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Single-Cycle-Lag Compensator-Based Active Damping for Digitally Controlled LCL/LLCL-Type Grid-Connected Inverters

Authors :
Wenxi Yao
Zheyu Miao
Zhengyu Lu
Source :
IEEE Transactions on Industrial Electronics. 67:1980-1990
Publication Year :
2020
Publisher :
Institute of Electrical and Electronics Engineers (IEEE), 2020.

Abstract

The control delay weakens the active damping (AD) performance of digitally controlled LCL/LLCL -type grid-connected inverters (GCIs). The equivalent virtual impedance paralleled with the filter branch explains the effect of the capacitor-current-feedback AD. However, the virtual impedance appears capacitive or even negative due to the delay, which significantly weakens the effectiveness of AD. This paper proposes a single-cycle-lag compensator (SCLC) to eliminate the adverse effects caused by the control delay. The method retains effectiveness in applications with high resonant frequency or large control delay. It keeps system a positive equivalent resistance with a high equivalent inductance. The positive equivalent resistance leads to positive damping effect, while the high equivalent inductance causing little resonant frequency deviation can be neglected. Moreover, the effect of the impedance variation that causes the resonant frequency deviation is analyzed and the restrictions of the proposed method are discussed. By optimizing the LCL/LLCL filter parameters, the adaptability of the SCLC to the grid impedance variation can be further improved. With the SCLC, the LCL/LLCL -type GCIs achieve better steady-state and dynamic performances. Finally, experimental results are presented to verify the proposed method.

Details

ISSN :
15579948 and 02780046
Volume :
67
Database :
OpenAIRE
Journal :
IEEE Transactions on Industrial Electronics
Accession number :
edsair.doi...........db45cdeb8bffc78881ea4fc6dfe23763
Full Text :
https://doi.org/10.1109/tie.2019.2903759