LCL滤波并网逆变器H_∞鲁棒控制设计与实现

发布时间：2018-03-31 20:16

  本文选题：电网阻抗　切入点：小信号模型　出处：《中国矿业大学》2017年硕士论文

【摘要】：并网逆变器作为分布式发电系统的核心部分,电网阻抗对逆变器稳定性的影响不可忽略。电网阻抗摄动会导致LCL滤波器谐振频率出现大范围波动,进而导致系统出现振荡;电网阻抗会影响公共耦合点电压,导致锁相环输出不稳定,影响并网质量。本文通过建立并网逆变器的小信号模型,分析在传统PI控制策略下,单电流闭环和包含电容电流反馈的电流闭环两种不同控制结构对电网阻抗摄动的抑制能力。单电流闭环对电网阻抗摄动容许范围小;包含电容电流反馈电流闭环存在固有不稳定频率范围,当谐振频率处于该范围时控制器始终无法保证系统稳定。此外本文分析了电网阻抗摄动对锁相环输出的影响。本文对电网阻抗摄动情况下并网逆变器控制提出采用H_∞鲁棒控制策略,通过建立包含电网阻抗不确定性的数学模型,合理选择加权函数,得到七阶H_∞鲁棒控制器。由于七阶控制器需要更多计算量和存储器,对七阶控制器进行降阶得到三阶控制器,该三阶控制器可以保留原控制器良好的系统跟踪性能和鲁棒性能。针对电网阻抗摄动导致锁相环输出不稳定的问题,本文采用基于复数滤波器的锁相环,有效抑制了电网阻抗对锁相环的干扰。本文对基于传统PI控制和H_∞鲁棒控制的LCL滤波并网逆变器系统进行了仿真,并且搭建了实验平台,仿真和实验通过对比两种不同控制策略,证明了本文设计的H_∞鲁棒控制器的优越性。
[Abstract]:Grid-connected inverter is the core part of distributed generation system. The influence of grid impedance on inverter stability can not be ignored. Power grid impedance perturbation will cause the resonance frequency of LCL filter to fluctuate in a wide range, and then lead to the oscillation of the system. Power grid impedance will affect common coupling point voltage, lead to unstable output of PLL and affect grid-connected quality. In this paper, a small-signal model of grid-connected inverter is established, and the conventional Pi control strategy is analyzed. The single current closed loop and the current closed loop with capacitive current feedback can restrain the impedance perturbation of the power network, and the single current closed loop has a small allowable range for the impedance perturbation of the power network. Contains the inherent unstable frequency range of the current closed-loop with capacitive current feedback, When the resonant frequency is in this range, the controller can not guarantee the stability of the system. In addition, the influence of impedance perturbation on the output of PLL is analyzed. The control of grid-connected inverter under the condition of grid impedance perturbation is proposed in this paper. Using H _ 鈭，

本文编号：1692283