Output feedback control of wind energy conversion system involving a doubly fed induction generator

This paper deals with the problem of controlling a wind energy conversion system (WECS) based on the doubly fed induction generator (DFIG), by IGBT‐based back‐to‐back rectifier‐inverter. The goal of control is to maximize wind energy extraction letting the wind turbine rotor operate in a variable‐speed mode. Interestingly, the present study features the achievement of the above energetic goal without resorting to sensors for wind velocity. The control strategy involves: (i) an output feedback non‐linear regulator designed by the backstepping technique and based on the use of a high gain observer; (ii) a sensorless online reference‐speed optimizer designed using the turbine power characteristic to achieve the maximum power point tracking (MPPT) requirement. It is formally shown that the proposed controller actually meets its control objectives. This theoretical result is confirmed by several simulations.     

Power control of a doubly fed induction generator connected to the power grid

In this paper, the regulation control problem of the active and reactive power at the common connection point between a doubly fed induction generator and the grid is approached. The proposed controller is developed exploiting the passivity properties of the considered model for the control system. It is considered the existence of a wind turbine that delivers a time-varying torque to the generation unit which exhibits a highly nonlinear structure due to the variations of the wind speed. From a theoretical perspective, the main feature of the contribution lies in the fact that it is formally proved that the equilibrium point of the closed-loop system that corresponds to the desired power exhibits practical global asymptotic stability properties. This characteristic is obtained applying well-known theory from the perturbed nonlinear dynamical systems theory. However, in the numerical evaluation of the proposed controller, it is illustrated how these properties are indeed stronger since asymptotic stability is achieved.     

功率硬件在环双馈风机仿真系统

基于模型设计开发的理念设计了功率硬件在环双馈风机仿真系统。该仿真系统由上位机、转速采集卡、变频器、异步电机硬件在环仿真实际风机,双馈电机采用模块式背靠背双PWM变流器控制。变流器采用双控制器控制,NI通用控制器进行PWM驱动控制,TI-28335 DSP辅助控制,NI控制器的程序由Simulink模型直接生成,辅助控制器运行普通控制算法、逻辑、软件保护,可根据实验需求配置两者的输出控制量。该系统能够完成各种复杂工况的研究,可以由Simulink模型直接生成控制器运行代码,能够快速实现变流器的复杂控制算法,提高科研效率,降低测试成本。     

Robust output feedback stabilization via risk-sensitive control

We consider a problem of robust linear quadratic Gaussian (LQG) control for discrete-time stochastic uncertain systems with partial state measurements. For a finite-horizon case, the problem was recently introduced by Petersen et al. (IEEE Trans. Automat. Control 45 (2000) 398). In this paper, an infinite horizon extension of the results of Petersen et al. (IEEE Trans. Automat. Control 45 (2000) 398) is discussed. We show that for a broad class of uncertain systems under consideration, a controller constructed in terms of the solution to a specially parameterized risk-sensitive stochastic control problem absolutely stabilizes the stochastic uncertain system.     

Modeling and control of the doubly fed induction generator wind turbine

The present paper deals with the modeling of wind turbine generation systems. The model of a doubly fed induction generator, along with the corresponding converter, crow bar protection and electrical grid is described. The different level control strategies both in normal operation and under voltage dig conditions are discussed, including speed control, torque and reactive power control for the rotor-side converter, reactive and DC voltage control for the grid-side converter and the corresponding current loops control. The results obtained with simulations are compared to experimental data obtained from voltage sags provoked to real wind turbines.     

Decentralized adaptive output feedback control via input/output inversion

A decentralized adaptive output feedback control design method is presented for control of large-scale interconnected systems. It is assumed that all the controllers share prior information about the subsystem reference models. Based on that information, a linear dynamic output feedback compensator and linearly parameterized neural network (NN) are introduced for each subsystem to partially cancel the effect of the interconnections on the tracking performance. Boundedness of error signals is shown through Lyapunov's direct method.     

双馈感应风力发电机实现LVRT控制策略研究

根据最新的风电场接入电网规定,在电网发生故障情况下风力发电机组应能保持与电网的连接。电网电压跌落是电网故障常见的形式之一,所以如何提高双馈感应风力发电机组低电压穿越能力成为了当今风电技术的研究热点。本文根据低电压穿越技术的基本原则,通过改进转子侧的控制策略和增加保护电路的方案来实现低电压穿越技术。通过仿真研究表明,改进的控制策略可以有效的抑制转子侧过电流,能够有效的提高双馈感应风力发电机在故障期间的低电压穿越能力。     

Quantised output feedback control via limited capacity communication networks

This article addresses the output feedback stability problem for single-input single-output (SISO) linear systems with quantised measurements of the plant output, where sensors and controllers are connected via errorless digital channels carrying a finite number of bits per unit time. The main idea here is to present a lower bound of data rates, above which there exists a quantisation, coding and control scheme to guarantee both stability and a prescribed control performance of the unstable plant. A quantisation and coding scheme, which is based on the distribution of measurements and the dynamics of the plant, is proposed. The proof techniques rely on both information-theoretic and control-theoretic tools. An illustrative example is given to demonstrate the effectiveness of the proposed scheme.     

Parametric control to a type of quasi-linear second-order systems via output feedback

This paper considers the design of output feedback control for a type of quasi-linear second-order systems with the time-varying coefficient matrices containing the state variables and a time-varying parameter vector. Based on the solution to a type of second-order generalised Sylvester matrix equations, general complete parameterisation of a quasi-linear output feedback controller is established with respect to the state variables, the time-varying parameter vector, the constant closed-loop system and another two groups of arbitrary parameters, and also for the left and right closed-loop eigenvectors matrices. With the proposed parametric output feedback control, the closed-loop system can be transformed into a constant linear system with desired eigenstructure. Finally, simulation results are provided to illustrate the convenience and effectiveness of application in the general spacecraft rendezvous problem.     

Robust output feedback learning control for induction motor servo drives

This paper addresses the output feedback tracking control problem for induction motor servo drives with mechanical uncertainties: rotor angle, rotor speed and stator currents are assumed to be available for feedback. A robust adaptive learning control is designed under the assumption that the reference profile for the rotor angle is periodic with known period: it ‘learns’ the periodic disturbance signal by identifying the Fourier coefficients of any truncated approximation; ??₂ and ??_∞ transient performances are guaranteed in the ‘learning phase’. It is shown that, for any motor initial condition belonging to an arbitrary given compact set, by properly setting the control parameters: (i) the rotor position and flux modulus tracking errors exponentially converge to residual sets, which may be arbitrarily reduced by increasing the number of terms in the truncated Fourier series; (ii) when the unknown periodic disturbance can be represented by a finite Fourier series, the rotor position and flux modulus tracking errors exponentially converge to zero. As in field oriented‐control, the control algorithm generates references for the magnetizing flux component and for the torque component of the stator current leading to significant simplifications for current‐fed motors. Copyright © 2008 John Wiley & Sons, Ltd.     

具有未知动态的船舶编队输出反馈控制

研究了仅利用相对位置信息和相对航向信息的船舶编队输出反馈控制问题.首先使用leader-follower策略,建立了船舶编队的运动学模型.然后应用微分同胚变换将系统解耦成3个子系统.根据船舶低频运动的特点,在跟随船水动力学模型中粘性水动力和力矩未知以及所有船舶速度都不可测量的假定下,提出了一种高增益广义比例积分观测器来估计这些未知和不可测量动态.在高增益广义比例积分观测器的基础上,分别设计了线性输出反馈控制器和输入饱和受限的输出反馈控制器,并分析了闭环系统的稳定性.最后仿真结果表明了方法的有效性.     

Simultaneous linear-quadratic optimal control design via static output feedback

In this paper, the problem of designing a fixed static output feedback control law which minimizes an upper bound on linear quadratic (LQ) performance measures for r distinct MIMO plants is addressed using linear matrix inequality (LMI) technique. An iterative LMI algorithm is proposed to obtain the solution. Examples are used to demonstrate its effectiveness. Copyright ©1999 John Wiley & Sons, Ltd.     

Global adaptive output feedback control of induction motors withuncertain rotor resistance

The authors design a global adaptive output feedback control for a fifth-order model of induction motors, which guarantees asymptotic tracking of smooth speed references on the basis of speed and stator current measurements, for any initial condition and for any unknown constant value of torque load and rotor resistance. The proposed seventh-order nonlinear compensator generates estimates both for the unknown parameters (torque load and rotor resistance) and for the unmeasured state variables (rotor flux); they converge to the corresponding true values under persistency of excitation which actually holds in typical operating conditions. The control algorithm generates references for the magnetizing flux component and for the torque component of stator current which lead to significant simplification for current-fed motors. Simulations show that the proposed controller is suitable for high dynamic performance applications     

Intelligent-controlled doubly fed induction generator system using PFNN

An intelligent-controlled doubly fed induction generator (DFIG) system using probabilistic fuzzy neural network (PFNN) is proposed in this study. This system can be applied as a stand-alone power supply system or as the emergency power system when the electricity grid fails for all sub-synchronous, synchronous, and super-synchronous conditions. The rotor side converter is controlled using the field-oriented control to produce three-phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field-oriented control, is primarily implemented to maintain the magnitude of the DC-link voltage. Furthermore, an intelligent PFNN controller is proposed for both the rotor and grid side converters to improve the transient and steady-state responses of the DFIG system at different operating conditions. The network structure, online learning algorithm, and convergence analyses of the PFNN are introduced in detail. Finally, the feasibility of the proposed control scheme is verified using some experimental results.     

Asymptotic stabilisation of a class of nonlinear systems via sampled-data output feedback control

This article considers sampled-data output feedback control of a class of nonlinear systems in output feedback form. The underlying continuous-time controller is designed based on backstepping technique, employing a linear dynamic filter, and globally asymptotically stabilises the system. Rigorous analysis shows that when implemented with a sampling and zero-order hold device, the sampled-data version of the continuous-time controller semi-globally asymptotically stabilises the original system, given that the sampling period is smaller than a specific value, which depends on the initial values and nonlinearity of the system. Simulation results of a physical system are included in the end.     

Decentralised output feedback for a class of nonlinear systems via quantised sampled-data control

We design a decentralised observer-based sampled-data controller with quantised output for a class of interconnected nonlinear systems. Instead of quantising the output directly, we quantise the sampled output to avoid sudden jump. It can be proved that by choosing suitable design parameters, global stability of the system is achieved. An example is given to illustrate the effectiveness of the proposed method.     

Markov跳变系统的输出反馈鲁棒预测控制

对离散时间Markov跳变系统, 当系统状态不完全可测时, 研究了一类基于输出反馈的鲁棒模型预测控制问题. 所研究系统为准线性参数时变的, 考虑在当前时刻系统的时变参数是已知的, 将来时刻未知的情况. 综合考虑系统存在多胞不确定性和有界噪声等因素, 通过运用线性矩阵不等式方法及变量变换思想, 将无穷时域性能指标的最小最大鲁棒预测控制问题转化为具有线性矩阵不等式约束的凸优化问题, 得到了系统的输出反馈控制律. 引入二次有界概念, 在满足输入输出约束的情况下, 保证闭环系统的随机稳定性. 数值算例验证了方法的有效性.     

Constrained robust model predictive control via parameter-dependent dynamic output feedback

This paper considers output feedback robust model predictive control for the quasi-linear parameter varying (quasi-LPV) system with bounded disturbance. The so-called quasi-LPV means that the varying parameters of the linear system are known at the current time, but unknown in the future. The control law is parameterized as a parameter-dependent dynamic output feedback, and the closed-loop stability is specified by the notion of quadratic boundedness. An iterative algorithm is proposed for the on-line synthesis of the control law via convex optimization. A numerical example is given to illustrate the effectiveness of the controller.     

Insensitive and robust control design via output feedback eigenstructure assignment

Insensitive and robust control design using output‐feedback eigenstructure assignment for linear multivariable systems is considered in this paper. A parametric expression of closed‐loop eigenvectors and generalized eigenvectors is developed. It can cope with the case where the closed‐loop eigenvalues are multiple and/or the same as the open‐loop ones so that the system to be designed can be uncontrollable and/or unobservable. The controller designed via output‐feedback eigenstructure assignment is expressed by proposed parameter vectors. The freedom provided by output‐feedback eigenstructure assignment is used to optimize some performance functions which are used to measure the sensitivity of the closed‐loop matrix and the robustness of the closed‐loop system. Copyright © 2000 John Wiley & Sons, Ltd.     

Flicker mitigation in a doubly fed induction generator wind turbine system

This paper describes a doubly fed induction generator (DFIG) control for wind energy generation. The DFIG model is established and the adopted control strategies for machine side and grid side converters are described. Flicker phenomenon is defined and its emission of variable speed wind turbine with DFIG during continuous operation is studied. Calculation of flicker severity is evaluated using flickermeter. Appropriate vector power control of the machine side converter is proposed and applied to achieve flicker mitigation.