摘要太阳能的光伏利用对未来能源发展有着举足轻重的作用。光伏发电系统因逆变器输入输出功率瞬时值并非一直保持相等，即使有直流母线电容的缓冲,也会有输入电流工频脉动的产生。该电流脉动不仅降低最大功率的跟踪精度，也会对系统的电磁兼容(EMC)及电池组的寿命等造成不良影响，故解决输入电流的工频脉动能够有效提高光伏发电系统的性能。

本文在单相双级光伏发电系统的基础上，介绍了光伏发电系统每一部分的工作原理，搭建了电路仿真图，并分析了输入端电流工频波动产生的原因，提出了解决输入电流工频波动的三种方法：电压反馈控制法、占空比补偿法、占空比直接改变法，并最终选择占空比直接改变法作为本文输入端电流问题的解决方法。利用Matlab/simulink对占空比直接改变前后的单相双级光伏发电系统进行仿真，对比前后的仿真结果，可以看到采用占空比直接改变法后输入端电流波动值减，输入端功率比改变前有所增加，波动值得以减小，并且在占空比改变前后Boost电路中的电感电流波动一直在电路允许范围内。65207

毕业论文关键词  电流工频脉动  光伏并网系统  直流母线电容  占空比  Matlab/simulink  

毕业设计说明书（论文）外文摘要

Title  Research on Minimizing the Grid-frequency Fluctuation Of Photovoltaic Grid-connected Inverter’ Input Current                                                                                                     

Abstract

Photovoltaic utilization of Solar will have play a decisive role in future energy development. In the photovoltaic power generation system, due to instantaneous value of input power and output power of the inverter is not identically equal, even with buffer of the DC bus capacitor, the input current still has grid-frequency ripple. The ripple current not only reduces accuracy of MPPT, but also has adverse effect on the electromagnetic (EMC) and the life of battery in the system, so, to solve the grid-frequency pulse of input current can effectively improve the performance of photovoltaic power generation system.

Based on the single-phase two-stage grid-connected photovoltaic system, the paper introduces the principle of each section of photovoltaic power generation system, builds up a circuit simulation diagram of each section, and analyzes the reason for the grid-frequency fluctuation of the input current. Then, three methods are proposed to solve the problem: the method of control of voltage feedback, the method of compensation for the duty ratio, the method of direct modification of the duty ratio. The method of direct modification of the duty ratio is chosen to solve the problem of input current of the inverter in this paper. The simulation of single-phase two-stage photovoltaic power generation system before and after direct change of the duty ratio is carried out using Matlab/simulink. Comparing the simulation results before and after that, we can see that after using the method of direct modification of the duty ratio, the value of the input current fluctuation decreases, the input power is increased and fluctuation decreases, and the current fluctuation of inductor in the Boost circuit has been in the allowable range of the circuit before and after direct modification of the duty ratio.

Keywords   grid-frequency pulse of current  grid-connected photovoltaic system   the DC bus capacitor  the duty ratio  Matlab/simulink