非隔离三相光伏逆变器漏电流抑制方法研究

发布时间：2018-05-23 18:41

本文选题：三相逆变器 + 寄生参数　；参考：《陕西科技大学》2017年硕士论文

【摘要】：为缓解能源和环境危机带来的迫切压力,以太阳能为代表的新能源开发势在必行。光伏发电作为实现太阳能利用的主要形式,其核心设备光伏逆变器转换性能的提高对于整个系统效率的提升,以及实现高质量电能输送都具有十分重要的意义。在逆变器的众多分类当中,非隔离型光伏逆变器更高的转换效率使其成为了现阶段的研究热点,但同时变压器消除所带来的漏电流,消耗了部分由光伏阵列输送的能量,严重影响了逆变器的转换效率。针对上述问题,现阶段众多的研究方法都是从硬件拓扑和调制技术两方面入手进行探索。前者在完成漏电流抑制目标的同时带来了成本增加、硬件体积过大等缺陷;后者虽然不存在这方面缺陷,但通常会造成直流电压利用率较低和输出电流质量下降等其他方面性能的不足。本文着重从调制方法入手,系统分析了针对三相逆变器具有漏电流抑制作用的相关算法,并进行了适当的改进,实现了对逆变器的漏电流和其它相关性能在一定程度上的优化,其主要研究内容如下:(1)首先对三相两电平逆变器的工作方式,以及二极管钳位三电平逆变器的工作模态进行了详细的理论分析。在对其工作原理充分理解的基础之上,搭建了非隔离三相光伏并网逆变器漏电流分析模型,并完善了系统中存在的寄生参数。基于模型获得了漏电流产生的根本原因,并讨论了各类电路和寄生参数对漏电流的影响,从而证明了从调制方案入手实现漏电流抑制的优势。(2)针对两电平和三电平逆变器,详细分析了其相应的传统SVPWM(空间矢量脉宽调制)算法实现原理,并从其原理分析证明了不连续五段式和单极性调制模式对漏电流具有一定的抑制作用,以为后文中实现调制算法的改进奠定基础。(3)对现有的一些基于调制的漏电流抑制方法分别进行了原理的阐述。综合分析对比了各种方法下的漏电流,直流电压利用率和输出谐波畸变率情况,并在此基础上,提出了应用于三电平逆变器的NSV-PWM漏电流调制方案。实现了在不改变任何硬件拓扑结构的前提下,完成光伏逆变系统漏电流抑制目标,并兼顾了对直流电压利用率和谐波含量等其他性能方面的优化。(4)本文基于Matlab/Simulink软件平台搭建了三相两电平和三电平逆变器通用仿真模型,以及各调制算法实现模型。对文中所涉及结论均进行了仿真分析。仿真结果验证了所提NSV-PWM算法在各方面性能上的均衡性,与算法原理分析结果相一致。
[Abstract]:In order to alleviate the urgent pressure brought by the crisis of energy and environment, the development of new energy represented by solar energy is imperative. Photovoltaic power generation as the main form of solar energy utilization, its core equipment photovoltaic inverter conversion performance to improve the efficiency of the whole system, as well as the realization of high-quality power transmission are of great significance. Among the many categories of inverters, the higher conversion efficiency of non-isolated photovoltaic inverter makes it a hot research topic at this stage, but at the same time the transformer eliminates the leakage current and consumes some of the energy transmitted by the photovoltaic array. The conversion efficiency of the inverter is seriously affected. In view of the above problems, many research methods are explored from hardware topology and modulation technology. The former has the defects of increasing cost and oversize of the hardware, while achieving the target of leakage current suppression, while the latter has no defects in this respect. However, it usually leads to low utilization of DC voltage and poor quality of output current. Based on the modulation method, this paper systematically analyzes the relevant algorithms for three-phase inverter with leakage current suppression, and makes appropriate improvements to realize the optimization of the leakage current and other related performance of the inverter to a certain extent. The main research contents are as follows: (1) firstly, the working mode of three-phase two-level inverter and the mode of operation of diode clamped three-level inverter are analyzed in detail. On the basis of fully understanding its working principle, a non-isolated three-phase photovoltaic grid-connected inverter leakage current analysis model is built, and the parasitic parameters in the system are improved. Based on the model, the fundamental cause of leakage current is obtained, and the influence of various circuits and parasitic parameters on leakage current is discussed. It is proved that the advantage of realizing leakage current suppression from modulation scheme is aimed at two-level and three-level inverters. The realization principle of the traditional SVPWM (Space Vector Pulse width Modulation) algorithm is analyzed in detail, and it is proved that the discontinuous five-segment modulation mode and the unipolar modulation mode can restrain the leakage current. It lays a foundation for the improvement of modulation algorithm in the following paper. (3) the principles of some existing modulation-based leakage current suppression methods are explained respectively. The leakage current, DC voltage utilization rate and output harmonic distortion rate of various methods are comprehensively analyzed and compared. Based on this, a NSV-PWM leakage current modulation scheme applied to three-level inverter is proposed. Under the premise of not changing any hardware topology, the leakage current suppression target of photovoltaic inverter system is achieved. This paper builds a general simulation model of three-phase two-level and three-level inverter based on Matlab/Simulink software platform, and the realization model of each modulation algorithm. All the conclusions in this paper are simulated and analyzed. The simulation results verify the equalization of the proposed NSV-PWM algorithm in all aspects, which is consistent with the analysis results of the principle of the proposed algorithm.
【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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