Browsing by Author "Nurminen, Tuure"

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  • Materials for flexible implantable electronics in Brain-Computer interface
    (2020-09-05) Nurminen, Tuure
     Sähkötekniikan korkeakoulu | Bachelor's thesis
  • Multifunctional Grid-Forming Cascade Control for Converters Equipped with an LCL Filter
    (2023) Mourouvin, Rayane; Nurminen, Tuure; Hinkkanen, Marko; Pirsto, Ville; Kukkola, Jarno
     A4 Artikkeli konferenssijulkaisussa
    A multifunctional control framework is presented for grid-forming converters. This structure enables to operate the voltage source converter (VSC) in voltage-source mode in normal operation while activating a current control loop if overcurrent limits are reached. The framework is obtained by merging a multifunctional cascade controller recently proposed for stand-alone applications and a hybrid synchronization loop, which relies on a combination of a power synchronization loop (PSL) and a phase-locked loop (PLL). These two together make it possible to control a grid converter in either current or voltage source mode while maintaining synchronism with the grid. The effectiveness of the proposed control framework is assessed through experimental validation using a 12.5-kVA converter connected to strong and weak grids in terms of both power reference tracking and rejection of grid voltage sag. In particular, the proper performance of the system is emphasized in both tested grid configurations.
  • Multifunctional Grid-Forming Converter Control Based on a Disturbance Observer
    (2024) Nurminen, Tuure; Mourouvin, Rayane; Hinkkanen, Marko; Kukkola, Jarno
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A multifunctional grid-forming control method based on a disturbance observer structure is proposed for grid converters. The proposed method has several different control modes, including the grid-forming, grid-following, and current control modes. The proposed method does not require any separate synchronization loop as it is incorporated in the disturbance observer. Links to existing control methods are shown and tuning recommendations are provided based on small-signal stability analysis. Furthermore, robustness against the inductance error in the grid-forming mode is analytically shown. Experiments with a 12.5-kVA converter are used to assess power-tracking performance. The method is shown to have excellent dynamic performance regardless of grid strength and to provide seamless switching between grid-forming and grid-following modes. In addition, the effect of grid voltage sags and grid-frequency deviations is studied.
  • Observer-Based Power-Synchronization Control for Grid-Forming Converters
    (2022-10-17) Nurminen, Tuure
     Sähkötekniikan korkeakoulu | Master's thesis
    Renewable energy sources connected to the grid via power converters are becoming increasingly common. Currently, most of these power converters are of the grid-following type that follow the frequency and voltage set by synchronous generators connected to the grid. Large scale adoption of these would put the stability of the grid at risk and thus their allowable amount is limited. A potential solution to this is the adoption of grid-forming control schemes that allow converters to set their own frequency and voltage references and thus no longer be reliant on synchronous generators. Power synchronization control (PSC) is one such method with two prominent versions, conventional PSC and reference-feedforward PSC (RFPSC). These two methods are, however, heuristic in design and a more coherent approach is more desirable. This thesis develops a novel observer-based PSC (OPSC) method for the control of grid-forming converters equipped with an L filter. Recommendations for the tuning of OPSC are developed based on the stability analysis of its linear model. Comparisons between RFPSC and OPSC are made based on their linear models and significant similarities between the two are found. Simulations are used to study the performance of conventional PSC, RFPSC and OPSC. RFPSC and OPSC are found to have not only excellent performance but also react in a very similar manner to changes in the output power reference when correct tuning is used. The potential for using LCL filters with OPSC is also confirmed using simulations. The performance of the three PSC-based methods is confirmed experimentally by means of a laboratory setup that includes physical converters and a real-time control system.
  • Observer-based power-synchronization control for grid-forming converters
    (2023-06-29) Nurminen, Tuure; Mourouvin, Rayane; Hinkkanen, Marko; Kukkola, Jarno; Routimo, Mikko; Vilhunen, Antti; Harnefors, Lennart
     A4 Artikkeli konferenssijulkaisussa
    This paper proposes an observer-based power-synchronization control (OPSC) method for grid-forming converters. The method can also be utilized for the starting of synchronous generators. It is analogous to observer-based volts-per-hertz (V/Hz) control of electric machine drives, consisting of state-feedback control and an observer. A linearized model of the closed-loop system is derived, passivity of the mechanical subsystem is studied and tuning recommendations are given. The power tracking performance is assessed and compared to that of reference-feedforward power-synchronization control (RFPSC) with the help of simulations and laboratory experiments using a 12.5-kVA converter. The results show that the proposed control method provides good performance in both weak and strong grids.