三相光伏并网逆变器系统并联运行控制的研究

发布时间：2018-05-24 14:05

本文选题：三相光伏并网逆变器 + 调制控制策略　；参考：《山东大学》2017年硕士论文

【摘要】：工业革命以后包括煤、石油在内的能源大量使用,由此引发的能源危机和环境问题使人们开始关注发展可再生能源。光伏发电不产生污染物,不需要燃料,在可再生能源发展进程中具有重要意义。逆变器的模块化并联运行作为大功率光伏发电应用背景下科学与技术的重大需求,对提高系统容量、灵活性和运行效益以及降低生产成本,居功至伟。然而,实际运行时存在零序环流,随之引发的电磁干扰、安全性冲击以及系统损耗的增加严重制约了并联逆变器的高效运行和应用推广。两电平三相光伏并网逆变器系作为一种低压大功率场合的主要拓扑表现形式,在近几年多电平技术应用突飞猛进的背景下,以其成本低廉、灵活高效的优势在大容量化市场中仍占据主导地位而不可替代。本文以两电平三相光伏并网逆变器系统为研究对象,首先介绍了光伏发电系统的研究现状以及发展趋势,通过文献综述,总结出三相光伏并网逆变器不同类型的拓扑及其特点,并详细介绍了光伏并网逆变器的模块化并联、环流抑制、开关损耗抑制的研究现状,为两电平逆变器的模块化并联运行控制的研究奠定理论基础。其次,采用基于单个桥臂开关周期平均模型,保留模型中的共模成分对基本级功率模块建模,使用两个并联的非隔离光伏并网逆变器作为主电路,运用电网电压定向的矢量控制理论设计了三环结构的控制器,内环为电压/电流双闭环控制器,外环为实现最大功率追踪(MaximumPowerPointTracking,MPPT)的功率环。再次,在建立并联系统模型的基础上,采用枚举的分析方法,分析了环流产生的机理以及环流抑制的基本原理,总结出了开关状态和零序环流的关系,并采用空间矢量调制(space vector pulse-width-modulated,SVM)方法合成指令电压以完成并网控制,针对逆变器并联时存在的零序环流,探讨了含有零矢量调节因子k的零序环流控制方法,该方法在零矢量交替分配的SVM调制情况下控制效果明显,但不适合最小开关损耗的SVM调制的情况,其在零矢量分配情况方面的局限性为新算法的提出提供了理论指导。基于上述研究,本文在分析开关损耗和系统效率问题的基础上,提出了零序环流的复合控制方案,既可以平抑零序环流,又减少了系统开关损耗。该复合控制方案通过调整开关导通时间实现。通过适当的加上或者减去三相导通时间中的最小导通时间重新简单计算得到调整后的开关导通时间。由于开关频率的减小,本方法可以减小开关损耗。采用RT-LAB实时仿真平台搭建三相光伏并网逆变器并联系统的仿真模型,实时仿真结果证明了方法的可行性和可靠性。
[Abstract]:The energy crisis and environmental problems caused by the industrial revolution, including coal and oil, have made people begin to pay attention to the development of renewable energy. Photovoltaic power generation does not produce pollutants, does not need fuel and is of great significance in the process of renewable energy development. The modular parallel operation of the inverter is used as a high-power light. The important demand of science and technology in the background of voltaic power generation is great to improve system capacity, flexibility and efficiency and reduce production cost. However, there are zero sequence circulation in actual operation, electromagnetic interference, security impact and increase of system loss, which seriously restrict the efficient operation of parallel inverters. The two level three-phase photovoltaic grid connected inverter system is the main topology of the low-voltage and high-power situation. In the background of the rapid application of multilevel technology in recent years, with its low cost and flexible and efficient advantages, it still occupies the dominant position in the large volume quantization market. This paper is based on the two level three-phase light. The current research status and development trend of PV grid inverter system are introduced. Through literature review, the different types of topology and characteristics of three-phase PV grid connected inverters are summarized, and the modular parallel, circulation suppression and switching loss suppression of photovoltaic grid connected inverters are introduced in detail. It lays a theoretical foundation for the study of modularized parallel operation control for two level inverters. Secondly, based on the periodic average model of a single bridge arm switch, the common mode components in the model are retained to model the basic level power module, and two parallel non isolated photovoltaic grid connected inverters are used as the main circuit, and the vector vector of the grid voltage is used. The controller of the three ring structure is designed by the theory of quantity control. The inner ring is a voltage / current double closed loop controller and the outer ring is the power loop of the maximum power tracking (MaximumPowerPointTracking, MPPT). In this principle, the relationship between the switch state and the zero sequence circulation is summarized, and the space vector pulse-width-modulated (SVM) method is used to synthesize the command voltage to complete the grid connected control. The zero sequence circulation control method with zero vector quantity regulation factor K is discussed. The zero sequence circulation control method with zero vector quantity regulation factor K is discussed. The control effect of vector alternately distributed SVM modulation is obvious, but it is not suitable for the SVM modulation of minimum switching loss. The limitation of the zero vector distribution is the theoretical guidance for the new algorithm. Based on the above study, the zero sequence circulation is proposed on the basis of the analysis of the switching loss and the system efficiency. The composite control scheme can both suppress the zero sequence circulation and reduce the switching loss of the system. The composite control scheme is realized by adjusting the switching time of the switch. The adjusted switching time is simply calculated by adding or subtracting the minimum pass time in the three phase conduction time. This method can reduce the switching loss. The simulation model of the three-phase photovoltaic grid connected inverter parallel system is built by the RT-LAB real time simulation platform. The real-time simulation results show the feasibility and reliability of the method.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

【相似文献】