This paper extends the concept of using dynamic braking resistors (DBRs) in series with the stator of doubly-fed induction generators (DFIGs) to improve low-voltage ride-through (LVRT) performance, specifically under asymmetrical grid faults. Although previous studies have demonstrated the effectiveness of fixed or discrete-valued DBRs in mitigating electrical transients, mechanical issues such as torque loss remain mostly underexplored. In this work, we leverage independent control of the resistance in each stator phase by means of pulse-width modulation to maintain generator torque and cancel the negative sequence component of the grid voltage. By shaping the DBR voltage drop through asymmetric resistances, the resulting negative sequence voltage opposes that of the grid, reducing torque oscillations and enabling more stable DFIG operation during unbalanced faults. Analytical derivations and simulation results validate the proposed control strategy., This work is part of the Projects PID2022-142791OB-I00 and TED2021-132604B-I00, funded by MICIU/AEI /10.13039/501100011033, by ERDF/UE and by the European Union NextGeneration EU/PRTR and supported by the Student Grant Competition of the Czech Technical University in Prague under Grant SGS25/140/OHK3/3T/13.

Thyristor rectifiers are currently the most common solution for supplying high-power electrolyzers. These rectifiers typically include a dc inductance, which significantly increases system costs. However, this inductance can be avoided by relying solely on ac-side inductances, required for grid current harmonic filtering, although this approach introduces specific challenges. Traditional analytical models of thyristor rectifiers are unable to determine the electrolyzer operating point for a given firing angle and may lead to incorrect system sizing, ultimately preventing the converter from delivering nominal power. This limitation arises from the fact that existing models are formulated for inductive or constant-current loads, whereas electrolyzers exhibit electrical behavior closer to constant-voltage loads. In this paper, a novel analytical model of 6- and 12-pulse thyristor rectifiers with constant-voltage load is developed. The model enables the analysis and optimal sizing of thyristor rectifiers directly connected to electrolyzers without a dc-side inductance. Its accuracy has been validated through both simulations and experimentally using a laboratory-scale prototype. Furthermore, the model has been applied to optimally size a 12-pulse rectifier supplying a 5.5 MW electrolyzer, demonstrating its suitability for the design of thyristor rectifier systems in industrial-scale electrolysis applications and highlighting its advantages over traditional approaches., This work is part of the projects PID2022-142791OB-I00 and PID2022-139914OB-I00 funded by MICIU/AEI/10.13039/501100011033 and by "ERDF/EU", and has also been supported by the Public University of Navarra under a Ph.D. scholarship.

To ensure the stability of modern power grids, particularly those dominated by power electronics, it is convenient for grid-connected converters to exhibit
passivity across the entire frequency spectrum. Furthermore, it is interesting not only for the system to be passive, that is, for the converter system's resistance to be positive, but also for this resistance to have a high value, as it helps dampen potential grid resonances. This article presents a
study of a grid-connected converter, achieving passivity and increasing the converter's resistance through control strategies. Given the growing use of Selective Harmonic Elimination (SHE) modulation techniques in high-power converters, the analysis will also focus on how to assess the passivity of a system employing these modulation techniques., This work is part of the Projects PID2022-142791OB-I00 and TED2021-132604B-I00, funded by MICIU/AEI/10.13039/501100011033, by ERDF/UE and by the European Union NextGenerationEU/PRTR. It has also been partially supported by Ingeteam Power Technology and the Public University of Navarre.

This paper presents an active damping strategy to mitigate resonances in offshore wind farms caused by the parasitic capacitance of submarine cables, which challenge system stability and grid code compliance. The proposed method emulates a virtual impedance damping the wide range of resonances that appear in offshore wind farms, depending on its configuration and number of turbines connected. Its effectiveness is evaluated for two modulation techniques: PWM and selective harmonic elimination PWM. PWM generates predictable harmonic content outside the resonance range, enabling robust
damping of resonances. In contrast, selective harmonic elimination PWM¿though optimized to eliminate the harmonics in the resonance frequency range¿introduces distortion in this range due to modulation-control interactions in closed-loop operation. This distortion demands excessive corrective action from the AD, limiting its practicality. The strategy and its results are validated through simulation., This work is part of the project PID2022-142791OB-I00 and TED2021-132604B-I00, funded by MCIN/AEI/10.13039/501100011033, by the FSE+, by ERDF/UE and by the European Union NextGenerationEU/PRTR. The authors want to acknowledge Ingeteam Power Technology for its financial and ongoing support.

This article proposes a novel approach to enhancing
the low-voltage ride-through capability of doubly-fed induction
generator wind turbines using a dynamically modulated braking resistor (DBR) connected in series with the stator windings.
Unlike conventional DBR-based methods that focus primarily on
mitigating electrical transients, the proposed approach emphasizes
maintaining the generator’s electromagnetic torque at its prefault
level during grid voltage dips. The DBR resistance is calculated in
real time based on analytical expressions derived from the system’s
model. By properly selecting the DBR resistance during the fault,
the excess mechanical power that cannot be transferred to the
grid is dissipated within the resistor, allowing the generator torque
to remain constant during the fault, which helps maintain rotor
speed and mitigate electrical transients. The proposed strategy is
validated through both simulation and experimental results under
symmetrical fault conditions, demonstrating superior torque stability, reduced current transients, and improved postfault recovery
compared to fixed-resistance DBR schemes., This work is part of the Projects PID2022-142791OB-I00 and TED2021-132604B-I00, funded by MICIU/AEI /10.13039/501100011033, by ERDF/UE and by the European Union NextGenerationEU/PRTR.

Due to their single-stage step-down nature, current source rectifiers (CSR) constitute attractive options for supplying high-power electrolyzers. To increase system power rating, parallel configurations can be adopted with interleaved Pulse Width Modulation (PWM) techniques that improve power quality and reduce the size of filtering elements. Optimal design of the output dc inductance is crucial to achieve cost-effective and competitive solutions. However, common design methods for one single CSR do not achieve optimal designs. There are hardly any specific design methods for interleaved CSRs either. This paper analyzes the operation of parallel interleaved CSRs supplying high-power electrolyzers and develops a methodology to optimally size the output dc inductances. In addition, a common mode equivalent circuit is developed to analyze the circulating currents caused by the interleaved operation and calculate the ripple in the inductances. When applied to a 3 MW electrolyzer, the results show that inductance size reductions of up to 69% can be obtained with the proposed methodology., This work is part of the project PID2022-142791OB-I00, funded by MCIN/AEI/10.13039/501100011033/ and by 'A way of making Europe'. It has also been supported by Ingeteam Power Technology. The authors also thank the Agencia Nacional de Investigación y Desarrollo (ANID) FONDECYT Regular grant number 1220556, the Research Project PINV01-743 of the Consejo Nacional de Ciencia y Tecnología (CONACYT), ENNOBLE-R02401, and IRCF 24932270 project from the University of Nottingham.

This paper investigates the impact of power supply and dc current ripple on the efficiency of water electrolyzers and demonstrates that optimally sized thyristor rectifiers meeting grid power quality regulations can effectively supply high-power electrolyzers with minimal impact on electrolyzer efficiency. Firstly, an equivalent electrical model for the electrolyzer is developed, and the efficiency reduction caused by dc current ripple is analyzed. This is validated by means of experimental data from a 5-kW alkaline electrolyzer operated with both thyristor- and IGBT-based rectifiers. Next, the paper explores the operation of high-power electrolyzers supplied by 6- and 12-pulse thyristor rectifiers complying with grid power quality standards. Results show that with optimal sizing of ac-side source voltage and filtering inductances, these solutions exhibit negligible dc current ripple impact on electrolyzer efficiency. These findings, validated through simulation of a 5.5 MW electrolyzer, highlight the viability of thyristor rectifiers in high-power electrolysis applications, and emphasize the importance of an optimal power supply design and sizing for enhancing water electrolyzers' performance., This work is part of the projects PID2022-142791OB-I00 and PID2022-139914OB-I00 funded by MICIU/AEI/10.13039/501100011033/ and by 'ERDF/EU', and has also been supported by the Public University of Navarra under a Ph.D. scholarship. It has also been supported by Ingeteam Power Technology. The authors also thank the Agencia Nacional de Investigación y Desarrollo (ANID) FONDECYT Regular grant number 1220556, the Centre for Multidisciplinary Research on Smart and Sustainable Energy Technologies for Sub-Antarctic Regions under Climate Crisis ANID/ATE220023, Fondap SERC 1522A0006 and IRCF 24932270 project from the University of Nottingham.

In power electronics converters, understanding the semiconductor turn-off process is key. During turn-off, the semiconductor withstands the bus voltage plus the overvoltage produced in the parasitic inductances and due to the di/dt in the turn-off. In SiC MOSFET turn-off, this overvoltage is critical since these devices operate with higher di/dt and can be operated with blocking voltage close to their breakdown voltage. In this paper, a simple equation-based procedure that allows for an accurate overvoltage calculation in SiC MOSFET turn-off is presented. The proposed step-by-step procedure is applied to calculate the overvoltage during the turn-off of the SiC module CAB016M12FM3 for different gate resistors and switched currents. This analysis can be used to select the correct value of the gate resistor. The obtained results are validated by comparison with LTspice simulation results., This work is part of the Projects PID2022-142791OB-I00 and TED2021-132604B-I00 funded by MICIU/AEI /10.13039/501100011033, by ERDF/EU and by the European Union NextGenerationEU/PRTR. It has also been supported by Ingeteam Power Technology.

In grid-forming mode (GFM) doubly-fed induction generator based wind turbines connected to the grid, the converter connected to the rotor side is normally responsible for providing the grid-forming characteristics, while the grid-side converter commonly controls the DC-bus voltage thanks to a current control loop implemented in a rotating reference frame. The angle for the rotating reference frame is obtained by means of a phase-locked loop, which synchronizes the converter with the grid. However, this synchronization loop can introduce stability problems in weak grids. This paper proposes to synchronize the grid-side converter by means of the power synchronization loop of the GFM control of the rotor-side converter. This eliminates the need to use of a specific phase-locked loop, improving small-signal stability as demonstrated in the small-signal stability analysis performed in this paper., This work is part of the Projects PID2022-142791OB-I00 and TED2021-132604B-I00, funded by MICIU/AEI /10.13039/501100011033, by ERDF/UE and by the European Union NextGenerationEU/PRTR. It has also been supported by Ingeteam Power Technology.