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Copyright of Electric Power is the property of Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The numeral of academic publications in the microgrid system field has rapidly grown. A microgrid system is a group of interconnected distributed generation, loads, and energy storage operating as a single controllable entity. Many published articles recently focused on distributed generation, system control, system stability, power quality, architectures, and broader focus areas. This work analyzes microgrid: alternating current (AC), direct current (DC), and hybrid AC/DC microgrid systems with bibliometric network analysis through descriptive analysis, authors analysis, sources analysis, words analysis, and evolutionary path based on the Scopus database between 2010 and 2021. The finding helps find out the top authors and most impact sources, most relevant and frequently used in the research title, abstract, and keyword, graphically mapping the research evolved and identifying trend topic. [ABSTRACT FROM AUTHOR]

This paper assessed the small-signal stability performance of a multi-converter-based direct current microgrid (DCMG). The oscillation and potential interactions between critical modes are evaluated. First, the complete analytical model of the DCMG is developed with the converter and associated controllers. Three methodologies, impedance scanning, eigenvalue analysis, and time-domain simulation, along with the fast Fourier transform (FFT) analysis, have been used to comprehensively investigate the oscillations and interactions. The simulation results show inherent weak modes, with a wide range of oscillations in the studied DCMG, which may destabilize the system under disturbances. Based on the sensitivity analysis, controller gains and DC-link capacitance are identified as the most critical parameters and substantially influence the weak modes leading to oscillations, interactions, and resonance. Finally, the performance of the various control synthesis methods is compared. This examination would help the researchers, planning, and design engineers to design and stably operate a multi converter-based DC microgrid. [ABSTRACT FROM AUTHOR]

Considering the problems of distributed power output instability, parameter perturbation and load fluctuations in direct current (DC) microgrids, an improved auto-coupling proportional-integral (ACPI) bus voltage tracking control method with strong anti-interference ability based on a three-phase AC/DC converter is proposed. Firstly, the uncertainty of the internal dynamics and external disturbances of the DC microgrid is defined as a total disturbance, and thus the nonlinear uncertain system is mapped to an unknown linear system. Secondly, a controlled error system under the inverse excitation of the total disturbance is constructed. Based on that, an ACPI controller model based on the improved adaptive speed factor is designed, and it effectively suppresses bus voltage fluctuations and improves the dynamic response speed of the system. Finally, the robust stability and anti-disturbance robustness of the ACPI closed-loop control system are theoretically analyzed, and a simulation model is built for verification. The simulation results of DC bus voltage tracking under different working conditions show that the proposed control method has a fast response speed, strong anti-interference ability for improing stability on DC bus voltage fluctuations.

In this paper, a novel microgrid (MG) concept suitable for direct current (DC) multibus architectures is depicted. Multibus feature is improved in order to distribute power in DC using a number of buses at different voltage level. A teachers offices building that houses several kinds of loads, including a charging station for electric vehicles (EV), is considered to validate the strategy. Several topologies of power electronics converters (PECs) are included in the system to perform specific tasks and providing isolation between bus and final loads. In order to develop the PECs, first, a switching function is used to obtain average model of each converter. Then, converters design is done by using well known methods that allow to obtain parameter values of all the devices in every version of each kind of converter. A hierarchical control is selected to govern the direct current microgrid (DCMG). At a lower control level, local control stage is implemented and tuned using models and designs obtained, with linear controllers in some PECs and classic strategies in others. In higher control level, there is a supervisory strategy that prioritizes the use of generated power to supply the building's loads. This energy management system (EMS) is based in Petri net theory; it consists of a start-up test, then source condition synchronous algorithm and load condition synchronous algorithm operate the DCMG according to the mentioned priority. Finally, PECs are tested on standalone, performing in closed loop, facing load changes to verify the adequate operation. Some trajectories of a simplified version of the CDMG are tested with local control in order to validate the multibus multivoltage concept. In order to verify coordinated control, some events managed by EMS are presented. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Management of battery at direct current (DC) microgrids is the essential factor to maintain the balance of power and the bus voltage's stability in the grids. To ensure the quality of battery management is necessary to simulate the operation of the battery management system. This paper presents the simulations in various battery management algorithms. The simulations were designed to determine the effect of these variations on the balance of the power balance, bus voltage stability, and battery consumption level. The configurations of one, two, and three battery groups could maintain a balance of power balance. The three arrangements could ensure the bus voltage stability at a value of 24 Volts. The variations in the battery group configurations cause different battery consumption levels. The three-battery group configuration has a lower power consumption rate of 0.1% than other battery group configurations. Variations in the battery management algorithms affect power balance, bus voltage stability, and battery electricity consumption. The result showed the best power balance achieved by an algorithm without counting a value-based state of charge (SoC). The algorithm also committed that the difference between the supply and demand equal to 0 Watts. For the voltage stability, the algorithms that were counting a value-based SoC can maintain bus voltage stability at a value of 24 Volts. Nevertheless, other algorithms that rely on less than one SoC value-based and have the lowest mean value of SoC reduction are equal to 0.19%.

In this paper, a novel microgrid (MG) concept suitable for direct current (DC) multibus architectures is depicted. Multibus feature is improved in order to distribute power in DC using a number of buses at different voltage level. A teachers offices building that houses several kinds of loads, including a charging station for electric vehicles (EV), is considered to validate the strategy. Several topologies of power electronics converters (PECs) are included in the system to perform specific tasks and providing isolation between bus and final loads. In order to develop the PECs, first, a switching function is used to obtain average model of each converter. Then, converters design is done by using well known methods that allow to obtain parameter values of all the devices in every version of each kind of converter. A hierarchical control is selected to govern the direct current microgrid (DCMG). At a lower control level, local control stage is implemented and tuned using models and designs obtained, with linear controllers in some PECs and classic strategies in others. In higher control level, there is a supervisory strategy that prioritizes the use of generated power to supply the building’s loads. This energy management system (EMS) is based in Petri net theory; it consists of a start-up test, then source condition synchronous algorithm and load condition synchronous algorithm operate the DCMG according to the mentioned priority. Finally, PECs are tested on standalone, performing in closed loop, facing load changes to verify the adequate operation. Some trajectories of a simplified version of the CDMG are tested with local control in order to validate the multibus multivoltage concept. In order to verify coordinated control, some events managed by EMS are presented.

The direct current (DC) microgrid requires a fast load shedding scheme that prevents instability and voltage collapse when the distributed energy resources are unable to meet the power demand. The load shedding scheme is also expected to prevent unnecessary service interruptions caused by over-shedding of loads. This paper proposes an adaptive voltage-based load shedding scheme utilizing voltage thresholds that are automatically adjusted depending on the rate of change of locally measured bus voltages. The performance of the proposed load shedding scheme is investigated and compared with that of the conventional voltage-based load shedding scheme, using a realistic and detailed study system, under various disturbances. The comprehensive simulation studies that are conducted using the PSCAD software indicate that the adaptive load shedding scheme (i) effectively maintains the DC microgrid power balance through fast and coordinated load shedding, (ii) prevents the DC bus voltages from falling below acceptable levels, (iii) ensures that the critical loads do not experience excessive steady-state voltage deviations, (iv) minimizes the durations and magnitudes of the temporary voltage drop caused by sudden disturbances, and (v) improves power supply reliability.

This study proposes a versatile decentralised control strategy for the direct current (DC) microgrid based on the DC bus signalling method. Performance of the proposed control strategy is investigated under various generation and load disturbances in both grid-connected and islanded operation modes of the DC microgrid. The studies are conducted using a realistic DC microgrid study system simulated in the PSCAD/EMTDC software. The study results indicate that the proposed control strategy: (i) effectively maintains the power balance in the DC microgrid, (ii) effectively limits the DC bus voltage deviations under large disturbances, (iii) improves stability and dynamic response, (iv) does not curtail renewable power generation unless it is necessary, (v) does not require excessively large grid-tied converter and battery energy storage systems, and (vi) enhances system reliability, flexibility, modularity, and expandability.

A direct current (DC) microgrid has become a superior power system in recent years due to the development of DC loads and higher efficiency of DC systems. One of the challenging problems on DC microgrids operation is protection, and it is still a particular concern associated with the challenges of developing a proper protection scheme owing to its characteristics and lack of standards in DC protection. Due to the significant increasing interest on DC microgrid; this study investigates protection problems and schemes that need to be addressed in modern power systems involving DC microgrids. This study analyses and presents a comprehensive review of the most recent growth in the DC microgrids protection. Additionally, the fault characteristics of DC microgrids, the impact of constant power loads, the protection devices and several proposed methods to overcome the protection problems are discussed. The differences between the proposed protection methods for the DC microgrids are also discussed.

Direct current (DC) microgrid is characterised by attractive features such as high efficiency, reduced cost and needless for synchronisation. The control and operation of the DC mirogrid become significantly important with the high penetration of distributed energy resources. Therefore, development of an advanced platform for testing control and operation of the DC microgrid has attracted more and more attention nowadays. This study proposes a hardware‐in‐the‐loop (HIL) simulation system as a new method to develop and test control algorithms and operation strategies for the DC microgrid. The proposed HIL simulation system is composed of a RT‐LAB for real‐time simulation, an actual controller under test, a cRIO for coordination control and the DC microgrid management system for optimal operation. Both the actual controller of key research objects and coordination control with different time scales can be tested in the proposed HIL simulation system. Hence, the platform is designed for flexibility and universality. Moreover, configuration and communication of the HIL simulation system are illustrated in this study. Finally, simulation tests are carried out to show the validation of the proposed HIL simulation platform. [ABSTRACT FROM AUTHOR]

A control system design based on an actively-controlled battery/ultracapacitor hybrid energy storage system suitable for direct current microgrid energy management purposes is presented in this paper. The proposed cascade control system arrangement is based on the superimposed proportional–integral voltage controller designed according to Damping Optimum criterion and a zero-pole canceling feed-forward load compensator aimed at voltage excursion suppression under variable load conditions. The superimposed controller commands the inner battery and ultracapacitor current control loops through a dynamic current reference distribution scheme, wherein the ultracapacitor takes on the highly-dynamic (transient) current demands, and the battery covers for steady-state loads. In order to avoid deep discharges of the ultracapacitor module, it is equipped with an auxiliary state-of-charge controller. Finally, for those applications where load is not measured, an adaptive Kalman filter-based load compensator is proposed and tested. The presented control strategy has been implemented on the low-cost industrial controller unit, and its effectiveness has been verified by means of simulations and experiments for the cases of abrupt load changes and quasi-stochastic load profiles using a downscaled battery/ultracapacitor hardware-in-the-loop experimental setup. [ABSTRACT FROM AUTHOR]

A hybrid DC/DC converter is studied for direct current microgrid applications to have benefits of low switching losses with wide range of operation load, less winding turns of transformer secondary side, low ripple current on output side and high circuit efficiency. The studied converter includes a phase‐shift pulse‐width modulation full‐bridge circuit and a half‐bridge circuit to reduce the switching losses at lagging‐leg switches. In the secondary side of the studied converter, two inductors, four diodes and two transformers are adopted to perform partial ripple current reduction and minimise the winding turns. The studied converters are verified with a 1200 W prototype by the experimental results. [ABSTRACT FROM AUTHOR]