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ABSTRACT Reliable synchronization is essential for ensuring stability during the transition of microgrids between islanded and grid-connected operation, particularly in converter-dominated low-inertia systems. This paper outlines a small signal analysis for the novel synchronization control of an islanded microgrid comprising two or more parallel-connected voltage source converters. It focuses on the development of simple and effective microgrid synchronization strategies with a minimum Rate of Change of Frequency (ROCOF), enabling the integration of Distributed Energy Resources (DER) into growing low-inertia power systems. The proposed method is based on a rotating reference frame-based algorithm with two Proportional-Integrator (PI) controllers at the secondary control level, minimizing the computational complexity by reducing the number of control loops compared with conventional approaches. A small-signal model has been developed and validated using eigenvalue analysis to ensure stability during the mode transitions. The developed controls were validated on a test setup comprising of a 25 kW Grid-Forming Converter (GFC) and a 25 kW Grid-Following Converter (GFL).

Resumo em Inglês:

ABSTRACT This study presents the modeling and control of a full-bridge DC-DC converter applied to Gas Metal Arc Welding (GMAW) in short-circuit transfer mode. GMAW is widely used in industrial manufacturing due to its versatility. However, achieving stable operation in short-circuit transfer requires precise regulation of the welding current and arc voltage. To address this challenge, a simplified yet representative model of the converter and load dynamics is developed. Based on this model, a dual-loop digital control strategy is implemented to ensure fast transient response, reference tracking, and improved stability of the welding process. The effectiveness of the proposed approach is experimentally validated on an industrial-grade prototype, demonstrating agreement between theoretical predictions and measured waveforms.

Resumo em Inglês:

ABSTRACT Electric vehicles (EVs) demand highly efficient power management systems to enhance reliability and extend operational autonomy. Unlike traditional internal combustion engine (ICE) vehicles, which use alternators to supply low-voltage systems, EVs rely on DC-DC converters, commonly referred to as Auxiliary Power Modules (APMs). This paper presents the analysis, design, and experimental validation of a half-bridge converter with a current-doubler (HB-CD) topology tailored for APM applications. A generalized structure is proposed to support the parallel operation of multiple modules, aiming to mitigate current stress and reduce output ripple. A 3 kW laboratory prototype was implemented using two 1.5 kW modules operating in parallel, enabling interleaved operation and effective current sharing. Experimental results demonstrate the converter’s ability to maintain high efficiency, reaching up to 94.6% under nominal conditions and 95.9% under minimum input voltage operation, confirming the feasibility of the proposed topology for high-current automotive applications.

Resumo em Inglês:

ABSTRACT The growing penetration of Electric Vehicles (EVs) poses new challenges to distribution system operation, particularly regarding peak demand and asset overloading. This paper proposes an optimization model for EV charging profiles based on time-varying and location-sensitive signals derived from the electrical impedance matrix of the distribution network. Building on a previously published tariff-sensitivity framework, this study develops an EV charging optimization model that uses nodal and hourly signals to reflect the marginal impact of current injections on line congestion. The optimization minimizes the total EV charging cost while mitigating adverse grid impacts. Simulation results using the IEEE 123-bus system demonstrate reductions in losses and line loading, as well as cost savings for EV owners. By combining the proposed approach with the existing tariff-sensitivity framework, Distribution System Operators (DSOs) can better align incentives for EV owners, without compromising their charging profiles, and mitigate network issues, thereby supporting the scalable integration of EVs.

Resumo em Inglês:

ABSTRACT Power converters provide energy interface in various applications; in photovoltaics, they interconnect solar panels to the grid, with two-level inverters being the most common across virtually all power ranges, followed by three-level neutral point clamped (3LNPC) converters. The proportional-integral (PI) controller is the most commonly employed controller for these converters. This paper proposes the use of Bayesian Optimization (BO) to tune the PI controller for a 3LNPC converter connected to the grid. The optimization algorithm was used to determine the controller’s tuning gains through computational simulation. Subsequently, the PI controller tuned using BO was implemented on an experimental test bench to validate the concept. The performance of the controller tuned with the proposed method was compared to PI controllers adjusted using classical methods widely found in the literature. The test results demonstrated that Bayesian Optimization is straightforward to implement and, when compared to the Genetic Algorithm (GA), it exhibited a more effective and targeted exploration of the search space. This led to superior PI controller tuning, with improved dynamic response and reduced total harmonic distortion relative to the benchmark methods.

Resumo em Inglês:

ABSTRACT This study explores the behavior of SiC MOSFETs in a half-bridge converter, emphasizing simulation and experimental validation under both ZVS and non-ZVS conditions. Fast switching and high efficiency make SiC attractive, but parasitic-induced oscillations and EMC require careful design. The influence of gate resistance on switching dynamics and loss mechanisms is analyzed, showing that higher gate resistance reduces oscillations but increases switching losses. For estimating the MOSFET dissipated power, traditional current sensing with current probes or shunt resistors introduces parasitic elements that affect the transistor switching and compromise the instantaneous power measurements. As a result, alternative methods were employed for loss estimation in high-frequency SiC converters. Results demonstrate that increasing gate resistance from 3 Ω to 30 Ω reduces oscillation amplitude by 41%, while increasing switching losses by 53.8%. These findings support gate-drive optimization in SiC-based converters.

Resumo em Inglês:

ABSTRACT This paper presents a comprehensive study on the influence of winding geometry on leakage inductance and proximity effect losses in coupled inductors applied to quasi-resonant flyback converters for LED drivers. Eleven coupled inductors were designed using the same PQ3220 core, varying the number of layers, interleaving level, and wiring geometry to evaluate their impact on performance. The leakage inductance of each inductor was calculated analytically and measured experimentally, showing strong correlation and validating the analytical method. Additionally, proximity effect losses were estimated through simulations based on winding temperature measurements, allowing the extraction of the AC resistance and proximity factor for each design. The experimental setup involved a 60 W quasi-resonant flyback LED driver operating at around 50 V output, where voltage spikes on the MOSFET, system efficiency, and critical component temperatures were analyzed. Results show that increasing the interleaving level significantly reduces leakage inductance, proximity losses, and electromagnetic emissions, leading to improved efficiency, lower thermal stress, and facilitated regulatory compliance. This study highlights the importance of magnetic design in achieving high-performance LED drivers and provides practical guidelines for minimizing parasitic effects in coupled inductors without increasing component count.

Resumo em Inglês:

ABSTRACT Research on hybrid microgrids has attracted significant interest mainly due to the advantages that this topology offers compared to a solely direct current (DC) or alternating current (AC) microgrid. Among these advantages, one of the most frequently mentioned is the increased system reliability, due to the possibility of operating in either islanded mode or grid-connected mode, depending on the need. Additionally, the ability to export power to the AC grid is a valuable application of this type of system. In this context, this paper proposes a new control and management strategy for a hybrid microgrid. The analyzed microgrid consists of a photovoltaic system, energy storage systems, and an emergency power source, as well as DC and AC loads. The interface with the AC side is achieved through an inverter, and the microgrid may or may not be connected to the external grid. The proposed strategy emphasizes the management of all subsystems, as well as the control of operations in both grid-connected and islanded modes. The system was implemented using Controller Hardware-in-the-Loop (C-HIL). The results demonstrated that the proposed strategy enabled effective microgrid management, particularly regarding the proper coordination of the batteries through SOC equalization and the maintenance of each operational state of the microgrid.

Resumo em Inglês:

ABSTRACT This paper presents a novel hybrid control architecture for grid-tied inverters with an LCL filter, combining a fractional-order proportional-integral-derivative controller, dedicated to reference tracking, and a robust model reference adaptive controller, employed for active rejection of grid disturbances. A systematic tuning procedure using the puma optimizer is provided to tune all eleven parameters of the composed control algorithm. Experimental results, performed on a TMS320F28335 Delfino microcontroller equipped in a laboratory prototype, corroborate the simulation findings, presenting fast current tracking and disturbance rejection, with low settling time and total harmonic distortion below the limits established by the IEEE 1547 standard, whose mean between the three-phases is 2.55% in steady state.

Resumo em Inglês:

ABSTRACT This work brings in a load-independent Class-E LCL resonant converter. The intertwined soft-switching and load-independent functions in resonant topologies require high mathematical effort and leads to trade-off designing characteristics related to the operating frequency, output power and load range. Therefore, this paper shows the exact analysis for the Class-E LCL converter by axiomatically dealing with the second, third and fourth-order polynomials. In addition, a design method is proposed based on the implicit equations while considering the soft-switching and load-independence features. The measured built prototype operates at 1.2 MHz, which outperforms most of the state-of-the-art compared converters by ×1.2, while maintaining comparable output power and efficiency (92 %).

Resumo em Inglês:

ABSTRACT The growing concern with reducing CO2 emissions and the demand for sustainable mobility have promoted the adoption of electric vehicles and the use of wide bandgap semiconductors. Thermal management for semiconductor devices is crucial to ensure reliability and efficiency, with junction temperature being a key variable that cannot be directly measured during operation. In this context, this paper proposes a method for junction temperature estimation of SiC MOSFET devices applied to electric traction inverters. A Luenberger state observer is applied to estimate the junction temperature from accessible variables such as ambient temperature, heat sink temperature, and calculated power losses. The method is formulated in a state-space representation, verified through simulations, and validated using an experimental setup, consisting of a single-phase full-bridge inverter. Infrared thermal imaging and physical sensors were employed to compare estimated and measured values. The results demonstrated high accuracy and fast dynamic response of the proposed observer, confirming its robustness and applicability for embedded thermal monitoring in power converters.

Resumo em Inglês:

ABSTRACT Bipolar direct current (DC) microgrids have emerged as a promising alternative for efficiently integrating of renewable energy sources. However, these systems are susceptible to voltage imbalance between the positive and negative poles, especially with asymmetric loads. This paper presents the modeling and control of a non-isolated DC–DC Boost converter with a symmetric bipolar output suitable for photovoltaic applications. The proposed topology eliminates issues related to voltage imbalance and leakage currents while providing continuous low-ripple input current, a reduced number of components, simplified operation, and common grounding with the output neutral point. The operating principle, modeling, and control strategy of the converter are discussed, and its performance is validated through simulations and experimental results from a 1500 W prototype. The results demonstrate stable operation under both balanced and unbalanced conditions.

Resumo em Inglês:

ABSTRACT This paper introduces a virtual plant method as the main contribution, applied independently to two discrete-time adaptive control strategies for a synchronous buck converter used in battery charging: an Adaptive PI Controller (API) and a Model Reference Adaptive Controller (MRAC). The system employs an LCL filter that interfaces the power converter with the batteries. The proposed virtual plant method enhances the transient performance of adaptive systems by pre-tuning the controller gains before the physical connection, enabling automatic gain initialization and mitigating the poor start-up dynamics typical of adaptive control. The API controller performs real-time adaptation of the parameters Kp and Ki, while the MRAC is based on a reduced-order reference model to simplify its design, updating three parameters: θr, θy and θvb. A simplified methodology for designing adaptive controllers is proposed, involving plant simplification and the use of a virtual plant to automate the controller design process. Controller Hardware-in-the-Loop (C-HIL) and experimental results are presented to validate the control approaches. A fixed PI controller is used as a benchmark for comparison with the adaptive control techniques. Quantitative and qualitative analyses are provided using performance indices such as ISE, IAE, ITSE and ITAE.

Resumo em Inglês:

ABSTRACT This paper presents the mathematical modeling and control design of a high-power-density bidirectional DC-DC converter topology based on the three-state switching cell (3SSC). The operation stages corresponding to distinct duty cycle intervals are thoroughly analyzed, and state-space techniques are employed to derive small-signal dynamic models for both Buck and Boost modes. These models serve as the foundation for the design of digital compensators using classical frequency-domain control methods, ensuring compliance with predefined performance specifications. To verify the accuracy and applicability of the derived models, a comparative analysis is conducted between simulated and experimental closed-loop responses. The same compensators, designed using the mathematical models, are implemented both in circuit-level simulations and in a 2 kW hardware prototype operating at 200 V in Buck mode and 550 V in Boost mode, with a switching frequency of 20 kHz. The observed agreement in dynamic behavior under both reference and load disturbances validates the proposed models and confirms their suitability for control-oriented applications. This comparative validation approach represents the main contribution of the work, demonstrating that the small-signal plant models faithfully reproduce the real converter dynamics and can be reliably used in the design of digital controllers for bidirectional power conversion systems.

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ABSTRACT The stable connection of energy sources to the grid via LCL-filtered inverters is often constrained by delays introduced by digital implementation and DPWM modulation. This paper proposes a novel notch-filter-based compensation strategy that explicitly mitigates such delays, extending the stability region of the current control system by increasing the critical frequency. In addition, a systematic methodology is introduced for tuning the active damping gain, demonstrating its direct influence on phase margin and robustness – an aspect not systematically addressed in previous studies. Unlike approaches based on auto-tuning or real-time resonance estimation, the proposed method imposes no additional computational burden while significantly expanding the stability limits. Analytical studies, frequency-domain analysis, and experimental validation using a hardware-in-the-loop (HIL) platform confirm that the proposed strategy extends the stable operating region, improves dynamic performance, and reduces harmonic distortion, representing a distinctive contribution to the control of LCL-filtered grid-connected inverters.

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ABSTRACT This work introduces a Cloud-in-the-Loop approach that combines Internet of Things (IoT) devices with Hardware-in-the-Loop simulation for testing control and monitoring applications. The proposed architecture employs a three-level hierarchical structure: the first level simulates the Battery Energy Storage System and local power flow control on a Digital Sampling Processor microcontroller, the second level uses an ESP32 microcontroller for Controller Area Network (CAN) communication and data transmission to the cloud, and the third level, implemented with an online broker, enables data storage, analysis and commands. A simplified power flow model and a battery model representation are considered to evaluate long-term operation with one year of climate and load data. Two load management strategies were compared: (i) total load shedding at 0% State of Charge, and (ii) hierarchical load disconnection at predefined SOC thresholds. Results showed that the hierarchical strategy increased the average State of Charge by 25.2% (54.66% vs. 43.64%), prevented interruptions to critical loads. The results show that the proposed framework serves as a flexible step before real deployment, since its cloud-based functions remain unaltered while only the physical hardware is replaced. This approach reduces implementation problems and allows the methodology to be extended to various case studies.

Resumo em Inglês:

ABSTRACT This article discusses the anachronism, insufficiency, and imprecision of the formulation and definitions of power factor (PF) in several regulatory texts. For consumer units in distribution networks, analyses are presented of how ANEEL defines this figure of merit. In the case of individual equipment, INMETRO's measurement procedures employ formulas that, depending on the tested device's operating principle, may yield technically erroneous results. For example, the results of LED luminaires, which are supposedly designed to have a high power factor, are analyzed and it is concluded that the solution for the errors in single-phase case is straightforward, and are achieved by using the correct formulation of the power factor, defined as the ratio between active and apparent power, with a sufficiently high sampling rate to capture the possible high-frequency spectral components of the current. Modern digital measuring instruments can easily obtain such quantities and do not incur errors that may arise from using quantities such as distortion factors or fundamental displacement.

Resumo em Inglês:

ABSTRACT Capacitor designs employed in DC-link applications of power electronic converters must minimize equivalent series resistance and parasitic inductance due to the adoption of wide bandgap semiconductors, which enable operation at significantly higher temperatures, voltages, and switching frequencies. The paper focuses on characterizing metallized plastic film capacitors by analyzing the influence of materials, dimensions, and construction features, both of the capacitive element and of the connections and terminals, on parasitic inductance and associated losses, thereby supporting the development of an equivalent circuit model. A comprehensive literature review establishes the theoretical foundation for the analytical formulation, which is then applied to the structural characteristics of the capacitor under investigation to derive the parameters of the equivalent circuit. The calculated values of equivalent series inductance and equivalent series resistance are validated through comparison with measurements obtained from different capacitor models. The results confirm the accuracy of the proposed calculation method, as the observed deviations remain within acceptable limits, considering the inherent variability of raw materials, manufacturing processes, and measurement procedures.

Resumo em Inglês:

ABSTRACT This work presents a methodology that employs the Gauss–Newton algorithm to perform online impedance estimation for grid-connected inverters. Conventional formulations for this class of problem typically lead to high-order nonlinear systems of equations, often of dimension 8×8. In contrast, the formulation proposed herein recasts the estimation task as a 3×3 least-squares problem, which is then solved via the Gauss–Newton method. To validate the proposed approach, a three-phase grid-connected inverter was adopted as the case study. The control system enforces three distinct active power injection levels into the grid, and the voltage, current, and phase-angle magnitudes at the point of common coupling are measured and used as inputs to the impedance estimation algorithm. Real-time validation was carried out to assess the performance of the method. The results confirm the feasibility of the proposed formulation and indicate that the approach substantially reduces the computational burden of embedded DSP-based algorithms for online grid impedance estimation.