Artificial Intelligence-based Control Methods for Optimal and Stable Operation of Converter-dominated Microgrids

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Journal Title
Journal ISSN
Volume Title
School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2023-03-31
Date
2023
Major/Subject
Mcode
Degree programme
Language
en
Pages
84 + app. 94
Series
Aalto University publication series DOCTORAL THESES, 13/2023
Abstract
The microgrid as a major player in future smart grids includes power-electronic-based distributed generation (DG) units, loads, energy storage system (ESS), and lines. The microgrid can operate either island or connected to the main grid. The voltage and frequency references in island microgrid are adjusted by individual DGs while in grid-connected mode these references are dictated to the DGs by the upstream grid. The droop control and virtual synchronous generator (VSG) control are well-known methodologies to control several converters in an island microgrid. The small-signal stability of a microgrid is defined as its ability to move from one permissible operating point to another permissible operating point after being subjected to a small-signal disturbance. The droop control coefficients, virtual impedances, and VSG parameters should be tuned in a feasible range to maintain the stability of microgrid. Despite the remarkable achievements, the state-of-the-art microgrid control methods face three major challenges: (1) These methods have not optimized the virtual impedances by considering the microgrid small-signal stability and power sharing in all operating points, inappropriate application of virtual impedances can jeopardize the microgrid stability; (2) VSG provides virtual inertia and damping in the microgrid including static and dynamic loads, however, inappropriate tuning of these parameters can threaten the microgrid stability, microgrid frequency, voltage, and reactive power sharing; (3) The application of artificial neural networks in online control of converters and VSGs is necessary to fulfil the stability and dynamic performance requirements in future microgrids. First and foremost, this thesis introduces a new perspective on microgrid control methods, which suggests to analyse the stability of all operating points and define an optimization problem according to the dynamics and stability preferences of microgrid. This optimization method concludes the stable operation of microgrid in all operating points and a desirable dynamic performance, simultaneously.Secondly, the thesis reports a novel method to optimize the virtual inertia, virtual damping, current state-feedback factor, and virtual impedances to enhance the microgrid small-signal stability. Moreover, the reactive power sharing, frequency Nadir, and voltage of buses are enhanced. Finally, the thesis introduces an online optimal control method based on adaptive network-based fuzzy inference system (ANFIS). In this method, the controller learns the optimal control policy for each value of active and reactive power and generates the optimal value of virtual inductance accordingly. The reactive power circulation among converters is minimized and the voltage drops on virtual inductances are negligible. Moreover, the small signal stability of microgrid is enhanced by the proposed control method.
Description
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
adaptive network fuzzy inference systems, microgrid, particle swarm optimization, small-signal stability, virtual impedance, virtual synchronous generator
Other note
Parts
  • [Publication 1]: Bahram Pournazarian, Edris Pouresmaeil, Meysam Saeedian, Matti Lehtonen, Ricky Chan, and Shamsodin Taheri. Microgrid Frequency & Voltage Adjustment Applying Virtual Synchronous Generator. In 2019 International Conference on Smart Energy Systems and Technologies(SEST), Porto, Portugal, Sep. 2019.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201910015550
    DOI: 10.1109/SEST.2019.8849032 View at publisher
  • [Publication 2]: Bahram Pournazarian, S. Sajjad Seyedalipour, Matti Lehtonen, Shamsodin Taheri, and Edris Pouresmaeil. Virtual Impedances Optimization to Enhance Microgrid Small-Signal Stability and Reactive Power Sharing. IEEE Access, 8, pp.139691-139705, Jul. 2020.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202008124707
    DOI: 10.1109/ACCESS.2020.3013031 View at publisher
  • [Publication 3]: Bahram Pournazarian, Meysam saeedian, Matti Lehtonen, Shamsodin Taheri, and Edris Pouresmaeil. Microgrid Stability Analysis Considering Current State-Feedback. In 2020 IEEE 11th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Dubrovnik, Croatia, Oct. 2020.
    DOI: 10.1109/PEDG48541.2020.9244320 View at publisher
  • [Publication 4]: Bahram Pournazarian, Maysam Saeedian, Bahman Eskandari, Matti Lehtonen, Edris Pouresmaeil. Feasible Ranges of Microgrid Parameters Based on Small-signal Stability Analysis. In 2020 IEEE 21st Workshop on Control and Modeling for Power Electronics (COMPEL), Aalborg, Denmark, Nov. 2020.
    DOI: 10.1109/COMPEL49091.2020.9265690 View at publisher
  • [Publication 5]: Bahram Pournazarian, Reza Sangrody, Meysam Saeedian, Oriol Gomis-Bellmunt, and Edris Pouresmaeil. Enhancing Microgrid Small-Signal Stability and Reactive Power Sharing Using ANFIS-Tuned Virtual Inductances. IEEE Access, 9, pp.104915-104926, Jul. 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202108258394
    DOI: 10.1109/ACCESS.2021.3100248 View at publisher
  • [Publication 6]: Bahram Pournazarian, Reza Sangrody, Meysam Saeedian, Matti Lehtonen, and Edris Pouresmaeil. Simultaneous Optimization of Virtual Synchronous Generators (VSG) Parameters in island Microgrids Supplying Induction Motors. IEEE Access, 9, pp.124972-124985, Sep. 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202109229335
    DOI: 10.1109/ACCESS.2021.3111015 View at publisher
  • [Publication 7]: Bahram Pournazarian, Reza Sangrody, Matti Lehtonen, Gevork B. Gharehpetian, and Edris Pouresmaeil. Simultaneous Optimization of Virtual Synchronous Generators Parameters and Virtual Impedances in Islanded Microgrids. IEEE Transactions on Smart Grid, 13, pp.4202-4217, Jun. 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202207014362
    DOI: 10.1109/TSG.2022.3186165 View at publisher
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