Integration of Renewable Energy Sources into Power Grids Applying Distributed Virtual Inertia and Model Predictive Controls

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2023-01-20
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Authors

Date

2022

Department

Sähkötekniikan ja automaation laitos
Department of Electrical Engineering and Automation

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Mcode

Degree programme

Language

en

Pages

80 + app. 84

Series

Aalto University publication series DOCTORAL THESES, 190/2022

Abstract

The current energy arena is changing, from fossil fuel-based generation to power electronic converter-interfaced renewable generation. Hence, the power system inertia and short-circuit current gradually reduce, making low-inertia grids more sensitive to frequency disturbances (i.e., power mismatch between generation and demand) and jeopardizes system stability. This thesis develops control methods for grid-following and grid-forming converters employed toward more power electronic-based generators. The thesis contributions are divided into two main approaches.  First, the distributed virtual inertia method, a grid-following converter solution aimed at synthetic inertia provision, is studied in detail. It is depicted that this method has two drawbacks: (1) small-signal stability analyses affirm that a local mode associated with the controller is prone to become unstable when the converter operates in weak grids, and (2) the DC-link voltage is not reverted to its reference value after the power mismatch between generation and demand occurred in the host grid. Herein, the aforesaid problems are addressed properly; efficient compensators are proposed which eliminate the adverse impact of distributed virtual inertia gain on the converter stability in weak grid connections. Moreover, the distributed virtual inertia controller is modified so as not to affect the outer-loop voltage regulator after transients. Then, the DC voltage restoration is possible.  Second, the conventional primary control, i.e., inner-loop cascaded linear controller and outer-loop droop, used in islanded AC microgrids is discussed. In sum, this approach has inferior dynamic response and rapid rate of change of frequency following perturbations. Accordingly, the thesis addresses these issues by introducing a modified virtual synchronous generator control. A Laguerre functions-based discrete-time model predictive controller with a multiobjective cost function is incorporated as the heart of the control system which supersedes the inner loop for hierarchical linear controllers of grid-forming converters. This yields realizing large prediction horizons, improved dynamic performance (very short rise time and slight overshoot), and inherent overcurrent protection in the case of fault or overloading without sacrificing the controller robustness. Finally, the merits of proposed techniques are verified by comparisons with corresponding primary methods. And, detailed model simulations are conducted in MATLAB/Simulink to show the efficacy of the proposed controllers.

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Supervising professor

Pouresmaeil, Edris, Assoc. Prof., Aalto University, Department of Electrical Engineering and Automation, Finland

Thesis advisor

Pouresmaeil, Edris, Assoc. Prof., Aalto University, Department of Electrical Engineering and Automation, Finland

Keywords

renewable energy, primary frequency regulation, weak grid, AC microgrid, virtual inertia, model predictive control, overcurrent protection

Other note

Parts

  • [Publication 1]: Meysam Saeedian, Mobina Pouresmaeil, Amir Sepehr, Shamsodin Taheri, and Edris Pouresmaeil. Small−Signal Stability Analysis of Synthetic Inertia−Based Photovoltaic Generators. In 2021 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), pp. 1-8, September 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202111019865
  • [Publication 2]: Meysam Saeedian, Bahman Eskandari, Shamsodin Taheri, Marko Hinkkanen, and Edris Pouresmaeil. A Control Technique Based on Distributed Virtual Inertia for High Penetration of Renewable Energies Under Weak Grid Conditions. IEEE Systems Journal, vol. 15, no. 2, pp. 1825-1834, June 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202008214779
    DOI: 10.1109/JSYST.2020.2997392 View at publisher
  • [Publication 3]: Meysam Saeedian, Bahram Pournazarian, Bahman Eskandari, Mahdi Shahparasti, and Edris Pouresmaeil. Enhancing Frequency Stability of Weak Grids with Modified Distributed Virtual Inertia Method. In 2020 IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Dubrovnik, Croatia, pp. 187-192, September/October 2020.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-2020113020564
    DOI: 10.1109/PEDG48541.2020.9244475 View at publisher
  • [Publication 4]: Meysam Saeedian, Reza Sangrody, Mahdi Shahparasti, Shamsodin Taheri, and Edris Pouresmaeil. Grid−Following DVI−Based Converter Operating in Weak Grids for Enhancing Frequency Stability. IEEE Transactions on Power Delivery, vol. 37, no. 1, pp. 338-348, February 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202102262020
    DOI: 10.1109/TPWRD.2021.3059898 View at publisher
  • [Publication 5]: Meysam Saeedian, Bahram Pournazarian, Shamsodin Taheri, and Edris Pouresmaeil. Provision of Synthetic Inertia Support for Converter Dominated Weak Grids. IEEE Systems Journal, vol. 16, no. 2, pp. 2068-2077, June 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202103312710
    DOI: 10.1109/JSYST.2021.3060866 View at publisher
  • [Publication 6]: Meysam Saeedian, Shamsodin Taheri, and Edris Pouresmaeil. Double-Stage Photovoltaic Generator Augmented with FLL−Based Synthetic Inertia Emulator. Electric Power Systems Research, vol. 204, pp. 107715, March 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-2021123111102
    DOI: 10.1016/j.epsr.2021.107715 View at publisher
  • [Publication 7]: Meysam Saeedian, Oriol Gomis-Bellmunt, and Edris Pouresmaeil. Multiobjective Laguerre Functions−Based Discrete−Time Model Predictive Control: A Fast Inner−Loop Controller for Grid−Forming Converters. Electric Power Systems Research, vol. 209, pp. 107976, August 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202204282907
    DOI: 10.1016/j.epsr.2022.107976 View at publisher

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https://urn.fi/URN:ISBN:978-952-64-1065-4

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[diss] Sähkötekniikan korkeakoulu / ELEC