基于电力电子变压器的光伏并网系统研究

发布时间：2018-05-31 15:42

本文选题：电力电子变压器 + 模糊PI　；参考：《西南石油大学》2017年硕士论文

【摘要】：近年来,环境污染日益严重,化石类能源日益枯竭。分布式新能源不仅能够缓解能源供应危机,解决环境污染等问题,还具有供电可靠性高、维修管理方便等特点。如何构建一个新能源系统,使其具有多种能源共同接入的能力,同时还能实现与传统电网的并联运行,已经成为了分布式新能源发、输、变电领域的研究热点。本文以电力电子变压器为研究对象,分别对其输入级、隔离级的一些关键问题展开了深入研究,并设计了电力电子变压器直流母线处的光伏系统并网方法。论文主要内容如下:首先,分析了电力电子变压器的拓扑结构和工作原理,建立了电力电子变压器的数学模型。针对电力电子变压器在抑制电能质量下降时动态响应慢,调节性能差等缺点,提出了一种基于dq解耦的输入级智能控制策略与隔离级移相控制策略。前者在系统输入级中采用基于模糊PI控制器的双闭环控制方法,实现了电压外环PI控制器参数的实时调整。后者在系统隔离级双向DC-DC变换器中采用单移相控制策略,以电力电子变压器二次侧直流母线电压为被控对象,对高频隔离变压器一次侧、二次侧H桥触发脉冲之间的移相角进行调整,提高二次侧直流母线电压的稳定性。其次,建立电力电子变压器直流母线上的光伏并网系统,分析了光伏电池的输出特性和最大功率点跟踪方法。针对光照强度变化引起的直流并网电压不稳的情况,提出了两级式DC-DC变换器结构以及相应的桥臂间移相控制算法。此外,在电力电子变压器直流母线处引入了超级电容储能系统,通过Buck-Boost变换器对超级电容进行充放电,实现了低电压穿越时超级电容储能系统向负载侧供电的孤岛运行方式,提高了光伏系统的稳定性与抗干扰能力。最后,基于Matlab/Simulink仿真平台,搭建了电力电子变压器及其光伏并网系统的仿真模型。通过模拟三相交流电网发生电压跌落、突升和闪变的电能质量问题,对电力电子变压器做了对比仿真研究,其结果表明本文所提的智能控制算法及移相控制算法对系统电能质量调节效果较为显著,明显优于传统的控制策略。同时搭建了光伏直流并网及其储能系统的仿真模型,通过模拟电网电压深度跌落和光照强度变化,对光伏并网系统进行仿真分析,其结果表明本文所提的直流并网方法和桥臂间移相控制方法能够有效抑制光照强度变化对并网电压的影响,并且可以实现光伏系统低电压穿越时系统的稳定运行,为负载提供持续的电能。
[Abstract]:In recent years, environmental pollution is increasingly serious, fossil energy is increasingly depleted. Distributed new energy not only can alleviate the crisis of energy supply and solve environmental pollution problems, but also has the characteristics of high reliability of power supply and convenient maintenance and management. How to build a new energy system with the ability of common access of multiple sources of energy, and at the same time to realize parallel operation with the traditional power grid, has become a research hotspot in the field of distributed new energy generation, transmission and transformation. This paper takes power electronic transformer as research object, studies some key problems of input stage and isolation stage, and designs the grid-connected method of photovoltaic system in DC bus of power electronic transformer. The main contents of this paper are as follows: firstly, the topology and working principle of power electronic transformer are analyzed, and the mathematical model of power electronic transformer is established. In order to overcome the disadvantages of slow dynamic response and poor regulation performance of power electronic transformers, an input level intelligent control strategy based on dq decoupling and an isolated phase shift control strategy are proposed. In the former, a double closed loop control method based on fuzzy Pi controller is used in the input stage of the system, and the parameters of the voltage outer loop Pi controller are adjusted in real time. The latter adopts the single phase shift control strategy in the system isolation stage bidirectional DC-DC converter. The secondary DC bus voltage of the power electronic transformer is taken as the controlled object, and the primary side of the high frequency isolation transformer is used as the control object. The phase shift angle between the trigger pulses of the secondary H-bridge is adjusted to improve the stability of the secondary DC bus voltage. Secondly, the photovoltaic grid-connected system on DC bus of power electronic transformer is established, and the output characteristics of photovoltaic cell and the maximum power point tracking method are analyzed. In view of the instability of DC grid-connected voltage caused by the change of illumination intensity, a two-stage DC-DC converter structure and the corresponding phase shift control algorithm between the arms are proposed. In addition, the super capacitor energy storage system is introduced at the DC bus of power electronic transformer, and the super capacitor is charged and discharged by Buck-Boost converter, which realizes the isolated operation mode of the super capacitor energy storage system to load side when the low voltage traverses. The stability and anti-interference ability of photovoltaic system are improved. Finally, the simulation model of power electronic transformer and its photovoltaic grid-connected system is built based on Matlab/Simulink simulation platform. By simulating the power quality problems of voltage sag, sudden rise and flicker in three-phase AC power network, a comparative simulation study of power electronic transformers is made. The results show that the intelligent control algorithm and phase shift control algorithm proposed in this paper are more effective than the traditional control strategy in regulating the power quality of the system. At the same time, the simulation model of photovoltaic DC grid-connected system and its energy storage system is built, and the photovoltaic grid-connected system is simulated and analyzed by simulating the voltage depth drop and the change of illumination intensity. The results show that the DC grid-connected method and the bridge arm phase shift control method proposed in this paper can effectively restrain the influence of the light intensity change on the grid-connected voltage, and can realize the stable operation of the photovoltaic system with low voltage traversing. Provide continuous power for the load.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41;TM615

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