Method of Current Disturbance Observation Control for LCL-Type Grid Connected Inverters With Additional Virtual Impedance

doi:10.3969/j.issn.1008-0198.2024.02.005

Abstract

Abstract: Aiming at the fact that the output current quality of actual LCL-type grid connected inverters is easily affected by grid voltage background harmonics and grid impedance under weak current grid conditions,this paper proposes a current disturbance observation and control method for LCL-type grid connected inverters with additional virtual impedance.Firstly,this paper introduces a disturbance observer on the basis of conventional double closed-loop control,treating the background harmonic of the grid voltage as an external disturbance of the system.The disturbance observer is used to estimate the disturbance momentum in real time and dynamically eliminate the influence of disturbance on the system through feedforward compensation.Secondly, impedance analysis method is used to analyze the robustness problem caused by grid impedance in weak current grid systems.Based on the current disturbance observation control method,virtual impedance is added for optimization design,so that the phase margin of the grid connected inverter system is still greater than the stability margin constrained by the system when the impedance intersection frequency changes within a large range.The simulation comparison results show,the proposed method improves the robustness of the system to grid impedance while maintaining good current quality.

Key words: LCL-type grid connected inverter, disturbance observer, virtual impedance, current quality, robustness

CLC Number:

TM464

ZHU Hongping, GUO Liwen, QIAN Wanming, ZHU Hongzhi, HAN Yinglong. Method of Current Disturbance Observation Control for LCL-Type Grid Connected Inverters With Additional Virtual Impedance[J]. Hunan Electric Power, 2024, 44(2): 35-43.

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