Examinando por Autor "Rodríguez, José"
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Ítem Adaptive fuzzy fractional-order sliding-mode control of LCL-interfaced grid-connected converter with reduced-order(ISA - Instrumentation, Systems, and Automation Society, 2023-01) Long, Bo; Lu, PengJie; Zhan, Danny; Lu, Xin; Rodríguez, José; Guerrero, Josep M.; Chong, Kil toThis paper proposes a discrete-time fuzzy fractional-order sliding-mode control (Fuzzy-FOSMC) dual loop current controller for a three-phase LCL-type grid-connected converter (GCC) with reduced order. Conventional sliding-mode control (SMC) has been widely used in GCC due to its robustness to disturbances. However, the chattering in SMC may reduce the tracking performance of the controller, and even lead to system instability. To solve this problem, a Fuzzy-FOSMC controller is proposed in this paper. The introduced fractional-order term can suppress the chattering, and the fractional-order of FOSMC is further adjusted by the fuzzy controller to improve the overall system performance. In addition, the inner loop is implemented by a Fuzzy-FOSMC controller to ensure the tracking of the converter-side current, making the LCL-GCC converter behave like a controllable current source converter with a capacitive-inductive filter, the grid current control problem falls from a third-order to a reduced order system, which solves some difficulties on the design of most controller types. The stability of the two-stage PV system is analyzed. Finally, the effectiveness of the proposed controller is verified by experiments. © 2022 ISAÍtem Advanced control strategies of induction machine: Field oriented control, direct torque control and model predictive control(MDPI AG, 2018-01) Wang, Fengxiang; Zhang, Zhenbin; Mei, Xuezhu; Rodríguez, José; Kennel, RalphField oriented control (FOC), direct torque control (DTC) and finite set model predictive control (FS-MPC) are different strategies for high performance electrical drive systems. FOC uses linear controllers and pulse width modulation (PWM) to control the fundamental components of the load voltages. On the other hand, DTC and FS-MPC are nonlinear strategies that generate directly the voltage vectors in the absence of a modulator. This paper presents all three methods starting from theoretic operating principles, control structures and implementation. Experimental assessment is performed to discuss their advantages and limitations in detail. As main conclusions of this work, it is affirmed that different strategies have their own merits and all meet the requirements of modern high performance drives. © 2018 by the authors.Ítem Characterization of Clostridioides difficile Persister Cells and Their Role in Antibiotic Tolerance(Multidisciplinary Digital Publishing Institute (MDPI), 2024-07) Inostroza, Osvaldo; Fuentes, Juan A.; Yáñez, Paulina; Espinoza, Giovanni; Fica, Omar; Queraltó, Camila; Rodríguez, José; Flores, Isidora; González, Ruth; Soto, Jorge A.; Calderón, Iván L.; Gil, FernandoClostridioides difficile is a Gram-positive pathogen known for its toxin production and spore formation. It is primarily responsible for most cases of antibiotic-associated diarrhea. Bacterial persisters are a small subset of the population that exhibits transient tolerance to bactericidal substances, and they are of significant medical concern due to their association with the emergence of antibiotic resistance and difficult-to-treat chronic or recurrent infections. Vancomycin, the predominant antibiotic utilized in the management of C. difficile infection, is extensively applied in the realm of clinical practice. Previous studies have demonstrated a persister-like phenotype with treatments involving this antibiotic. However, the mechanism in C. difficile remains largely unknown, primarily due to the challenge of isolating this small population at any given time. To better characterize C. difficile persister cells, we present a study that enables the enrichment and characterization of persister cells from bacterial cultures in both the exponential and stationary phases. Moreover, we could differentiate between triggered (induced using antibiotics such as vancomycin) and spontaneous (stochastic) persister cells. Additionally, we observed the involvement of toxin-antitoxin systems and Clp proteases in persister cell formation.Ítem El impacto en la vida moderna de los avances científicos y tecnológicos(Universidad Andrés Bello, 2017-11-28) Rodríguez, JoséCharla inaugural de José Rodríguez, igeniero eléctrico, rector de la Universidad Andrés Bello y Premio Nacional de Ciencias Aplicadas y Tecnológicas 2014. V Conferencia Internacional de Cultura Científica UNAB. Santiago de Chile, 28 de noviembre de 2017.Ítem Model-Free Predictive Control of Motor Drives and Power Converters: A Review(Institute of Electrical and Electronics Engineers Inc., 2021) Khalilzadeh, Mohammad; Vaez-Zaez, Sadegh; Rodríguez, José; Heydar, RasoolPredictive control has emerged as a promising control method in a variety of technological fields. Model predictive control, as one of the subdivisions of this control method, has found a growing number of applications in power electronics and motor drives. In practical implementations, model predictive control faces performance degradation of the controlled plant due to its dependency on a model. There are considerable numbers of review papers that are devoted to the different points of view of predictive control. However, the existing literature lacks a review study that addresses the solutions for parameter dependency of the model predictive control method. Recently, model-free predictive control has been used in drives and power electronics as a solution for dealing with the model-dependency of the model predictive control method. There are many papers that have used such methods. In this paper, a classification is proposed for the different implementation types of model-free predictive control or similar methods that address model parameter uncertainties. Additionally, a comparison between the methods is also presented.Ítem MPC-Controlled Virtual Synchronous Generator to Enhance Frequency and Voltage Dynamic Performance in Islanded Microgrids(Institute of Electrical and Electronics Engineers Inc., 2021-03) Long, Bo; Liao, Yong; Chong, Kil; Rodríguez, José; Guerrero, Josep M.The use of high penetration converter-interfaced renewable energy (RE) based microgrids (MGs), due to the absence of rotational masses from conventional synchronous generators (SGs), may lead to a lack of inertia, which may lead the steeper frequency and voltage fluctuations that may in turn cause instability issues and challenges the normal operation of sensitive loads. To suppress these fluctuations and enhance the MGs stability, a novel model predictive control (MPC)-controlled virtual synchronous generator (VSG) for an energy storage system (ESS) is introduced. The proposed method can provide inertia support during transient states and enhance the dynamic characteristics of system voltage and frequency. By establishing the prediction model of VSG and designing the cost function for frequency and power, the increments of the needed active and reactive power are calculated then superposed on the power reference of VSG. The results show that the suppression performance of the voltage and frequency variations under loading transition with the proposed method is better than those of other techniques. Simulation and hardware-in-the-loop (HIL) results further demonstrate the effectiveness of the proposed method.Ítem Multistep Model Predictive Control for Electrical Drives— A Fast Quadratic Programming Solution(MDPI, 2022-03) Xie, Haotian; Du, Jianming; Ke, Dongliang; He, Yingjie; Wang, Fengxiang; Hackl, Christoph; Rodríguez, José; Kennel, RalphDue to its merits of fast dynamic response, flexible inclusion of constraints and the ability to handle multiple control targets, model predictive control has been widely applied in the symmetry topologies, e.g., electrical drive systems. Predictive current control is penalized by the high current ripples at steady state because only one switching state is employed in every sampling period. Although the current quality can be improved at a low switching frequency by the extension of the prediction horizon, the number of searched switching states will grow exponentially. To tackle the aforementioned issue, a fast quadratic programming solver is proposed for multistep predictive current control in this article. First, the predictive current control is described as a quadratic programming problem, in which the objective function is rearranged based on the current derivatives. To avoid the exhaustive search, two vectors close to the reference derivative are preselected in every prediction horizon. Therefore, the number of searched switching states is significantly reduced. Experimental results validate that the predictive current control with a prediction horizon of 5 can achieve an excellent control performance at both steady state and transient state while the computational time is low. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Ítem Power-frequency admittance model of multi-VSGs grid-connected system considering power coupling(Elsevier Ltd, 2024-01) Long, Bo; Yang, Wandi; Zhu, Shihan; Tianxu, Cao; Guerrero, Josep M.; Rodríguez, José; Zang, XianThe high penetration of renewable energy decreases the inertia of power systems. The virtual synchronous generator (VSG) control technology has good inertia compensation effect and has attracted considerable attention because of the similar external characteristics of synchronous generators. However, the power and frequency oscillation of multi-VSG grid-connected systems seriously threatens the stability of power system. Existing multi-VSG power frequency admittance (PFA) models ignore the power coupling caused by the large line impedance ratio in medium- and low-voltage microgrids, and the accuracy of these models needs improvement. Thus, this study aims to establish a multi-VSG grid-connected PFA model considering power coupling. The influence of power coupling on model accuracy is analyzed, and the impacts of line impedance and reactive loop coefficient on the power-frequency response characteristics are investigated. Simulation results verify that the proposed model has higher accuracy over existing models. © 2023 The Author(s)