【作者】 李涛；

【导师】 刘军； 霍连文；

【作者基本信息】 西安理工大学 ， 控制工程（专业学位）， 2017， 硕士

【摘要】 风能作为一种可再生能源,是一种取之不尽用之不竭的绿色环保型能源,它的开发利用对于减少矿物资源的消耗和减小环境污染有着十分重要的意义。直驱永磁同步风力发电系统采用永磁同步发电机与风力机直接相连,减少了齿轮箱等变速环节,提高了系统的可靠性并降低了噪声,具有低速性能好、发电效率高等优点,从而得到了广泛的应用。为了充分利用风能,在额定风速以下,风力发电系统通常根据风速的变化实时调节风力机的转速,获得最隹叶尖速比,实现最大风能跟踪。矢量控制作为交流电机的一种有效控制策略,具有动态性能好等优点,但是其对电机参数依赖性较大,并且需要进行一系列的坐标变换,算法复杂。而直接转矩控制策略具有算法简单、对电机参数依赖性小、动态响应快等优点。为此本文围绕永磁同步风力发电机直接转矩控制开展研究。首先,建立了直驱永磁同步风力发电机的数学模型,并对永磁同步风力发电机工作原理及直接转矩控制策略进行了分析研究。由于直接转矩控制存在转矩脉动较大的问题,本文提出了基于转矩和磁链预测的直驱永磁同步风力发电机直接转矩控制策略,通过对下一时刻的转矩和磁链预测,计算出需要补偿的电压矢量。仿真结果表明该控制策略能够实现最大风能跟踪,并且转矩脉动大大降低。其次,分析了三电平变流器中点电压不平衡所产生的原因及其危害,讨论了各种开关矢量对中点电位的影响。在此基础上,提出了基于小矢量作用时间调整的中点电位平衡控制策略,有效地抑制了小矢量所产生的中点电位波动,但此控制策略无法抑制中矢量引起的中点电位波动。为此,提出了基于变流器直流侧中点电荷量为零(△Q=0)的中点电位平衡控制策略,通过使中点电流为零,实现中点电压波动抑制。仿真结果表明该控制策略能够大幅度减小中点电位波动,并且对输出电压波形有所改善,谐波含量大大降低。最后,在Matlab/Simulink平台上对本文所提出的控制策略进行了仿真分析,验证了控制策略的有效性和正确性。更多还原

【Abstract】 As a kind of renewable energy, wind energy is an inexhaustible green energy source, and its development and utilization is of great significance to reduce the consumption of mineral resources and reduce environmental pollution.The direct drive permanent magnet synchronous wind power generation system is connected directly with the wind turbine by a permanent magnet synchronous generator, reduce the gear box transmission links, improve system reliability and reduce noise, has good low-speed performance, power efficiency etc.,which have been widely used.In order to make full use of wind energy, under the rated wind speed, the wind power generation system usually adjusts the speed of the wind turbine according to the change of wind speed. As an effective control strategy of AC motor, vector control has the advantages of good dynamic performance, but its dependence on motor parameters is large, and it needs a series of coordinate transformation.The direct torque control strategy has the advantages of simple algorithm, small dependence on motor parameters, fast dynamic response and so on.In this paper, the direct torque control of permanent magnet synchronous generator is studied.Firstly, the mathematical model of direct drive permanent magnet synchronous generator is established, and the working principle and direct torque control strategy of permanent magnet synchronous generator are analyzed. Due to the existence of direct torque control for the large torque ripple, proposed direct drive direct torque control strategy for permanent magnet synchronous generator torque and flux prediction based on the torque and flux prediction for the next time, to calculate the voltage vector to compensate. The simulation results show that the control strategy can achieve maximum wind energy tracking, and the torque ripple is greatly reduced.Secondly, this paper analyzes the causes and harms of the unbalanced voltage of the three level converter, and discusses the influence of various switching vectors on the neutral point potential. On this basis, based on the midpoint potential balance control strategy of small vector time adjustment, neutral point potential fluctuations effectively inhibited the small vector generated, but the fluctuation of neutral point potential of this control strategy can not suppress the vector caused by. Therefore, the proposed converter DC side based on zero point charge (△Q=0) the neutral point balance control strategy, through the neutral point current is zero, the fluctuation of neutral point voltage suppression. The simulation results show that the control strategy can greatly reduce the neutral point potential fluctuation, and improve the output voltage waveform, harmonic content is greatly reduced.Finally, the simulation results of the proposed control strategy on Matlab/Simulink platform are given to verify the effectiveness and correctness of the control strategy.更多还原