A method for the investigation of high-order two-frequency asynchronous oscillators

A general method for analysing asynchronous high-order two-frequency oscillators is presented. the oscillator model is made up of a GC non-linear parallel group embedded in a linear lumped time-invariant network of any order. the approach devised rests on the identification of a pair of narrow-band impedance operators which permit one to derive first-approximation steady state and dynamic equations in the phasor domain—as well as stability criteria—in a simple and expressive manner. Previous results from averaging and perturbation treatments on fourth-order asynchronous oscillators are shown to be obtainable from this theory as particular cases. the sixth-order oscillator chosen as an application example shows that computational efficiency and accuracy are among the features of the method.     

Evaluating the spectrum of periodic pulling in subharmonic resonant LC circuits

We analyze the features of the oscillations arising in forced inductor–capacitor (LC) oscillators when they operate in the periodic pulling mode, under the action of a weak injection signal. In radio frequency integrated circuits, both voltage‐controlled oscillators subject to undesired couplings and injection‐locked frequency dividers behave like forced LC oscillators. These are modeled as second‐order driven oscillators working in the subharmonic (secondary) resonance regime. The analysis is based on the generalized Adler's equation, which we introduce to describe the phase dynamics of dividers of any division ratio and to derive closed‐form expressions for the spectrum components of the system's oscillatory response. We show that the spectrum is double‐sided and asymmetric, unlike the single‐sided spectrum of systems with primary resonance. Numerical and experimental results are given to validate the presented results, which significantly generalize those available in the literature. Copyright © 2014 John Wiley & Sons, Ltd.     

A method for analysing the transient and the steady‐state oscillations in third‐order oscillators with shifting bias

We provide an asymptotic method for systematically analysing the transient and the steady‐state oscillations in third‐order oscillators with shifting bias. The method allows us to construct the general solution of the weakly non‐linear differential equation describing these oscillators through an iteration procedure of successive approximations typical of perturbation methods. The approximation to first order is obtained solving a system of two first‐order non‐linear differential equations in the leading terms of solution (dc component and fundamental harmonic), whereby the dominant dynamics, the stationary states and their stability can be easily analysed. Unlike existing approaches, our method also enables us to determine the higher harmonics as well as the frequency shift from the system's natural frequency in the exact solution through analytical formulae. In addition, formulae for higher‐order approximations of the above quantities are determined. The proposed method is applied to a practical circuit to show its usefulness in both analysis and design problems. Copyright © 2001 John Wiley & Sons, Ltd.     

Adaptive tuning of fuzzy logic identifier for unknown non-linear systems

An on-line approximator using a linear fuzzy logic model with automatic tuning mechanism is presented in this paper. the proposed approximation method can be used to model a class of unknown non-linear systems as long as they are Caratheodory ones. the structure of the fuzzy model is fixed but the parameters are tuned by the state errors. the fuzzy model is composed of several semi-closed, continuous, totally ordered and well-defined fuzzy numbers defined in each state variable dimension and a number of appropriately defined condition-action rules. Either the min-inference or product-inference technique is utilized to generate the weighted average of the linear coefficients which make the whole unknown non-linear system piecewise linearized. No off-line preprocessing is needed. the initial values of the parameters of the fuzzy model can be arbitrarily assigned. Then they are tuned to their true values through adaptive update law and therefore it is guaranteed that the unknown non-linear system is linearized and approximated to any degree of accuracy by the linear fuzzy logic model.     

Subharmonic phase-lock criteria for a class of weakly non-linear high-order oscillators

Subharmonic frequency entrainment of high-order weakly non-linear oscillators is investigated. For the class of circuits considered, equations are first derived which provide the first approximation values for the amplitudes and phases of the two main spectral components of the steady-state waveform. Necessary and sufficient stability criteria are then derived in explicit from. The example worked out (a negative conductance double-tuned oscillator) shows the efficiency and ease of use of the proposed method.     

基于二次 CEEMD 与时域特征分析的去噪方法

为克服经验模态分解(EMD)去噪方法存在的模态混叠以及噪声分量与信号分量区分困难问题,本文提出了一种基于二次互补集合经验模态分解(CEEMD)与时域特征分析的去噪方法。该方法利用CEEMD来克服模态混叠问题,同时基于对CEEMD本征模态函数(IMF)的时域特征分析来确定噪声主导IMF分量与信号主导IMF分量的分界点,据此区分噪声分量与信号分量,并对分界点相邻两侧的噪声主导IMF分量与信号主导IMF分量进行二次CEEMD分解,在保留更多有用信号的同时进一步滤除剩余噪声。对含冲击噪声干扰的实际机载平台数据的去噪实验结果表明,新方法通过对噪声分量与信号分量的有效分离,可以更好地抑制噪声干扰,明显提升信噪比。     

三相电压型PWM逆变器的建模研究

根据三相电压型PWM逆变器的工作原理,引入开关周期平均算子将离散的系统变换为连续的系统,应用坐标旋转变换将三相交流电量变换成直流量,使用小信号扰动法将非线性的系统变换为线性的系统.建立了三相电压型PWM逆变器系统的小信号动态数学模型,以SPWM调制法为例,建立了从调制器输入到逆变器输出的动态数学模型,仿真和实验结果验证...     

基于数学形态学的短时傅里叶分析

为了提取恰当的短时傅里叶分析(STFT)时间窗宽度和中心,进而利用STFT分析暂态信号成分,提出了基于数学形态学的STFT方法.针对电力系统信号特点,讨论了结构元素的选择问题,推导了结构元素大小公式及离散化的结构元素方程.同时提出了奇异点定位算法,进而得到了基于数学形态学的STFT算法.在MATLAB中的仿真结果表明该方法能够快速准确地得到暂态信号中主要频率成分及其幅值,可提高STFT的精度和效率.     

Design criteria for high-frequency RC-active sinusoidal oscillators

High-frequency RC-active sinusoidal oscillators using two op amps are surveyed from a unified viewpoint. Information about their performance is obtained using linear and non-linear approaches. As a consequence of this analysis, two main criteria are proposed to optimize these systems and to select the best configuration for a given application. the first criterion is related to the feasibility of obtaining an oscillation frequency independent of the op amps used in the design. the second criterion is connected with the level of harmonic distortion present in the signal. Experimental measurements obtained agree closely with the theoretical analysis carried out.     

一起特高压站用变绕组连接错误的分析

皖电东送特高压交流输电示范工程,以1 000 k V特高压淮南站为例,其站用变系统采用两级降压方式。通过110/35 k V、35/0.4 k V两级变压器串联,中间由电缆连接且不设任何开断设备,差动保护动作时不区分故障元件。针对站用变系统两级降压的方式,指出了站用变保护需要解决的特殊问题,阐述了电流互感器变比的选定原则及站用变保护的配置方案。并且重点对发现的站用变绕组连接错误的问题,深入分析了接线钟点数的变化以及对站用变差动保护的影响。提出了解决措施,有效防止了差动保护的误动作,有力保障了特高压站用变系统的安全稳定运行。     

基于Duffing振子的弱信号频率检测研究

现有Duffing振子弱信号检测方法检测频率信号时存在检测频率范围窄的缺点,在检测宽频带信号时需要用到多振子阵列,增加了实现的复杂度。文章充分利用周期信号频率特性和Duffing振子的弱信号检测技术,提出了一种新的Duffing振子检测频率信号的方法,该方法摒弃了传统外加周期策动力的方式,将待测信号直接送入Duffing振子,然后对振子输出量作频谱分析,降低了调谐的难度并增加了振子运行的稳定性。仿真结果表明,该方法可实现对信号频率的精确检测,具有精确度高（10-4数量级）、复杂度低的优点。     

Floquet theory and non‐linear perturbation analysis for oscillators with differential‐algebraic equations

Oscillators are key components of electronic systems. In RF communication systems, they are used for frequency translation of information signals and for channel selection, and in digital electronic systems, they are used as a time reference, i.e. a clock signal, in order to synchronize operations. Undesired perturbations in practical electronic systems adversely affect the spectral and timing properties of oscillators, which is a key performance limiting factor, being a major contributor to bit‐error‐rate (BER) of RF communication systems, and creating synchronization problems in clocked and sampled‐data systems. Characterizing how perturbations affect oscillators is therefore crucial for practical applications. The traditional approach to analysing perturbed nonlinear systems (i.e. linearization) is not valid for oscillators. In this paper, we present a theory and efficient numerical methods, for non‐linear perturbation and noise analysis of oscillators described by a system of differential‐algebraic equations (DAEs). Our techniques can be used in characterizing phase noise and timing jitter due to intrinsic noise in IC devices, and evaluating the effect of substrate and supply noise on the timing properties of practical oscillators. In this paper, we also establish novel results for periodically time‐varying systems of linear DAEs, which we rely on in developing the above theory and the numerical methods. Copyright © 2000 John Wiley & Sons, Ltd.     

A collocation algorithm for calculating the periodic solutions of non-linear oscillators

An approximation method is given for calculating the periodic solutions of non-linear oscillators based upon the well-known method of collocation, which belongs to the class of projection methods. Unlike available techniques, the method leads to a simple and efficient algorithmic procedure which consists of solving a system of non-linear equations given in a simple explicit form. To demonstrate the effectiveness of the proposed algorithm, the results of some typical oscillator circuits are provided.     

滑模变结构控制在高压直流输电系统上的应用研究

高压直流输电是一个典型的非线性控制系统，常规的PI控制在系统遭受大扰动时，难以产生有效的控制作用。为此，将微分几何与变结构控制相结合，提出了一种新型的非线性控制算法。即通过微分几何法将系统非线性反馈线性化。再用成熟的滑模变结构控制理论设计控制策略。通过PSCAD／EMTDC仿真验证，该算法是有效的。     

Numerical solution of inhomogeneous and non-linear ordinary differential equations using the TLM multicompartment model

The paper presents a simple algorithm for solving a system of inhomogeneous high order differential equations with variable coefficients. The method also provides a numerical solution to non-linear ordinary differential equations. The technique is based on reducing the high order equations into a system of first order rate equations. Through a simple translation process, the variables in the reduced set of equations are solved simultaneously by an iterative scheme using the TLM multicompartment model. The numerical technique is demonstrated by solving well-known second order differential equations. The numerical solutions are compared with the analytical solutions to the differential equations.     

一种冲击波形发生电路的设计方法

瞬态冲击波形发生器一般用于评价电子设备、电力设备、避雷器及非线性电阻在雷电干扰下的电磁兼容性能。通用发生电路的设计方法以理论估算为主、电脑仿真优化和经验判定为辅,它利用Laplas反变换作为理论基础,但设计方法未系统总结,电压波和电流方程的参数关系曲线选取不统一,使设计缺乏条理。为此,通过方程变换将电压、电流波形参数和电路参数的关系统一化,并利用穷举和插值法计算得出它们之间的关系曲线,从而使发生器的参数选择过程更有条理,提高了设计效率,精度也相应上升。经过Pspice软件仿真和试验测试,证实了该方法的可靠性,准确度达到了IEC标准,满足科研工作者的设计和使用要求。     

Current differential amplifiers: new circuits and applications

New CMOS current differential amplifiers are proposed suitable for analogue signal processing at high frequencies. They consist of simple current mirrors, which are easy to design and to implement in IC form. Low‐voltage low‐power design is feasible. Relying on these devices a number of applications are obtained, including lossy and lossless integrators, simulated inductors, active filters, and harmonic oscillators. Theoretical expressions are given for all of the proposed new circuits. The verification of the circuits is also achieved by simulation. Copyright 2001 © John Wiley & Sons, Ltd.     

智能变电站SCD文件二维校验码校验方法研究

所介绍的智能变电站SCD文件二维校验码校验方法,目的在于校验SCD文件的内容是否变化,对SCD文件进行版本管理。该方法是基于集合、函数、映射和变量比较的数学原理,首先将SCD文件的各组成部分、元素、数据属性分别抽象成集合、函数、变量,并用行号、列号分别统计元素、数据属性的个数。然后对集合、函数、变量进行二维定位、编码赋值,即将行号、列号唯一确定的数据属性的实际值作为校验量的赋值。最后通过校验校验量的赋值,得出SCD文件的校验结果。其中,校验量的唯一性,由对象标识Ref(引用)的唯一性保证。该方法能够可靠地校验SCD文件内容的差异性,校验精度精确到版本编号、数据属性的值、虚端子数目及外部/内部信号描述。该校验方法和校验流程为SCD文件的审核、修改、管理提供了技术手段,能有效地防止SCD文件的误改动。     

Design equations for fractional‐order sinusoidal oscillators: Four practical circuit examples

Four practical sinusoidal oscillators are studied in the general form where fractional‐order energy storage elements are considered. A fractional‐order element is one whose complex impedance is given by Z = a(jω)^±α, where a is a constant and α is not necessarily an integer. As a result, these oscillators are described by sets of fractional‐order differential equations. The integer‐order oscillation condition and oscillation frequency formulae are verified as special cases. Numerical and PSpice simulation results are given. Experimental results are also reported for a selected Wien‐bridge oscillator. Copyright © 2007 John Wiley & Sons, Ltd.