双馈风力发电机最大风能捕捉及低电压运行技术研究

发布时间：2018-03-22 20:34

本文选题：风力发电　切入点：双馈发电机　出处：《武汉大学》2014年博士论文　论文类型：学位论文

【摘要】：风能发电经过半个多世纪的研究和应用,并网型风力发电技术取得了长足的进步。双馈异步风力发电机系统具有功率变频器容量小、有功功率与无功功率可以实现解耦调节、转速可调范围广等特点,在现代风电产业发展过程中,得到广泛的应用。双馈风力发电机组能较好的实现将风能转换为电能的基本功能,对能源结构的优化调整的作用逐渐显现。随着双馈风力发电机组的单机容量的不断增大,提高机组发电效率成为风电行业的重点研究问题；随着风电在一次能源发电所占的比例逐步升高,风力发电的随机性和波动性会影响电网的稳定性,电网对风力发电机组的要求也越来越高。本文首先总结了国内外风能利用和风力发电发展现状和风力发电产业化状况,分析和阐述风力发电技术特点和热点研究问题,提出了本文的选题背景和选题意义。然后分析了变速恒频的双馈异步风力发电机的数学模型和控制原理,建立了双馈风力发电机在两相旋转坐标系下的数学模型。在建立的数学模型的基础上,分别对双馈风力发电机的最大风能捕捉；不平衡电网电压下双馈风力发电机的谐波抑制；电网低电压故障下,双馈风力发电机组的低电压穿越技术展开研究。研究了风力发电机组的最大风能捕捉机理,分析现有控制方法和和最大风力捕捉策略。指出现有最大风能捕捉主要控制对象为发电机,忽略了风力机桨距角调节可提高风力发电机组最大风能捕捉效果的作用。将变桨系统引入最大风能捕捉控制闭环,阐述引入的原因和方法,提出了一种基于微距变桨极值法变速双馈异步风力发电机组的最大风能捕捉策略。通过试验对所提出的控制策略进行了验证,试验结果验证了所提控制策略的优越性。分析了不平衡电压下双馈异步风力发电机的响应特性,研究了不平衡电网电压对风力发电机定子、转子、网侧变频器电流和直流母线的影响,得出在不对称电网电压下,变频器电流控制环偏离设计控制工况会产生控制偏差,导致转子电流中包含明显的谐波分量,导致直流母线电压也产生震荡,使网侧变频器电流输出电流波形发生畸变。基于现有变频器的控制算法,提出了一种基于陷波滤波的改进型矢量控制策略,分别对网侧和机器变频器电流控制环dq轴中的交流分量进行了滤波,消除了变频器在偏离设计工况下的控制输出的震荡。通过仿真计算,验证了所提出控制策略有效的抑制双馈风力发电机的谐波。分析了双馈风力发电机组的低电压故障的暂态过程,重点探讨了电网低电压下的转子故障电流的暂态过程,转子故障电流分解为两部分,一部分是跌落后的稳态电流,另外一部分是随时间衰减的电流。转子电流在电网电压跌落时快速上升,此故障电流可达到额定电流的3-5倍,可超过机侧变频器的过流能力。故障电流会随时间衰减,可降至机侧变频器电流容量以下,可启动变频器恢复风力发电机的励磁调节。结合对现有的双馈发电机低电压穿越方案的分析,提出了基于DBR的交直流复用Crowbar低电压穿越控制方案。所提出方案在发电机转子侧与直流母线之间增加一组不可控整流桥。对电压轻度跌落故障,风力发电机为背靠背变频连接,低电压穿越工作在直流Crowbar方法,故障过程持续全可控,通过励磁调节对定子侧功率进行控制,实现低电压穿越全过程持续向电网提供无功支撑；对电压深度跌落故障,故障前期机侧变频器因故障切除运行,通过增加的不可控整流桥单元替代机侧变频器输送转子故障能量至直流母线,低电压穿越工作在交流Crowbar方式,规避了机侧变频器过流能力不足的缺陷。随故障电流下降,机侧变频器重启,风力发电机恢复交直交变频连接,低电压穿越工作在直流Crowbar方式,提高了双馈风力发电机组在电网电压深度跌落低电压穿越能力。所提出方案通过Crowbar工作方式自动切换,实现了风力发电机组对不同深度电网电压跌落的低电压穿越,提高了双馈风力发电机组的低电压穿越能力,故障期间无功的支撑满足电网导致的要求。最后,系统的总结了本文主要研究成果,并指出了进一步研究的方向。
[Abstract]:The research and application of wind power after more than half a century of wind power generation technology has made considerable progress. The doubly fed induction generator system with power inverter capacity is small, can realize decoupling regulation of active power and reactive power, speed adjustable range and other characteristics, in the process of development of modern wind power industry. Has been widely used. To achieve a better convert wind energy into electrical energy to the basic function of doubly fed wind turbine generator system, to optimize the energy structure adjustment effect gradually. With the capacity of doubly fed wind power generation unit is increasing, improve the efficiency of power generation unit has become the focus of research on wind power industry with the wind; for an electric energy generation proportion gradually increased, the randomness and volatility of wind power grid stability requirements for wind turbine power grid is more and more high.
This paper first summarizes the utilization of wind energy and wind power and wind power industry development situation, analyzes and expounds the characteristics of wind power generation technology and the hot research problems, put forward the background and significance of the topic. Then the analysis of the mathematical model and control principle of DFIG VSCF, establishes the mathematical model of doubly fed wind power generator in the two-phase rotating coordinate system. The mathematical model is established based on the maximum wind power, respectively for DFIG capture; unbalanced harmonic suppression of doubly fed wind power generator under grid voltage; low voltage power grid fault, DFIG LVRT technology research.
Research on the maximum wind energy capture unit mechanism, analysis method and capture maximum wind current control strategy. The maximum wind capture the main control object for the generator, ignoring the wind turbine pitch angle control can improve the wind turbine maximum wind capture effect. The pitch system introduced the maximum wind power capture control loop, this the reasons and methods of introducing, proposes a maximum wind power pitch extremum method based on macro variable speed DFIG capture strategy. Through the test to verify the proposed control strategy, experimental results verify the superiority of the proposed control strategy.
Analysis of the unbalance response characteristics of doubly fed asynchronous wind generator voltage, the unbalanced grid voltage of the wind generator stator, rotor, influence of grid side converter current and DC bus, the unbalanced grid voltage, the inverter current control loop from design control conditions will produce control deviation, lead containing harmonic component significantly the rotor current, causing the DC bus voltage also produces shock, make network side of the inverter output current waveform distortion. The existing control algorithm based on the inverter, this paper proposes an improved vector control strategy based on notch filter, respectively, on the network side and the inverter current control loop machine AC component of DQ axis filter, eliminates the control output of inverter in off design condition of shock. Through simulation, the proposed control strategy of double effective suppression The harmonic of the wind power generator.
Analysis of the transient process of low voltage fault of doubly fed wind turbines, focusing on the transient process of rotor fault current of power grid low voltage of the rotor fault current is decomposed into two parts, one part is the steady state current after the fall, the other part is the current decay with time. The rotor current rapid increase in the grid voltage drop, 3-5 times the rated current of the fault current can be achieved, can be more than machine side converter over-current capability. The fault current will decay with time, can be reduced to the current capacity of the machine side converter, excitation frequency converter start recovery wind generator regulation. Combining with the analysis of the doubly fed generator low voltage ride through the existing scheme. The AC / DC low voltage across the DBR multiplexing Crowbar control scheme based on the proposed scheme for adding a group of controlled rectifier bridge between the rotor side of the generator and the DC bus of electric. The pressure drop of mild fault, the wind generator is connected to the low voltage ride through back-to-back inverter, DC in the Crowbar method, the failure process for all controllable by adjusting excitation control of the stator power, through the implementation of the whole process lasted to the grid to provide reactive power support low voltage drop of voltage; fault depth, fault pre machine side converter for the fault clearing operation, by increasing the uncontrolled rectifier unit instead of machine side converter transmission rotor fault energy to the DC bus, low voltage ride through work in the exchange of Crowbar, to avoid the defect of insufficient ability of the machine side flow through the frequency converter. With the decline of the fault current, restart the machine side converter, wind power generator recovery AC-DC-AC converter connection, low voltage through working in DC Crowbar, improve the doubly fed wind turbine in the power grid voltage drop depth of low voltage ride through capability of the proposed party. The case is automatically switched by Crowbar operation mode, which realizes low voltage ride through of wind turbines to voltage sag in different depths, improves the low voltage ride through capability of doubly fed wind generators, and supports reactive power during failure to meet the requirements of power grid.
Finally, the main research results of this paper are summarized, and the direction of further research is pointed out.

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM315

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