An Enhanced Control of Grid-forming Converters for Systems with High Penetration of Renewable Energies

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Journal Title
Journal ISSN
Volume Title
School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2023-02-03
Date
2022
Major/Subject
Mcode
Degree programme
Language
en
Pages
83 + app. 83
Series
Aalto University publication series DOCTORAL THESES, 200/2022
Abstract
Renewable energies (REs) are increasingly important to provide a clean, reliable, and cost-effective energy system to meet the growing electricity demand. REs comprise a growing number of components that connect to the grid via power converters. Even current consumption levels present a considerable challenge in terms of just energy balance, but the near future is highly likely to contain significant load growth. In addition to the energy balance challenge arising from the increased load, larger frequency deviations coupled with the loss of inertia and voltage regulation problems will also appear in future power grids. Besides, phasing out the synchronous generators (SGs) leads to larger equivalent impedance and lower short-circuit current levels, resulting in a weaker grid, with an increased risk of instability. The thesis aims to enable the grid-forming (GFM) converters to offer power grid support functions and ancillary services in a way similar to or more advanced than the conventional SGs do both in steady-state and in dynamic/transient operating conditions. GFM converters are the more reliable choice to be employed for the future converter-dominated power grid with high penetration of renewable energy sources (RESs), so the focus is on this type of converter. The thesis contribution is mainly related to improving the performance of the GFM converters as follows: First, the inertia and oscillation-damping features of SGs are emulated in the control of the GFM converters to work as grid-supporting GFM virtual synchronous generators (VSGs). The employed parameters for implementing the VSG-based converter are adaptive to the mode of operation, so the best performance for both islanded and grid-connected modes of operation as well as the transition between these modes of operation are obtained, resulting in the plug-and-play capability of the VSG. A detailed small-signal model for each mode of operation is provided, and the small-signal analysis is used to identify the required parameter for the best performance in each mode of operation. Second, the fault ride-through (FRT) capability, i.e., the ability of the converter to stay connected and continue working at a lower voltage level under fault conditions, is added to the control of the GFM converter. A PI-based FRT control is proposed at first and then model predictive control (MPC) as a superior control concept is employed in the control of the GFM converter for both normal and fault-mode conditions. The MPC-based FRT protects the GFM converter from overcurrent while keeping its voltage mode functionality. Both the VSG and FRT capability of the GFM converter are validated through simulation results in MATLAB/Simulink as well as hardware-in-the-loop (HIL) test results.
Description
Supervising professor
Pouresmaeil, Edris, Prof., Aalto University, Department Electrical Engineering and Automation, Finland
Thesis advisor
Pouresmaeil, Edris, Prof., Aalto University, Department Electrical Engineering and Automation, Finland
Keywords
renewable energies, grid-forming converter, virtual synchronous generator, adaptive oscillation-damping, model predictive control, overcurrent protection, fault ride-through
Other note
Parts
  • [Publication 1]: Mobina Pouresmaeil, Amir Sepehr, Reza Sangrody, Shamsodin Taheri, and Edris Pouresmaeil. Control of Multilevel Converters for High Penetration of Renewable Energies. In 2021 IEEE 12th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Chicago, IL, USA, pp. 1-5, June 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202108258401
    DOI: 10.1109/PEDG51384.2021.9494249 View at publisher
  • [Publication 2]: Mobina Pouresmaeil, Reza Sangrody, Shamsodin Taheri, and Edris Pouresmaeil. An Adaptive Parameter-Based Control Technique of Virtual Synchronous Generator for Smooth Transient Between Islanded and Grid-Connected Mode of Operation. Accepted for publication in IEEE Access, vol. 9, pp. 137322 - 137337, October 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202111019888
    DOI: 10.1109/ACCESS.2021.3117617 View at publisher
  • [Publication 3]: Mobina Pouresmaeil, Meysam Saeedian, Amir Sepehr, Reza Sangrody, and Edris Pouresmaeil. Fault-Ride-Through Capability of VSGBased Grid-Forming Converters. In 2021 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), Ghent, Belgium, pp. 1-7, September 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202111019886
  • [Publication 4]: Amir Sepehr, Mobina Pouresmaeil and Edris Pouresmaeil. Enhancing Transient Stability of Power Synchronization Control via Deep Learning. In 2021 23rd European Conference on Power Electronics and Applications (EPE’21 ECCE Europe), Ghent, Belgium, pp. 1-10, September 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202111019934
  • [Publication 5]: 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), Ghent, Belgium, pp. 1-8, September 2021.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202111019865
  • [Publication 6]: Mobina Pouresmaeil, Amir Sepehr, Basit Ali Khan, Jafar Adabi, and Edris Pouresmaeil. Model predictive-based control technique for fault ride-through capability of VSG-based grid-forming converter. In 2022 24rd European Conference on Power Electronics and Applications (EPE’22 ECCE Europe), Hannover, Germany, pp. 1-7, September 2022.
    Full text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-202211096406
  • [Publication 7]: Mobina Pouresmaeil, Reza Sangrody, Shamsodin Taheri, and Edris Pouresmaeil. A Model Predictive Control-based Fault Ride Through for Grid-forming Virtual Synchronous Generators. Submitted to a journal, July 2022.
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