Browsing by Author "Mora, Andres"

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    An Improved Reference Generator Based on MPC of Circulating Currents and Common-Mode Voltage for Modular Multilevel Matrix Converters
    (IEEE-Inst Electrical Electronics Engineers Inc, 2024) Cuzmar Leiva, Rodrigo Hernan; Mora, Andres; Pereda, Javier; Aguilera, Ricardo P.
    This article proposes an improved reference generator based on model-predictive-control (MPC) for the modular multilevel matrix converter (M3C). The novelty of the proposal is in optimally obtaining the circulating currents and CMV references to achieve the intercluster balancing (ICB) control and low-frequency oscillations mitigation (LFOM) of the M3C. Additionally, the proposed optimal control problem is designed in the original framework and includes bound constraints for circulating currents and CMV for a proper operation of the M3C. As a result, the MPC-based reference generator allows to regulate the cluster energies with low capacitor voltage ripple and operate at low and equal frequencies while keeping the cluster currents under safe limits. Experimental results have been conducted using a 3 kVA prototype to validate the proposed strategy's effectiveness and high-quality performance.
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    Closed-Loop Performance Improvement for MMCs Based on Optimal Reference Governor
    (2021) Poblete, Pablo; Neira, Sebastian; Cuzmar, Rodrigo; Aguilera, Ricardo P.; Mora, Andres; Pereda Torres, Javier
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    Model Predictive Control in Multilevel Inverters Part I: Basic Strategy and Performance Improvement
    (2024) Garcia, Cristian; Mora, Andres; Norambuena, Margarita; Rodriguez, Jose; Aly, Mokhtar; Carnielutti, Fernanda; Pereda, Javier; Acuna, Pablo; Aguilera, Ricardo; Tarisciotti, Luca
    Multilevel inverters (MLIs) have lately become important due to their extended application to electrical transmission and distribution systems. At the same time, the control and modulation of MLIs are especially challenging due to the high number of switching states, many of them redundant in terms of output voltage generation, and their nonlinear characteristics. In order to ease their implementation in real environment, model predictive control (MPC) is often considered, where the main control targets are: 1) to generate a the desired output current and 2) to keep the internal converter capacitor voltages at their reference value. However, a major issue with the implementation of MPC in MLIs is that the number of calculations to be done online increases dramatically with the number of levels, making it almost impossible to apply MPC in some practical cases. For these reasons, one of the main research trend in MPC for MLIs is to provide an algorithm which can reduce the computational burden necessary to operate the control. The article proposes a review of such control techniques. Starting from the basic MPC implementation and using a flying capacitor converter as an example the article review the basic strategies to avoid calculating the weighting factor in the cost function, simplifying the implementation. Also, methods to reduce the number of calculations necessary to implement MPC are shown and applied to cascaded H-bridge converters. These techniques allow to keep an high load current quality while reducing more than 95% in the number of calculations necessary to implement the control. Finally, other operation improvements of MPC are also included, such as fixed switching frequency operation and multistep MPC, reaching an important performance improvement compared to the basic MPC strategy.
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    Model Predictive Control in Multilevel Inverters Part II: Renewable Energies and Grid Applications
    (2024) Norambuena, Margarita; Mora, Andres; Garcia, Cristian; Rodriguez, Jose; Aly, Mokhtar; Carnielutti, Fernanda; Pereda, Javier; Castillo, Cristian; Zhang, Zhenbin; Yaramasu, Venkata; Tarisciotti, Luca; Yin, Yafei
    This article presents the use of model predictive control (MPC) in multilevel inverters for some applications, such as, first, wind generation and, second, photovoltaics, showing that the particular restrictions of each of them can be very easily included in the control algorithm, which is an important advantage of this technique. Another application is in modular multilevel cascaded converters, where it is demonstrated that MPC can operate with very few calculations and fixed switching frequency. The second part of this article is dedicated to comparing MPC with linear control and pulsewidth modulation for multilevel inverters. The main comparison criteria are the switching losses, the distortion in the load current, and the number of commutations. The main conclusion is that MPC is a competitive alternative to linear control for application in multilevel inverters.