非隔离型光伏逆变器漏电流分析及硬件设计

发布时间：2018-08-01 16:50

【摘要】：近年来,随着化石燃料的常规式利用不断增加,不仅资源的利用效率低而且对环境造成了很大污染。在政府部门的积极推进下,光伏发电以其清洁、广泛、无污染的特点,从最初的军用到如今走进千家万户,既解决了能源短缺和环境污染的难题,又推动了当地经济发展。在光伏发电系统中最为关键的是系统的效率,与传统的隔离型逆变器相比,非隔离型逆变器凭借着体积小、效率高、功率密度大等优势成为研究的热点。然而由于缺少了变压器,系统存在着漏电流的问题,本文以漏电流为重点展开分析。第一,通过分析常规光伏并网系统的拓扑,针对三电平逆变中母线电压不平衡的问题,提出一种可以实现母线电压平衡的拓扑,详细分析了其补偿原理;同时,为了抑制非隔离型逆变器的漏电流,提出了一种新型拓扑。第二,本文重点对抑制非隔离型逆变器的漏电流进行研究。首先,从漏电流产生的源头,分析了逆变系统中分布电容的产生机理;其次,对系统中谐振电路建立等效数学模型并推导出:当系统中共模电压保持恒定的幅值,系统中的漏电流为零。并且对比了单极性调制和双极性调制对系统共模电压和漏电流的影响;然后,对H6拓扑的拓扑结构及工作原理进行分析,并且通过Matlab仿真出系统的共模电压和漏电流;最后,对本文提出的新型拓扑从电路搭建、工作模态分析到Matlab仿真都作了细致而全面的推导和分析。第三,针对系统中滤波电感和辅助开关电源进行设计。首先根据系统的实际参数计算电感量,然后运用迭代计算的方式确定磁环型号并且进行了参数的验证,最后根据磁环的参数计算出电感的损耗和温升。对于辅助电源主要是对RCD缓冲电路、反馈补偿电路、UC3842及其外围电路的参数进行了详细的推导计算。第四,为了验证文中设计的滤波电感、辅助电源以及新型拓扑抑制漏电流的正确性与合理性,按照理论设计搭建出实验样机,对系统的滤波电流、共模电压、漏电流以及辅助电源的关键信号进行了测量,达到了设计的要求。
[Abstract]:In recent years, with the increasing of the conventional use of fossil fuels, not only the efficiency of resource utilization is low, but also the environment is polluted greatly. With the active promotion of government departments, photovoltaic power generation with its clean, extensive, pollution-free characteristics, from the initial military to now into thousands of households, not only solve the problem of energy shortage and environmental pollution, but also promote the development of local economy. In photovoltaic power generation system, the efficiency of the system is the most critical. Compared with the traditional isolated inverter, the non-isolated inverter has become a research hotspot because of its advantages of small size, high efficiency, high power density and so on. However, due to the lack of transformer, the system has leakage current problem, this paper focuses on leakage current analysis. First, by analyzing the topology of conventional photovoltaic grid-connected system, aiming at the imbalance of bus voltage in three-level inverter, a topology that can realize bus voltage balance is proposed, and its compensation principle is analyzed in detail. In order to suppress leakage current of non-isolated inverter, a new topology is proposed. Second, this paper focuses on the suppression of leakage current of non-isolated inverter. Firstly, from the source of leakage current, the generation mechanism of distributed capacitance in inverter system is analyzed. Secondly, the equivalent mathematical model of resonant circuit in the system is established and deduced: when the common-mode voltage in the system keeps constant amplitude, The leakage current in the system is zero. The effects of unipolar modulation and bipolar modulation on the common mode voltage and leakage current of the system are compared. Then, the topological structure and working principle of the H6 topology are analyzed, and the common mode voltage and leakage current of the system are simulated by Matlab. This paper presents a detailed and comprehensive derivation and analysis of the new topology proposed in this paper, from circuit construction, working mode analysis to Matlab simulation. Thirdly, the filter inductor and auxiliary switching power supply are designed. First, the inductance is calculated according to the actual parameters of the system, then the type of the magnetic ring is determined by iterative calculation and the parameters are verified. Finally, the loss and temperature rise of the inductor are calculated according to the parameters of the magnetic ring. For auxiliary power supply, the parameters of RCD snubber circuit, feedback compensation circuit UC3842 and its peripheral circuits are deduced and calculated in detail. Fourthly, in order to verify the correctness and rationality of the filter inductor, auxiliary power supply and new topology suppression leakage current, the experimental prototype is designed according to the theory, and the filtering current and common-mode voltage of the system are designed. The leakage current and the key signals of the auxiliary power supply are measured to meet the design requirements.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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