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This article evaluates the power conversion efficiency of the buck three-level dc–dc converter, when operating in unbalanced bipolar dc microgrids. Bipolar dc microgrids adopt a positive, neutral, and negative wire to double the power transfer capability, reduce conduction losses, and provide two voltage levels. Additional converters are however required to balance the pole-to-neutral voltages in the presence of unbalanced loading conditions. Previous work has shown that the buck three-level dc–dc converter features voltage balancing capability and can serve, at the same time, as an interface for battery storage and photovoltaic systems for example. Nevertheless, available conversion loss models are only valid for balanced loading conditions. Therefore, this article derives a conversion loss model for a buck three-level dc–dc converter, also valid in unbalanced conditions. The model is decomposed in balanced and unbalanced components in order to separate losses arising in balanced and unbalanced conditions. Furthermore, the model accounts for nonideal common-mode currents as experimental results will reveal that they have a profound impact on the conversion efficiency in unbalanced and balanced conditions. [ABSTRACT FROM AUTHOR]

A new implementation of an iron-loss model for laminated magnetic cores in the MATLAB/Simulink environment is proposed in this paper. The model is based on numerically solving a one-dimensional diffusion problem for the eddy currents in the core lamination and applying an accurate hysteresis model as the constitutive law. An excess loss model is also considered. The model is identified merely based on the catalog data provided by the core material manufacturer. The implementation is validated with analytical and finite-element models and experimentally in the case of a toroidal inductor supplied from a GaN FET full-bridge inverter with 5–500 kHz switching frequencies and a deadtime of 300 ns. Despite the simple identification, a good correspondence is observed between the simulated and measured iron losses, the average difference being 3.3% over the wide switching frequency range. It is shown that accounting for the skin effect in the laminations is significant, in order to correctly model the iron losses at different switching frequencies. Some differences between the measured and simulated results at high switching frequencies are also discussed. The model is concluded to be applicable for designing and analyzing laminated magnetic cores in combination with power-electronics circuits. The Simulink models are openly available. [ABSTRACT FROM AUTHOR]

Recently, novel magnetic materials have been developed for high-efficiency and high power density electric motors. In addition, next-generation semiconductor devices, like silicon carbide (SiC) or gallium nitride (GaN), have been introduced for power converters due to their high-frequency operation. Therefore, high-frequency operation of new magnetic materials is possible when they are driven by GaN or SiC inverters. Nevertheless, iron loss characterization of magnetic materials when they are excited by high-frequency signals have not been conducted yet. This paper introduces the iron losses characterization of a magnetic material at high carrier frequency excitation using a GANFET inverter. This characterization was carried out by the experimental evaluation of iron losses at carrier frequencies from 5 to 500 kHz at different deadtimes. As a result of the measurements, iron losses seem to have a trend to increase at high carrier frequencies and large deadtimes. In addition, filtering is introduced and it seems to be an effective technique for reducing iron losses. [ABSTRACT FROM AUTHOR]

Power density and conversion efficiency are two critical parameters of inductive power transfer (IPT) systems. These parameters are related to the number of components in the power conversion circuit as well as its modulation method. The combination of Midpoint Matrix Converter and pulse-density modulation (PDM) has a potential to improve these parameters, due to a low number of semiconductor switches utilization as well as constant efficiency at the maximum output and partial load operations. In this context, this paper analyzes the performance of a three-phase to single-phase Midpoint Matrix Converter using a Free-wheeling Switch (MMCFS) and the PDM in a high coupling factor series-none IPT application. This converter utilizes on–off control to manage power transfer, which automatically tracks the load resonant frequency. Dynamic and steady-state mathematical equations were derived to represent the converter and the IPT system characteristics. These equations show a relationship between the link efficiency, the link gain, the damping ratio and the coupling factor. A kick-start method and a multistep switching strategy were developed to start and operate the converter, respectively. Additionally, a 150 W MMCFS-based IPT prototype was built to verify the improvement, which demonstrated an efficiency of around 80% at the maximum output and partial load operations. [ABSTRACT FROM AUTHOR]

• Analyzes the development of power generation systems in the Galapagos Islands. • Describes the island's energy matrix and RES-based power generation proposals. • Presents a state-of-the-art analysis carried out to introduce RES in the Islands. • Analyzes the regulations and policies governing RES installation on the islands. The sources of electricity generation in the Galapagos Islands have been diversified due to the high risk represented by the use and transportation of fossil fuels and the application of the Zero Fossil Fuels initiative. This has increased the implementation of projects using different renewable energy sources. Despite being a World Heritage Centre, very little research has been carried out that presents the current situation of the electrical system in the Galapagos Islands. Therefore, this study reviews the current electricity sector situation in the Galapagos Islands. The characteristics of generation, distribution, and demand in the Galapagos Islands are presented. Also, the research studies and the regulations to be met for designing and implementing electric power generation projects based on renewable energy sources are detailed. In addition, this study presents the changes in the energy matrix of the Galapagos Islands in recent years, where the generation capacity and investment in hybrid systems (photovoltaic, wind, biomass, and vegetable oil - Jatropha) have been diversified and increased, encouraging research into new sources such as geothermal, biomass, waves, tides and green H2. Finally, the central policies and regulations that govern the installation of renewable generation systems in the Galapagos Islands are analyzed. [ABSTRACT FROM AUTHOR]

• A complete Fuzzy-based energy management system design for an isolated microgrid comprising a photovoltaic system, diesel generator, and energy storage system. • The complete procedure for tuning the parameters of a fuzzy logic controller using metaheuristic optimization algorithms. • Analyzes the state of health of the energy storage system of an isolated microgrid in a rural area of Ecuador. • A hardware-in-the-loop validation using the Typhoon HIL-405 device and Matlab. Rural areas have increased directly with the growth of the world population. Although, isolated rural areas do not have the energy infrastructure to supply essential services such as electricity. In Ecuador, as in the rest of the world, these areas of the rural population usually present access problems due to the topography of the place. This makes the construction of power lines to connect them to the Interconnected National Energy System unfeasible. In this regard, isolated microgrids have emerged as a great solution to cover the energy demands in these locations. However, an optimal implementation of isolated microgrids depends on several factors, such as geographical location, weather conditions, sizing, load demand, operating costs, and social impacts. Therefore, this study proposes the design of a new energy management system (EMS) for isolated microgrids comprising a photovoltaic system, diesel generator, and battery energy storage system (ESS). Since fuzzy logic control (FLC) has proven to be a powerful tool for dealing with the nonlinearities of a microgrid and the application of fuzzy-based EMS for isolated microgrids is rarely reported in the literature, this study proposes the application of an FLC for the EMS's design of an isolated microgrid. The proposed fuzzy-based EMS uses generation and demand forecasts, enhances the operating time of diesel generators (DLG), and takes advantage of the available solar resource to supply the energy required by a community while preserving the ESS lifetime. An adjustment of the FLC parameters by Particle Swarm Optimization (PSO) and Cuckoo Search (CS) algorithms is performed to improve the behavior of the proposed EMS. Furthermore, a battery degradation model is applied to estimate the ESS State of Health (SOH). To highlight the advantages of the proposed approach, a case study in a specific community in Ecuador is presented. In this location, the proposed EMS is compared with an EMS without parameter adjustment developed in previous work, demonstrating improved performance in DLG limits, preserving the battery lifespan by controlling the battery SOC limits more efficiently, and minimizing the microgrid operating costs by maximizing the use of photovoltaic power (i.e., reducing the wasted photovoltaic energy). The results provide evidence that the EMS adjusted with the PSO algorithm presents an enhanced behavior than the one adjusted by the CS algorithm. Finally, the fuzzy-EMS is validated using Matlab® and Hardware-in-the-Loop Typhoon HIL-402 device. Results demonstrate that the proposed approach limits DLG usage, make the most of the available solar resources, and extends the battery life by controlling overcharges and deep discharges. [ABSTRACT FROM AUTHOR]

The battery State of Charge (SoC) is critical information to overcome agricultural robots' limitations related to battery and energy management. Although several SoC estimation methods have been proposed in the literature, the performance of these methods has not been validated for different battery chemistries in agricultural mobile robot applications. Compared to previous work, this paper evaluates the limits of the SoC estimation using the RC model and the Thevenin model for a Lithium Iron Phosphate (LFP) battery and a Sealed Lead Acid (SLA) battery. This evaluation used a custom agricultural robot in a controlled indoor environment. Consequently, this work assessed the limitations of two ECM-based SoC estimation methods using battery packs, low-cost sensors and discharge cycles typically used in agricultural robot applications. Finally, the results indicate that the RC model is not suitable for SoC estimation for LFP battery; however, it achieved a mean absolute error (MAE) of 2.2% for the SLA battery. On the other hand, the Thevenin model performed properly for both chemistries, achieving MAE lower than 1%. [ABSTRACT FROM AUTHOR]

One of the short-coming challenges of power systems operation and planning is the difficulty to quantify the variability of power systems Kinetic Energy (KE) to unveil online additional information for the system operators’ decisions support. KE monitoring requires innovative methods to analyse the continuous fluctuations in the KE power’s systems. In this paper, we propose the use of information theory, specifically the concept of Information Length (IL), as a way to provide useful insights into the power system KE variability and to demonstrate its utility as a starting point in decision making for power systems management. The proposed IL metric is applied to monthly collected data from the Nordic Power System during three consecutive years in order to investigate the KE evolution. Our results reveal that the proposed method provides an effective description of the seasonal statistical variability enabling the identification of the particular month and day that have the least and the most KE variability. Additionally, by applying a Long Short-Term Memory (LSTM) neural network model to estimate the value of the IL on-line, we also show the possibility of using the metric as data-driven support. [ABSTRACT FROM AUTHOR]

Interleaved dc–dc converters with integrated magnetic components capable to achieve high power density have recently gained attention in automotive applications for eco-friendly transportation. These circuits may contribute to the downsizing of powertrains for electric vehicles (EVs) and hybrid electric vehicles (HEVs) using close-coupled inductors (CCIs) and loosely coupled inductors (LCIs). In this study, a novel core model for size and loss calculation of the interleaved converter with integrated winding coupled inductors (IWCIs) is proposed to assess the size of magnetic components. This assessment was carried out using the parameters of a 1-kW circuit. As a result, interleaved converters with IWCIs proved to be more effective than the converters with LCIs and CCIs for downsizing the magnetic components. In contrast, it was also found that the interleaved converter with LCIs achieved downsizing of the magnetic component at a duty ratio close to 50%. Finally, the effectiveness of the calculation model was validated through experimental tests. [ABSTRACT FROM PUBLISHER]

• A model predictive control-based energy management for an electro-thermal microgrid. • The strategy minimizes operating costs and pollution avoiding battery degradation. • Analyze the state of health of the battery system to reduce degradation. • A comparison with a Unit Commitment approach under different generation scenarios. Access to electricity is a fundamental key to developing countries' growth. Microgrids (MG) have become potential solutions to provide energy to isolated rural areas in a safe and environmentally friendly way. Therefore, proposals for alternative solutions to bridge the electrification gap in the Ecuadorian Amazon – which has the most significant percentage of its population without access to electricity – are of significant interest. Consequently, this paper presents the design of an Energy Management System (EMS) based on Model Predictive Control (MPC) for an isolated electro-thermal microgrid comprising a photovoltaic generator, a diesel generator, a lithium-ion battery Energy Storage System (ESS), electrical loads, and a domestic hot water system. The EMS aims to supply energy reliably and safely, minimize the MG's operation costs, and extend the ESS's useful life while satisfying the end users' comfort. This study includes an estimated degradation model for the ESS's State of Health (SOH), an essential parameter contributing to reducing the microgrid's operating costs in the long term. Simulation results using one-year data present the influence of the prediction horizon on the MG's scheduling. In addition, the benefits of the proposed EMS are highlighted by comparing it with the results achieved by a Unit Commitment approach, where it is demonstrated that the proposed EMS presents a reduction in MG operating costs and greenhouse gas emissions while maximizing the utilization of renewable energy and extending the lifespan of the ESS. Finally, an experimental validation, using a Typhoon Hardware-in-the-loop HIL-402 device in real-time operation, stands out the effectiveness and feasibility of the proposed MPC-based EMS. [ABSTRACT FROM AUTHOR]

Multiphase topologies are preferably employed in power conversion systems to lessen the per-phase circuit current, conduction losses, devices thermal stresses, and to reduce the output current ripples. A multiphase LLC resonant dc/dc converter usually possesses a number of magnetic cores equal to the number of phases. These magnetic cores are the major contributors to supply volume, weight, and size. For these reasons, circuit designers tend to select the topologies that have a minimal number of magnetic cores. In this paper, the authors aim to promote the industrial applications of the three-phase LLC resonant converter by integrating three transformers into a single commercially available magnetic core to reduce the volume, weight, and cost of the power converter. A comprehensive magnetic analysis for the three-phase-integrated transformer is conducted. Finite element method (FEM) simulation and experimental tests are carried out to validate the proper operation of the integrated transformer utilized in a 390-/12-V to 500-W prototype. Furthermore, the power losses distribution has been presented. The proposed integrated transformer has been proven effective, and it realized a uniform thermal distribution along the core compared to the three-discrete transformers. [ABSTRACT FROM AUTHOR]

High power density and high efficiency in dc/dc converters are required in various applications such as the automotive application. Interleaved multiphase circuits with integrated magnetic components can fulfill these requirements because passive components occupying significant space in power converters can be downsized without high-switching frequency driving of power devices. However, dc-biased magnetization is a drawback of integrated magnetic components because of unbalanced inductor average currents. This imbalance arises from the tolerance among the phase components. To overcome this problem, inductor average current control is implemented in interleaved multiphase dc/dc converters. Nevertheless, the imbalance cannot be completely eliminated because the current sensors inserted into each phase have gain errors. The purpose of this paper is to present a magnetic design method to improve the immunity to unbalanced currents. A comprehensive analysis is carried out with two main objectives: to prevent magnetic saturation, which may arise due to the current unbalance and to downsize the magnetic components by selecting the optimal coupling coefficient taking into consideration the maximum permissible percentage of unbalanced currents. Simulation case studies are presented to support the analysis. Finally, a 1-kW prototype of the interleaved boost converter is built to validate the accuracy of the design method. [ABSTRACT FROM PUBLISHER]

State-of-the-art reliability assessment typically starts from a given circuit topology, for which the most suitable components are selected using a Physics of Failure analysis. This paper, however, addresses the topology selection stage, which is the foundation in designing reliable converters. Based on an overview of the reliability performance of different components, a methodology is presented as a guideline for comparing topologies to one another. The focus is directed at practical consequences associated with certain designs. Furthermore, an overview is provided on the latest developments in component technology reliability improvements. The developed methodology is mainly intended for demanding applications, where long lifetimes are required or elevated ambient temperatures are present. After the topology selection, an overview of possibilities is given that allows further increasing converter availability. Finally, the methodology is applied to the design of module level converters for building integrated photovoltaics, which is a high temperature application with a high desired lifetime. A prototype and experimental results are presented. [ABSTRACT FROM AUTHOR]