【作者】 葛俊旭；

【导师】 童水光；

【作者基本信息】 浙江大学 ， 化工过程机械， 2010， 博士

【摘要】 保持经济持续、快速发展与维持生态平衡、保护环境的矛盾是当前国际社会也是我国面临的首要问题,为了保护我们赖以生存的地球环境资源,中国和国际社会、特别是发达国家一道为减少碳排放、提高能效,做出了重要的承诺,在未来的经济活动中采用清洁能源替代技术、可再生能源技术、新能源技术来代替化石能源。相对传统能源领域,风能利用技术正在走向成熟,因而风能在施工周期、投资方式上优势明显,具有较好的社会、经济效益。我国在风电的理论研究、工程应用方面与发达国家相比存在很大差距,目前技术条件下的风电成本、并网电能质量以及设备制造和控制技术等均处于劣势。国内对风电产品的需求迫切,风电技术的研究基础薄弱,风电机组大型化、形式多样化等技术问题尚待解决,诸多缘由促使我国逐渐沦为国际风电行业巨头的垃圾产品倾销市场和新产品试验田。因此,深入研究各项风电技术对风能的持久开发、高效利用以及形成自主创新设计、取得自主知识产权的风电产品具有重要的现实意义。风电技术属于综合性系统工程,涉及空气动力学、计算流体力学、自动控制、电机学等诸多学科。目前,随着新技术、新材料的应用,突破传统形式的风电机组逐渐成为风电领域的研究热点。风电机组是非线性的复多变量杂系统,而且风能具有时变性和不稳定性,因此,对新形式风电机组关键技术的研究是解决机组运行安全、经济高效的关键。本文针对垂直轴风力发电机组的关键技术展开研究,主要内容归纳如下：1)基于贝茨理论、动量理论等风力机建模的基础理论以及低速翼型的空气动力学特性,建立了垂直轴风力发电机动力装置的非线性理论模型,综合考虑Re、计算攻角的修正值等对翼型空气动力学特性的影响。基于该风轮模型,分别对H型垂直轴风力发电机、美国圣地亚国家实验室34米直径的垂直轴风力发电机以及浙江大学40米垂直轴风力发电机完成了算例分析,围绕风轮的风能利用系数、风轮输出扭矩以及叶片的气动载荷等主要问题分别进行了讨论,分析了不同形式的风轮在不同风速、叶片处于不同位置以及风轮转速对叶片空气动力学性能和风轮输出扭矩的影响,在此基础上完成该模型的进一步优化设计2)根据垂直轴风力机风轮模犁的分析结果,总结出翼型攻角平面图解方法：“矢量-圆”法,即：远端风速矢最一定时,空间中处于任意位置、圆周运动的叶片,通过建立以风力机风轮旋转过程中的叶片切向速度值为半径的圆,在圆心处建立以远端风速为一个轴的直角坐标系,叶片运动的位置滞后于叶片切向速度π/2,相对风速与远端风速、叶片切向速度组成矢量三角形关系,攻角α为此矢量三角形中叶片切向速度、相对风速的夹角或其补角。文中完成了“矢量-圆”法的理论推导,该方法属于创新性研究,对今后风轮模型的进一步研究工作具有指导作用。3)根据兆瓦级永磁同步发电机的电磁设计和其结构的几何特点,基于集总参数法建立发电机的等效热路模型,该模型对内转子发电机具有通用性,为同类型产品的温升计算提供了理论依据。4)基于热交换定律编制了电机内热交换微分方程,采用有限差分来近似代替微分,利用等效热路图的计算结果来确定热联系,将温度场求解域内的导热偏微分方程及边界条件,转化为成适用于计算区域内部和边界上各个节点处的差分方程组；基于迭代法求解方程组,可得到电机求解域温度的分布。该温升计算方法对电机的设计、试验提供了理论指导。5)根据永磁同步发电机的特点,对兆瓦级垂直轴风力发电机的并网控制策略进行了研究,提出了基于背靠背双脉宽调制整流器的并网控制策略和基于双电压源型脉宽调制整流器的并网控制策略,建立了兆瓦级风电机组全功率控制并网策略的等效电路模型。该并网策略等效电路模型中,发电机侧与永磁同步发电机定子连接的电压源型脉宽调制整流器采用直接电流控制,控制系统结构为同步坐标系下的直流电压外环、交流输入电流内环的双闭环级联结构,与网侧基于三相电压源型脉宽调制逆变模块共同构成的双脉宽调制整流器或双电压源型脉宽调制整流器电路模型,其拓扑结构的通用性较强,在整流器建模、控制算法以及提高其故障运行能力等方面具有优势；同时,永磁同步发电机侧和网侧整流器都使用基于数字信号处理器的数字化控制,采用矢量控制,控制方法灵活,具有四象限运行功能,能够实现对永磁同步发电机的调速和并网电能的质量控制。该并网控制策略有利于解决风电机组并网对电网产生的谐波污染、电压波动、电流不平衡,对今后我国大型风力发电机组并网发电具有重要的现实意义。更多还原

【Abstract】 The contradiction between keeping sustained and rapid economic development and maintenance of ecological balance and protecting environment is an urgent issue faced by all over the world. In order to protect our environmental resources on which we survived, China and the international community, particularly developed countries, have made their important commitments for reducing carbon emissions and improving energy efficiency. In the future industrial production, they will use clean energy to replace traditional energy, renewable energy technologies and new energy technologies to replace fossil fuels. Compared with traditional energy, utilization technology of wind energy is maturing. As a result, the superiority of wind energy is obvious in the construction cycle and the way of investment. Besides, wind energy has better social and economic benefits.There is a big disparity between China and developed countries in the research level of wind power theory and engineering applications. Under the current condition of the technology in our country, the cost of wind power, grid electricity quality and the level of equipment manufacturing and control technologies are all at a disadvantage. Many problems of wind power are waiting for being tackled, for example, urgent domestic demand for wind power product, weak research foundation of wind electricity technology, large scale and form diversification of electrical machinery. Various reasons urge our country to degenerate gradually into the trash product dumping market of international wind power manufactory giants and the new product experimental plot. Therefore, doing deep research on every aspect of wind power technology has vital practical significance for holding lasting development and efficient use of wind power, forming independent and innovative design, and obtaining absolute intellectual property rights of wind power products.Wind power technology is a comprehensive and systematic project involving aerodynamics, computational fluid dynamics, automatic control, electrical science and many other subjects. Nowadays, with the applications of new technologies and materials, the breakthrough of the traditional forms of wind turbine has gradually become the research focus in this field. Wind turbine is a complex multi-variable nonlinear hybrid system. and wind power has the qualities of variability and instability with time. Therefore. research on the key technologies of wind turbine with new form is the sticking point for the solution of security of generator operation and economical high efficiency.The current studv focuses the on key technologies for megawatt level vertical-axis wind turbine. The major research is summarized as the following points:1). Based on Betz theory, the momentum theory and other fundamental theories of wind turbine modeling, and the aerodynamic characteristics of low-speed airfoil, the current study established the non-linear theoretical model for wind wheel of vertical axis wind turbine with the effect of the Reynolds number and the correct value of calculated attack angle in aerodynamic characteristics of airfoil being considered. On the basis of this model, numerical analyses have been done on H-type vertical axis wind turbine, 34-meter diameter vertical axis wind turbine in U.S. Sandia National Laboratories and 40-meters vertical axis wind turbine in Zhejiang University. The wind energy utilization coefficient of the wind wheel, output torque of wind wheel, the blade aerodynamic loads and other major issues have been discussed. Besides, the current thesis has analyzed the influence of blade of different types on aerodynamics performance and output torque of wind wheel under the condition of different wind speeds and locations. As a result, the designed model of wind turbine has been further optimized.2). According to the analysis of vertical axis wind turbine model, the thesis summarized the plan solution method for calculation attack angle of all airfoils:"Vector-Circle" method. The method refers to when the remote wind speed vector is constant, for the blades in circular motion in space, we can draw a circle with the radius which is numerically equal to the value of tangential velocity of one blade and establish the system of rectangular coordinated with remote speed vector as one axis. In the model of "Vector-Circle", the vector of blade’s location lags behind vector of blade’s tangential velocity forπ/2. The vector of remote wind speed v, vector of blade’s tangential velocity u and vector of relative wind speed w form triangular. In this vector triangle the angle of attack a is an acute angle between u and w or its supplementary angle. The thesis has completed the derivation of "vector-Circle" which is an innovative research. It has a guiding role in the further research work of mathematical models for wind turbine.3). According to megawatt-level electromagnetic design of permanent magnet synchronous generators and its geometrical characteristics, the current study established the model of equivalent thermal circuit diagram in generator based on the lumped parameter. This model has generaliability for the same type of generators with rotor in structure, which provides a theoretical basis for the calculation of temperature rising of generators.4). The current study composed the heat exchange equation of in generators based on the heat exchange law. Through adopting finite difference to approximately replace differential and using the results of calculation for equivalent thermal circuit diagram to determine the thermal contact within generator, the current study converted the partial differentia] equations and boundary conditions in the calculated temperature field to become applicable to the differential equations of various nodes in calculated region and on the calculated boundary. Based on method of iteration for solving equations, the temperature distribution of calculated field in generator could be obtained. The method of temperature rising calculation in generator provides a theoretical guidance for motor design and testing.5). According to the characteristics of permanent magnet synchronous generator, the thesis did a research on grid control strategies of permanent magnetism synchronization generator. The article also proposed double pulse-width modulation rectifier and double voltage source rectifier for wind turbine generators. Besides, the equivalent circuit model was established. In this model, voltage source PWM rectifier connected with the permanent magnet synchronous generator stator uses direct current control. Its control system structure is dual PWM rectifier or dual voltage source PWM rectifier circuit model which is composed of inner double loop cascade of outer DC voltage, AC input current and PWM inverter module based on three-phase voltage source. Its generaliability of typology is strong and has great advantages in the rectifier modeling, control algorithm and the ability of enhancing its operational capability failure. At the same time, both permanent magnet synchronous generator-side and network side of the rectifier adopt digital control based on digital signal processor. The vector control method possesses capabilities of four-quadrant operation and flexible control. It also could realize the speed governing of permanent magnet synchronous generators and grid power quality control. These grid-control strategies are beneficial to resolve the harmonic pollution, voltage fluctuations, current imbalance of power system caused by Wind Turbines. They also have important practical significance for the grid-control of large-scale wind turbine in China.更多还原