Model predictive control of three-phase four-leg bidirectional VSC operating as ac or dc grid former

Victor Cordeiro de Arruda

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Author(s):	Victor Cordeiro de Arruda Total Authors: 1
Document type:	Master's Dissertation
Press:	Campinas, SP.
Institution:	Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
Defense date:	2023-10-19
Examining board members:	José Antenor Pomilio; Tárcio André dos Santos Barros; Tiago Davi Curi Busarello
Advisor:	José Antenor Pomilio; Joel Filipe Guerreiro
Abstract
In this work, a bidirectional converter is designed to operate as a dc and ac grid/source former. For the dc grid or source, the converter operates as a dc grid or source former, draining power from the ac source or grid. On the other hand, the inverter may also operate as an ac grid or source former, draining power from the dc source or grid. The application foresees a 220V line-line ac rms connection, on the dc side, a 380V (bipolar +190 V, GND, -190V). In this regard, it is advantageous that the voltage of a dc and ac microgrid is within the voltage levels supported by universal power supplies. In this scenario, the dc grid/source former might operate with a high modulation index, when draining power from the ac grid/source. The same applies to the ac grid/source former draining power from the dc grid/source. The model predictive control technique enables high-speed response and is advantageous for applications requiring high modulation indexes. Therefore, this technique will be investigated for controlling the grid/source former in either the ac or dc modes. The control methodology to be applied, the converter modeling, and the filter parameters selection will be investigated. For investigating converter stability an analysis considering the Lyapunov theory for both modes of operation, as an ac or dc grid former is done. Simulation and experimental results will be used to evaluate the performance of the system when connected to linear and non-linear loads on the ac side and balanced or unbalanced loads on the dc side. In relation to the results, the system maintains the variables control in a stable operation for simulation and Hardware-In-the-Loop (HIL) cases. Regarding to experimental results, the ac grid former operates in a stable way, in accordance with what was shown in the simulations and theoretical analysis. Regarding the dc grid former, the system did not work properly due to LC filter capacitor failure that occurred due to a significant point of common coupling (PCC) voltage distortion. The LC filter value definition for this application using predictive control was published in the following work: V. C. Arruda, J. F. Guerreiro and J. A. Pomilio, "Design of a FCS MPC-based three-phase four-leg bidirectional VSC for application in ac or dc microgrids," 2023 International Conference on Future Energy Solutions (FES), Vaasa, Finland, 2023, pp. 1-7, doi: 10.1109/FES57669.2023.10182661 (AU)

FAPESP's process:	21/10349-7 - Bidirectional AC-DC converter operating as AC or DC grid former in hybrid microgrid
Grantee:	Victor Cordeiro de Arruda
Support Opportunities:	Scholarships in Brazil - Master

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