Artículos (Ingeniería Electrónica)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11357

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Decoupling Patrolling Tasks for Water Quality Monitoring: A Multi-Agent Deep Reinforcement Learning Approach
(IEEE, 2024) Seck Diop, Dame; Yanes Luis, Samuel; Perales Esteve, Manuel Ángel; Toral, S. L.; Gutiérrez Reina, Daniel; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE)
This study proposes the use of an Autonomous Surface Vehicle (ASV) fleet with water quality sensors for efficient patrolling to monitor water resource pollution. This is formulated as a Patrolling Problem, which consists of planning and executing efficient routes to continuously monitor a given area. When patrolling Lake Ypacaraí with ASVs, the scenario transforms into a Partially Observable Markov Game (POMG) due to unknown pollution levels. Given the computational complexity, a Multi-Agent Deep Reinforcement Learning (MADRL) approach is adopted, with a common policy for homogeneous agents. A consensus algorithm assists in collision avoidance and coordination. The work introduces exploration and reinforcement phases to the patrolling problem. The Exploration Phase aims at homogeneous map coverage, while the Intensification Phase prioritizes high polluted areas. The innovative introduction of a transition variable, ν, efficiently controls the transition from exploration to intensification. Results demonstrate the superiority of the method, which outperforms a Single-Phase (trained on a single task) Deep Q-Network (DQN) by an average of 17% on the intensification task. The proposed multitask learning approach with parameter sharing, coupled with DQN training, outperforms Task-Specific DQN (two DQNs trained on separate tasks) by 6% in exploration and 13% in intensification. It also outperforms the heuristic-based Lawn Mower Path Planner (LMPP) and Random Wanderer Path Planner (RWPP) algorithms, by 35% and 20% on average respectively. Additionally, it outperforms a Particle Swarm Optimization-based Path Planner (PSOPP) by an average of 26%. The algorithm demonstrates adaptability in unforeseen scenarios, giving users flexibility in configuration.
Variational model-based Deep Reinforcement Learning for Non-Homogeneous Patrolling aquatic environments with multiple unmanned surface vehicles
(Elsevier, 2025-04-25) Yanes Luis, Samuel; Basilico, Nicola; Antonazzi, Michele; Gutiérrez Reina, Daniel; Toral, S. L.; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC201: ACE-TI
This paper addresses the challenge of Non-Homogeneous Patrolling for Autonomous Surface Vehicles in non-homogeneous importance water environments with a dissimilar biological monitorization criterion. Traditional monitoring methods fail, especially in expansive areas such as Lake Ypacaraíin Paraguay. The proposed solution employs a cooperative Deep Reinforcement Learning framework, specifically a multi-agent version of the Double Deep Q-Learning algorithm based on safe-consensus decision making. This framework optimizes adaptive policies for such vehicles by simultaneously modeling the environment and patrolling high-importance zones. The incorporation of a Variational Auto-Encoder based on the U-Network architecture directly addresses the non-observability of the environment by predicting biological importance from partial observations. The methodology is validated in a realistic algae bloom contamination scenario, demonstrating superior performance and computational efficiency compared to traditional approaches like Gaussian Processes and K-Nearest-Neighbors. The Deep Reinforcement Learning framework, coupled with the Variational Auto-Encoder model, showcases flexibility and efficiency in addressing multi-agent cooperation and long-term objective optimization for water quality monitoring. The results reveal significant improvements, with the proposed model exceeding well-founded approaches with a 30% faster minimization of the patrolling score compared to these methods.
Cascade Control of Grid-Connected NPC Converters Via Sliding Mode Technique
(Institute of Electrical and Electronics Engineers, 2023-02) Shen, Xiaoning; Liu, Jianxing; Lin, Hao; Yin, Yunfei; Márquez Alcaide, Abraham; León Galván, José Ignacio; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
This paper proposes a two-stage control strategy including an adaptive sliding mode control (ASMC) and a nonlinear high-gain observer (HGO) for the three-level neutral-point-clamped (NPC) converter in dc microgrids. In the outer loop, an ASMC is utilized to regulate the dc-link voltage. By introducing an adapted gain, the tradeoff between the chattering and dynamic performance of the classic sliding mode control is overcome, thus the transient response of the NPC converter can be further enhanced without increasing the chattering. In addition, a nonlinear HGO is cooperated with the ASMC method to reject exogenous disturbance for the NPC converter, which not only assures a high disturbance rejection capacity but also accommodates the inevitable measurement noise in the actual applications. For the inner loop, in consideration of the parameter uncertainty, a high-gain observer-based second-order sliding mode (SOSM) control is adopted to assure the steady state performance and the robustness of the NPC converter. Finally, a set of comparative experimental results confirm the effectiveness and superiority of the proposed control scheme implemented in the NPC converter. Additionally, the robustness under parameter variation of the proposed method is also validated.
Towards a Retrieval-Augmented Generation Framework for Originality Evaluation in Projects-Based Learning Classrooms
(MDPI, 2025-06) Yanes Luis, Samuel; Gutiérrez Reina, Daniel; Toral, S. L.; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Junta de Andalucía; Universidad de Sevilla. TIC201: ACE-TI
Project-Based Learning is central to modern engineering education, but assessing the originality of student work poses significant challenges, particularly when previous project repositories are accessible. This paper addresses the issue by proposing a framework based on Retrieval-Augmented Generation and Large Language Models to evaluate the originality of project proposals in the context of a master’s course in Electronic Engineering. The system processes and summarizes prior work—including reports, code, and presentations—creating a semantically indexed knowledge base. Upon receiving a new proposal, the RAG system compares it to this base, identifies the most similar previous works, and generates an originality assessment. Results show the effectiveness of the approach, with a strong correlation (coefficient of 0.87) between the originality scores assigned by the system and those given by expert instructors in a blind evaluation. The proposed RAG system demonstrates its ability to systematically detect similarities and potential lack of originality that might be overlooked by human evaluators due to the volume of prior work. This framework provides an objective and efficient tool to support originality assessment, benefiting both instructors and students by promoting genuine innovation in PBL settings.
Computational Analysis of the Long Horizon FCS-MPC Problem for Power Converters
(Institute of Electrical and Electronics Engineers, 2024-06) Zafra, Eduardo; Vázquez Pérez, Sergio; Geyer, Tobías; Aguilera, Ricardo P.; Freire Macías, Emilio; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. Departamento de Matemática Aplicada II (ETSI); Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TIC109: Tecnología
Long prediction horizon finite control set model predictive control (LPH-FCS-MPC) for power converters can be reformulated as a box-constrained integer-least squares (ILS) problem to find the optimal control action without requiring an exhaustive search. Instead, the solution can be found by means of a sphere decoding method that still presents several intricacies regarding its complexity and its variable computational cost. This article provides a study of the computational behavior of this approach. Special emphasis is placed on how the generator matrix is calculated, either as a lower or an upper triangular structure. This choice decides whether the switching sequences are explored forward- or backward-in-time during the optimization process. In this work, it is explained how this selection holds a great impact on the computational burden of the algorithm. Similarly, it is also analyzed how the tuning of the FCS-MPC and system parameters also drastically impacts the computational cost.
Common DC-link Capacitor Lifetime Extension in Modular dc/dc Converters for Electric Vehicle Fast Chargers via Variable-Angle Interleaved Operation
(Institute of Electrical and Electronics Engineers, 2022-12) Márquez Alcaide, Abraham; Guenter, Sandro; León Galván, José Ignacio; Buticchi, Giampaolo; Kouro, Samir; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TIC109: Tecnología
The global shift toward the electrified transportation as a means of achieving decarbonized economy has led to an increase in the demand of electric vehicles. In order to enhance the transition, there is a need to develop fast and ultrafast charging substations. Hence, power converters play an inherently vital role in the mass adoption of electric vehicles. However, the reliability and active maintenance scheduling of these converters are becoming prominent issues for manufacturers and operators. As a result, optimization of the operation of an interleaved dc/dc converter present in the charging poles plays a significant role. This article proposes an alternative modulation technique for interleaved dc/dc power converters of fast chargers aiming to improve the harmonic performance of the common dc-link capacitor current. This technique leads to an extension of lifetime of the capacitor, which is one of the most critical component of the power system. Experimental results are shown in order to validate the effectiveness of the proposed method.
Capacitor Lifetime Extension of Interleaved dc-dc Converters for Multi-String PV Systems
(Institute of Electrical and Electronics Engineers, 2022-07) Márquez Alcaide, Abraham; Ko, Youngjong; Andresen, Markus; León Galván, José Ignacio; Vázquez Pérez, Sergio; Monopoli, Vito Giuseppe; Buticchi, Giampaolo; Liserre, Marco; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TIC109: Tecnología
Interleaved dc–dc converters are being vastly applied for a wide range of applications. Inherent power sharing between the power modules and reduction of the output waveforms ripple are the main advantages of these power systems. However, in some cases, such as the multistring photovoltaic converters, each power module manages different power, leading to an unbalanced operation of the interleaved converters. In this case, the harmonic response of the conventional interleaving operation is degraded. This fact affects directly the expected lifetime of the dc-link capacitor of the power converter, which is one critical components of the system. In this article, a variable-angle phase displacement angle is proposed in order to mitigate this problem, achieving an extension of the converter lifetime.
Generalized Multi-Carrier PWM Technique for Two-level Voltage Source Inverters
(Institute of Electrical and Electronics Engineers, 2022-07) Márquez Alcaide, Abraham; Monopoli, Vito Giuseppe; Zafra, Eduardo; Buticchi, Giampaolo; León, Galván, José Ignacio; Vázquez Pérez, Sergio; Liserre, Marco; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Ministerio de Ciencias, Innovación y Universidades; Universidad de Sevilla. TIC109: Tecnología
Two-level voltage source inverters are the mainstream solution for many power applications. The conventional modulation method of such inverters is the single-carrier pulsewidth modulation (PWM) technique. In this article, the usage of a generalized PWM method with three independent carriers is analyzed. The carrier phase-displacement angles are evaluated in order to reduce the common-mode voltage (CMV) total harmonic distortion (THD), the dc-link capacitor current THD, and the phase currents THD. These targets are difficult to be met at the same time and a cost function is deployed in order to look for a suitable solution that develops a tradeoff between all the targets. The proposed method has been tested in a laboratory prototype demonstrating its superior performance.
Lifetime Extension Approach Based on Levenberg-Marquardt Neural Network and Power Routing of DC-DC Converters
(Institute of Electrical and Electronics Engineers, 2023-05) Zhang, Jiusi; Tian, Jilun; Marquez Alcaide, Abraham; León Galván, José Ignacio; Vázquez Pérez, Sergio; García Franquelo, Leopoldo; Luo, Hao; Yin, Shen; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
The power conversion system based on the modular connection has widespread applications in various power electronic systems. To accurately estimate the state of health without recognizing the systematic mathematical model and to extend the lifetime, this article proposes a lifetime extension approach based on the Levenberg–Marquardt back propagation neural network (LM-BPNN) and power routing of interleaved dc–dc boost conversion systems. The LM-BPNN model is constructed based on the voltage, current, and temperature data generated by the system. On the basis of the trained LM-BPNN, the real-time cumulated damage estimation of each power cell in the conversion system can be accomplished. Applying the power routing concept, the dc–dc boost conversion system allocates different power to the cells according to the cumulated damage of each cell, thereby delaying the failure of cells with higher cumulated damage. Numerical simulation results show that the proposed lifetime extension approach can extend the overall system lifetime. Furthermore, an experimental setup of the interleaved dc–dc boost conversion is constructed to verify the proposed approach, which is of great significance for predictive maintenance in the industrial system.
An Artificial Intelligence Approach for Real-Time Tuning of Weighting Factors in FCS-MPC for Power Converters
(Institute of Electrical and Electronics Engineers, 2021-12) Vázquez Pérez, Sergio; Marino, Daniel; Zafra, Eduardo; Valdés Peña, María Dolores; Rodríguez-Andina, Juan J.; García Franquelo, Leopoldo; Manic, Milos; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TIC109: Tecnología
In this paper a finite control set model predic- tive control is used to track a current reference in a power converter connected to an RL load. An artificial intelligence (AI) approach is presented for real-time determination of the weighting factor that regulates the average switching frequency, independently of the operating point. The paper focuses on the design, training, and digital implementation of an artificial neural network (ANN) that can be developed in a low-cost control platform. It is presented a sampling and offline ANN training procedure, together with a low- cost hardware implementation based on integer quantiza- tion of the ANN. The above approach provides a standalone application, serving as a framework for development of ANN applications for power-converters. The main advan- tage of the presented approach is that the ANN inference is executed in real-time. In this way, the weighting factor is automatically updated in real-time, allowing the system to quickly adapt to any reference step changes, and conse- quently provide the desired behavior. Executing the setup in laboratory prototype confirmed the theoretical analysis and successful tracking of the reference frequency
Period Control Approach FCS-MPC Switching Phase Control for Interleaved DC/DC Converters
(Institute of Electrical and Electronics Engineers, 2023-11) Aguirre, Matías; Vázquez Pérez, Sergio; Márquez Alcaide, Abraham; Portillo Guisado, Ramón Carlos; Kouro, Samir; León Galván, José Ignacio; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TIC109: Tecnología
The control of interleaved converters is commonly implemented through pulsewith modulation (PWM) techniques. A common element in these implementations is the use of phase shift between carriers to improve the system performance. When working with a balanced system, this phase shift is equally distributed between modules, but for an unbalanced system, this is no longer the best alternative. Changing the phase shift in these controllers requires the implementation of new capabilities in the control platforms, and for the controller to manage more variables of different nature. On the other hand, finite control set model predictive control (FCS-MPC) has shown to be a promising control strategy, especially when managing multiple control objectives of different natures or dynamics. In general, FCS-MPC does not present a fixed switching pattern, but this issue has been recently addressed with the so called period control approach (PCA). This article expands on the PCA-FCS-MPC to achieve the switching phase regulation for interleaved dc/dc power converters. A switching pattern similar to that of PWM techniques is achieved, while keeping the advantages of FCS-MPC and achieving the phase shift required for interleaved operation. Simulation and experimental results confirm the effectiveness of the proposed method.
Hybrid Sphere Decoder for Long Prediction Horizon FCS-MPC
(Institute of Electrical and Electronics Engineers, 2022-08) Zafra, Eduardo; Vázquez Pérez, Sergio; Márquez Alcaide, Abraham; Pérez Martín, Emilia; García Franquelo, Leopoldo; León Galván, José Ignacio; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TIC109: Tecnología
In finite control set model predictive control strategies, extending the prediction horizon length provides important closed-loop performance improvements. However, the computational costs are increased in exponential fashion. Transforming the problem to an equivalent box-constrained integer least-squares formulation enables the usage of sphere decoding algorithms (SDA) that can efficiently solve this problem. Recently, a K-best sphere decoder was proposed and designed for hardware platforms. This algorithm follows a breadth-first strategy different to the conventional SDA. In this work, a hybrid SDA that combines the merits of both the K-best SDA and the conventional SDA is proposed with the objective of increasing optimality likelihood and improve control performance. In particular, it is proposed that a K-best sphere decoder delivers a preliminary optimal solution. Then, a conventional SDA uses the available calculation time to search for a better solution. Simulation and experimental results confirm the validity of the proposal in terms of performance and computational efficiency.
A Furtherance of High-Power Adjustable Speed Drive System
(Institute of Electrical and Electronics Engineers, 2022-11) Deng, Fujin; Hou, Jiehua; Zhang, Yue; Cheng, Ming; Hu, Yihua; Vázquez Pérez, Sergio; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
The high-power machine drive system is the power heart of the modern power industry, which has been used in a broad range of industry applications. Extensive research and development efforts have been carried out on the design and implementation of high-power machine drive systems. In this article, various converter topologies and research progress for high-power machine drive systems are reviewed. And a novel medium-frequency ac link powered machine drive system is analyzed and discussed for a furtherance of high-power adjustable speed drive systems. In addition, some prospects for future research are highlighted to provide a feasible reference for practitioner
Discontinuous PWM Technique with Reduced Low-order Harmonic Distortion for High-Power Applications
(Institute of Electrical and Electronics Engineers, 2023-10) Balenciaga, Jon Xabier; Márquez Alcaide, Abraham; León Galván, José Ignacio; Aldazabal, Eritz; Madariaga, Danel; Legarra, Iraitz; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Universidad de Sevilla. TIC109: Tecnología
The modulation techniques used in high power applications have to generate high quality waveforms with reduced switching losses. As an attractive alternative, discontinuous PWM (DPWM) techniques present lower device switching frequencies than conventional continuous PWM methods lowering the converter switching loss. Considering the same cooling system, this allows to increase the carrier frequency of DPWM methods displacing the main switching harmonics to higher frequencies. As a main drawback, when low carrier to fundamental ratios are used, DPWM methods present some undesired low-order harmonics that are required to be filtered. This article presents a low-order harmonic minimization method for synchronous DPWM methods by modifying the conventional modulating reference to limit low order harmonics amplitude, while keeping the same effective switching frequency and thus limited switching losses.
A Novel Continuous Control Set Model Predictive Control for LC-Filtered Three-phase Four-wire Three-level Voltage-Source Inverter
(2023-01) Yang, Yong; Xiao, Yang; Fan, Mingdi; Wang, Kaixin; Zhang, Xinan; Hu, Jiefeng; Zeng, Weibo; Vázquez Pérez, Sergio; Rodríguez, José; Universidad de Sevilla. Departamento de Ingeniería Electrónica; European Union (UE); Universidad de Sevilla. TIC109: Tecnología
In this paper, a novel continuous control set Model predictive control (CCS-MPC) is proposed for an LC-filtered three-phase three-level four-wire voltage-source inverter (3P- 4W-3L-VSI). The proposed MPC algorithm provides independent control of each phase of the 3P-4W -3L-VSI under various unbalanced load conditions, which shows superior performance under unbalanced loads. Furthermore, different from conventional MPC methods, the CCS-MPC achieves fixed switching frequency (FSF), hence simplifying the design of LC filters. In addition，dc offsets are introduced to the proposed modulation to effectively balance the neutral-point (NP) voltage of the 3P-4W-3L-VSI. Experimental r
Low Computational Burden Model Predictive Control for Single-Phase Cascaded H-Bridge Converters Without Weighting Factor
(Institute of Electrical and Electronics Engineers, 2022-04) He, Tingting; Wu, Mingli; Aguilera, Ricardo P.; Dah-Chuang Lu, Dylan; Liu, Qiujiang; Vázquez Pérez, Sergio; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
In this article, a low computational burden model predictive control (MPC) strategy without weighting factor is proposed for the single-phase cascaded H-bridge CHB converters. To reduce the switching state candidates, a hierarchy control algorithm is proposed. The grid current is controlled by selecting a subregion from the designed 2-D control plane, instead of the entire area. Two vectors are chosen in one sampling period for more accurate tracking. Then, the voltage balancing is achieved by selecting the optimal switching state from the subregion candidates to form the above two vectors. The cost function can be constructed of one variable: load voltage. Therefore, the weighting factor can be eliminated. No tuning or retuning processes are required in the proposed method. To reduce the computational time further, the principle of eliminating the switching state candidates operating the same voltage balancing performance is proposed. Conventional and proposed MPC methods are verified by experimental tests via a laboratory setup of a three-cell connected CHB converter. Steady-state and transient operations demonstrate that the proposed method guarantees less distortion grid current and shorter execution time (reduced from 15 to 3 μs). Fast response speed to variations in voltage reference and load resistance can be achieved t.
A Hybrid Modulation Technique for Operating Medium-Voltage High-Power CHB Converters Under Grid Voltage Disturbances
(2023-02) Monopoli, Vito Giuseppe; Marquez Alcaide, Abraham; Bruno, Lara; Rendine, Giuseppe; León Galván, José Ignacio; Liserre, Marco; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TIC109: Tecnología
Power converters, and particularly multilevel converters, are key elements in the current energy scenario. Among them, cascaded H-bridge converters are a popular and versatile solution for many industrial applications. Technical literature provides multiple modulation techniques for its operation. Among them, hybrid pulsewidth modulation techniques provide a good tradeoff between switching loss and output voltage quality. In this article, a hybrid modulation technique is presented, which allows not only the fundamental block switching operation of some power cells but also a harmonic control over a specific harmonic distortion present in the grid. To validate the operation of the proposal, several experimental results have been reported to demonstrate the good behavior of the proposed modulation technique.
Extremely Low Frequency PS-PWM-based Technique for Cascaded H-Bridge Converters with Grid Voltage Compensation Capability
(2023-05) Marquez Alcaide, Abraham; Monopoli, Vito Giuseppe; Bruno, Lara; León Galván, José Ignacio; Liserre, Marco; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Universidad de Sevilla. TIC109: Tecnología
Cascaded H-Bridge Converters (CHB) are good can- didates for many industrial applications. Among the modulation techniques that can be applied to CHB converters, the Phase- shifted PWM method (PS-PWM) provides very good harmonic quality being the most popular modulation technique at the expense of presenting high switching losses. On the contrary Block Switching technique as well as Selective Harmonic elimina- tion/mitigation (SHE/SHM) techniques provides lower switching frequency and losses with a lower harmonic quality. Additionally with these techniques the converter operation becomes stiff. In this work a modification of PS-PWM based on an extremely low frequency carrier is proposed with the objective of achieving both low switching losses and an acceptable harmonic quality, simultaneously. The main advantage of the proposed solution is the capability of adjusting the phase-shift angle among the carriers to compensate for harmonic grid voltage disturbance. Several experimental results have been reported to demonstrate the good performance of the proposed modulation technique
Alternate Search Pattern for Parallel Sphere Decoder in Long Prediction Horizon FCS-MPC
(Institute of Electrical and Electronics Engineers, 2023-09) Zafra, Eduardo; Vázquez Pérez, Sergio; Márquez Alcaide, Abraham; León Galván, José Ignacio; García Franquelo, Leopoldo; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
The sphere decoding algorithm (SDA) is used in power electronics as a solver of the optimization stage for long prediction horizon finite control set model predictive control (LPH-FCS-MPC). In the literature, a parallel SDA was proposed to enable concurrent search. This strategy increases the number of candidates explored per time, improving the likelihood of finding the optimal solution in real time. In this work, an alternate search pattern for the parallel SDA is proposed. The main idea is that each parallel sphere decoder block explores a region of the search space following a different search pattern, increasing diversification of candidates before a solution has to be delivered. This approach improves the average optimality of parallel SDA, which in turns enhances the control performance.
An Improved Indirect Pulsewidth Modulation Technique for Modular Multilevel Converters
(Institute of Electrical and Electronics Engineers, 2024-01) Yin, Jiapeng; Dai, NingYi; Vázquez Pérez, Sergio; Márquez Alcaide, Abraham; León Galván, José Ignacio; Pérez, Marcelo A.; Universidad de Sevilla. Departamento de Ingeniería Electrónica; Universidad de Sevilla. TIC109: Tecnología
For a modular multilevel converter (MMC) operating in the medium-voltage range, carrier-based pulsewidth modulation (PWM) methods are good options for modulating the converter, as harmonic contents of the phase voltage/current can be centered around the carrier frequency and/or its multiples. However, in the relevant literature, arm voltage references are mostly normalized by the submodule (SM) capacitor voltage reference, leading to the so-called direct modulation, while the indirect modulation considering the capacitor voltage ripples receives much less attention. This article investigates the indirect modulation of MMCs, focusing on a specific PWM method where only two SMs per phase operate in PWM mode in each control period. It is found that the direct PWM (DiPWM) generates phase voltages/currents that contain high-amplitude low-order harmonics, while the indirect PWM (IndiPWM) presents well-suppressed low-order harmonics but significant distortions around the carrier frequency. The cause of the above problem of the IndiPWM is revealed theoretically through Fourier analysis, and a solution with simple implementation is developed by rearranging the switching pulses of the PWM-mode SMs. Both simulations and experiments are carried out. The results show that the proposed method combines the advantages of both DiPWM and IndiPWM, achieving low harmonic distortions simultaneously in the low frequency and around the carrier frequency.

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