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.     

Variable Parameter Nonlinear Control for Maximum Power Point Tracking Considering Mitigation of Drive-train Load

Since mechanical loads exert a significant influence on the life span of wind turbines, the reduction of transient load on drive-train shaft has received more attention when implementing a maximum power point tracking (MPPT) controller. Moreover, a trade-off between the efficiency of wind energy extraction and the load level of drive-train shaft becomes a key issue. However, for the existing control strategies based on nonlinear model of wind turbines, the MPPT efficiencies are improved at the cost of the intensive fluctuation of generator torque and significant increase of transient load on drive train shaft. Hence, in this paper, a nonlinear controller with variable parameter is proposed for improving MPPT efficiency and mitigating transient load on drive-train simultaneously. Then, simulations on FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code and experiments on the wind turbine simulator (WTS) based test bench are presented to verify the efficiency improvement of the proposed control strategy with less cost of drive-train load.      

小型风电系统变步长扰动MPPT控制仿真研究

最大功率跟踪(MPPT)策略是提高风电系统功率转换效率的重要方法.文中提出了变步长扰动MPPT策略,并在MATLAB仿真环境中,开发了带有此策略的小型风电系统仿真模型.该模型包括风力机模型、永磁发电机(PMSG)模型、DC/DC斩波器模型、负载功率采样模型和MPPT控制模型等.利用该模型进行计算机仿真,给出了一定风速下负载功率和发电机输出功率的仿真结果.结果表明:实现了变步长扰动MPPT策略控制的仿真,与传统固定步长MPPT策略相比,提高了最大功率跟踪的快速性和准确性,进而提高了风能转换效率.     

Adaptive Nonlinear Control of Wind Energy Conversion System Involving Induction Generator

This paper presents a theoretical framework for adaptive control of a wind energy conversion system (WECS), involving a squirrel cage induction generator (SIG) connected with an AC/DC/AC IGBT‐based PWM converter. A multi‐loop nonlinear controller is designed to meet two main control objectives, i.e., (i) speed reference optimization in order to extract a maximum wind energy whatever the wind speed, and (ii) power factor correction (PFC) to avoid net harmonic pollution. These objectives must be achieved despite the mechanical parameters uncertainty. First, a nonlinear model of the whole controlled system is developed within the Park coordinates. Then, a multi‐loop nonlinear controller is synthesized using the adaptive backstepping design. A formal analysis based on Lyapunov stability is carried out to describe the control system performances. In addition to closed‐loop global asymptotic stability, it is proven that all control objectives (induction generator speed tracking, rotor flux regulation, DC link voltage regulation and unitary power factor) are asymptotically achieved.     

Sensorless adaptive output feedback control of wind energy systems with PMS generators

This paper addresses the problem of controlling wind energy conversion (WEC) systems involving permanent magnet synchronous generator (PMSG) fed by IGBT-based buck-to-buck rectifier–inverter. The prime control objective is to maximize wind energy extraction which cannot be achieved without letting the wind turbine rotor operate in variable-speed mode. Interestingly, the present study features the achievement of the above energetic goal without resorting to sensors of wind velocity, PMSG speed and load torque. To this end, an adaptive output-feedback control strategy devoid of any mechanical sensor is developed (called sensorless), based on the nonlinear model of the whole controlled system and only using electrical variables measurements. This control strategy involves: (i) a sensorless online reference-speed optimizer designed using the turbine power characteristic to meet the maximum power point tracking (MPPT) requirement; (ii) a nonlinear speed regulator designed by using the backstepping technique; (iii) a sensorless interconnected adaptive state observer providing online estimates of the rotor position as well as speed and load/turbine torque. The proposed output-feedback control strategy is backed by a formal analysis showing that all control objectives are actually achieved. Several simulations show that the control strategy enjoys additional robustness properties.     

变桨距风力发电机组恒功率反馈线性化控制

在额定风速以上时,为保证风电机组的安全稳定运行,需要降低风力机捕获风能,使风力机的转速及功率维持在额定值,基于微分几何反馈线性化方法,提出变桨距风力发电机组恒功率控制策略.建立了风力机的仿射非线性模型,采用微分几何反馈线性化变换实现全局精确线性化;根据新的线性化模型,以风力机转速为输出反馈变量,叶片桨距角为输入控制变量,设计桨距角控制器;在风速高于额定值时调节风力机维持在额定转速,从而实现额定风速以上的恒功率控制.仿真结果表明,所提控制策略能较好地解决变桨距风力发电机组额定风速以上的恒功率控制问题,控制方法具有较好的适应性和鲁棒性.     

风力发电系统变浆距模糊自适应PID控制器仿真与研究

为解决普通PID对风力发电机输出功率控制不稳定的问题。针对整个风力发电系统的非线性特点提出了模糊自适应PID变桨距控制的方案。以输出功率值与额定功率值的偏差以及偏差的变化率作为模糊控制的输入,把模糊推理出的三个整定参数和初始PID参数进行叠加后控制变桨距,最后在Matlab/Simulink上搭建整体模型并仿真得到输出功率波形。结果表明:模糊自适应PID比普通PID能更好提高输出功率的稳定性。     

双馈风力发电机的最大风能追踪技术研究

如何提高风能的利用率,实现最大功率点追踪(MPPT)成为世界各国研究的热点。变速恒频(VSCF)双馈风力发电机作为当前风力发电的主流机型,对其MPPT研究更具有较强的现实意义。通过对风力机运行特性的分析,结合目前的MPPT控制方式,提出将模糊控制与改进的变步长扰动法结合来实现MPPT,并通过MATLAB仿真验证该策略的有效性及稳定性。     

风力发电机组桨距角鲁棒控制器的设计与仿真

在空气动力学原理基础上建立了变浆距风力发电机组非线性数学模型,以此为基础采用基于动态逆的非线性内模控制方法设计了风力发电机组在额定风速以上工作时的桨距角鲁棒控制律,以使输出功率维持在额定值附近。设计是针对风力机的非线性数学模型进行的,克服了基于局域近似线性化模型设计方法的缺点,适应工况点大范围变动的情形,而且对系统参数摄动具有良好的鲁棒性,求解过程相对比较简单。以一台额定功率为300kW的实际风力发电机组为实例进行了对比仿真,结果表明了该方法能够满足控制要求,具有较好的动、静态特性和鲁棒性。     

基于RBF神经网络的风光互补路灯系统MPPT研究

为了提高风光互补路灯的稳定性和使用寿命,根据风光互补路灯系统非线性、多物理量等特性,分别对风力发电和光伏发电采取最大功率点跟踪(MPPT)控制。该方法基于径向基函数(RBF)神经网络,分别以风力发电整流器输出的电压、电流和太阳能电池板输出的电压、电流作为RBF神经网络的输入,通过RBF神经网络直接改变Boost电路的占空比,使风光互补系统工作在最大功率点。仿真和试验结果表明,所提出的MPPT算法与扰动观察法算法相比,有更好的快速性和能量利用效率。     

基于反馈线性化的液压型风力发电机组最佳功率追踪控制

液压型风力发电机组在额定风速以下时为获得最多电能,需随风速变化追踪最佳功率点.建立并网液压型风力发电机组仿射非线性数学模型,基于反馈线性化方法,分别以风力机转速和液压系统传输功率为输出,以变量马达摆角为控制输入,线性化系统,设计最佳转速与最佳功率追踪控制器,实现机组在额定风速以下随风速变化输出最佳功率.仿真结果表明,以液压系统传输功率为控制输出的功率追踪过程动静态特性较好.理论分析表明,控制器中高压腔压力变化率是否可以规划,是影响功率追踪过程稳定性的关键因素.     

具有尾缘襟翼风力机的恒功率反步法控制

尾缘襟翼风力机控制技术在大型风力机领域具有巨大的应用潜力.本文首先基于修正的叶素动量方法建立了具有可变尾缘襟翼的风力机气动模型.针对襟翼风力机的非线性模型,采用反步法设计了非线性控制器,保证系统的控制量和状态变量全局有界,并且风机的输出功率可以收敛到额定功率的一个小邻域内.此外,控制器设计过程中没有将实时风速信息纳入反馈系统,因而降低了工程实施的难度.最后针对12 m/s～15 m/s的阶跃风、基于四分量模型模拟的风载扰动、执行机构受到外部扰动以及总转动惯量具有10%不确定性的工况进行了仿真,仿真结果表明所设计的控制器能有效地稳定风力发电系统的输出功率,控制系统具有较强的鲁棒性.     

新型双馈风力发电机有功功率平滑控制策略研究

针对由于风能的不确定性、风力发电机的大惯性以及风力发电系统的响应延迟性等造成的风力发电机输出有功功率在一定范围内有波动的问题,提出了一种新型双馈风力发电机有功功率平滑控制策略。该控制策略在全风速范围内采用变浆与变速协调控制策略,并在其基础上增加了一个有功功率误差控制环节,将转子电压辅助控制指令值作为反馈量加入原来的转子电压控制指令值,通过控制SPWM脉冲发生器来实现风力发电机定子输出有功功率的平滑控制。Matlab/Simulink仿真结果表明,与传统有功功率控制策略相比,该新型有功功率平滑控制策略有效抑制了双馈风力发电机输出有功功率的波动。     

智能全功率MPPT风光互补路灯控制器设计

针对一类普通风光互补路灯控制器转换能效低、稳定性差等问题,设计一种智能全功率MPPT风光互补路灯控制器.采用双MCU处理器PIC16F877A单片机为控制器核心,硬件采用模块化的设计方法,整个控制器由主控制模块、从控制模块、风力发电机智能升压MPPT模块,以及风力发电机点刹控制模块、太阳能智能升压MPPT模块、蓄电池充/放电模块、负载LED灯模块组成,在分析光伏电池和风力发电机最大功率点跟踪问题的基础上,采用风力发电机和太阳能智能全功率MPPT跟踪控制策略.最后,在实验室搭建测试平台,测试结果表明,控制器可以可靠稳定运行,跟普通控制器相比,其充电效率与能源利用能效提高22.1％,能够实现能源的最大化利用.     

基于微分几何的风力发电机组恒功率控制

当风速超过额定值时, 可以通过降低风力机的转速实现恒功率控制从而避免使用复杂的变桨距机构, 本文基于微分几何理论设计了非线性控制器, 实现了变速风力发电机组的恒功率控制. 首先, 分析了风力机的空气动力学特性, 这是所提出的恒功率控制方法的理论依据; 然后, 通过微分几何反馈线性化变换, 将风力机的非线性模型全局线性化; 最后, 基于新的线性化模型设计了非线性控制器, 实现了变速风力机的全局精确线性化控制. 仿真结果表明, 所提出的控制方法在风速大范围变化的情况下能有效的实现变速风力发电机组额定风速以上的恒功率控制.     

Intelligent maximum power tracking control of a PMSG wind energy conversion system

A comparative control study for a maximum power tracking strategy of variable speed wind turbine is provided. The system consists of a direct drive permanent magnet synchronous generator (PMSG) and an uncontrolled rectifier followed by a DC/DC switch‐mode step down converter connected to a DC load. The buck converter is used to catch the maximum power from the wind by generating an efficient duty cycle. Distinct Maximum Power Point Tracking (MPPT) algorithms are analyzed and compared: a classical Proportional‐Integral controller (PI) and two based Fuzzy Logic Controllers (FLC), including a conventional Fuzzy‐PI and an Adaptive FLC‐PI. The main aim of the presented study is to develop an advanced control scheme for wind generators to ensure a high level operating of the system and a maximum power extraction from the wind. This is achieved by analyzing the behavior of the system under fluctuating wind conditions employing Matlab Simpower Systems tool. Simulation results confirm that the Adaptive FLC‐PI controller algorithm has better performances in terms of dynamic response and efficiency especially in comparison with the ones of a PI controller under variable wind speed.     

双馈异步风力发电机功率控制扰动法仿真研究

双馈异步风力发电机有功功率、无功功率的解耦控制是变速恒频风力发电系统的关键技术,也是保证风力发电机组安全高效运行的关键.介绍了交流励磁变速恒频风力发电的基本原理,提出了功率控制扰动策略.利用定子磁链定向的矢量控制方法建立了双馈异步发电机在d-q坐标系下的数学模型,实现了定子有功功率、无功功率的解耦控制.推导了双馈异步发电机的线性化模型并分析了其特件.利用MATLAB/Simulink建立了系统的仿真模型,并就主要扰动参数对系统功率控制性能的影响进行了分析.仿真结果验证了功率控制扰动策略的正确性和可行性,为风力发电技术的进一步研究提供了理论依据.     

双PWM直驱同步风力发电机最大风能捕获

以直驱同步风力发电机组为研究对象,为了提高发电机的系统的效率,降低电机的损耗,采用双PWM变流器拓扑结构,提出了一种最大风能捕获（MPPT）的控制方式。不需要风速信号、风机转速及与风力机系统参数有关的最大功率运行表格,仅需对输出功率进行跟踪计算,使得能达到捕获最大风能的控制效果。采用PSCAD／EMTDC软件进行仿真,仿真结果验证了控制方法的有效性。     

HIERARCHAL CONTROL SYSTEM FOR A VARIABLE SPEED CAGE MACHINE WIND GENERATION UNIT USING NEURAL NETWORKS

A hierarchal control strategy, that addresses three control objectives for a wind generation system, is proposed in this paper. It controls the local bus voltage (to avoid voltage rise), captures the maximum power in the wind and also minimizes the power loss in the induction generator. In the first level, given the instantaneous wind speed, electrical torque and output power, the designed neural networks calculate the desired rotor speed, air‐gap flux and the grid side reactive power. In the second level, the desired current wave shapes (instantaneous three‐phase currents) of the rectifier and the inverter in a double‐sided PWM converter system are calculated. In the third level, the PWM controller guides the system towards the optimum operating conditions. Simulation results show that even as the wind speed changes randomly, the proposed control strategy leads the system to the optimum operating conditions.     

低风速风力机最大风能追踪的互补滑模控制

针对风力机系统在最大功率点跟踪(MPPT)阶段易受风速等不确定因素的影响,为了进一步提高风力机的风能捕获效率,本文在滑模控制的基础上提出了一种互补滑模控制方法.首先,建立了含有干扰项的风力机系统的线性化模型,采用广义滑模面与互补滑模面相结合的方法设计了互补滑模控制器,并在理论上证明了此控制方法能够有效保证风力机转速跟踪误差的收敛性,且能提高转速跟踪精度.其次,采用风力机专业仿真软件FAST对美国可再生能源实验室(NREL)的600 kW风力机进行了仿真实验,结果表明本文所提出的控制方法不但能提高风力机的风能捕获效率,而且能有效减小转速跟踪误差.最后,将本文所提方法与现有常见的几种控制方法相比较发现:风力机系统在互补滑模控制策略下,具有更高的风能捕获效率和更小的转速跟踪误差.