【作者】 孔屹刚；

【导师】 王志新；

【作者基本信息】 上海交通大学 ， 电机与电器， 2009， 博士

【摘要】 相比化石能源和核电,风能是一个开发成本较低,清洁环境,安全,可再生的能源形式,目前越来越受到重视。根据贝兹理论,理论上风机从风中吸收的能量不超过空气动能的59.3%,实际当中该数值由于机械结构上的缺陷要更小一些。因此,如何才能够获取最大能量,实现风能规模化利用,一直为学者及业界所关注。近年来,大型风机都采用了变速变桨距控制技术。采用变速变桨距技术的主要目的是提高响应速度,同时获得最大能量(低风速时捕获最大功率,高风速时捕获额定功率)。但是风能转换系统由于一些不确定因素的存在表现出强非线性特征,同时,风机产生的能量随着风速和风向的连续波动是快速变化的。另一方面,在一个新能源系统中,电能质量和可靠性是两个最重要的指标。一般传统线性定常控制器都会引起超调和损失系统的稳定性,同时由于大型变速变桨距风机的复杂性,例如控制算法、高阶、耦合、强非线性特征等,常规的控制方法就不太适合了。根据风速的不同,风电系统由四个动态过程构成:启动、变速运行、变桨距运行、刹车。启动和刹车过程的主要控制目标是使系统能在最短时间内有较快响应速度;变速控制的主要控制目标是调节风能、减少或消除风能产生过程中的急剧波动,捕获最大能量、减弱暂态负荷的影响;变桨距控制的主要控制目标是通过调节桨距角来维持风机输出额定功率不变。本文对大型风力机系统模型的建立和最优功率控制策略问题进行了探讨。针对1.5MW变速变桨距双馈感应风力发电机组,研究其控制策略,以得到系统的最优功率输出和加强系统的工作性能。仿真研究证明本文提出的控制策略是有效的。主要研究内容和创新成果包括:(1)对大型双馈风电机组风轮、齿轮箱、传动轴、双馈电机、变桨机构等环节进行了理论分析和数学建模,最终得到了一个完整的双馈风电机组数学模型。基于易于实现风电机组最大能量捕获控制的考虑,重点分析了双馈型感应异步发电机的运行理论,通过对双馈感应发电机在dq0同步旋转坐标变换下按定子q轴磁场定向的方法,建立了一个简化的精确的双馈感应发电机的数学模型。(2)以大型水平轴风力机为研究对象,详细研究了风力机在进行载荷计算时坐标系的确定原则和方法,通过matlab和VB.net混合编程对风力机基本数据、翼形数据、空气动力数据进行分析和计算,计算得到风力机桨叶轴向诱导因子、周向诱导因子,相对风速、桨距角、入流角、攻角、扭角等参数对应不同风速的值,最终根据这些参数,综合分析得到了变桨载荷的计算算法。(3)在完成了风电机组建模和载荷计算的基础上,对电气独立变桨和液压统一变桨这两种变桨方式进行了系统设计,包括理论计算、原理图分析和元件选型等,对电气独立变桨进行了实验研究,对液压统一变桨进行了仿真研究。通过对液压变桨系统的液压泵、电液比例阀、液压缸、曲柄连杆机构等环节进行分析和建模,最终得到了一个真实的完整的液压变桨系统数学模型,即输入控制信号是电液比例阀的电流,输出信号是桨距角,并通过仿真实验验证了其稳定性和可靠性。(4)制定了低风速下以发电机转速作为控制输入量,采用变速恒频控制策略;高风速下以发电机功率作为控制输入量,采用变桨距控制策略来捕获最大风能的控制方法。同时针对风电机组高阶强耦合强非线性特性,考虑到模糊控制无需精确的数学模型,滑模控制能提高系统的鲁棒性和稳定性,设计了一种模糊滑模变结构控制器,对大型风电机组变速和变桨距过程进行控制,最终实现风电机组最大功率的输出控制。(5)探讨了整个风电机组启动、变速、变桨距、制动的全过程,基于缩短系统响应时间,提高风机对应低风速、额定风速、高风速不同工况下的工作特性,且在保证风电机组安全性和可靠性前提下,实现最大功率捕获的考虑,提出了一种分层多模最优控制策略:bang-bang控制应用于启动和刹车过程,模糊控制应用于变速运行过程,自适应PID控制应用于变桨距运行过程。本文得到上海市白玉兰科技人才基金(2007B073)、教育部留学回国科研启动基金项目(教外司[2007]1108号)、中国博士后基金项目(2005038435)、上海博士后基金项目(05R214133)、上海市教育发展基金(200603)的资助。更多还原

【Abstract】 Compared with fossil fuel and nuclear power, wind power is of cost competitive, environmentally clean, safe, renewable power sources, and being paid more attention recently. An actual turbine cannot extract more than 59.3% of the air kinetic energy according to Betz theory. In practice, this factor is less because of mechanical imperfections, but we also hope get maximum energy by adopting various methods.Recently, an increasing number of large-scale wind turbines are being developed with a variable speed-variable pitch (VS-VP) technology. The main objective of adopting a VS-VP technology is to improve the fast response speed and capture maximum energy, which means to obtain the maximum power at low wind speed and the rated power at high wind speed. But wind energy conversion systems are of strong nonlinear characteristics because of many uncertain factors. At the same time, the power generated by wind turbine changes rapidly because of the continuous fluctuation of wind speed and direction. On the other hand, in a renewable energy system, both power quality and reliability are two most vulnerable issues. The ordinary linear constant gain controller will cause overshoot or even loss of system stability, meanwhile the adaptive control method is not applicable in this case due to the complexity, such as algorithm, high order, coupling and strong nonlinear characteristics of large-scale VS-VP wind turbine.The control strategy is one of the most basilical renewable technology. According to different wind speed range, the wind generating set consists of four dynamic processes: starting, variable speed running, variable pitch running and braking. The main objective for starting and braking process is that the system has faster response speed in the most short time. Objectives for variable speed control system are summarized by the following general goals: to regulate and smooth the power generated, to maximize the energy capture, to alleviate the transient loads; Objectives for the variable pitch control are similar to the variable speed ones but only can be match a rotational power by regulating pitch angle.This dissertation has studied establishing system model and optimizing power control for large wind turbien. This paper describes a 1.5 MW variable speed-variable pitch wind turbine DFIG where control strategy has been used extensively to optimize the power output and enhance system performance. The validity of obtained result can be illustrated by the simulation research.The main results and contributions of this dissertation are listed as follows:(1) With a view to the fact that the wind turbine system is a very complicated nonlinear system consisting of wind blade, gear box, doubly-fed induction generator (DFIG), variable pitch mechanism etc. To place emphasis on analyzing DFIG and hydraulic variable pitch mechanism, we establishing reliability nonlinear model of DFIG wind turbine system using the electric motor convention and adopting the d ? q reference frame.(2) The calculation and analysis of the variable-pitch load are very important work for variable-pitch mechanism design. This Paper investigates the method of determining the reference frame, ascertains the means of classification load, and obtains the variable-pitch load for large horizontal axis wind turbine by analysing and calculating the incident coefficient out of plane, incident coefficient in-plane, chord, relatine wind speed, inflow angle, attack angle, pitch angle using matlab and VB.net.(3) The collective pitch control and the individual pitch are two primary variable-pitch methods. The design of electric individual pitch and hydraulic collective pitch are proposed, including theoretical calculation,analysis of the scheme and the selection of units etc. Using subsistent experiment condition, the electric individual pitch is analyzed by experiment and the hydraulic collective pitch is analyzed by simulation.(4) When the wind speed range varies from cut-in wind speed to rated wind speed, we adopt variable speed control method by adjusting the rotor speed in order to get optimal power. When the wind speed range varies from rated wind speed to cut-out wind speed, we adopt variable pitch control method by adjusting the pitch angleβin order to make generator work in the case of rated power. Considering that there exists the case that fuzzy control needs no accurate mathematical model and sliding-mode control can provide a good robustness and stability of system. In this paper a new kind of state controller is proposed by fuzzy sliding-mode control theory is established. This control strategy can eliminate the steady state error, compensate the nonlinearity and have excellent robustness.(5) In view of the fact that The main objective of adopting a variable speed-variable pitch technology is to improve the fast response speed and capture maximum energy, a kind of layered multi-mode optimal control strategy is proposed: bang-bang control strategy is adopted in starting and braking process; meanwhile, fuzzy control strategy is adopted in variable speed running process and adaptive proportional integral derivative PID control strategy is adopted in variable pitch running process. This control method can shorten the system response time, improve the wind turbine performance at low, rated and high wind speed.This work was supported by the Baiyulan Foundation for Science & Technology Talents, Shanghai (No. 2007B073), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No. [2007]1108), the Postdoctoral Foundation of China (No. 2005038435), the Postdoctoral Foundation of Shanghai, China (No. 05R214133) and the Shanghai Educational Development Foundation (No. 200603).更多还原