【作者】 唐芬；

【导师】 金新民；

【作者基本信息】 北京交通大学 ， 电力电子与电力传动， 2012， 博士

【摘要】 随着电力电子技术和永磁材料的快速发展,基于变速运行、变桨距调节的直驱永磁风力发电系统因其在效率、可靠性、并网控制灵活等方面的优势显示了较大的发展潜力。本文主要围绕直驱永磁风力发电系统并网技术展开理论研究,对永磁同步电机无传感器控制、并网变流器建模与控制和低电压穿越(LVRT)等技术进行分析探讨,并通过仿真和实验验证了理论研究成果的正确性。第一,围绕直驱永磁风力发电机数学模型展开分析。阐述了永磁同步电机在不同坐标系下数学模型；研究了永磁同步电机结构和饱和凸极性；简要介绍了零d轴电流控制(ZDAC)原理和特点；为后续章节的研究工作提供理论基础。第二,围绕直驱永磁风力发电机无传感器控制的相关技术磁链位置观测与初始位置检测展开研究。在磁链位置观测方面,首先分析了基于坐标变换的饱和反馈双积分器(SFDICT)和低通滤波补偿积分器(LPFCI)两种磁链位置积分器的工作原理和性能。针对SFDICT,为寻求限幅值设置方法,首次对其在不同限幅值、不同谐波含量下工作特性进行了理论分析和仿真研究；提出了SFDICT在各限幅值下的误差公式；并基于此提出小限幅值加角度补偿法进行磁链位置估算,可同时达到较好的位置精度和谐波效果。针对LPFCI,给出了LPFCI在不同谐波含量下的误差特点。其次,比较了基于两种磁链位置积分器的无传感器控制应用于兆瓦级直驱永磁风力发电系统优缺点。最后,对两种无传感器控制相关技术进行了仿真研究。在初始位置检测方面,针对现有转子初始位置检测方法存在的问题,并结合直驱永磁风力发电机负载特性,提出了一种低成本、易实施的三相两相混合导通法来进行转子初始位置检测。阐述了该方法的实现原理和工作特性,并给出了其理论分析及仿真结果。第三,围绕并网变流器建模与控制展开研究。针对不同坐标系下实施的电流调节器,提出采用复矢量法进行评估比较。首先,建立了三相并网变流器的复矢量模型,给出了静止PI、静止PR、同步PI在不同坐标系间的等效关系。其次,基于复矢量模型应用经典控制理论对静止PI、静止PR、同步PI和解耦同步PI从解耦控制、阶跃跟踪性能、抗电网电压扰动性能等方面进行了分析比较和仿真研究。针对并网变流器并联振荡问题,在建立了n台并网变流器并联等效模型的基础上用复矢量法进行了分析,得出了系统振荡原因。提出采用低次前馈法来防止振荡,并将其应用于风电场现场实验中,解决了振荡问题。第四,围绕直驱永磁风力发电系统LVRT建模和控制展开研究。首先,给出了直驱风力发电系统功率关系；对电网电压跌落期间直驱永磁风力发电系统行为特性进行了分析。其次,针对能耗型卸荷电路的LVRT方案缺点以及改进算法目前存在的难点,提出了机侧网侧协调控制与小卸荷支路相结合或机侧网侧协调控制与电容储能相结合两种LVRT方案。介绍了两种方案的实现原理：在网侧变流器方面,重点阐述了应对不对称跌落的控制策略；在机侧变流器方面,重点分析了机侧变流器不同控制策略下,电网电压跌落初期直驱风力发电系统的响应特点,进而给出小卸荷支路和电容量的选取公式。最后,搭建了仿真模型,仿真结果表明了所提方案有效性。作为对理论分析结果的实验验证,给出了25kW直驱永磁风力发电机对拖实验平台、2MW直驱永磁风力发电机对拖实验平台和风电场现场实验的主要实验结果,对包括SFDICT在各限幅值下的误差公式、两种无传感器控制技术、初始位置检测方案、低次前馈法消除并联振荡等方面研究成果进行了验证。更多还原

【Abstract】 With the rapid development of power electronics technology and permanent magnet materials, direct-drive permanent magnet wind power generation systems based on variable pitch control, variable speed operation have become a promising research direction in wind generation technology area due to their superiorities of high reliability, high efficiency, flexible power control ability, etc. This dissertation gives theoretical research on grid-connected technology for direct-drive permanent magnet wind power generation systems. Sensorless control of direct-drive permanent magnet wind generators, modeling and control of grid-connected converters and low voltage ride through (LVRT) are discussed comprehensively. Simulations and experiments demonstrate the correctness of the research results. The main research works are introduced as follows.Firstly, mathematical models of direct-drive permanent magnet wind generators are discussed, which provide theoretical basis for the subsequent chapters. In this section, mathematical models of permanent magnet synchronous machines (PMSMs) in different frames are given; structural and saturation saliencies of PMSMs are studied in detail; principles and characteristics of zero d-axis current control are briefly introduced.Secondly, sensorless related technologies rotor flux linkage position observation and initial position detection of PMSMs are discussed. As to rotor flux linkage position observation aspect, working principle and characteristics of saturation feedback double integrator based on coordinate transform (SFDICT), low pass filter compensation integrator (LPFCI) are analyzed in detail. For SFDICT, performance of SFDICT under different harmonic components and different amplitude limits is firstly presented; error expressions under different amplitude limits are proposed; based on them, small amplitude limit with angle compensation is proposed, which can get better accuracy and quality. For LPFCI, operation characteristics and error features under different harmonic components are presented. Furthermore, advantages and disadvantages of two sensorless methods used in direct-drive permanent magnet wind generators are analyzed and compared. The related simulation results are also given. As to initial position detection aspect, rotor initial position detection methods are studied. Given advantages and disadvantages of the existing methods and load characteristics of direct-drive permanent magnet wind generators, a low-cost easy-implementation rotor initial position detection method is proposed. Its principle and implementation procedures are introduced in detail. Simulation results indicate feasibility and simplicity of the proposed method.Thirdly, modeling and control of grid-connected converters are discussed. Many current regulators implemented in many frames exist in grid-connected converters. An evaluation method using complex vectors is proposed. Complex vector model of grid-side converter is given. Equivalent relationship of stationary PI regulators, stationary PR regulators and synchronous PI regulators among different frames are presented. Using complex vectors, stationary PI regulators, stationary PR regulators, synchronous PI regulators and decoupled synchronous PI regulators are comparative analyzed and evaluated from three aspects of decouple control, reference tracking performance, voltage disturbance rejection performance. The related simulation results are also given. To solve oscillation problem in the parallel of grid-connected converters, the model of n-paralleled grid-connected converters is built. Based on it, oscillation mechanism is studied using complex vectors. To suppress oscillation, a method using low order grid-voltage feed-forward is proposed, feasibility of which is demonstrated by experimental results in wind farm.Fourthly, modeling and control of LVRT are discussed. Based on instantaneous power theory, power relationship among main parts in direct-drive permanent magnet wind power generation systems are given in detail. Furthermore, their behavior during voltage sags is presented. Given the disadvantages of tradition un-loading branches and difficulties of modified algorithms, two LVRT control strategies are proposed. One is the combination of coordinate control of generator-side and grid-side converters and small un-loading branch. The other is the combination of coordinate control of generator-side and grid-side converters and energy storage capacitor. Their principle and implementation procedures are introduced in detail. As to control aspect of grid-side converters, the control method under un-balanced voltage sags is introduced in detail. As to control aspect of generator-side converters, system response properties at the beginning of voltage sags under different generator-side control goals are analyzed comprehensively. Based on the analysis, selection criteria of small un-loading branch and electrolytic capacitor are presented. The related simulation results are also given. Simulation results indicate feasibility of the proposed methods.As to experiment demonstration aspect, main experimental results in the25kW direct-drive permanent magnet wind generator experimental platform, the2MW direct-drive permanent magnet wind generator experimental platform, wind farm experiments are given, which demonstrate the correctness of theoretical research results including error expressions under different amplitude limits for SFDICT, the conclusion of two sensorless control strategies based on SFDICT and LPFCI, the proposed rotor initial position detection method, the proposed low order grid-voltage feed-forward.更多还原