An Efficient Robust Power–Voltage Control for Three-Level NPC Converters in Microgrids

Depósito de investigación de la Universidad de Sevilla https://idus.us.es/ This is an Accepted Manuscript of an article published by IEEE Transactions on Industrial Informaticsavailable at: 10.1109/TII.2023.3331548 “© 2024 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other Works” This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. 7 AUTHOR et al.: TITLE mitigating the chattering and enhancing steady-state accuracy. Using the same 氏jsw, the QISMC without DSTO would achieve poor robustness or may even lead to system instability. The robustness and chattering suppression of DSTO QISMC for the voltage regulation loop are similar to the above. This analysis process will not be detailed here due to space limitations. V. EXPERIMENTAL RESULTS This section validates the effectiveness of the proposed control scheme on a laboratory-built 3L-NPC power con verter prototype, as shown in Fig. 3. The proposed control scheme is implemented using the IMPERIX control platform. Parameters of the experimental platform are listed in Table II, DSTO-QISMC, discrete-time extended state observer-based QISMC (DESO-QISMC), DSTO-based quasi sliding mode control (DSTO-QSMC), and discrete-time PI (DPI) control parameters are shown in Table III. A comprehensive set of guiding principles is applied to comparative experimental analysis in order to ensure maximum objectivity and accuracy (DSTO-QISMC, DESO-QISMC, DSTO-QSMC, DPI) in the comparative analysis of control methods1. A. An Overall Evaluation Comparison To better validate the superiority of the proposed control scheme in overall control performance, the proposed DSTO QISMC control scheme is compared to the DESO-QISMC, DSTO-QSMC, and DPI schemes. From Fig. 5, it can be observed that the proposed control scheme outperforms the DESO-QISMC, DSTO-QSMC, and DPI methods in terms of transient/steady-state responses, including dc-link voltage, active power, reactive power, grid current quality (THDs) and chattering suppression. Specifically, the proposed con trol method had less overshoot/undershoot, faster transient response speed, smaller chattering, and lower THDs when reg ulating the dc-link voltage and tracking power. More detailed comparisons refer to Table IV. The underlying reason is that DSTO combines the robustness of sliding mode control with a high-order sliding mode control law to effectively address issues such as chattering, multi-disturbances (including load uncertainties, parameter variations, and bias caused by current path changes and switch mode noise) for power converter system, achieving rapid and accurate state estimation. Ad ditionally, it self-compensates power/voltage bias in QISMC, leading to significant improvements in voltage/power control performance. In QISMC, the integral component serves the purpose of alleviating steady-state errors and enhancing sys tem robustness compared with QSMC. Overall, DSTO-ISMC exhibits a good robustness and control performance. 1 These principles encompass: (1) Rigorous testing under identical con ditions, including consistent hardware configurations and systems, as well as identical initial conditions to efuninate external variables. (2) Utilizing a fixed-variable analysis to accurately assess the impact of specific variables on the 3L-N伈power converter system. (3) Evaluation under the same input conditions (i.e., the same control goals). (4) The adoption of common perfor mance metrics (stability, response speed, control error) to ensure consistency throughout the analysis. (5) Conducting diverse experiments to reveal the performance of these control methods across various real-world scenarios. The experimental comparisons are carried out with due attention to objectivity, both quantitatively and qualitatively, to be sure the assessments are accurate, reliable, and practical. B. Comparative voltage regulation performance The effectiveness and superiority of DSTO-QISMC voltage regulation are verified by comparing three kinds of voltage regulators (DESO-QISMC, DSTO-QSMC, DPI), and a com parative analysis is performed in Fig. 6. The DPI method is employed for the power tracking loop and balancing voltage loop during these tests. It proves that the proposed con trol method achieves better transient and steady-state per formances. Accordingly, the proposed method exhibits minor voltage amplitude variations, smaller overand undershooting, better chattering suppression, and faster convergence proper ties than DESO-QISMC, DSTO-QSMC, and DPI methods. Meanwhile, Table V provides a more detailed dynamic and static comparison of voltage regulation performance, enabling an evaluation of effectiveness and feasibility of the proposal. The main reason is that DSTO is capable of effectively estimating multi-disturbances as the voltage reference changes, so as to further offset QISMC power/voltage bias, thereby improving voltage regulation performance. DSTO is combined with QISMC to further suppress chattering and increase the robustness of voltage regulation. C. Comparative power tracking performance To evaluate the effectiveness of the proposed DSTO-QISMC method in power tracking, comparisons are made with DESO QISMC, DSTO-QSMC, and DPI, respectively, as depicted in Fig. 7. The DPI method is employed for the voltage regulation loop and balancing voltage loop during these tests. As depicted in Fig. 7, the proposed method exhibits superior perfom诅nce in reactive power dynamics, reduced power chattering, and improved grid-current quality compared to DESO-DQISMC, DSTO-QSMC, and DPI methods. It is attributed to the ro bustness achieved by DSTO against uncertainties and external disturbances as opposed to DESO and DPI methods, and QISMC shows superior chattering suppression compared to QSMC. Additionally, the proposed solution achieves lower harmonics, meaning fewer noises in the power tracking loop. The more detailed performance evaluation indicators of re active power are shown in Table VI. It can be seen that the proposed method exhibits better perfom诅nce than DESO QISMC, DSTO-QSMC, and DPI methods. The robustness achieved by DSTO against multi-disturbances as opposed to DESO and DPI methods, and ISMC shows superior the chattering suppression generated by compared to SMC. D. Evaluating control performance via trajectory motion The voltage/power control performance of the proposed DSTO-QISMC and DESO-QISMC methods are evaluated in the presence of unknown interference, parameter mismatch, and measurement noise through voltage/power smooth trajec tory and travel distance on the QISM surface. Fig. 8 shows trajectories of voltage regulation, and the working mode is to adopt DPI control in both power tracking and voltage bal ancing loops. Fig. 9 illustrates trajectories of power tracking, where DPI control is employed in both the voltage regulation and voltage balancing loops. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information. This article has been accepted for publication in IEEE Transactions on Industrial Informatics. This is the author's version which has not been fully edited and content may change prior to final publication. Citation information: DOI 10.1109/TII.2023.3331548 © 2023 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See https://www.ieee.org/publications/rights/index.html for more information.