双馈风力发电系统在非理想电网条件下的控制策略研究

发布时间：2018-03-28 13:26

本文选题：双馈风力发电系统　切入点：矢量控制　出处：《电子科技大学》2017年硕士论文

【摘要】：风力发电是目前利用新能源发电的重要部分之一,其中以基于双馈感应电机(Doubly-Fed Induction Generator,DFIG)的风力发电系统为主。本文的主要研究内容是双馈风力发电系统在非理想电网条件下的控制策略研究,其中非理想电网条件包括电网电压骤降,谐波电压以及不平衡电压,主要研究内容和结论如下:(1)分别建立三相静止坐标系和两相同步旋转坐标系下单质量体风力机,双馈电机和背靠背PWM变流器数学模型,在此基础上,选择定子、转子和网侧变流器输入电流为状态变量,机端电压与转子电压为输入变量,建立全阶双馈风力发电系统矩阵模型;最后分析了双馈风力发电系统功率关系。(2)在PLECS中搭建2MW双馈风电系统并在非理想电网条件下进行仿真分析,结果显示传统矢量控制策略下,当电网电压最大跌落至正常值得20%时,转子电流脉冲将达到正常值的3倍左右,功率脉动与电磁转矩脉动幅值将达到2倍左右;电网电压谐波导致DFIG输出电流畸变,功率、转速以及电磁转矩出现高频振荡,不平衡电压导致DFIG输出电流发生更大的不平衡度,功率、转速以及电磁转矩出现100Hz振荡。(3)针对电网电压骤降,通过设计改进转子侧变流器控制算法与直流Crowbar结合的方式,该方法能够抑制50%左右的转子瞬态过电压,40%左右的瞬态功率脉冲以及电磁转矩脉冲。针对电网电压谐波情况,设计改进锁相环算法在谐波情况下准确快速提取电网电压相位;基于LCL型三相逆变器设计谐波电压补偿算法,通过仿真验证该方法保证了DFIG定子端电压为理想正弦,从根本上消除了电网谐波对DFIG风电机组的影响。针对不平衡电压情况,基于改进锁相环设计各相电压跌落幅值提取算法,并设计了不平衡电压补偿算法平衡双馈电机机端电压,通过仿真分析可以得到,该控制策略可以使机端电压在电网电压不平衡发生后25ms内恢复正常,实现风力发电系统在不平衡电压下的正常运行。(4)设计三相LCL型逆变器实验平台,通过阻性负载验证该实验平台的有效性,在非线性负载条件下研究了谐波控制算法;最后用逆变器模拟了DFIG风电系统转子侧变流器输出特性,通过仿真与实验对比的方式证明了该三相逆变器实验平台能够有效的模拟次同步、超同步稳态过程以及DFIG运行状态转变的变化过程。
[Abstract]:Wind power generation is one of the most important parts of power generation using new energy. The wind power generation system based on Doubly-Fed Induction Generator (DFIGG) is mainly used in this paper. The main content of this paper is to study the control strategy of doubly-fed wind power generation system under non-ideal power grid conditions, including the voltage drop of power grid. The main contents and conclusions of harmonic voltage and unbalanced voltage are as follows: (1) the mathematical models of three-phase static coordinate system and two-phase synchronous rotating coordinate system are established, respectively, for bulk wind turbine, double-fed wind turbine and back-to-back PWM converter. The input current of stator, rotor and grid side converter is selected as the state variable, the terminal voltage and rotor voltage are selected as input variables, and the matrix model of full-class doubly-fed wind power generation system is established. Finally, the power relationship of doubly-fed wind power generation system is analyzed. The 2MW doubly-fed wind power system is built in PLECS and simulated under the condition of non-ideal power grid. The results show that the traditional vector control strategy is used. When the maximum voltage drop to normal value is worth 20, the rotor current pulse will reach about 3 times the normal value, the amplitude of power ripple and electromagnetic torque ripple will reach about 2 times. Rotating speed and electromagnetic torque appear high frequency oscillation, unbalanced voltage leads to greater imbalance of DFIG output current, power, speed and electromagnetic torque appear 100Hz oscillation. By designing and improving the control algorithm of rotor side converter combined with DC Crowbar, the method can suppress about 50% transient overvoltage of rotor and 40% of transient power pulse and electromagnetic torque pulse. The improved phase-locked loop algorithm is designed to accurately and quickly extract the voltage phase of the power network under the condition of harmonics, and the harmonic voltage compensation algorithm based on LCL three-phase inverter is designed. The simulation results show that the terminal voltage of the DFIG stator is an ideal sinusoidal voltage. The influence of power grid harmonic on DFIG wind turbine is eliminated fundamentally. In view of the unbalanced voltage, the algorithm of extracting the drop amplitude of each phase voltage based on the improved phase-locked loop is designed, and the unbalanced voltage compensation algorithm is designed to balance the terminal voltage of the double-fed machine. Through simulation analysis, it can be concluded that the control strategy can make the terminal voltage return to normal in 25ms after the voltage imbalance occurs, and realize the normal operation of wind power system under unbalanced voltage. (4) the three-phase LCL inverter experimental platform is designed. The effectiveness of the experimental platform is verified by resistive load, and harmonic control algorithm is studied under nonlinear load. Finally, the output characteristics of rotor side converter of DFIG wind power system are simulated by inverter. The comparison between simulation and experiment proves that the experimental platform of three-phase inverter can effectively simulate the process of sub-synchronization, supersonic steady state and the change of DFIG operation state.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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