Abstract
In this study, a comparison of five topologies of active AC/DC conversion chain rectifiers is performed. The purpose of this work is to investigate the implementation of these topologies in the context of an electrolyzer system. The main purpose is to help identify the eventual advantages of active rectifiers. The studies under consideration provide an appreciation of typical three-phase two-level PWM rectifiers and three-phase Vienna rectifiers with an additional stage based on buck DC-DC conversion, for electrolyzer application. The comparative analysis is based on the following metrics: the current ripple, the power factor, the total harmonic distortion, the active switch utilization ratio, and the complexity of the solution. A Simulink model corresponding to each topology was developed to obtain the performance values for the comparison. The procedure involved conducting a steady-state analysis of each topology through simulations to obtain the main waveforms and the values for each criterion. The scores for each technical solution were then calculated. The solution based on the Vienna 3-switch rectifier presented the best results overall.

Abstract
This paper presents a current estimation approach for four-phase Switched Reluctance Machines (SRMs) using only two current sensors. The power converter structure under consideration is an asymmetric half-bridge topology in which the upper switch is shared by two phases, resulting in a reduced number of measurable current paths. Two current estimation methods are developed and compared in a simulation environment. Both techniques aim to reconstruct the instantaneous phase currents to enable advanced torque and flux control strategies without the need for individual current sensors on each phase. The effectiveness of each method is validated through Matlab/Simulink simulations, and their performance is assessed under different operating scenarios.

Abstract
The polarization curve characteristics of proton exchange membrane (PEM) hydrogen electrolyzers lead to large variations in the equivalent load impedance over the operating current range. This results in a varying closed-loop system time response when traditional fixed-gain PI controllers are employed. In this work, the design and experimental validation of a 3-phase interleaved buck converter controlled via a proposed adaptive lead-lag current control strategy for a PEM hydrogen electrolyzer load is presented. The incremental load conductance method is used to obtain a control-oriented model of the converter-electrolyzer system, enabling real-time calculation of controller parameters via pole-zero cancellation and user-specified transient performance. A laboratory prototype is implemented to experimentally verify the approach under step-load changes, ramp-load changes, and 50% input voltage sag conditions. The results show less than 1% current ripple, identical transient performance over the entire operating range, and improved disturbance ride-through performance compared to a traditional PI controller. The proposed approach offers a viable and robust control solution for high-current PEM electrolyzer applications.