大型光伏并网系统谐振现象分析

发布时间：2018-07-11 13:33

本文选题：大型光伏并网系统 + 电网阻抗　；参考：《重庆大学》2014年硕士论文

【摘要】：大型光伏电站通常建在远离负荷中心、光照资源丰富的荒漠地区，光伏发电系统经过长距离输电线路与负荷连接，当变压器与长距离输电线路等构成电网阻抗较大时，易引起大型光伏并网系统产生谐振现象，造成系统出现谐振过电压、过电流等问题，威胁着系统的安全稳定运行。因此，本文以大型光伏并网系统为研究对象，以提高大型光伏电站的系统稳定性和并网电能质量为研究目标，探索大型光伏电站与电网之间的谐振机理。在建立大型光伏并网系统数学模型的基础上，，探讨光伏电站容量、电网阻抗等参数对系统稳定运行的影响，提出大型光伏并网系统的稳定性判定方法，研究抑制谐振引发系统不稳定问题的逆变器控制策略，为大型光伏电站的发展及其推广应用奠定理论基础。论文研究内容主要包括： 1）建立大型光伏并网系统等效电路模型：对于大型光伏并网系统建模主要可以划分为输电网络建模和逆变器建模两部分，分别建立输电网络和大型光伏电站两个子系统的等效模型后获得大型光伏并网系统等效模型。对于升压变压器以及长距离输电线路构成的输电网络建模，通常采用线性无源二端网络表示。然后，采用降阶建模法将直流侧电压假定为常数，忽略逆变器直流侧电容后建立并网光伏逆变器的等效电路模型。最后，结合由无源二端网络表示的输电网络等效模型以及整个大型光伏电站的等效电路模型，形成大型光伏并网系统的等效电路模型。 2）大型光伏并网系统的谐振现象研究：在建立大型光伏并网系统等效电路模型基础上，本文主要针对大型光伏并网系统中的谐振现象进行深入研究，在考虑分裂变压器等效电感及电网阻抗情况下，深入分析大型光伏电站与电网之间的谐振交互式影响，探讨系统谐振引发的不稳定现象。本文首先分析大型光伏并网系统谐振问题对系统谐波含量的影响，推导大型光伏并网系统阻抗稳定性判据，然后采用根轨迹分析了各参数对大型光伏并网系统的稳定性影响。 3）光伏并网系统谐振抑制策略研究：由于电网阻抗会导致光伏并网系统中光伏电站与电网之间的谐振交互式影响，严重时甚至造成系统出现不稳定现象，导致系统不能正常工作，因此如何对光伏并网系统中的谐振现象进行有效抑制是目前国内外专家的研究热点。本文从简单的单台光伏逆变器并网系统的谐振现象分析出发，采用基于状态反馈的极点配置策略对系统中的谐振现象进行了有效抑制，并通过仿真验证了极点配置策略对谐振抑制的有效性。
[Abstract]:Large photovoltaic power plants are usually built in desert areas far from load center and rich in light resources. Photovoltaic power generation systems are connected to loads through long distance transmission lines. When transformers and long distance transmission lines make up the power grid impedance is large. It is easy to cause resonance phenomenon in large-scale photovoltaic grid-connected system, resulting in resonance overvoltage, over-current and other problems, which threaten the safe and stable operation of the system. Therefore, this paper takes the large-scale photovoltaic grid-connected system as the research object, with the aim of improving the system stability and grid-connected power quality of the large-scale photovoltaic power station, and explores the resonance mechanism between the large-scale photovoltaic power station and the grid. Based on the mathematical model of large-scale photovoltaic grid-connected system, this paper discusses the influence of the parameters such as the capacity of photovoltaic power station and the impedance of power grid on the stable operation of the system, and puts forward a method for judging the stability of large-scale photovoltaic grid-connected system. The inverter control strategy to suppress the instability of the resonant induced system is studied, which lays a theoretical foundation for the development and application of large photovoltaic power plants. The main contents of this paper are as follows: 1) establishing equivalent circuit model of large-scale photovoltaic grid-connected system: the modeling of large-scale photovoltaic grid-connected system can be divided into two parts: transmission network modeling and inverter modeling. The equivalent models of two subsystems of transmission network and large photovoltaic power station are established, and the equivalent model of large-scale photovoltaic grid-connected system is obtained. The linear passive two-terminal network is usually used to model the transmission network composed of booster transformers and long-distance transmission lines. Then, the DC side voltage is assumed to be constant by using the reduced order modeling method, and the equivalent circuit model of grid-connected photovoltaic inverter is established by ignoring the DC side capacitance of the inverter. Finally, the equivalent model of transmission network represented by passive two-terminal network and the equivalent circuit model of the whole large photovoltaic power station are combined. Forming equivalent circuit model of large-scale photovoltaic grid-connected system. 2) Resonance phenomenon of large-scale photovoltaic grid-connected system: on the basis of establishing equivalent circuit model of large-scale photovoltaic grid-connected system, In this paper, the resonance phenomenon in large-scale photovoltaic grid-connected system is studied deeply. Considering the equivalent inductance and grid impedance of split transformer, the resonant interaction between large-scale photovoltaic power station and power grid is deeply analyzed. The instability caused by system resonance is discussed. In this paper, the influence of resonance problem on harmonic content of large-scale photovoltaic grid-connected system is analyzed, and the impedance stability criterion of large-scale photovoltaic grid-connected system is derived. Then the influence of various parameters on the stability of large-scale grid-connected photovoltaic system is analyzed by root locus. 3) Resonance suppression strategy of grid-connected photovoltaic system: because of the impedance of the grid, the photovoltaic power station and the photovoltaic power station in the grid-connected system The interactive effects of resonance between power grids, When the system is seriously unstable, the system can not work properly. Therefore, how to effectively suppress the resonance phenomenon in photovoltaic grid-connected system is a hot research topic at home and abroad. Based on the simple resonance analysis of a grid-connected system with a single photovoltaic inverter, the pole placement strategy based on state feedback is used to effectively suppress the resonance phenomenon in the system. The effectiveness of pole placement strategy for resonance suppression is verified by simulation.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615

【参考文献】