Nonlinear Phase Noise Reduction of DQPSK Signals by a Phase-Preserving Amplitude Limiter Using Four-Wave Mixing in Fiber

It is experimentally shown that phase-preserving amplitude regeneration by an all-optical amplitude limiter using saturation of four-wave mixing in a highly nonlinear fiber can enhance differential quadrature phase-shift keying (DQPSK) transmission performance. The limiter suppresses amplitude fluctuations of the signal, by which the nonlinear phase variance caused by self-phase modulation in the transmission fiber is reduced. The 10-GSymbol/s short-pulse DQPSK transmission experiment over densely dispersion-managed fiber shows that the amplitude limitation after an imperfect transmitter increases maximum transmitted signal power by 5 dB.     

Reducing interchannel crosstalk in long-haul DWDM systems

Nonlinear interaction between signal channels may result in significant performance degradation in transoceanic dense wavelength-division-multiplexing (WDM) transmission systems operated at high bit rates. In this paper, we report that the nonlinear crosstalk for systems with high spectral efficiency can be suppressed if WDM channels are launched with orthogonal relative states of polarization. It is shown that for adjacent channels (that experience the strongest nonlinear interaction) the launched relative state of polarization is maintained over the large distance of low polarization-mode dispersion fiber typically used in undersea systems. Numerical studies, as well as experimental results, are presented for standard and dispersion slope-matched dispersion maps     

Ultrahigh-speed long-distance TDM and WDM soliton transmissiontechnologies

Recent progress on time-division multiplexed (TDM) and wavelength-division multiplexed (WDM) soliton transmission is described, in which dispersion management (DM) plays an important role in increasing the power margin and the dispersion tolerance. The characteristics of the DM soliton are compared with those of return-to-zero (RZ) and nonreturn-to-zero (NRZ) pulses. With a small dispersion swing, the system can still be described as an average soliton with a nonlinear Schrodinger equation (NLSE), whereas with a large dispersion swing, the soliton-like steady-state pulse becomes a chirped Gaussian pulse, in which the master equation is closer to a linear Schrodinger equation (LSE) with a parabolic potential well. An in-line modulation scheme up to 80 Gb/s per channel and its two-channel WDM transmission over 10000 km are described. A 640-Gb/s (40 Gb/s×16 channels) WDM soliton transmission over 1000 km is also reported with a DM single-mode fiber, without the use of in-line modulation. Finally, dark soliton transmission at 10 Gb/s over 1000 km is described as a different nonlinear pulse application     

基于多层感知器的低压电力线时变信道非线性均衡方法

通过添加适当的循环前缀(CP)的正交频分复用(OFDM)技术是一种去除高速通信中符号间干扰的有效方法，但低压电力线作为载波通信通道使用时是一种时变多径信道，采用OFDM技术进行高速载波通信时信号的正交性会因此而受到一定程度的破坏，产生子载波间干扰（ICI）。该文采用基于多层感知器（MLP）的均方差(MSE)准则实现了一种时变信道的非线性均衡。为了验证所提出的非线性均衡方法的有效性，选取具有宽带耦合放大器的实际低压电力线通信(PLC)信道作为实验用非线性信道模型。对比了基于MSE准则的线性和非线性均衡器对系统性能的影响，表明该文采用的非线性均衡方法可以更有效地补偿信道的多径性和时变性造成的影响和改善电力线载波通信系统的性能。     

UPFC新型非线性控制策略

统一潮流控制器(UPFC)可以有效控制线路的有功和无功功率。基于UPFC控制线路功率的非线性数学模型,提出了一种新型的非线性控制方法:根据系统能量守恒的特点构造出一个满足Lyapunov大范围渐近稳定的函数,再结合精确线性化方法,将控制系统转化为一个简单的线性系统,最后通过线性反馈确定系统的输入量。基于软件EMTP/EMTPWorks对UPFC的控制装置进行建模,并在典型的长距离输电线路的测试系统中运行,仿真结果验证了所提新型非线性控制策略的正确性,较之于传统的PI控制方法,提出的非线性控制方法具有更高的有效性和动态性能;同时也表明了小容量的UPFC装置能够很大程度地补偿线路的有功功率,当发生单相接地故障时,UPFC能提高系统的稳定性。     

Modelling and control of six‐phase induction motor servo‐driven continuously variable transmission system using blend modified recurrent Gegenbauer orthogonal polynomial neural network control system and amended artificial bee colony optimization

Because the nonlinear and time‐varying characteristics of the continuously variable transmission system operated using a six‐phase copper rotor induction motor are unknown, improving the control performance of the linear control design is time‐consuming. To capture the nonlinear and dynamic behaviour of the six‐phase copper rotor induction motor servo‐driven continuously variable transmission system, a blend modified recurrent Gegenbauer orthogonal polynomial neural network (NN) control system, which has the online learning capability to return to the nonlinear time‐varying system, was developed. The blend modified recurrent Gegenbauer orthogonal polynomial NN control system can perform overseer control, modified recurrent Gegenbauer orthogonal polynomial NN control, and recompensed control. Moreover, the adaptation law of online parameters in the modified recurrent Gegenbauer orthogonal polynomial NN is based on the Lyapunov stability theorem. The use of amended artificial bee colony optimization yielded two optimal learning rates for the parameters, which helped improve convergence. Finally, comparison of the experimental results of the present study with those of previous studies demonstrated the high control performance of the proposed control scheme. Copyright © 2016 John Wiley & Sons, Ltd.     

A nonlinear equalization method based on multilayer perceptron for OFDM power-line communication

A high-speed data-communication over low-voltage power line is currently an active field of broad application. Power-line communication (PLC), based on orthogonal frequency-division multiplexing (OFDM), is developing rapidly. OFDM with an appropriately selected guard interval is considered as one of the most effective ways to eliminate the intersymbol interference of high-rate signal transmission. However, it is unable to deal with the orthogonality degradation between the subchannels due to the time-variant characteristics of the multipath power-line channels, which are known as the interchannel interference problem. It is, therefore, necessary to introduce a nonlinear channel equalizer. In this paper, a multilayer perceptron scheme trained with a mean square error (MSE) criterion is proposed for the design of the nonlinear channel equalizer. The performances of the traditional linear equalizer and the proposed nonlinear one are compared. In order to evaluate the robustness of the proposed approach against the channel distortion, experimental measurements are made in a real PLC network. The effectiveness of the proposed approach is verified via the experiments on the test system.     

Efficient frequency-domain modelling and simulation of nonuniform coupled transmission lines: application in transient analysis of VLSI circuits

A new method of analysis of the transients in nonuniform lossy multiconductor transmission lines with frequency-dependent parameters is presented. The terminations may be nonlinear, and the interconnections networks are arbitrary. The method of the solution is based on steplines approximation of the nonuniform transmission lines and quasitransverse electromagnetic mode (quasi-TEM) assumptions. Using steplines approximation, the system of coupled nonuniform transmission lines is subdivided into an arbitrarily large number of coupled uniform lines (steplines) with different characteristics. Then, using the modal decomposition method, the system of coupled partial differential equations for each step is decomposed into a number of uncoupled ordinary telegraph equations, which are then solved in the frequency domain. Thereafter each step of the system is modelled as a linear filter with frequency-dependent coefficients. The terminations for linear and nonlinear cases are then modelled as linear or nonlinear systems. Finally, the transfer matrix of the system is obtained. Some examples from the literature are then solved to demonstrate the validity of the method. The method proposed here is very fast and can easily be implemented using general-purpose software packages like MATLAB.     

TCIPC提高系统稳定性的逆系统方法最优控制

可控相间功率控制器(TCIPC)对电力系统潮流控制,提高线路输送能力具有一定的作用,在研究可控相间功率控制器(TCIPC)基本原理的基础上,分析了电感、电容支路对带TCIPC联络线传输功率的控制特性,进行了TCIPC提高系统暂态稳定性的机理分析。基于逆系统方法,将含调谐型TCIPC的非线性电力系统线性化,构造出一个伪线性系统,并且依据线性二次型调节器(LQR)最优控制理论推导出TCIPC的非线性控制规律。搭建了带调谐型TCIPC的单机无穷大系统简化模型进行仿真。仿真结果验证了采用逆系统方法设计的控制策略可以在系统发生大干扰后具有良好的控制性能,能够达到提高电力系统暂态稳定性的作用。     

高压直流输电系统用SHE多脉冲逆变器

高压直流输电损耗小、纹波小、灵活性好、可靠性高,可实现不同频率网互联等,已被广泛应用于长距离架空和电缆输电。通过对SHE-PWM原理的分析,推导出了SHE-PWM数学模型。在高压直流输电用逆变器拓扑结构的基础上应用SHE-PWM技术进行Matlea和功率系统实验仿真,结果表明该逆变器系统具有优良的性能,可有效的降低受电端电网的谐波畸变率,畸变率完全符合国际谐波限制标准。     

Coordinated design of STATCOM and excitation system controllers for multi-machine power systems using zero dynamics method

FACTs devices are being used in transmission networks for increasing the power transfer limit and stability improvement. They also help damp out both local and inter-area low frequency oscillations. However, uncoordinated design of these devices with excitation systems may deteriorate the power system performance. Moreover, power system is a large, complex and nonlinear system, and the controllers that are designed based on linear control theories may have a detrimental effect on the system performance, especially when there are large disturbances occurring in the system. The design method of a nonlinear control technique, named zero dynamics is given in this paper to design the controllers of STATCOM and excitation systems coordinately for multi-machine power systems. This technique is able to provide the stability of both external and internal dynamic performances of the system. Simulations results clearly verify that the proposed method improves the power system stability.     

交直流联合输电系统中HVDC的自适应全局快速Terminal滑模控制

为了提高阻尼系数未知的交直流联合输电系统的运行稳定性,对系统未知参数进行动态估计,同时考虑到自适应backstepping滑模控制器的不足,采用自适应全局Terminal滑模控制方法,设计了一种新型直流输电系统的非线性附加控制器。该方法通过快速调节直流输电线路的输送功率,实现对整个系统稳定性的调节;综合线性滑动模态与非线性滑动模态的优点,使失稳系统能够快速、精确地收敛至平衡状态;考虑系统受具有未知上界的不确定小扰动及三相短路大扰动的影响,分别对干扰未知上界及系统未知参数进行实时动态估计。通过与自适应backstepping滑模控制器进行数值仿真对比,结果表明,该控制器具有更小的超调量,更短的控制响应时间,更准确的未知参数估计性能和更强的鲁棒性,能够更有效地提高系统的稳定性。     

基于RTW的直线电机伺服系统自抗扰控制研究

竖直方向由直线电机驱动的伺服系统,没有传动误差和反向间隙,但是由于其自身结构特点致使系统模型变化,影响了系统的控制性能.在分析了俯仰向采用直线电机控制的伺服平台的非线性因素,继而在辨识的系统标称模型的基础上,进行了自抗扰控制器设计.通过基于RTW和xPC的半实物仿真平台的实验,验证了设计的控制器和半实物仿真设计的有效性.     

基于微分同胚映射和扩张状态观测器的高压直流非线性控制器的设计

为提高高压直流输电系统的抗干扰能力以及模型辨识的准确性,提出了一种基于微分同胚映射和扩张状态观测器的高压直流非线性控制器设计方法。首先利用微分同胚映射将高压直流输电系统模型中的非线性因素作为系统的控制输入,利用线性最优反馈和非线性误差反馈率确定最优预控变量;然后运用扩张状态观测器来辨识所有不确定因素,从而实现非线性控制...     

基于神经网络非线性模型的多级工作点阶跃响应扩展DMC预测控制

利用前馈神经网络建立对象的非线性预测模型,在不同工作点对阶跃响应,建立它的局部线性模型,利用隶属函数进行加权得全局线模型,利用全局线性模型进行滚动优化,利用非线性预测模型校正线模型,实现非线性预测控制,仿真表明,文中提出了方法控制效果良好,满足实时要求。     

南方电网“西电东送”通道损耗特性及影响因素

为进一步挖掘电网节能潜力并为后续电网发展提供指导,基于南方电网"西电东送"发展历程及历年线损的统计分析,从时间、交易构成、输电通道等维度对直流输电通道、交流输电通道及整个南方电网"西电东送"通道线损率的变化趋势进行对比分析,对南方电网"西电东送"通道的损耗特性进行全面总结。采用成功关键分析法对南方电网"西电东送"通道损耗的关键影响因素进行分析和辨识,指出电网运行管理和直流输电通道的线损特性是整个"西电东送"通道损耗的关键影响因素。结合南方电网"西电东送"发展技术路线,提出了进一步优化未来直流工程关键技术指标等降损工作重点。     

发电机励磁及SVC非线性最优协调控制

发电机励磁和静止无功补偿器(static var compensator,SVC)对远距离输电的稳定性有很大影响。为了提高系统在大扰动情况下的暂态稳定性,提出一种发电机励磁系统与SVC协调非线性最优控制方法。通过建立发电机励磁与SVC系统的综合模型,将微分几何反馈线性化理论与线性最优控制理论相结合,设计了发电机励磁与SVC系统的非线性最优协调控制规律。控制信号实现了本地化,避免了远距离的信号传输。仿真结果证明,该控制方法能同时改善系统的功角稳定性和电压稳定性。     

A distributed state estimation method for power systems incorporating linear and nonlinear models

High-voltage transmission networks are commonly equipped with phasor measurement units (PMU), and some of them are PMU observable. However, PMUs are seldom installed in distribution networks due to budget limitations. The state estimation equations of PMU observable areas are linear, while those of other areas remain nonlinear. This paper proposes a new distributed state estimation method for solving multi-area state estimation problems, in which linear models are used for high-voltage transmission network, while nonlinear models are adopted for other areas. In PMU observable area, we select coordinating variables as generalized cost functions which accurately represent the sensitivity between the linear SE objective function and boundary states. Consequently, SE results identical to a centralized estimator can be obtained without iterations at the coordination level. This paper presents the problem model and theoretical analysis of the proposed method, and shows its effectiveness by numerical tests.     

A cross-layer adaptive transmission scheme over correlated fading channels

Conventional adaptive transmission schemes perform poorly in wireless correlated slow-fading channels. A cross-layer adaptive transmission scheme combined with selective repeat automatic repeat request (SR-ARQ) is proposed. We apply a multi-state Markov system model for analyzing the performance of systems and optimizing the selection of modulation levels and packet sizes in correlated fading channels, which is also described by a finite-state Markov chain. A general closed-form expression of the average throughput for our suggested scheme is presented. Numerical results show that our adaptive scheme combined with SR-ARQ can obtain good performance in correlated fading channels. Translated from Journal on Communications, 2006, 45(1): 35–41 [译自: 通信学报]