一种基于H6桥的单相光伏并网逆变器的研究

发布时间：2018-05-16 21:49

本文选题：并网逆变器 + 共模电流　；参考：《陕西科技大学》2017年硕士论文

【摘要】：在传统能源短缺和环境日益恶化的大背景下,寻求环保的可再生能源迫在眉睫。太阳能作为一种绿色、储存量足的可再生能源越来越受到关注,其中,光伏并网发电技术是利用太阳能的有效途径之一,而并网逆变器作为光伏并网发电系统的核心部件,其拓扑结构和并网控制技术决定了光伏并网发电系统的发电效率和电能质量。本文采用了一种高效的H6拓扑,解决了传统桥式拓扑用于非隔离系统存在的逆变效率低、共模电流大等问题。本文所做的主要工作包括以下几个方面:(1)非隔离型传统桥式逆变器拓扑及H6拓扑的共模电流分析。分析了非隔离型单相光伏并网逆变器拓扑普遍存在的寄生电容和直流分量问题。在非隔离型传统桥式拓扑模型的基础之上,详细分析了此类拓扑共模电流产生的机理,得到了抑制共模电流的条件,给出了一种能够有效抑制共模电流的H6逆变拓扑。(2)基于H6桥两级式光伏并网系统总体控制方案的设计。前级DC-DC电路实现最大功率点跟踪和母线电压稳定,后级H6逆变器实现并网控制功能。结合本系统实际情况,选择L型滤波器,并对L型滤波器参数进行了设计。在电感电流连续模式下,分析了Boost电路的升压原理,为后面的Matlab仿真提供理论基础。(3)研究了并网逆变器的控制策略。对前级部分和后级部分的控制策略进行了独立的设计。针对传统电导增量法存在的“误判”问题,采用了一种基于恒定电压法结合变步长电导增量法的MPPT控制策略;重点分析了并网电流逆变控制技术,分别探究了PI控制和PR控制的原理及优缺点,针对两种控制方法的局限性,提出了基于PI+QPR复合并网控制策略,并对控制器进行理论分析,对改善并网电流质量有一定的意义。(4)基于H6桥单相光伏并网逆变系统的仿真分析。在Matlab R2016b/Simulink平台上搭建基于H6桥单相光伏并网逆变系统仿真模型,根据控制器所设计的参数,分别对PR控制、PI控制和PI+QPR控制仿真实验,从无静差跟踪能力、抗干扰性和抑制直流分量能力等三个方面性能进行对比,来体现PI+QPR复合控制的优越性,另外,复合控制还具备对电网低次谐波的补偿能力;同时,通过仿真验证了恒定电压法结合变步长电导增量法良好的动态特性。(5)基于H6桥光伏并网逆变器的软硬件设计。研制一台1.5kW的H6桥单相光伏并网逆变器实验样机,设计了H6逆变器的硬件部分和软件部分,并对H6桥样机进行性能测试,得到了部分实验波形和数据,并对样机性能进行分析。仿真和实验结果表明:基于H6拓扑提出的PI+QPR控制策略不仅可以实现无静差跟踪,而且还可以抑制低频直流分量,有效地减小了并网电流THD,实现了单位功率因数并网。
[Abstract]:Under the background of the shortage of traditional energy and the worsening of environment, it is urgent to seek renewable energy for environmental protection. Solar energy, as a kind of green and abundant renewable energy, has been paid more and more attention. Among them, grid-connected photovoltaic (PV) grid-connected power generation technology is one of the effective ways to utilize solar energy, and grid-connected inverter is the core component of grid-connected photovoltaic power generation system. Its topology and grid-connected control technology determine the generation efficiency and power quality of grid-connected photovoltaic system. In this paper, an efficient H6 topology is used to solve the problems of low inverter efficiency and large common-mode current in traditional bridge topology for non-isolated systems. The main work of this paper includes the following aspects: 1) Common-mode current analysis of traditional bridge inverter topology and H6 topology. The parasitic capacitance and DC component problems of non-isolated single-phase photovoltaic grid-connected inverter topology are analyzed. Based on the traditional bridge topology model, the mechanism of the common mode current is analyzed in detail, and the condition of restraining the common mode current is obtained. A H6 inverter topology, which can effectively suppress the common-mode current, is presented. The overall control scheme of the two-stage photovoltaic grid-connected system based on H6 bridge is designed. The front-stage DC-DC circuit achieves maximum power point tracking and bus voltage stability, while the hind H6 inverter realizes grid-connected control function. According to the actual situation of the system, the L type filter is selected and the parameters of L type filter are designed. In the continuous mode of inductance current, the boost principle of Boost circuit is analyzed, and the control strategy of grid-connected inverter is studied. The control strategy of the former part and the later part is designed independently. Aiming at the problem of "misjudgment" in traditional conductance increment method, a MPPT control strategy based on constant voltage method and variable step length increment method is adopted, and the grid-connected current inverter control technique is analyzed emphatically. The principle, advantages and disadvantages of Pi control and PR control are discussed respectively. Aiming at the limitation of the two control methods, a hybrid grid-connected control strategy based on Pi QPR is proposed, and the controller is analyzed theoretically. It is significant to improve the quality of grid-connected current. 4) Simulation analysis of single-phase photovoltaic grid-connected inverter system based on H6 bridge. The simulation model of single-phase photovoltaic grid-connected inverter system based on H6 bridge is built on Matlab R2016b/Simulink platform. According to the parameters designed by the controller, the simulation experiments of PR control Pi control and Pi QPR control are carried out, respectively. In order to reflect the superiority of Pi QPR compound control, the performance of anti-interference and DC component suppression is compared. In addition, the compound control also has the ability to compensate the low order harmonics of the power network, at the same time, The software and hardware design of H6 bridge photovoltaic grid-connected inverter based on constant voltage method combined with variable step length conductance increment method is verified by simulation. An experimental prototype of H6 bridge single-phase photovoltaic grid-connected inverter of 1.5kW is developed. The hardware and software parts of H6 inverter are designed. The performance of H6 bridge prototype is tested, and some experimental waveforms and data are obtained, and the performance of the prototype is analyzed. The simulation and experimental results show that the Pi QPR control strategy based on H6 topology can not only realize static error tracking, but also suppress low-frequency DC component, reduce grid-connected current effectively, and realize grid-connected unit power factor.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

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