LAPSE:2018.0584
Published Article
LAPSE:2018.0584
An LQR-Based Controller Design for an LCL-Filtered Grid-Connected Inverter in Discrete-Time State-Space under Distorted Grid Environment
Thuy Vi Tran, Seung-Jin Yoon, Kyeong-Hwa Kim
September 21, 2018
In order to alleviate the negative impacts of harmonically distorted grid conditions on inverters, this paper presents a linear quadratic regulator (LQR)-based current control design for an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter. The proposed control scheme is constructed based on the internal model (IM) principle in which a full-state feedback controller is used for the purpose of stabilization and the integral terms as well as resonant terms are augmented into a control structure for the reference tracking and harmonic compensation, respectively. Additionally, the proposed scheme is implemented in the synchronous reference frame (SRF) to take advantage of the simultaneous compensation for both the negative and positive sequence harmonics by one resonant term. Since this leads to the decrease of necessary resonant terms by half, the computation effort of the controller can be reduced. With regard to the full-state feedback control approach for the LCL-filtered grid connected inverter, additional sensing devices are normally required to measure all of the system state variables. However, this causes a complexity in hardware and high implementation cost for measurement devices. To overcome this challenge, this paper presents a discrete-time current full-state observer that uses only the information from the control input, grid-side current sensor, and grid voltage sensor to estimate all of the system state variables with a high precision. Finally, an optimal linear quadratic control approach is introduced for the purpose of choosing optimal feedback gains, systematically, for both the controller and full-state observer. The simulation and experimental results are presented to prove the effectiveness and validity of the proposed control scheme.
Keywords
digital signal processor (DSP) TMS320F28335, distorted grid, grid-connected inverter, internal model, LCL filter, linear quadratic regulator
Suggested Citation
Tran TV, Yoon SJ, Kim KH. An LQR-Based Controller Design for an LCL-Filtered Grid-Connected Inverter in Discrete-Time State-Space under Distorted Grid Environment. (2018). LAPSE:2018.0584
Author Affiliations
Tran TV: Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea
Yoon SJ: Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea
Kim KH: Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea [ORCID]
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Journal Name
Energies
Volume
11
Issue
8
Article Number
E2062
Year
2018
Publication Date
2018-08-08
Published Version
ISSN
1996-1073
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PII: en11082062, Publication Type: Journal Article
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LAPSE:2018.0584
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doi:10.3390/en11082062
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Sep 21, 2018
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Sep 21, 2018
 
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Calvin Tsay
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