分布式单相非隔离光伏并网逆变器的研究

发布时间：2018-06-26 11:23

本文选题：光伏并网 + 误判　；参考：《杭州电子科技大学》2017年硕士论文

【摘要】：随着化石燃料的不断使用,人类生存面临巨大的威胁,清洁能源的开发利用已经迫在眉睫。太阳能具有分布区域广,可用途径多的特点,是未来最有应用前景的清洁能源之一。太阳能发电作为利用太阳能的主要方式之一,其清洁无污染,是未来缓解用电紧张和改善生态环境的有效方式。大型集中光伏发电的形式在我国仍然拥有绝对的优势。随着大型光伏电站的输电难和我国西部地区光伏电站弃光问题越来越严重,大型光伏电站并没有达到我国利用太阳能发电的预期。利用太阳能发展分布式发电将能很好地避免现阶段我国在光伏发电中遇到的问题,并且其投入较小,从规划到发电周期较短。其必然会取代集中式光伏发电成为主要的光伏发电形式。目前分布式光伏发电中所使用的逆变器仍需改进的方面有:1、逆变器前级电路的选型和误判问题。逆变器增加前级升压环节提高了系统日工作时间,使光伏阵列输出功率最大化,但是就逆变器本身而言增加了功耗,并且在最大功率点追踪过程中存的误判将会导致功率发生抖动。2、逆变器内部的低次谐波问题。单相逆变器并网运行时的瞬时输出功率具有的波动性造成直流母线电压产生二次纹波,这将降低逆变器寿命并造成输出电流三次谐波增大。3、对地共模电流问题。逆变器内部在无变压器隔离的情况下并网运行时,光伏电池与接地金属外壳之间的寄生电容与电网形成回路,高频的共模电压通过回路产生电流,使系统的安全性下降。本文针对以上三方面首先提出前级采用了ZVT-Boost电路降低前级的损耗,并优化传统的电导增量法,增加光伏电池功率估计避免工作时的误判问题。其次为了降低输出电流谐波提高逆变器使用寿命,提出在直流母线上加入源滤波装置对二次纹波进行滤除。第三分析了能够在工作时保持共模电压不变的逆变拓扑,结合共模等效电路阐述了共模电流高频分量产生的原因,提出了一种采用双共模内回路的方法抑制共模电流高频分量。最后通过仿真和实验平台对本文中所研究的内容进行了分析和验证,证明了本文中研究成果的有效性。
[Abstract]:With the continuous use of fossil fuels, human survival is facing a huge threat, the development and utilization of clean energy is imminent. Solar energy is one of the most promising clean energy in the future because of its wide distribution and many available ways. As one of the main ways to utilize solar energy, solar power generation is clean and pollution-free, which is an effective way to relieve the shortage of electricity and improve the ecological environment in the future. The form of large-scale concentrated photovoltaic power generation still has absolute advantage in our country. With the difficulty of transmission of large-scale photovoltaic power stations and the more and more serious problem of light abandonment of photovoltaic power stations in western China, large-scale photovoltaic power plants do not meet the expectations of solar power generation in China. Using solar energy to develop distributed power generation can avoid the problems encountered in photovoltaic power generation in China at present, and its investment is relatively small, and the cycle from planning to generating electricity is short. It will replace the centralized photovoltaic power generation as the main form of photovoltaic power generation. At present, the inverter used in distributed photovoltaic power generation still needs to be improved in the aspects of: 1, the selection and misjudgment of the inverter's front-stage circuit. The increase of the front stage boost of the inverter increases the daily working time of the system and maximizes the output power of the photovoltaic array, but increases the power consumption of the inverter itself. And the misjudgment in the process of maximum power point tracking will lead to the power jitter. 2, the low order harmonic problem in the inverter. The fluctuation of instantaneous output power of single-phase inverter in grid-connected operation results in the secondary ripple of DC bus voltage, which will reduce the life of inverter and cause the third harmonic increase of output current. When the inverter is connected to the grid without transformer isolation, the parasitic capacitance between the photovoltaic cell and the grounding metal shell forms a circuit with the grid, and the high frequency common-mode voltage generates current through the circuit, which reduces the security of the system. In this paper, the ZVT-Boost circuit is used to reduce the loss of the front stage, and the traditional conductance increment method is optimized to increase the power estimation of photovoltaic cells to avoid the misjudgment. Secondly, in order to reduce the output current harmonics and improve the service life of the inverter, the secondary ripple is filtered by adding the source filter device to the DC bus. Thirdly, the inverter topology which can keep the common-mode voltage constant is analyzed, and the cause of the high frequency component of the common-mode current is explained by combining the common-mode equivalent circuit. A method to suppress the high-frequency component of the common-mode current is proposed by using a double-common-mode internal loop. Finally, the contents of this paper are analyzed and verified on the platform of simulation and experiment, which proves the validity of the research results in this paper.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

【参考文献】