三相T型三电平光伏逆变器技术研究

发布时间：2018-04-09 04:21

本文选题：T型三电平　切入点：非隔离　出处：《燕山大学》2015年硕士论文

【摘要】：在快速增长的光伏应用市场中,DC/AC逆变器作为光伏并网系统的重要组成部分,其开发与研究备受世界各国学者的关注。三电平逆变器因其输出电能质量高、输出容量大等优点,广泛应用于新能源发电领域。在众多三电平拓扑电路中,T型三电平拓扑在近几年得到了快速发展,该拓扑是一种改进的中点钳位(Neutral Point Clamped,NPC)型三电平拓扑,解决了传统二极管中点钳位型拓扑存在的器件过多、损耗分布不均等问题。因此,本文以三相T型三电平逆变器为基础展开研究。首先,本文详细分析了三相T型三电平逆变器的工作原理和换流过程,在此基础上,利用器件的损耗特征参数对逆变器的开关损耗和通态损耗进行了计算,并介绍了三电平逆变器空间矢量脉宽调制(Space Vector Pulse Width Modulation,SVPWM)方法的基本原理和实现方法。其次,针对非隔离型三相T型三电平逆变器中存在共模电流的问题,建立了系统共模等效模型,对影响共模电流的因素进行了分析。本文采用了两种基于传统三电平SVPWM调制方式的改进方法,通过对开关序列和基本矢量的合理选取及排序,使系统共模电压减小,从而实现共模电流的抑制,并通过仿真验证了其有效性。再次,针对三相T型三电平逆变器中点电位不平衡的问题,分析了基本矢量对中点电位产生的影响,总结出造成中点电位不平衡的主要原因。在共模电流抑制方法的基础上,根据正负小矢量对中点电位的不同影响,得到了一种基于SVPWM的中点电位平衡控制方法,并给出了其详细的实现步骤和仿真结果。最后,搭建了以TMS320F28335 DSP为控制核心的三相T型三电平并网逆变器系统平台,并对系统的软硬件设计作了介绍。在该平台上对改进型调制策略进行了实验研究,实验结果验证了理论分析的正确性和可行性。
[Abstract]:As an important part of photovoltaic grid-connected system, the development and research of DC / AC inverter has attracted the attention of scholars all over the world in the rapidly growing market of photovoltaic applications.Three-level inverter is widely used in the field of new energy generation because of its high output power quality and large output capacity.In recent years, the T-type three-level topology has been developed rapidly in many three-level topology circuits. It is an improved Neutral Point Clamped-NPC-type three-level topology, which solves the problem that there are too many devices in the traditional diode neutral-point clamping topology.The problem of uneven distribution of loss.Therefore, this paper is based on three-phase T-type three-level inverter.Firstly, the principle and commutation process of three-phase T-type three-level inverter are analyzed in detail. On the basis of this, the switching loss and on-state loss of the inverter are calculated by using the loss characteristic parameters of the device.The basic principle and implementation method of Space Vector Pulse Width Modulation (SVPWM) method for three-level inverter are also introduced.Secondly, aiming at the problem of common mode current in unisolated three-phase T type three-level inverter, the common mode equivalent model of the system is established, and the factors influencing the common-mode current are analyzed.In this paper, two improved methods based on traditional three-level SVPWM modulation are adopted. The common mode voltage is reduced and the common mode current is suppressed by reasonably selecting and ordering the switch sequence and the basic vector.The effectiveness of the method is verified by simulation.Thirdly, aiming at the unbalance of neutral point potential in three-phase T type three-level inverter, the influence of basic vector on neutral point potential is analyzed, and the main causes of neutral point potential imbalance are summarized.On the basis of common mode current suppression method, according to the different effects of positive and negative small vectors on midpoint potential, a neutral point potential balance control method based on SVPWM is presented, and its detailed implementation steps and simulation results are given.Finally, a three-phase T type three-level grid-connected inverter platform with TMS320F28335 DSP as the control core is built, and the software and hardware design of the system is introduced.Experimental research on the improved modulation strategy is carried out on this platform, and the experimental results verify the correctness and feasibility of the theoretical analysis.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM464

【参考文献】