Low‐complexity robust adaptive generalized sidelobe canceller detector for DS/CDMA systems

A novel low computational complexity robust adaptive blind multiuser detector, based on the minimum output energy (MOE) detector with multiple constraints and a quadratic inequality (QI) constraint is developed in this paper. Quadratic constraint has been a widespread approach to improve robustness against mismatch errors, uncertainties in estimating the data covariance matrix, and random perturbations in detector parameters. A diagonal loading technique is compulsory to achieve the quadratic constraint where the diagonal loading level is adjusted to satisfy the constrained value. Integrating the quadratic constraint into recursive algorithms seems to be a moot point since there is no closed‐form solution for the diagonal loading term. In this paper, the MOE detector of DS/CDMA system is implemented using a fast recursive steepest descent adaptive algorithm anchored in the generalized sidelobe canceller (GSC) structure with multiple constraints and a QI constraint on the adaptive portion of the GSC structure. The Lagrange multiplier method is exploited to solve the QI constraint. An optimal variable loading technique, which is capable of providing robustness against uncertainties and mismatch errors with low computational complexity is adopted. Simulations for several mismatch and random perturbations scenarios are conducted in a rich multipath environment with near–far effect to explore the robustness of the proposed detector. Copyright © 2008 John Wiley & Sons, Ltd.     

Robust CAWOF Kalman predictors for uncertain multi-sensor generalized system

Robust centralized and weighted observation fusion (CAWOF) prediction algorithm is addressed in this article for an uncertain multi-sensor generalized system with linear correlation between observation noises and an input white noise. This uncertainty in the generalized system primarily means that the variances of the aforementioned types of noise, as well as the multiplicative noise variances, are uncertain. Through singular value decomposition and virtual noise compensation, the original generalized system is changed to non-generalized reduced-order subsystems in which only noise variances are uncertain. Utilizing the minimax robustness estimation criterion, robust CAWOF Kalman predictors are put forward on account of the first subsystem with conservative upper bounds of noise variances. Eventually, robust observation fusion Kalman predictors of the original generalized system are proposed. The Lyapunov equation method is applied to verify two fusion predictors' robustness. With regard to all permissible uncertain practical noise variances, CAWOF predictors are robust, namely, the practical prediction error variances of two robust predictors will have minimum upper bounds. This equivalence between CAWOF Kalman predictors is proved by an information filter. In this article, the precision relationship of fusion predictors is given. Meanwhile, robust Kalman predictors for steady-state case are proposed, and the astringency of robust time-variant Kalman predictors is analyzed through the analysis of dynamic error system. The validity and correctness of proposed algorithm are proved by the simulation example of random dynamic input and output system in an economic system.     

A generalized global adaptive tracking control scheme for robot manipulators with bounded inputs

In this work, a generalized adaptive scheme for the global motion control of robot manipulators with constrained inputs is proposed. It gives rise to various families of bounded adaptive controllers defined through a general class of saturation functions. Compared with adaptive tracking control algorithms previously developed in a bounded input context, the proposed adaptive approach guarantees the motion control objective for any initial condition, avoiding discontinuities throughout the scheme, preventing the inputs to reach their natural saturation bounds, and permitting innovation on the saturating structure through its generalized form, giving a wide range of possibilities for performance improvement. Experimental results corroborate the efficiency of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.     

基于故障电流解析表达的FCL协助DFIG低电压穿越研究

双馈感应电机(DFIG)与公共耦合点(PCC)间投入故障电流限制器(FCL)实现低电压穿越(LVRT)时,定子电压受FCL阻抗与网侧变流器(GSC)电流影响,无法设定定子电压,需要对DFIG与FCL整体建模以分析故障电流。基于恒定电流控制策略推导转子侧变流器(RSC)与GSC电流,提出DFIG故障电流的解析表达式。考虑到电压定向下定子相角振荡会导致dq轴恒定电流在xy轴下变化,不利于定子电流稳定,采用dq轴与xy轴相重合的定向方案。对比不同的RSC与GSC电流参考值、FCL阻抗值与切出时间下DFIG LVRT过程中的电磁转矩振荡,选择LVRT性能较好的一组控制参数。仿真结果表明,FCL阻抗取值受RSC与GSC电流参考值影响,且FCL阻抗越大,所取切出时间越短。     

DFIG网侧变换器反馈线性化与滑模控制

为了提高双馈风力发电机(DFIG)网侧变换器(GSC)的动态性能,在建立GSC仿射非线性模型基础上,提出一种非线性复合控制策略。该控制策略在静止坐标系下对电流进行反馈线性化解耦,无需电网电压定向,同时电压外环采用含饱和函数的滑模控制,从而达到直流母线电压快速恒定以及电流跟踪控制的目的。仿真结果表明,该控制实现了GSC的稳定以及功率因数控制,验证了理论的正确性。上述控制策略相较于传统的控制方式,减少计算变量,能够保证系统快速收敛。     

A new CDMA/SDMA structure with transmit diversity

Space division multiple access (SDMA) is a technique which can be used to increase the capacity of mobile communication systems by exploiting the spatial separation between different users. Space-time block codes can provide good performance in wireless fading channels through spatial diversity. Here these two techniques are combined to produce a new cooperative diversity architecture for code division multiple access (CDMA)/SDMA cellular systems using a space-time block code. An analysis of the system performance is given for a Rayleigh fading channel. This analysis can easily be generalized to similar systems. The bit error rate performance for this architecture with the Universal Mobile Telecommunications System, UMTS Terrestrial Radio Access, time-division duplex (UMTS UTRA TDD) and time-division synchronous CDMA (TD-SCDMA) systems is presented.     

Robust backstepping controller for grid‐side converter of DFIG‐based wind energy conversion systems

A robust backstepping controller with nonlinear damping is designed for the grid‐side converter (GSC) of a grid‐connected doubly fed induction generator (DFIG) in wind energy conversion systems (WECSs). The designed controller achieves the exponential ultimate boundedness of both the DC‐link voltage and GSC current errors with an arbitrarily fast decay rate and an arbitrarily small bound in the presence of both model uncertainties and time‐varying external disturbances. A desirable feature that distinguishes the proposed controller from other existing controllers is that the control input of GSC is constructed only by the static feedback of the measurable states. As a result, the control input becomes smooth and easy to implement without requiring differentiation or switching operations. The exponential boundedness and performance of the designed controller are demonstrated by simulation using a 1.5‐MW DFIG‐based WECS model built in MATLAB/SimPowerSystems and compared with a standard proportional‐integral controller. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A high-performance generalized discontinuous PWM algorithm

In this paper, a generalized discontinuous pulsewidth modulation (GDPWM) method with superior high modulation operating range performance characteristics is developed. An algorithm which employs the conventional space-vector PWM method in the low modulation range, and the GDPWM method in the high modulation range, is established. As a result, the current waveform quality, switching losses, voltage linearity range, and the overmodulation region performance of a PWM voltage-source inverter (PWM-VSI) drive are optimized online, as opposed to conventional modulators with fixed characteristics. Due to its compactness, simplicity and superior performance, the algorithm is suitable for most high-performance PWM-VSI drive applications. This paper provides detailed performance analysis of the method and compares it to the other methods. The experimental results verify the superiority of this algorithm to the conventional PWM methods     

Coordinated Controller Design of Grid-connected Variable-speed Wind Energy Conversion System with Model-based Predictive Control Using Response Surface Methodology

This paper presents an optimum design procedure for the coordinated tuning of machine side converter (MSC) and grid side converter (GSC) controllers of grid connected permanent magnet synchronous generator (PMSG). Model based predictive controller (MBPC) is used to control the MSC. MBPC based speed control design consists of two steps. A linearized state space model is employed to predict the future output (rotor speed). An optimal control law is derived by minimizing a quadratic performance index that considers the control effort and the difference between the predicted rotor speed and the reference rotor speed. A proportional-integral (PI) controller is used to control the GSC. The MSC and GSC controller parameters are determined by simultaneously optimizing the controller performance indices. The coordinated controller design is carried out in two steps. The analytical expression that relates the performance indices and the controller parameters is arrived using response surface methodology (RSM). The determination of controller parameters is posed as a constrained multi-objective optimization problem and solved employing NSGA-II (non-dominated sorted genetic algorithm II). The proposed methodology is tested on a sample power system with PMSG based WECS (Wind Energy Conversion System). Simulation results demonstrate the effectiveness of the proposed methodology.     

弱电网下双馈风电机组电网电压扰动补偿控制策略

针对弱电网下双馈风电并网系统的稳定性问题,文中提出了一种基于电网电压扰动补偿的双馈风电机组补偿控制策略。首先,在同步旋转坐标系下建立双馈风电机组,包括转子侧变换器和网侧变换器的统一阻抗模型。然后,基于所建立的阻抗模型分析了并网点电压扰动到控制器输出的传递关系,分别在转子侧电流环和网侧电流环引入了电压扰动补偿对变换器进行改进控制,并通过广义奈奎斯特判据证明了该方法能有效提高双馈风电机组在弱电网下的并网稳定性。理论分析表明,基于并网点电压扰动补偿的转子侧和网侧补偿控制能很好地改善双馈风电机组的输出阻抗特性,从而提高其在弱电网下的稳定性。最后,通过仿真分析验证了该补偿控制方法的有效性。     

线性时滞系统的鲁棒广义H2弹性控制

研究了系统被控对象存在不确定性,同时控制器也存在摄动的控制问题,采用Lyapunov稳定性理论和线性矩阵不等式(LMI)方法,以一组LMI形式给出了控制器存在的充分条件,并给出了弹性控制器的设计方法。仿真实例表明,该方法提高了时滞系统的广义H2控制的鲁棒性,验证了所提出方法的有效性。     

提升双馈风力发电系统低电压穿越能力的跟踪控制方法

为提升双馈风力发电系统的低电压穿越(LVRT)能力,提出一种基于状态相关Riccati方程(SDRE)技术的网侧换流器(GSC)跟踪控制方法。并网导则要求风电场在LVRT过程中须注入一定无功功率支撑电压恢复,为了改进非线性状态调节器在无功支撑能力上的不足,针对双馈风力发电系统的GSC设计非线性无功功率跟踪控制器,并采用SDRE技术求解状态反馈控制律。在维持LVRT过程中直流电压稳定的基础上,该方法能充分利用GSC的无功功率调节能力,为电网提供无功功率支撑以避免电压恶化。最后,在Matlab/Simulink平台搭建9 MW双馈风力发电系统,并在三相接地故障下进行仿真验证,结果显示,所提出的GSC控制方法具有良好的暂态表现,能够有效提高双馈风力发电系统的LVRT能力。     

A novel moment generating function based performance analysis over correlated Nakagami-m fading channels

The bit-error rate and channel capacity have been regarded as fundamental information theoretic performance measure to predict the maximum information rate of a communication system. In contrast, with the analysis of other important performance measures of the wireless communication systems, a novel and unified general approach for computing the bit-error-rate and channel capacity over the correlated Nakagam-m fading channels have been proposed. In this paper, we have analyzed and numerically simulated the bit-error-rate and channel capacity of the correlated Nakagami-m fading channel by using the moment generating function (MGF) based approach. The derived mathematical expression for the channel capacity is in terms of the Meijer G function which is valid for both integer and non-integer values of the fading parameters.     

A control strategy of Hamilton realization and mechanics Lagrangization in doubly-fed wind power generation system

With the nonlinear characteristic of doubly-fed wind power generation (DFWPG) system, Hamilton realization based on analytical mechanics plays a significant role in the system problems of stability analysis and controller design. Hamilton system expression of grid-side converter (GSC) and machine-side converter (MSC) is obtained and the stability control is designed with Lagrange theory of analytical mechanics in this paper. Firstly, to obtain the differential equations which satisfy satisfies self-adjoint conditions, coordinate transformations of dynamic equations of GSC and MSC are conducted. The system Hamilton function and Hamilton realization expression are determined based on Euler–Lagrange process and generalized force method. On the basis of feedback control theory the controller is designed, which can make the system tend to be asymptotically stable in the neighborhood of the equilibrium point. With Hessian matrix positive-definite the Hamilton system is determined to be stable. Additionally, within Matlab/Simulink environment, the transient simulation of DFWPG system is carried out and the effectiveness of controller derived in this paper is verified, by comparisons of response effects with PI control and regulation performances under different wind speeds. The rapid response of the dc bus voltage control, grid-side unit power factor control, a maximum capture of wind energy can be realized, using control design process of Hamilton realization. The system analysis and control design process of Hamilton realization have broad prospects of applications and developments.     

Analysis of confidence bounds in power system state estimation with uncertainty in both measurements and parameters

A method for uncertainty analysis in power system state estimation is proposed. The uncertainty is expressed in both measurements and network parameters. Uncertainties in both measurements and parameters are known and bounded. The problem is formulated as a constrained non-linear optimization problem. To find the tightest possible upper and lower bounds of any state variable, the problem is solved by sequential quadratic programming (SQP) techniques. When applied to the 6-bus, IEEE 14-bus and IEEE 30-bus networks, the proposed method shows reliability and accuracy in estimating the uncertainty bounds in power system state estimation. In addition, assessment of time performance is carried out to demonstrate that the proposed method is suitable for either an on-line or an off-line application.     

An optimal load flow study by the generalized reduced gradient approach

A new operations research model of optimal load flow solved by nonlinear programming methods (the generalized reduced gradient algorithm) is presented. As compared to existing optimal power flow models, this model incorporates network performance variables such as scheduled bus voltages as well as topological and elemental constraints.In addition, the development, sensitivity, optimality and efficiency of the model are explored. Several example problems are implemented and solved. Detailed discussions about the ability of the model to work under a wide variety of network contingencies such as loss of generation or load, loss of a line, and network faults are presented. The model is also briefly examined for its use in the study of network voltage regulation.     

基于矩生成函数近似的双媒质协作通信功率优化分配

针对通用无线接入和电力线中继传输的混合通信场景,首先采用通用Nakagami分布的无线衰落和对数正态(LogN)分布的电力线衰落混合衰落模型,综合应用基于矩生成函数(MGF)方程组的Gamma分布—LogN分布近似转化、LogN变量和近似等方法,推导了系统采用译码转发协议和选择式合并之后的中断概率和误码率理论公式。其中针对MGF方程组,提出了适用于瞬时信噪比概率密度近似转化的关键参数确定方法。接着利用理论性能公式分析了混合信道衰落因子、多维脉冲噪声参数和功率分配影响系统性能的规律,并利用黄金分割等数值算法确定最佳功率分配因子。最后采用蒙特卡洛仿真,验证了理论分析的有效性与可靠性。     

不对称电网故障下双馈风力发电机的比例-积分-谐振滑模控制器设计

针对不对称电网故障下,双馈风力发电机的控制策略进行了研究。讨论了电网故障时转子侧变流器(RSC)和网侧变流器(GSC)的控制目标,合理安排了电网严重故障时的控制优先级。基于比例-积分-谐振滑模控制原理设计了机侧和网侧变流器协同控制方案。通过MATLAB/Simulink仿真软件搭建了所设计控制方案的仿真模型。仿真结果表明,在电网正常运行的情况下,与传统的矢量控制策略相比,比例-积分-谐振滑模控制策略对输出功率、电流变化的响应更迅速,具有更好的动态性能和抗扰动能力;在电网不对称故障下,能够有效地抑制电磁转矩振荡和直流母线电压波动,提高了双馈式风力发电机的低电压穿越能力。     

The generalized theory of indirect vector control for AC machines

The instantaneous torque produced by an AC machine is controllable when vector control is applied. However, the published papers on vector control deal with either induction machines or synchronous machines. A generalized vector-control theory is developed, considering a generalized AC machine as a salient-pole synchronous machine having three kinds of torque, i.e., the field torque, the reluctance torque, and the induction torque. The theory can be extended to the AC machines producing a voluntarily combined torque among the three. The experimental system consisted of applying the generalized vector control theory to a nonsalient-pole synchronous machine with damper winding. It was verified experimentally that the instantaneous torque was controllable, not only in synchronous or induction-machine operation, but also in the transient state between the synchronous-machine operation and induction-machine operation, without any change of the control circuit     

Adaptive prescribed performance tracking control for uncertain strict-feedback Multiple Inputs and Multiple Outputs nonlinear systems based on generalized fuzzy hyperbolic model

This article proposes an adaptive prescribed performance tracking control methodology for a class of strict-feedback Multiple Inputs and Multiple Outputs nonlinear systems. A combination of backstepping technique and the generalized fuzzy hyperbolic model was used in recursive design of adaptive controller. A novel performance constraint function guarantees the tracking control performance. Lyapunov stability analysis proves that the designed controller can ensure the predefined transient and all signals within the closed-loop systems are semiglobally uniformly ultimately bounded. In the end, simulation results illustrate the validity of the proposed approach.