论文总字数：21936字

摘 要

关键词：单级式；模块化级联；DC-DC变换器；MPPT；均压控制策略

A study on the new cascaded DC-DC converter for grid connected photovoltaic power generation

16012518 Song Chao

Supervised by Cheng Wu

Abstract: At present, photovoltaic system is mainly in the form of AC grid, but there are many people are studying medium and high voltage DC grid connected now due to the requirements of the photovoltaic system capacity continues to improve. The common structure of the photovoltaic power generation system based on the modular cascaded eliminates the intermediate link and the boost transformer, reduces the cost and improves the overall efficiency of the photovoltaic power generation system. In addition, the use of modular design also improves the redundancy and reliability of the system. But the structure of two-stage, system integration is still not high enough and the number of devices used is not the least, accordingly, the work will be more loss because the majority of the number of devices, cost is also correspondingly increased, especially for the many sub modules cascade structure. In order to adapt to the need of grid connected photovoltaic power generation, to improve the system integration degree and reduce the number of devices used, this paper studies a single stage modular cascade DC-DC converter. First, understanding the working principle of the photovoltaic power generation is the basis of the work. In this paper, the perturbation and observation method is used to achieve photovoltaic maximum power point tracking maximum power point tracking (MPPT), power proportion control method based on the fixed phase angle is used to achieve each sub module output voltage mean pressure and constant pressure. Finally, a simulation system is built to verify the simulation results by using the simulation software PLECS, and the simulation results are analyzed and explained.

Key words: single stage; modular cascaded; DC-DC converter; MPPT; voltage oriented control strategy

目 录

第一章 绪论 1

1.1引言 1

1.2光伏发电直流并网DC-DC变换器研究现状 2

1.3本文的研究目的和主要研究内容 6

第二章 光伏最大功率点跟踪的实现方法 7

2.1定电压跟踪法 7

2.2 短路电流比例系数法 8

2.3电导增量法 9

2.4扰动观察法 10

第三章 模块化级联结构的均压控制策略 12

3.1 电容电压排序法 12

3.2基于固定移相角的功率比重控制法 12

第四章 模块化级联DC-DC变换器 14

4.1两级式模块化级联DC-DC变换器 14

4.2单级式模块化级联DC-DC变换器 16

4.2.1 控制方法 17

4.2.2仿真验证 21

第五章 总结 25

致谢 26

参考文献 27

第一章 绪论

1.1引言

随着中国经济迅猛发展，在生产和生活中，人们对于能源的需求与日俱增。但由于传统化石能源如煤、石油、天然气等正在被不断开采，化石能源日益枯竭。据相关专家估计，大部分化石能源本世纪将被开采殆尽^[1]。另一方面，由于化石能源的使用过程中会产生大量温室气体CO₂，同时还可能产生一些污染性的有毒气体，破坏了生态环境平衡。

因此，人类必须开发更为清洁的可再生能源，如太阳能、核能、风能、水能、生物质能、生物质能、潮汐能等。在我国，尤其是西部偏远地区，太阳能资源十分充足。我国太阳能的理论储量可达到每年17000亿吨标准煤，因此太阳能开发利用前景十分光明^[2]。

利用太阳能的一种重要方式就是太阳能光伏发电，光伏发电是采用光伏电池直接进行光电转换得到电能的发电方式。而且随着社会的不断发展，科学技术日益先进，太阳能光伏发电无疑是发展前景最好的新能源技术之一^[3]。因为它不受地理环境条件限制，也不需要铺设大量的电力网络，从而成为解决电力短缺或没有电力的边远地区、沿海岛屿电力供应问题的重要手段，对促进该地区人民脱贫致富、经济社会协调发展、生态环境改善和社会稳定与发展具有重要意义。

与传统化石能源及其他新能源，如生物质能、核能和风能等发电技术相比较，太阳能光伏发电系统具有以下几种特有优势，总结如下^[4]：

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