【作者】 李波；

【导师】 唐文虎；

【作者基本信息】 华南理工大学 ， 电力系统及其自动化， 2017， 博士

【摘要】 随着世界能源紧缺问题的突出,风电系统的运行效率越来越受到关注。针对低风速下的最大风能捕获MPPT(Maximum Power Point Tracking)技术一直是风力发电系统研究的热点问题。本文的研究对象为永磁同步风力发电系统,其中包括直驱式永磁风力发电系统和半直驱式永磁风力发电系统。在此研究对象基础上,本文对风能MPPT算法进行了全面的研究。针对现有的MPPT控制策略在模型参数不确定、风速随机变化、外界环境扰动的背景下存在的暂态跟踪性能较差、跟踪方向错误、在操作点附近振荡等问题给出了详细的分析和解决方案。扰动观测法具有结构简单、实时性高、易于数字控制器实现的特点。本文基于扰动观测法的概念,提出了一种具有滑模结构特点的鲁棒型控制器设计方法。在此设计方法的基础上,本文设计了三种鲁棒型控制器:扰动观测控制器(第三章内容)、MPPT控制器(第四章内容)和速度控制器(第四章内容),并对上述三种控制器进行了李亚普洛夫可收敛性证明。由于前面三种控制器的设计均是基于整数阶理论,本文在传统的滑模控制中引入分数阶微积分算子,在此基础上设计一种应用于风能MPPT控制的分数阶滑模控制器,该控制器能利用分数阶微积分算子的遗传特性和记忆性进一步提高系统的控制品质和综合性能。本文的主要研究内容包括:1)扰动观测控制器(第三章内容)引入了电压斜率检测机制,用以快速检测风速的剧烈变化信息,并将此信息传递给扰动观测控制器的观测环节,解决了传统爬山算法在风速快速剧烈变化时搜索方向错误的问题,提高风电系统的风能捕获效率;此外,在风速急剧下降时,该检测机制也能防止风电系统出现失速的问题。由于本文设计的扰动观测器具有滑模的特性,所以该控制器具有良好的鲁棒性能,增强了系统在外界发生强扰动情形下的暂态稳定性。通过MATLAB/simulink仿真验证了电压斜率检测机制的有效性;在与传统爬山算法的比较过程中,仿真验证了扰动观测控制器在风能MPPT中良好的暂态性能和较高的风能捕获效率。2)在研究传统最大功率跟踪曲线的基础上,本文推导出一种新型最优功率常数曲线(第四章内容)。与传统最优跟踪曲线不同的是,最优功率常数曲线是一条具有固定值的直线,因此最优功率常数曲线简化了风电系统MPPT控制策略的设计难度,提高了系统的稳定性。根据本文提出的最优功率常数曲线,通过本文设计的鲁棒型MPPT控制器和速度控制器(第四章内容)来实现风能的最大功率跟踪控制。通过MATLAB/simulink软件对基于上述两个控制器的改进型最大功率跟踪控制策略与传统的爬山算法、PI控制器、改进型爬山算法在系统模型参数不确定、复杂外界环境干扰的情形下做了全面的比较分析。在模拟永磁同步风力发电系统的实验平台上,对本文设计的基于鲁棒型控制器的最大功率控制策略进行了实验验证。3)本论文采用Riemann-Liouville分数阶微积分定义设计了一种分数阶滑模控制器(第五章内容),并对此进行了李亚普洛夫稳定性证明。通过构造考虑齿轮间隙非线性的风力机传动链两质量模块模型,来验证本文设计的分数阶滑模控制器的强鲁棒性和良好的暂态性能。在仿真环节,本文给出了分数阶滑模控制器的参数调节方法;并在模型参数不确定的情况下,对分数阶滑模控制器和PI控制器的暂态性能、稳态性能、捕获风能的效率几个方面进行了全面的仿真研究,以说明分数阶滑模控制器良好的暂态性能和鲁棒性能。更多还原

【Abstract】 With the prominent energy shortage in the world,more and more attention has been paid to the operation efficiency of wind power generation system(WPGS).Maximum power point tracking(MPPT)technology has been a hot topic in the research of WPGS for the MPPT under low wind speed.The output characteristics of WPGS are greatly affected by the external environment,and the instability of wind energy will lead to large fluctuations in the output characteristics of wind turbines.Therefore,an effective control strategy is needed to realize the stable operation of the system and the MPPT of WPGS under the complicated environment and the uncertain model parameters.The perturb and observe(P&O)algorithm has the characteristics of simple structure,high real time and easy realization of digital controller.Based on the concept of P&O method,a nonlinear design method of robust controller with sliding mode structure is proposed.On the basis of this design method,three robust controllers are designed: P&O controller(the third chapter),MPPT controller(the fourth chapter)and speed controller(the fourth chapter),and the convergence of the three controllers is proved based on the Lyapunov theory.The control structure of the three controllers is composed of the observation process and the perturbation process.In the view of the structure of the controllers,the three controllers have the characteristics of unity;For different control purposes and application backgrounds,the three controllers introduce different control techniques and define different reference thresholds in their control structures to meet the specific control requirements of the WPGS.From the point of view of controller’s function,the three controllers are independent.This paper mainly focuses on the theoretical and experimental analysis of the unified and independent features of the three controllers.Since the design of the previous three controllers are based on the integer order theory,the fractional calculus operator is introduced into the traditional sliding mode control.On the basis of the design of a fractional order,sliding mode controller is applied to realize MPPT,the genetic characteristics and the memory of the controller can use the fractional calculus operator can improve the control quality and the comprehensive performance of the system.The main contents of this paper include:1)The P&O controller(the third chapter)introduces the voltage slope detection mechanism,which can be used to detect the steep change of wind speed.The information of wind speed is transferred to the observation section of the perturb and observe controller.By this way,the problem that the traditional hill climbing searching(HCS)algorithm has the wrong searching direction is solved when the wind speed changes rapidly,and improves the wind energy capture efficiency of the WPGS.In addition,when the wind speed drops sharply,the detection mechanism can also prevent the stall problem of the WPGS.Because the perturb and observe controller designed in this paper has the characteristics of sliding mode,the controller has good robust performance,and enhances the transient stability of the system under the condition of strong disturbance.Through the MATLAB/simulink simulation to verify the validity of the voltage slope detection mechanism;In comparison with the traditional HCS algorithm,the simulation proves that the P&O has good transient performance and high wind energy capture efficiency in MPPT.2)On the basis of studying on the traditional maximum power tracking curve,a new optimal power constant(OPC)curve is derived.Different from the traditional optimal tracking curve,the OPC curve is a straight line with a fixed value.Therefore,the OPC curve simplifies the design difficulty of the MPPT control strategy and improves the stability of the system.According to the proposed optimal power constant curve,the MPPT strategy can be realized by the MPPT controller(the fourth chapter)and the speed controller(the fourth chapter).Finally,the transient performance of the designed MPPT controller and speed controller is analyzed and compared with the traditional HCS algorithm,PI controller and improved high climbing searching(IHCS)algorithm by MATLAB/simulink software.On the experimental platform of simulated PMSG,the maximum power control strategy based on robust controller is tested experimentally.3)This paper designed a fractional order sliding mode controller using the RiemannLiouville definition of fractional calculus(the fifth chapter),and the controller is proved by the Lyapunov theory.Through the construction of the two mass module model of the wind turbine drive chain considering the nonlinear gear angle,the robustness and the excellent transient performance of the fractional order sliding mode controller are verified.In the simulation part,the method of adjusting the parameters of fractional order sliding mode controller is given.And when the model parameters are uncertain,the transient performance,steady state performance,and the efficiency of capturing wind energy are studied comprehensively by the fractional order sliding mode controller and the PI controller,to illustrate the superior transient performance and robust performance of fractional order sliding mode controllers.更多还原