并网逆变器重复控制及其电网频率适应性研究

发布时间：2019-06-04 03:07

【摘要】：随着新能源的开发和利用,分布式发电系统受到广泛关注。在分布式发电系统中并网逆变器具有重要作用,其性能直接影响系统输出电能的质量。在并网逆变器的各种电流控制方法中,重复控制因其较高的控制精度成为研究热点。本文以并网逆变器为研究对象,对重复控制器的控制结构、设计方法以及应对电网频率变化的改进等问题进行了深入的研究。对于重复控制结构,首先讨论了重复控制单独作用于系统时不稳定的原因,说明了重复控制中前向通道对于系统稳定性的意义。其次,在传统重复控制与PI控制的复合控制中,详细分析了重复控制与PI控制串联结构和并联结构的频率特性,指出并联结构在幅频特性中存在的缺陷。在串联结构下的重复控制的内模、补偿器、增益系数等参数,根据系统的稳定性条件分析不同参数设计的利弊,得到更优的参数设计方法。最后,分析了电网频率变化对重复控制性能的影响,并介绍基于分数阶理论的频率自适应重复控制方法。借鉴了谐振控制中应对电网频率变化所采用的准谐振控制的思想,基于重复控制与谐振控制之间的数学关系而提出了选取较小内模系数的改进方法,有效提高了重复控制器的谐振带宽,能够应对电网频率变化的问题。对于内模系数减小导致重复控制增益较低的问题,在对系统各个环节对于重复控制稳定性影响分析的基础上,整理得到了一种更优的重复控制器参数设计流程,提高了重复控制在谐波频率处的增益。最后,对并网逆变器的重复控制参数设计及改进方法进行了仿真和实验验证,结果表明:以重复控制与PI控制串联结构为基础的传统重复控制能够具有较高的控制精度,但受电网频率波动的影响较大,而改进内模的重复控制可以较好的适应电网频率变化,同时也具有很好的跟踪性能。
[Abstract]:With the development and utilization of new energy, distributed power generation system has received extensive attention. Grid-connected inverter plays an important role in distributed power generation system, and its performance directly affects the quality of output power. Among all kinds of current control methods of grid-connected inverter, repetitive control has become a research focus because of its high control accuracy. In this paper, the control structure of repetitive controller, the design method and the improvement of power grid frequency change are deeply studied with the grid-connected inverter as the research object. For the repetitive control structure, the causes of instability when repetitive control acts on the system alone are discussed, and the significance of forward channel for system stability in repetitive control is explained. Secondly, in the compound control of traditional repetitive control and PI control, the frequency characteristics of series structure and parallel structure of repetitive control and PI control are analyzed in detail, and the defects of parallel structure in amplitude-frequency characteristics are pointed out. According to the stability conditions of the system, the advantages and disadvantages of different parameter design are analyzed, and a better parameter design method is obtained according to the internal model, compensator, gain coefficient and other parameters of repeated control in series structure. Finally, the influence of power grid frequency change on repetitive control performance is analyzed, and the frequency adaptive repetitive control method based on fractional order theory is introduced. Based on the idea of quasi-resonance control used in resonant control to cope with the frequency change of power grid, an improved method for selecting smaller internal model coefficient is proposed based on the mathematical relationship between repetitive control and resonant control. The resonant bandwidth of the repetitive controller is effectively improved and the problem of power grid frequency change can be dealt with. For the problem of low repetitive control gain caused by the decrease of internal model coefficient, based on the analysis of the influence of each link of the system on the stability of repetitive control, a better parameter design flow of repetitive controller is obtained. The gain of repetitive control at harmonic frequency is improved. Finally, the design of repetitive control parameters and the improved method of grid-connected inverter are simulated and verified by experiments. The results show that the traditional repetitive control based on repetitive control and PI control series structure can have high control accuracy. However, it is greatly affected by the frequency fluctuation of the power grid, and the repeated control of the improved internal model can better adapt to the frequency change of the power grid, and also has a good tracking performance.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM464

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