Browsing by Author "Rojas, Félix"

Now showing 1 - 20 of 24
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    A decoupled Nearest Level Control for a Modular Multilevel Cascade Converter based on Triple Star Bridge Cells (MMCC-TSBC)
    (2021) Shamshuddin, Mohammed Azharuddin; Arancibia, David; Rojas, Félix; Pereda Torres, Javier; Kennel, Ralph
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    A Design Methodology of Multiresonant Controllers for High Performance 400 Hz Ground Power Units
    (2019) Rojas, Félix; Cárdenas, Roberto; Clare, Jon; Díaz, Matías; Pereda Torres, Javier Eduardo; Kennel, Ralph
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    A Modular Solid State Transformer for Future Hybrid Distribution Networks
    (2021) Lillo, Jonathan; Verdugo, Diego; Rojas, Félix; Azharuddin, Mohammed; Pereda Torres, Javier
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    Asymmetrical Triangular Current Mode (ATCM) for Bidirectional High Step Ratio Modular Multilevel Dc–Dc Converter
    (IEEE, 2020) Pineda Fornerod, Cristian Andrés; Pereda Torres, Javier Eduardo; Rojas, Félix; Cerda, Carlos; Zhang, Xiaotian; Watson, Alan J.
    Direct current (Dc) networks have proven advantages in high voltage direct current (HVDC) transmission systems, and now they are expanding to medium- and low-voltage distribution networks. One of the major challenges is to develop reliable dc-dc voltage transformation achieving high efficiency and performance, especially at high voltage and high step ratio. New resonant modular multilevel topologies have arisen as an alternative, mainly because of advantages such as optional use of transformers, natural voltage balance, simple control, and soft-switching capability. However, this type of operation generates a high peak current, does not allow control of power flow in all power range, and has a limited range of voltage variation. This article proposes an asymmetrical triangular current mode applied to high step ratio modular multilevel dc-dc converters. The proposed modulation increases the efficiency and achieves bidirectional control of the power, soft-switching, and a natural balance of the voltage in the cell capacitors. The experimental results show the bidirectional operation and the capacitor voltage balance of the converter under different operating conditions with higher efficiency (97.72%) and lower peak current compared to previous reports of this topology using resonant operation.
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    Back To Back Modular Multilevel Converter With Dynamic Hybrid Link For High Performance Drive
    (2021) Lillo, Jonathan; Rojas, Félix; Pereda Torres, Javier; Valdes, Dario; Cardenas, Roberto
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    Capacitor Balance Control of a Modular Multilevel Converter Based on Parallel Connected Branches for a MVAC/LVDC Solid State Transformer
    (2021) Verdugo, Diego; Lillo, Jonathan; Rojas, Félix; Azharuddin, Mohammed; Pereda Torres, Javier
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    Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters
    (2021) Moreno, M.; Pereda Torres, Javier Eduardo; Rojas, Félix; Dominguez-Lopez, I.
    The LLC series resonant converter has emerged as a solution to applications requiring power conversion with isolation, reduced volume and high efficiency, such as PV systems and EV chargers. However, the LLC resonant converter is limited in power, so it requires a multi-phase configuration in order to provide higher currents. This configuration connects the outputs of two or more LLC converters in parallel, increasing the output current but introducing imbalance and circulating currents due to the mismatch and tolerance values of components in each resonant tank. This paper proposes a simple PI control scheme to compensate the current imbalance and eliminate circulating currents generated when several LLC resonant converters are connected in parallel. Unlike reported current sharing methods, the proposed control scheme is based on multiple current control loops operating independently, using the switching frequency of each parallel-connected unit as a degree of freedom of the overall converter. The proposed control scheme has been successfully validated under simulations and experimental assessment, implementing two resonant tanks with ±5% tolerance of parameters, providing excellent steady-state and transient performance.
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    Design and implementation of dual active bridge converter with single phase shift modulation for electric vehicle charging system
    (2021) Navarro, Guillermo; Rojas, Félix; Pereda Torres, Javier; Diaz, Matias; Gatica, Gustavo
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    Dynamic DC-Link Voltage Control of Back to Back Modular Multilevel Converter for Drive Applications
    (IEEE, 2019) Lillo, Jonathan; Rojas, Félix; Verdugo, Diego; Dí­az, Matias; Pereda Torres, Javier Eduardo; Gatica, Gustavo; Espinoza, Mauricio
    In this work a dynamic control of the dc-link voltage in a hybrid Back-to-Back (BtB) Modular Multilevel Converter for medium-voltage drive applications is presented. The proposed control scheme relates the speed of the machine with the dc-link voltage magnitude to reduce the large circulating currents and common-mode voltage of the converter when the machine operates at low speed. Simulation results, performed in the software PLECS, validate the model of the BtB converter and the proposed control scheme, reducing circulating currents and common mode voltage in almost 70% and 60% respectively, when the machine operates at very low speed.
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    Grid Forming Operation for a High Step Ratio Modular Multilevel DC-DC Converter
    (2020) Cerda, Carlos; Rojas, Félix; Pineda, Cristian; Pereda Torres, Javier; Diaz, Matias; Gatica, Gustavo
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    Inductor design for a High performance DC-DC Modular Multilevel Converter
    (IEEE, 2019) Cerda, Carlos; Rojas, Félix; Cristian Andres, Pineda Fornerod; Pereda Torres, Javier Eduardo; Diaz, Matias; Salgado, Jordan; Droguett, Gabriel; Valdés, Darío; Gatica, Gustavo
    In this paper is presented a simple method to design an inductor for high performance on a DC-DC Modular Multilevel Converter(MMC). This element is one of the main limitations for a proper fulfilment. A high-frequency inductor for high power applications is a key element to achieve high efficiency in such type of converters. The theoretical design of the inductor is compared with an experimental prototype, which is then implemented in a high-power DC-DC converter. Experimental results validate the accuracy of the theoretical design and the improvements in the efficiency of the overall DC-DC high power converter.
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    Linear Control applied to a non-isolated bidirectional DC-DC converter with Interleave technique powered by variable sources
    (IEEE, 2019) Salgado, J.; Rojas, Félix; Pereda Torres, Javier Eduardo; Díaz, M.; Gatica, Gabriel N.
    In this article, a linear control strategy is presented applied to a Synchronous Buck converter, which allows N sub-converters to operate in parallel, operating in Interleave mode, balancing the currents in each of the sub-converters and maintaining their dynamic response invariant over a wide range of operation, even when their DC links vary as it would be in a system with electric batteries. Simulation results validating this behavior, using variable DC sources are presented and discussed in this article.
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    Modelling and control of a multi-cell converter based on Input-Parallel Output-Parallel bridge-cells with discontinuous interleaved modulation
    (2021) Verdugo, Diego; Rojas, Félix; Pereda Torres, Javier; Diaz, Matias; Gatica, Gustavo
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    New dual H-bridge converter for continuous space vector modulation
    (2019) Durán Godoy, Tomás Antonio; Neira, Sebastián; Pereda Torres, Javier Eduardo; Rojas, Félix
    Multilevel converters are a significant improvement in the DC-AC conversion technology, reaching higher power quality in medium-voltage applications and using standard semiconductors in a smarter way than conventional converters, without necessarily increasing the cost. However, multilevel technology remains discrete and its only way to reduce the overall total harmonic distortion leads on the generation of several discrete levels on the output voltage. Therefore, it is not possible to reduce the harmonic distortion to negligible values, unless a big number of semiconductors are used, which is not cost-effective for low-voltage applications, limiting the reliability of the system. This study proposes a new dual H-bridge inverter that generates a three-phase output voltage with negligible distortion using two variable DC-DC power sources and a new continuous space vector modulation. Simulation and experimental results show high-quality output voltages. The topology is simple and uses only 12 semiconductors, but it requires special attention in the variable DC voltage converters, which can limit the maximum output frequency. Therefore, the solution is suitable for low power applications that require high power quality using small filters or none filters at the AC side. The results were obtained and validated using an experimental laboratory prototype under different operating conditions.
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    Optimal ZCS Modulation for BidirectionalHigh-Step-Ratio Modular Multilevel dc-dc Converter
    (2021) Pineda Fornerod, Cristian Andres; Pereda Torres, Javier Eduardo; Rojas, Félix; Droguett Olea, Gabriel; Burgos Mellado, Claudio; Watson, Alan J.
    Recent developments in dc powered technologies have increased interest in highly efficient dc-dc converters, especially at high voltage and high-step voltage ratios. Modular multilevel converters (MMCs) are an attractive alternative approach to this demand because they can manage medium and high dc voltages while using standard semiconductor devices with high efficiency if they employ soft-switching techniques. However, the latest soft-switching techniques require resonant circuits, limiting their operation. This paper proposes an optimal modulation technique for a high-step-ratio dc-dc MMC, which achieves minimal rms current and zero-current switching. The proposed optimization generates trapezoidal or triangular current to operate the converter over a wide output voltage and power range, while using a simple control scheme to regulate the output voltage and the voltage balance among the floating cell capacitors. The theoretical analysis has been verified with a laboratory-scaled prototype, demonstrating the effectiveness of the approach and excellent dynamical response.
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    Phase-shifted Pulse Width Modulation with alternate zeros voltage for parallel connection of H-Bridges for High-Current Low-Voltage applications
    (IEEE, 2019) Verdugo, D.; Rojas, Félix; Lillo, J.; Diaz, M.; Pereda Torres, Javier Eduardo; Gatica, Gabriel N.
    Phase-Shifted Modulation (PSM) applied to multilevel converters is an effective method for reducing the output THD. In this paper, a new unipolar PSM method is proposed to control internal circulating current of a high-current low-voltage power converter, composed of parallel connected H- Bridges. The proposed method reduces the H-bridge currents distortions and the power losses of the overall converter. Simulation results comparing the standard unipolar modulation with the proposed unipolar modulation technique are performed to demonstrate its effectiveness.
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    Power Imbalance Analysis of Modular Multilevel Converter with Distributed Energy Systems
    (2024) Salvadores Viertel, Tomás; Pereda Torres, Javier Eduardo; Rojas, Félix
    The modular multilevel converter (MMC) can integrate distributed energy systems (DES), such as a battery energy storage system, to expand its functionalities and carry out multiple simultaneous tasks. However, a DES induces power imbalances within the MMC, which affects the operating currents and voltages of the converter. This phenomenon has been partially covered in recent works, but an analytical analysis has not yet been carried out to see the behavior and implications in different MMC-DES applications. This article introduces a novel analytical analysis of the power imbalances between MMC clusters. It pioneers the development of general equations and imbalance capability metrics, enabling the assessment of maximum currents and voltages supported by the MMC clusters. The developed tools allow the evaluation of any MMC-DES application regarding the current and voltage rating requirements of MMC clusters. The analysis shows that the MMC operating mode can substantially restrain or enlarge its imbalance capacity, affecting its suitability for different DES applications. While it needs around 33% current overrating in the worst imbalances, under some operating modes it can reach most imbalances without requiring current overrating. The ac compensation mode is much more capable of achieving imbalances than the dc compensation mode, reaching 88.37% and 16.74% of the imbalance points, respectively, without requiring any overrating.
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    Solid State Transformers : Concepts, Classification, and Control
    (2020) Shamshuddin, M. A.; Rojas, Félix; Cardenas, R.; Pereda Torres, Javier Eduardo; Diaz, M.; Kennel, R.
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    Three-Port Full-Bridge Bidirectional Converter for Hybrid DC/DC/AC Systems
    (IEEE, 2020) Neira Castillo, Sebastian Felipe; Pereda Torres, Javier Eduardo; Rojas, Félix
    Sustainable solutions such as renewable energies, distributed generation, energy storage, and electric vehicles require power conversion and advance control techniques. This process is usually done in two stages by more than one power converter, specially in hybrid systems, increasing power losses and costs. The configuration with two dc stages and one ac port is widely used in several applications, such as grid-connected photovoltaic inverters; fuel cells, hybrid and electric vehicles; and ac/dc microgrids. Thus, three-port topologies have been developed to operate such systems, most of them comprising multiple power processing stages for the connection of the different elements. This article proposes a three-port full-bridge converter with a single power processing stage for dc/dc/ac systems. The ac port can be single-phase or three-phase, using two legs like an H-bridge or three legs like the conventional three-phase inverter. In both configurations, each leg is used as an inverter and as a buck-boost converter at the same time. The converter is able to manage the power flow among three ports with just four or six switches through a multivariable control strategy. Simulation and experimental results show the capability of the converter to manage the interaction between a battery and a capacitor connected to the grid achieving a fast dynamic response, bidirectional capability in all ports and reduction of components.