基于软开关和MFAC的光伏并网发电系统研究

发布时间：2018-12-22 09:14

【摘要】：光伏发电以其广阔的开发利用前景,成为当前国内外研究和关注的热点。本文以光伏并网系统为研究对象,对光伏发电系统中的最大功率点跟踪问题,对DC/DC和DC/AC的变换控制问题进行了深入研究,并进行了仿真和实验验证。针对常规最大功率点跟踪(MPPT)存在的跟踪速度和精度不能兼得的问题,提出了步长自适应的扰动观察法,该方法在最大功率点处通过改变相应的步长来提高精度,在精度达到一定值后再控制步长防止系统出现振荡现象。与传统的最大功率点跟踪方法比较,减少了系统运行的盲目性,提高了响应速度,改善了跟踪效果。针对系统中DC/DC变换器难以精确建模的问题,提出了基于数据驱动无模型自适应(MFAC)的控制方法,将MFAC应用于BOOST电路的控制中,并进行了仿真和实验验证。结果表明,该方法不仅兼顾了传统控制方法设计简单以及现代控制方法控制精确的优点,而且对模型失配现象也有一定的改善。针对DC/DC变换器变换过程中的开关损耗问题,引入了无源无损耗缓冲器单元,有效解决了变换过程中的开关损耗问题,提高了系统的运行效率。研究分析了并网逆变器的控制方式和控制目标,将基于SVPWM的控制方式应用于三相并网控制当中,建立了三相光伏并网逆变器在三相静止坐标系和两相旋转坐标系下的数学模型,分析了基于同步坐标系直接电流控制技术的电压电流双闭环控制策略。设计了电压外环和电流内环的PI参数。针对逆变过程中的开关损耗,将软开关技术引入到并网逆变器中,最后,在Matlab/Simulink的环境下,搭建了整个光伏并网发电系统。对基于同步坐标系直接电流控制技术的电压电流双闭环控制策略的可行性进行了仿真验证,结果表面,系统运行良好,能够有效满足并网要求。
[Abstract]:Photovoltaic power generation has become the focus of research and attention at home and abroad because of its broad prospect of development and utilization. In this paper, the maximum power point tracking problem in photovoltaic power generation system is studied, and the conversion control problem of DC/DC and DC/AC is deeply studied, and the simulation and experiment are carried out. Aiming at the problem that the tracking speed and precision of conventional maximum power point tracking (MPPT) can not be obtained simultaneously, a step size adaptive perturbation observation method is proposed, which improves the accuracy by changing the corresponding step size at the maximum power point. After the precision reaches a certain value, the step size is controlled to prevent the system from oscillating. Compared with the traditional maximum power point tracking method, the blind operation of the system is reduced, the response speed is improved and the tracking effect is improved. Aiming at the difficulty of accurate modeling of DC/DC converter in the system, a data-driven model-free adaptive (MFAC) control method is proposed. The MFAC is applied to the control of BOOST circuit, and the simulation and experiment are carried out. The results show that this method not only has the advantages of simple design of traditional control method and accurate control of modern control method, but also improves the mismatch of model. In order to solve the switching loss problem of DC/DC converter, a passive loss buffer unit is introduced, which solves the switching loss problem effectively and improves the efficiency of the system. The control mode and control target of grid-connected inverter are studied and analyzed. The control mode based on SVPWM is applied to three-phase grid-connected control, and the mathematical model of three-phase photovoltaic grid-connected inverter under three-phase static coordinate system and two-phase rotating coordinate system is established. The voltage and current double closed loop control strategy based on synchronous coordinate system direct current control technology is analyzed. The PI parameters of voltage outer loop and current inner loop are designed. The soft switching technology is introduced into grid-connected inverter in view of the switching loss in the inverter process. Finally, in the environment of Matlab/Simulink, the whole grid-connected photovoltaic power generation system is built. The feasibility of voltage and current double closed loop control strategy based on direct current control technology in synchronous coordinate system is verified by simulation. The results show that the system works well and can effectively meet the requirements of grid connection.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615

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