混沌理论在光伏直流微电网系统中的应用研究

发布时间：2018-05-28 23:41

本文选题：光伏阵列 + 混沌　；参考：《北京交通大学》2017年博士论文

【摘要】：光伏直流微电网是由光伏电池板将太阳能转换为准直流电能,并可对供电区域内的用户负荷直接供电的微电网系统。在光伏直流微电网系统中,存在着复杂的非线性现象,混沌现象便是其中之一。当处于混沌状态时,系统将有可能无法正常运行甚至失去控制。目前对光伏直流微电网中的混沌现象以及对混沌的控制等方面的研究还处于起步阶段。因此,开展混沌理论在光伏直流微电网中的应用研究具有重要的现实意义,它将会对分布式光伏发电系统性能的提高具有促进作用。以光伏直流微电网中常用的低阶DC-DC变换器为研究对象,推导出电压模式Buck、电流模式Boost和Buck-Boost变换器在CCM条件下的状态方程并建立分段开关模型和离散迭代映射模型,从分岔图、相图、庞加莱截面、电感电流和输出电压的时域波形方面分别分析这三种变换器中的混沌现象。提出一种基于Wigner-Ville分布的DC-DC变换器混沌状态识别方法,解决DC-DC变换器是工作在单周期、2倍周期、4倍周期还是混沌状态的判断问题。研究了高阶DC-DC变换器中四阶Superbuck变换器的非线性现象。通过分析CCM条件下Superbuck变换器的状态方程,建立了电流模式Superbuck变换器的分段开关模型和离散迭代映射模型。通过分析电感电流和输出电压的时域波形、分岔图、相图、Wigner-Ville分布以及庞加莱映射截面,得到Superbuck变换器从稳定到倍周期分岔直至混沌状态的演化过程。通过对DC-DC变换器的稳定性分析,推导出了基于参考电流的电流模式Boost、Buck-Boost、Superbuck变换器的稳定判据;采用参数共振微扰法,通过改变扰动信号参数的大小实现了电流模式Boost、Buck-Boost和Superbuck变换器的混沌控制,使变换器从混沌状态变换到单倍周期状态。应用最大功率点跟踪技术,可以使光伏直流微电网系统输出更多的能量。为解决混沌搜索方法无法直接应用于光伏电池板的最大功率点跟踪中,本文采用幂级数改进Logistic映射产生的混沌变量,提出一种基于变尺度混沌优化搜索的光伏阵列最大功率点跟踪方法。通过仿真和与PO方法对比表明,本文提出的方法能快速准确地跟踪外部环境变化,避免了阴影条件下陷入局部最优的缺陷。
[Abstract]:The photovoltaic DC microgrid is a micro-grid system which converts solar energy into quasi-direct current energy and can directly supply the user load in the power supply area. There are complex nonlinear phenomena in the photovoltaic DC microgrid system, and chaos is one of them. When the system is in a chaotic state, it may not work properly or even lose control. At present, the research on chaos phenomenon and chaos control in photovoltaic DC microgrid is still in its infancy. Therefore, it is of great practical significance to study the application of chaos theory in photovoltaic DC microgrid, which will promote the performance improvement of distributed photovoltaic power generation system. Taking the low-order DC-DC converters commonly used in photovoltaic DC microgrid as the research object, the state equations of voltage-mode, current-mode Boost and Buck-Boost converters under CCM conditions are derived, and the piecewise switching model and discrete iterative mapping model are established. Phase diagram, Poincare cross section, inductance current and output voltage in time domain waveforms are used to analyze the chaotic phenomena in these three converters. A method of chaotic state recognition for DC-DC converters based on Wigner-Ville distribution is proposed to solve the problem of whether the DC-DC converters are working in a single period of 2 times a period of 4 times a period or a chaotic state. The nonlinear phenomena of four order Superbuck converters in high order DC-DC converters are studied. By analyzing the state equations of Superbuck converters under CCM, the piecewise switching model and discrete iterative mapping model of current-mode Superbuck converters are established. By analyzing the time domain waveforms of inductance current and output voltage, bifurcation diagram, phase diagram Wigner-Ville distribution and Poincare mapping cross section, the evolution process of Superbuck converter from stable to periodic bifurcation to chaotic state is obtained. By analyzing the stability of DC-DC converter, the stability criterion of current-mode boost Buck-boost superbuck converter based on reference current is derived, and the parametric resonance perturbation method is used. The chaos control of current-mode boost Buck-Boost and Superbuck converters is realized by changing the parameters of the disturbance signal. The maximum power point tracking technology can make the photovoltaic DC microgrid system output more energy. In order to solve the problem that the chaotic search method can not be directly applied to the maximum power point tracking of photovoltaic panels, the chaotic variables generated by the power series improved Logistic mapping are used in this paper. A maximum power point tracking method for photovoltaic arrays based on variable scale chaotic optimization search is proposed. The simulation and comparison with PO method show that the proposed method can track the changes of external environment quickly and accurately and avoid the defect of falling into local optimum under shadow condition.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM727

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