光伏发电系统低电压穿越技术的研究

发布时间：2019-01-22 15:55

【摘要】：随着光伏并网电站安装容量不断上升，光伏并网系统在电网故障情况下的应对能力变得尤为重要，国家规定光伏发电系统在电网电压跌落一定时间段内不能脱网运行，并对电网提供一定的无功支撑。本文研究电网电压跌落时光伏发电系统的低电压穿越技术，提高系统稳定性和应对故障能力，并采用MATLAB软件进行仿真分析。本文建立了光伏并网逆变器在ABC三相静止坐标系、αβ两相静止坐标系和dq旋转坐标系下的数学模型，从光伏并网逆变器的拓扑结构和工作原理着手，分析了传统的光伏并网逆变器的控制策略，分析了同步PI电流控制法，，即在同步旋转坐标系下，采用前馈解耦控制方法，以固定开关频率实现交流侧电流控制。该控制策略结构简单，参数设计容易，但需在电网电压三相对称环境下使用。本文在传统控制策略基础上建立光伏并网逆变器数学模型，即在传统电压外环、电流内环双闭环控制策略的基础上增加并网电流负序内环控制，在电网三相不对称时提高逆变器的适应能力，再结合DC-DC控制实现光伏发电系统的低电压穿越。本文提出一种用超级电容储能的低电压穿越方法，在电网电压跌落期间继续保持光伏阵列的输出，逆变器直流端的冗余电量储存到超级电容当中，在保持了光伏发电系统发电量的同时实现低电压穿越。采用Matlab/Simulink软件平台，搭建了基于低电压穿越技术的光伏发电系统仿真模型，进行相应的仿真实验。该方法既有较快的电流响应速度和系统恢复速度，又能储存直流侧部分冗余电量。在电压跌落期间光伏逆变器能够并网运行，还能根据电网需要输送一定量的无功功率以支撑并网点电压，减少光伏系统的脱网给电网带来的冲击。最后和相关企业合作对低电压穿越技术的仿真模型的正确性进行实验验证，实验结果表明该低电压穿越技术是可行的。
[Abstract]:With the increasing installation capacity of grid-connected PV power station, the ability of photovoltaic grid-connected system to deal with the power grid fault becomes particularly important. The state stipulates that the photovoltaic power generation system can not be removed from the grid in a certain period of time when the grid voltage drops. And provide certain reactive power support to the power grid. In this paper, the low voltage traversing technology of photovoltaic power generation system with voltage drop is studied to improve the stability and fault response ability of the system, and the simulation analysis is carried out by using MATLAB software. In this paper, the mathematical models of photovoltaic grid-connected inverter in ABC three-phase stationary coordinate system, 伪尾 two-phase stationary coordinate system and dq rotating coordinate system are established. The topology and working principle of photovoltaic grid-connected inverter are discussed. The control strategy of the traditional photovoltaic grid-connected inverter is analyzed, and the synchronous PI current control method is analyzed. In the synchronous rotating coordinate system, the feedforward decoupling control method is used to realize AC side current control with fixed switching frequency. The control strategy is simple in structure and easy in parameter design, but it needs to be used in the three-phase symmetrical environment of grid voltage. In this paper, the mathematical model of photovoltaic grid-connected inverter is established on the basis of traditional control strategy, that is, adding grid-connected current negative sequence inner loop control on the basis of traditional voltage outer loop and current inner loop double closed loop control strategy. The adaptive ability of inverter is improved when the power grid is three phase asymmetry, and the low voltage traversing of photovoltaic generation system is realized with DC-DC control. In this paper, a low voltage traversing method using super capacitor to store energy is proposed. The output of photovoltaic array is maintained during the voltage drop of the power grid, and the redundant power at the DC end of the inverter is stored in the super capacitor. Low voltage traversing is realized at the same time as the photovoltaic power generation system is maintained. The simulation model of photovoltaic power generation system based on low voltage traversing technology is built by using Matlab/Simulink software platform and the corresponding simulation experiments are carried out. This method not only has faster current response speed and system recovery speed, but also can store part of the DC side redundant power. During the voltage drop the photovoltaic inverter can be connected to the grid and can transport a certain amount of reactive power according to the need of the power grid to support and network voltage so as to reduce the impact to the grid caused by the de-grid of the photovoltaic system. Finally, the correctness of the simulation model of low-voltage traversing technology is verified by experiments in cooperation with relevant enterprises. The experimental results show that the low-voltage traversing technology is feasible.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464;TM615

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