable complexity is proposed within following steps: firstly,based on the link state we formulate the ideal subchannel allocation strategy as a convex optimization problem,which can be efficiently solved by our proposed lagrange multiplier technique subchannel allocation( LMTSA) algorithm; secondly,according to the obtained channel allocation matrix,a power allocation algorithm based on the water-filling power allocation( WPA) idea is deployed to get the optimal power allocation matrix combining with adaptive modulation and coding( AMC); finally,through a greedy algorithm,the ultimate subchannel and power allocation matrix can be obtained based on iterative method. The simulation results illustrate that we can achieve the higher throughput and better Qo S performance than the widely-used maximum throughput( MT) algorithm and round robin( RR) algorithm.     

含时变时滞和不确定项中立系统鲁棒稳定

文章研究了一类含不确定项中立系统鲁棒稳定问题,以线性矩阵不等式给出系统鲁棒稳定的充分条件,由于不引进算子并将不确定项整体处理,巧妙地运用了一个积分不等式,使得保守性较小,数值例子说明了设计方法的有效性和可行性。