Javier Muñoz

With the rapid global expansion of wind energy and increasing deployment of large offshore turbines, achieving reliable sensorless control of wind energy conversion systems (WECSs) has become increasingly important. This paper presents a comprehensive review of modern sensorless control techniques for the doubly fed induction generator (DFIG), which is a dominant technology in variable-speed WECSs. This review focuses on control strategies and rotor speed and position estimation techniques, covering their theoretical foundations, operational characteristics, and emerging research trends. In addition, sensorless operations of the DFIG beyond power generation, including grid synchronisation and stand-alone operation, are presented, providing a foundation for future research in the field.

The integration of batteries and supercapacitors in a photovoltaic (PV) system using a multiport dc-dc converter is an attractive solution compared to conventional configurations with multiple two-port dc-dc converters. However, the high-order, cross-coupled, and multivariable nature of most multiport converters poses significant control design challenges. This paper proposes a digital control strategy based on state feedback, decouplers, and PI controllers to efficiently regulate a four-port dc-dc converter topology that connects a photovoltaic module, a battery, a supercapacitor, and a load. The proposed approach achieves reduced settling times for PV and load voltages and battery and supercapacitor currents, minimizing overshoots and undershoots. Experimental results also demonstrate smooth transitions between modes, highlighting the ability of the system to simultaneously perform MPPT, regulate charge and discharge currents, and maintain stable voltage control at load. With settling times for reference changes of less than 20 ms for all controlled variables and a cross-coupling deviation of less than 2% between PV and load voltages, the proposed control strategy ensures robust and stable operation in all operating modes studied.

Background Wearable technologies focused on maintaining strength in older people are limited. A low-cost smart legging for daily use was developed, designed to stimulate the lower limbs through focal muscle vibration. The objective was to determine the effect of Myoviber® Smart Leggings with focal muscle vibration devices (MSLv) on knee extensor muscle strength in older people. The effect on participants with or without frailty was also determined. Methods Randomized, controlled experimental design. Healthy older people from the community (sample size analyzed, n = 52), distributed in an experimental group (EG, n = 29; 69 ± 4 years) treated with MSLv and a control group (CG, n = 23; 69 ± 4 years) treated with sham MSLv. Both groups used the respective MSLv at home for 30 days, for three continuous hours. Three 10 min doses of MSLv were administered along with the activities of daily living guide. Knee extensor strength was measured with a transducer before and after the intervention. Data were analyzed with two-way ANOVA and Bonferroni post hoc test. Results Muscle strength increased in both groups post-intervention, with a significant relative increase in the EG (p < 0.01) but not in the CG (p = 0.225). Participants classified as having pre-frailty or frailty conditions in the EG showed greater strength gains than their counterparts in the CG (p < 0.05). Conclusion The use of MSLv increases knee extensor muscle strength in older people, particularly those with pre-frailty or frailty conditions. MSLv is an innovative, practical solution that integrates health technologies for older adults.

The advantage of multiport dc-dc converters over a configuration of several two-port dc-dc converters with a common dc bus is the reduction in the number of components. However, certain multiport dc-dc converter topologies still present significant challenges, such as cross-coupling. This article introduces a two-stage system composed of a dual-input single-output dc-dc converter for dual MPPT, linked with a single-phase full-bridge inverter for grid integration. The mathematical model and digital control strategy based on state variable feedback and decoupler are presented to regulate the voltages of the photovoltaic modules. The results show a maximum deviation of voltage v_pv1 of 2.47% when there are variations of 6 V in the reference voltage in v_pv2 and a maximum deviation of voltage v_pv2 of 6.7% when there are variations of 4 V in the reference voltage in v_pv1. These outstanding results enable independent and flexible MPPT algorithms to operate stably under different environmental conditions. With respect to the experimental results, they show that the proposal can operate independent MPPT algorithms between two PV modules with reduced cross-coupling, and it is also possible to regulate the dc-link voltage and the grid current under different conditions.

The objective of this work is to analyze and compare AC microgrid (ACMG) solutions to introduce the topic to new researchers. The methodology used to achieve this goal is a systematic literature review using five questions: (1) How have ACMGs evolved in five years? (2) What are the standards for ACMGs? (3) What are the different schemes for connecting MGs to the utility grid? (4) What are the different control schemes in ACMGs? (5) What is an appropriate way to compare results when working with ACMGs? The articles were published in Q1/Q2 journals as based on either the Scimago Journal Rank (SJR) and/or the Journal Citation Report (JCR) between 2018 and 2022 and were from three databases: (1) Web of Science (WoS), (2) Scopus, and (3) IEEE Xplore. Publications not describing pure ACMGs, review papers, publications not related to the questions, and papers describing work that did not meet a quality assessment were excluded, resulting in 34 articles being included in this review. Results show: (1) the energy sources and AC bus nature of microgrids over five years, (2) the identification and quantification of cited standards for microgrids, (3) the pros and cons of different schemes for connecting an AC microgrid to the main grid, (4) the control schemes, classified in a hierarchical control structure, and (5) the simulation tools and experimental benches used in microgrids. Most studies considered a generic energy source and a low-voltage three-phase AC bus, 16 standards were found, and the most cited standard was IEEE Standard 1547. The most common connection scheme to the utility grid was a direct connection, most of the works proposed a modification to a hierarchical control system scheme, and the most common simulation tool was MATLAB. The preferred experimental setup consisted of parallel inverters for testing a control scheme, a prototype when proposing a power electronic system, and a laboratory microgrid for testing fault detection methods.