LCL型并网逆变器对电网阻抗鲁棒性的研究

发布时间：2018-05-28 06:46

本文选题：并网逆变器 + LCL滤波器　；参考：《华中科技大学》2014年硕士论文

【摘要】：传统化石能源的开发利用导致能源危机和环境污染问题，以太阳能、风能为代表的分布式并网发电越来越受到重视。LCL型并网逆变器是连接分布式源和电网的接口装置之一。为保证其稳定工作，，通常采用电容电流反馈有源阻尼来抑制LCL滤波器的谐振峰。采用数字控制时，控制延时会导致系统稳定约束条件复杂且对电网阻抗的鲁棒性差。本文针对数字控制电容电流反馈有源阻尼的LCL型并网逆变器，分析考虑电网阻抗的控制参数设计方法，以提高并网逆变器对电网阻抗鲁棒性。本文首先建立数字控制时电容电流反馈有源阻尼LCL型并网逆变器的数学模型。通过控制框图的等效变换，分析控制延时对阻尼效果的影响，并讨论系统的稳定约束条件。在此基础上，进一步考虑电网阻抗的变化，给出阻抗交截和极点轨迹图两种判断系统稳定性的方法。通过分析电网阻抗与系统稳定约束条件之间的关系，本文推导出并网逆变器不稳定的电网阻抗值域，并提出一种提高系统对电网阻抗鲁棒性的控制参数设计方法。采用该方法设计的控制参数，如果电网阻抗变化时LCL滤波器的谐振频率不跨越1/6采样频率，则电网阻抗变化时LCL型并网逆变器系统恒稳定；如果电网阻抗变化时谐振频率跨越1/6采样频率，则除一临界点外系统恒稳定。针对电容电流滞后一拍反馈存在的稳定性问题，本文讨论电容电流即时反馈在提高并网逆变器稳定性方面的效果，并对这两种电容电流反馈有源阻尼方式的等效物理模型和对电网阻抗的鲁棒性进行分析。以单相LCL型并网逆变器为例，在实验室研制一台6kW的原理样机，并完成相关的实验研究，实验结果验证了理论分析的正确性。
[Abstract]:The development and utilization of traditional fossil energy lead to energy crisis and environmental pollution. Distributed grid-connected power generation, represented by solar and wind energy, is paid more and more attention to. LCL grid-connected inverter is one of the interface devices to connect distributed source and power grid. In order to ensure its stable operation, the capacitive current feedback active damping is usually used to suppress the resonant peak of LCL filter. When digital control is adopted, the control delay will lead to complex system stability constraints and poor robustness to grid impedance. In order to improve the robustness of grid-connected inverters to grid-connected inverters based on digital control capacitive current-feedback active damping LCL grid-connected inverter, the design method of control parameters considering grid impedance is analyzed in order to improve the robustness of grid-connected inverters to grid impedance. In this paper, the mathematical model of capacitive current feedback active damping LCL grid-connected inverter is established. Through the equivalent transformation of the control block diagram, the influence of control delay on damping effect is analyzed, and the stability constraints of the system are discussed. On the basis of this, two methods to judge the stability of the system are given, which are the impedance intersecting and the pole trajectory diagram, considering further the variation of the impedance of the power system. Based on the analysis of the relationship between power impedance and system stability constraints, the unsteady range of grid impedance of grid-connected inverters is derived, and a control parameter design method to improve the robustness of the system to power impedance is proposed. If the resonant frequency of the LCL filter does not exceed 1 / 6 sampling frequency when the power impedance changes, the LCL grid-connected inverter system will be stable when the power impedance changes. If the resonant frequency exceeds 1 / 6 sampling frequency when the impedance of the power system changes, the system is stable except for a critical point. Aiming at the stability problem of capacitor current lag beat feedback, this paper discusses the effect of capacitor current instant feedback on improving the stability of grid-connected inverter. The equivalent physical models of the two kinds of capacitive current feedback active damping methods and their robustness to the grid impedance are analyzed. Taking single-phase LCL grid-connected inverter as an example, a prototype of 6kW is developed in the laboratory. The experimental results verify the correctness of the theoretical analysis.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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