单相多电平光伏并网逆变器研究

发布时间：2018-03-19 22:37

本文选题：光伏发电　切入点：三电平　出处：《北京交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：多电平逆变器具有输出电压谐波含量低、电磁干扰小、输出滤波器体积小等优点,有助于光伏并网系统提高效率,减小体积,在光伏发电领域中具有广泛的应用前景。本文以单相多电平光伏并网逆变器为研究对象,在对单相控制系统进行分析的基础上,对单相三电平光伏并网逆变器以及一种具有共模电流抑制能力的多电平混合级联型光伏并网逆变器进行了研究。本文首先对光伏并网发电系统的体系分类及并网逆变器种类进行了介绍。针对单相并网控制策略,研究了几种调节器对于双闭环控制系统中交流电流环的影响,其中重点分析了比例谐振调节器的控制效果。随后研究了对称型及非对称型单相三电平逆变器的工作方式及其结构中三电平桥臂对于逆变器输出、损耗等方面的影响,分析了其各自的应用领域,并针对这两种逆变器的直流侧中心点电位平衡方式进行了研究。本文在传统非隔离型三电平半桥光伏并网逆变器的基础上,重点对一种多电平混合级联型光伏并网逆变器进行了研究,该结构在降低逆变器直流输入侧电压等级的同时,可以进一步减小输出电压谐波含量,从而降低了开关频率,减小了滤波电感体积。文中对其工作状态及共模模型进行了分析,并由此得出了逆变器的最佳调制方式以及一种基于该方式的直流支撑电容电压控制策略,并根据该电路的死区效应给出了一种死区补偿方式。针对单相多电平逆变器SPWM调制方式占用系统资源多的问题,对其进行改进,给出了一种单载波SPWM实现方式,并将该方式应用于非对称型单相三电平逆变器及多电平混合级联型逆变器的调制过程中。介绍了一种矢量调制方式,分析了上述两种方法的优缺点。最后,搭建了单相三电平逆变器及多电平混合级联型逆变器的实验平台,通过实验验证了本文对于对称型及非对称型单相三电平逆变器和混合级联型逆变器输出特性的分析结论,以及混合级联型逆变器直流支撑电容电压控制策略和单载波SPWM调制方式的可行性。
[Abstract]:Multilevel inverter has the advantages of low output voltage harmonic content, small electromagnetic interference and small output filter size, which is helpful to improve the efficiency and reduce the volume of photovoltaic grid-connected system. In this paper, the single-phase multilevel photovoltaic grid-connected inverter is taken as the research object, and the single-phase control system is analyzed. The single-phase three-level photovoltaic grid-connected inverter and a multi-level hybrid cascade photovoltaic grid-connected inverter with common mode current suppression capability are studied. In this paper, the classification of photovoltaic grid-connected generation system and the type of grid-connected inverter are introduced, and the influence of several regulators on AC current loop in double-closed-loop control system is studied in view of single-phase grid-connected control strategy. The control effect of proportional resonant regulator is analyzed. Then, the working mode of symmetrical and asymmetric single-phase three-level inverter and the influence of tri-level leg on the output and loss of inverter are studied, and their respective application fields are analyzed. The DC-side center-point potential balance of these two inverters is studied. Based on the traditional three-level half-bridge photovoltaic grid-connected inverter, this paper focuses on a hybrid cascaded photovoltaic grid-connected inverter. This structure reduces the voltage level of DC input side of the inverter at the same time. The harmonic content of the output voltage can be further reduced, thus the switching frequency and the volume of the filter inductor can be reduced. The working state and the common mode model of the filter inductor are analyzed in this paper. The optimal modulation mode of the inverter and a DC supported capacitor voltage control strategy based on this mode are obtained, and a dead-time compensation method is given according to the dead-time effect of the circuit. Aiming at the problem that the SPWM modulation mode of single-phase multilevel inverter occupies more system resources, this paper improves it, and presents a single carrier SPWM implementation method. This method is applied to the modulation process of asymmetric single-phase three-level inverter and multilevel hybrid cascaded inverter. A vector modulation method is introduced, and the advantages and disadvantages of the two methods are analyzed. Finally, the experimental platform of single-phase three-level inverter and multilevel hybrid cascaded inverter is built. The analysis of the output characteristics of symmetric and asymmetric single-phase three-level inverters and hybrid cascaded inverters is verified by experiments. The feasibility of DC-supported capacitor voltage control strategy and single carrier SPWM modulation for hybrid cascade inverter is presented.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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