光伏发电最大功率跟踪及微网运行控制策略研究

发布时间：2018-03-29 21:33

本文选题：光伏发电　切入点：微网　出处：《中国矿业大学》2014年硕士论文

【摘要】：光伏发电将成为21世纪获取能源最重要的手段之一。提高微网中光伏发电能源利用率及依各个分布式能源特点而制定微网运行控制策略是两个重要的研究方向，具有很好的实用价值。提出基于爬坡算法的模糊控制。首先理论推导了光伏电池I-U输出特性方程及光伏电池工程用模型；分析了光伏电池元组成光伏列阵的基本原则，并以此为根据建立了光伏电池及光伏列阵的Matlab/Simulink仿真模型；依据爬坡法的基本思想，根据光伏并网系统输入输出特性，设计了模糊最大功率跟踪控制。设立了模糊控制规则，决定了隶属函数类型及其相关参数。与传统爬坡算法MPPT相较，本文设计的基于爬坡算法的模糊控制，通过输出变化的占空比步长，消除了传统爬坡算法存在的震荡问题，能达到很好的跟踪效果和稳态特性。其次，为提高光伏电池发电效率，综合考虑阴影及光伏列阵结构对最大功率点分布的影响是非常必须的。本文研究了加装旁路二极管光伏电池等效模型及其组成光伏列阵之后的数学特性，并进行了Matlab仿真建模。着重探讨了加装旁路二极管、光伏列阵拓扑结构、光照强度大小及分布形状对光伏列阵输出特性的影响。重点分析了加装旁路二极管的原因及其输出特性、分析了传统最大功率跟踪算法的适用范围及其失效原因，为最大功率跟踪控制的算法提供了理论依据。再次，为提高光伏发电系统的能量利用率，针对局部阴影下光伏列阵输出特性曲线多峰值问题，，提出了一种全局最大功率搜索加局部功率跟踪算法。局部功率跟踪算法采用了电导增量法，全局最大功率搜索算法采用了基于电压跳跃的全局扫描法。与传统全局扫描法相比，能在保证准确性的前提提高扫描速度，准确搜索到全局最大功率点。从考虑电压波动及能量损耗的角度，对局部功率跟踪算法的适用范围、电压跳跃步长、全局功率搜索范围等概念进行了研究。在Matlab/Simulink仿真环境中建立了光伏并网仿真模型，验证了该算法的快速性及准确性。最后，本文提出了一种基于模糊PID的改进P-f、Q-V下垂控制方法。首先分析了光伏列阵微网PQ控制和P-f、Q-V下垂控制的微网综合控制策略的仿真模型控制结构，研究了模型参数的选择和设计方法，获得了微网在负荷投切、逆变器离网和光伏列阵输出功率变化时的运行特性。传统的下垂因子固定，作为一种有差控制使得在负荷变化时母线电压的幅值和频率波动较大。基于模糊PID的改进P-f、Q-V下垂控制方法，有效减小了传统下垂法控制的微网逆变器在负荷波动时母线电压幅值和频率的不稳定。通过Matlab进行了相应的仿真，验证了本文提出基于模糊PID的改进P-f、Q-V下垂控制方法的有效性。
[Abstract]:Photovoltaic power generation will become one of the most important means to obtain energy in the 21st century. It has good practical value. Fuzzy control based on climbing algorithm is proposed. Firstly, the I-U output characteristic equation of photovoltaic cell and the model of photovoltaic cell engineering are derived theoretically, and the basic principle of photovoltaic array composed of photovoltaic cell elements is analyzed. Based on this, the Matlab/Simulink simulation model of photovoltaic cell and photovoltaic array is established, the fuzzy maximum power tracking control is designed according to the basic idea of climbing method and the input and output characteristics of photovoltaic grid-connected system, and the fuzzy control rules are established. Compared with the traditional climbing algorithm (MPPT), the fuzzy control based on the climbing algorithm is designed in this paper. By outputting the duty cycle step size, the oscillatory problem of the traditional climbing algorithm is eliminated. It can achieve good tracking effect and steady state characteristic. Secondly, in order to improve the efficiency of photovoltaic cells, It is necessary to consider the influence of shadow and photovoltaic array structure on the distribution of maximum power points. In this paper, the equivalent model of photovoltaic cell with bypass diode and its mathematical characteristics after composing photovoltaic array are studied. The simulation modeling of Matlab is carried out, and the topology of photovoltaic array is discussed by adding bypass diode and photovoltaic array. The effect of illumination intensity and distribution shape on the output characteristics of photovoltaic array is analyzed. The reason of adding bypass diode and its output characteristics are analyzed, and the application range and failure reason of traditional maximum power tracking algorithm are analyzed. It provides a theoretical basis for the algorithm of maximum power tracking control. Thirdly, in order to improve the energy efficiency of photovoltaic power generation system, the output characteristic curve of photovoltaic array under local shadow is multi-peak. A global maximum power search plus local power tracking algorithm is proposed. The local power tracking algorithm adopts conductance increment method, and the global maximum power search algorithm adopts the global scanning method based on voltage jump. The scanning speed can be improved on the premise of accuracy, and the global maximum power point can be accurately searched. From the angle of voltage fluctuation and energy loss, the applicable range of local power tracking algorithm and the voltage jump step can be obtained. The concept of global power search range is studied, and the photovoltaic grid-connected simulation model is established in the Matlab/Simulink simulation environment, which verifies the rapidity and accuracy of the algorithm. Finally, this paper presents an improved P-f-Q-V droop control method based on fuzzy PID. Firstly, the simulation model control structure of PQ control and P-fFQ-V droop control strategy for photovoltaic array microgrid is analyzed. The selection and design method of model parameters are studied, and the operating characteristics of microgrid under load switching, inverter off-grid and photovoltaic array output power change are obtained. The traditional droop factor is fixed. As a kind of differential control, the amplitude and frequency of bus voltage fluctuate greatly when the load changes. Based on fuzzy PID, an improved P-fFQ-V droop control method is proposed. The instability of bus voltage amplitude and frequency in the load fluctuation of the microgrid inverter controlled by the traditional droop method is effectively reduced. The corresponding simulation by Matlab verifies the effectiveness of the improved P-fFQ-V droop control method based on fuzzy PID.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615

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