三相并网逆变器锁相与电流控制技术

发布时间：2019-06-01 14:40

【摘要】：随着一次能源的不断消耗和所造成的环境污染等问题的日益严重化，，可再生绿色能源的发展得到了人们越来越多的关注。光伏发电被认为在是最具有潜力在将来取代一次能源作为电力发电的新能源形势。因此，国内外学者们已经将运用于光伏发电的并网逆变器技术当作重要研究方向。本文以一台250kW单级式的三相并网逆变器为基础，重点研究了并网控制策略中的锁相环技术和并网电流控制技术。本文首先研究了单同步旋转dq坐标系锁相法(SSRF-PLL)在电网电压不平衡条件下存在的锁相问题。总结了几种已有的不平衡锁相控制技术，经过分析得到锁相动态响应速度慢的缺点。所以，本文提出了一种基于不平衡电网对称分量法快速相序分离的锁相技术，从而提高了锁相环的动态性能。针对电网不平衡对并网逆变器电流控制技术的影响，本文通过建立网侧逆变器和功率模型，研究了不平衡条件下的两种控制目标：一是抑制直流输入电压脉动；二是抑制并网电流的负序分量。根据并网逆变器的自身特点，本文采用了电网电压正、负序分量前馈抑制负序电流的不平衡控制策略。通过仿真验证了本文所采用的不平衡锁相与电流控制方法的有效性。本文搭建了一台250kW的三相并网逆变系统，对系统主电路功率器件参数进行了简单介绍，并对整个并网的数字控制结构进行了详细设计。在实验平台的基础上，采用本文所研究的不平衡锁相控制和电流控制方法在理想电网和不平衡电网下分别进行了实验，并对实验波形进行详细分析。实验结果，验证了快速不平衡锁相方法在电网突变条件下能够迅速跟踪电网相位信息；也验证了不平衡抑制负序电流控制技术在电网不平衡后仍能保证并网电流完全对称。
[Abstract]:With the continuous consumption of primary energy and the increasing severity of environmental pollution, the development of renewable green energy has received more and more attention. Photovoltaic power generation is considered to be the most potential to replace primary energy as a new energy situation in the future. Therefore, scholars at home and abroad have used grid-connected inverter technology for photovoltaic power generation as an important research direction. Based on a 250kW single-stage three-phase grid-connected inverter, the phase-locked loop technology and grid-connected current control technology in grid-connected control strategy are studied in this paper. In this paper, the phase-locked problem of single synchronous rotating dq coordinate system phase-locked method (SSRF-PLL) under the condition of unbalanced voltage of power grid is studied. Several existing unbalanced phase-locked control techniques are summarized, and the shortcomings of slow phase-locked dynamic response are obtained by analysis. Therefore, a phase-locked technique based on unbalanced power grid symmetric component method for rapid phase sequence separation is proposed in this paper, which improves the dynamic performance of phase-locked loop. In view of the influence of grid imbalance on the current control technology of grid-connected inverter, this paper studies two kinds of control objectives under unbalanced condition by establishing grid-side inverter and power model: one is to suppress DC input voltage pulsation; The second is to suppress the negative sequence component of grid-connected current. According to the characteristics of grid-connected inverter, this paper adopts the unbalanced control strategy of voltage positive and negative sequence component feedforward to suppress negative sequence current. The effectiveness of the unbalanced phase-locked and current control method used in this paper is verified by simulation. In this paper, a three-phase grid-connected inverter system of 250kW is built, the parameters of the main circuit power device of the system are briefly introduced, and the whole digital control structure of the grid-connected system is designed in detail. On the basis of the experimental platform, the unbalanced phase-locked control and current control methods studied in this paper are used to carry out experiments in ideal power grid and unbalanced power grid respectively, and the experimental waveforms are analyzed in detail. The experimental results verify that the fast unbalanced phase-locked method can quickly track the phase information of the power grid under the condition of sudden change of the power grid, and also verify that the negative sequence current control technology of unbalanced suppression can still ensure the complete symmetry of the grid-connected current after the imbalance of the power grid.
【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】：2014
【分类号】：TM464

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