弱电网下光伏并网逆变器稳定运行控制技术研究

发布时间：2018-12-10 12:38

【摘要】：随着人类面临的能源危机和环境问题越来越严峻，作为一种清洁的可再生能源，太阳能光伏发电近年来得到了迅猛的发展。光伏发电系统常用于解决偏远地区的供电需求，而偏远地区、海岛等末端电网通常为相对较小的负载设计，其电力供应多为中低压等级，，电网阻抗较高、短路容量较低，呈现弱电网特性。弱电网低短路容量、高电网阻抗的电气特性对光伏并网发电系统的稳定运行提出了新的挑战。为此，本文针对弱电网条件下的光伏并网逆变器，从电网同步技术、稳定性控制方法等角度提出改善逆变器并网性能的具体措施和控制策略，保障其在弱电网条件下能够可靠稳定运行。本文首先建立两级式单相光伏并网逆变器拓扑结构系统模型，推导出电流源型逆变器输出阻抗一般表达式，并分析系统各参数变化对输出阻抗的影响及变化规律；其次建立电流源型光伏并网发电系统的阻抗稳定性判断标准，在此基础上研究不同电网条件对逆变器稳定性的影响，通过分析发现电网阻抗的增大会使系统稳定性降低，结合滤波参数对输出阻抗的影响提出虚拟电抗控制方法来提高系统稳定性；与此同时，针对弱电网下传统过零检测同步方法存在的弊端，提出采用基于二阶广义积分器锁频环技术来解决电网同步问题，以实现弱电网下逆变器可靠、稳定地并网。最后，搭建了弱电网下以TMS320F2812为控制芯片的单相光伏并网逆变器实验平台，设计硬件电路及软件控制算法，在此平台上进行实验验证。实验结果验证了本文提出的虚拟电抗控制方法以及电网同步方法在弱电网下应用的正确性和有效性，与理论分析相符。
[Abstract]:As a kind of clean renewable energy, solar photovoltaic power has been developing rapidly in recent years with the increasingly severe energy crisis and environmental problems faced by human beings. Photovoltaic power generation systems are often used to solve the power demand in remote areas. In remote areas, islands and other terminal networks are usually designed for relatively small loads. The power supply is mostly of medium and low voltage grade, with high impedance and low short-circuit capacity. Presents the characteristic of weak current network. The low short-circuit capacity of weak grid and the electrical characteristics of high impedance put forward a new challenge to the stable operation of grid-connected photovoltaic system. Therefore, aiming at the grid-connected photovoltaic inverter under the condition of weak grid, this paper puts forward the concrete measures and control strategies to improve the grid-connected performance of the inverter from the point of view of grid synchronization technology and stability control method. It can operate reliably and stably under the condition of weak electric network. In this paper, the topology structure model of two-stage single-phase photovoltaic grid-connected inverter is established, and the general expression of output impedance of current-source inverter is deduced, and the influence of system parameters on output impedance is analyzed. Secondly, the impedance stability criterion of current source photovoltaic grid-connected generation system is established. On this basis, the influence of different grid conditions on inverter stability is studied. It is found that the increase of grid impedance will reduce the stability of the system. Combined with the influence of filter parameters on the output impedance, a virtual reactance control method is proposed to improve the stability of the system. At the same time, aiming at the disadvantages of the traditional zero crossing detection and synchronization method under weak electric network, a frequency locking loop technique based on the second order generalized integrator is proposed to solve the problem of power network synchronization, so as to realize the reliable and stable grid connection of the inverter under the weak electric network. Finally, the experiment platform of single-phase photovoltaic grid-connected inverter with TMS320F2812 as control chip is built, and the hardware circuit and software control algorithm are designed and verified on this platform. The experimental results verify the correctness and effectiveness of the proposed virtual reactance control method and the power grid synchronization method under the weak current network, which is consistent with the theoretical analysis.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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