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Worldwide, renewable energy sources, mainly wind and solar power, prove their efficacy to provide a sustainable solution to meet the growing energy demand. Research and investigation on a natural system are uneconomical and depend upon various environmental and seasonal circumstances. The wind emulator can replicate the static and dynamic behavior of a realistic wind turbine system. This paper presents the wind energy conversion system (WECS) using the wind turbine emulator (WTE) hardware model. The mathematical model of wind turbine has been developed using LabVIEW. The WTE consists DC shunt motor coupled with a three-phase self-excited induction generator (SEIG), which is further integrated with the utility grid through a DC microgrid. Various types of control devices such as DC-DC converter, current PI controller, speed PI controller, rectifier, etc., are employed to control the emulator's performance concerning the rotational speed of the wind turbine. The NI-sbRIO-9607 data card and the graphical user interface (GUI) based on the LabVIEW system provide real-time data acquisition and flexibility in the variation of wind speed and various turbine parameters during experimental validation of WECS. The energy flow with the utility grid, static and dynamic characteristics under different wind speeds are successfully emulated by the experimental setup of a wind turbine emulator. [ABSTRACT FROM AUTHOR]

This paper studies the resilient current controller design for the networked DC microgrid system with multiple constant power loads (CPLs) under a new type of time-constrained denial-of-service (DoS) attack. Different from the existing DoS attack models, which are often characterized by DoS frequency and DoS duration, this paper only considers the duration characteristics of the sporadic/aperiodic DoS attacks, and proposes a new type of time-constrained DoS attack model. Under the effects of such DoS attacks, a switching state feedback control law is constructed and a switching-like DC microgrid system model is then established. Furthermore, based on an attack-parameter-dependent time-varying Lyapunov function (TVLF) method, the exponential stability criterion of the resulting DC microgrid system under aperiodic DoS attacks is derived, and a new resilient controller design method is proposed. Finally, simulation studies are given to verify the effectiveness and merits of the proposed resilient control design scheme on achieving the desired control performance and attack resilience. • In contrast to [19], the proposed DoS attack model does only require to know the uniform lower and upper bounds on the sleeping and active periods of the attacks, respectively. • Different from [19-21], in this paper, an attack-parameter-dependent TVLF method is used to obtain the exponential stabilization conditions of the considered DC microgrid. • The proposed resilient controller design procedure is non-conservative, implying that we obtain the optimal controller without any estimation like [20] or approximation [21]. [ABSTRACT FROM AUTHOR]

Renewable energy sources can contribute a lot to deliver reliable/resilient power to isolated communities and the world's sustainable energy future. In this paper, a novel DC microgrid system has been proposed for multipurpose use for isolated communities. The system taps the unused potential of the storage water to generate electricity. The system is configured to reduce complexity and cost by reducing the sensors in the solar pumping unit. Source, storage, and loads are the parts of an isolated system. The DC microgrid includes solar PV, battery, and domestic loads (All types' loads, that is, DC, AC, and dynamic loads). Incremental conductance algorithm has been chosen for the MPPT control, and sliding mode controls have been implemented to supply the sinusoidal supply for the AC loads. The system has included a battery unit to support the DC bus voltage and stable DC microgrid operation. The centrifugal pump has been taken to operate the pump as a turbine to extract the partial power potential from the water. The proposed system's MATLAB/Simulink model was designed for a village and presented as a case study. [ABSTRACT FROM AUTHOR]

The integration of distributed generation (DG) units into a DC microgrid presents a research challenge in terms of a proper protection scheme. The network must be protected due to the sudden change in the amplitude and direction of the fault current. In addition, due to the absence of zero-crossing of the DC fault current, protecting the network from these potential faults is a challenging task. The DC fault can be diagnosed using an appropriate detection technique after monitoring the movement of current. In this paper, a least-square estimation (LSE) technique has been adopted, which has been proven to be able to detect the faulty line strongly, so that the fault is detected by estimated parameters. This fault detection technique has been evaluated on six-lines, with faults analyzed on each line. The six-bus DC microgrid is designed in PSS®SINCAL, and the proposed method is simulated in MATLAB. Two sets of simulations are designed to validate the reliability of the proposed method: (1) pole–ground (P–G) and (2) pole–pole (P–P) fault estimation of inductance and capacitance (C) in a separate line. Simulation results show that the proposed methodology can able to accurately detect (i.e., 95% accuracy) the faulty line in the DC microgrid with respect to designated 'trip' value. Thus, the proposed fault detection methodology can be utilized for protection of modern DC microgrids. An experimental PV-battery-load-based fault detection technique has been developed in the laboratory and tested under P–P fault conditions in order to validate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Tight voltage regulation of the DC microgrid bus may lead to instability issue which leads to microgrid system collapse. Constant power load (CPL) is a serious problem that exists in cascaded power electronic converters which must have a robust controller to mitigate instability issue. The controller based on mathematical model is vulnerable to model mismatch which could lead to instability especially with highly nonlinear plant. Boost converter feeding CPL is a highly nonlinear non-minimum phase system which is difficult to control based on mathematical model. In this paper a supervisory stable Fuzzy Logic Controller (SFC) based on Lyapunov theory is designed to mitigate the instability issue that is caused by the negative incremental impedance which behaves as CPL of dc boost converter. The proposed SFC is able to stabilise the output voltage of the boost converter under nominal and uncertain conditions. The proposed controller is validated through simulation using Matlab/Simulink. To the best of the authors' knowledge this method hasn't been introduced before. [ABSTRACT FROM AUTHOR]

Stand-alone DC microgrids have multiple distributed generation (DG) sources that meet the required demand (load) by using droop control to achieve load (current) sharing between the DGs. The use of droop control leads to a voltage drop at the DC bus. This paper presents a distributed secondary control scheme to simultaneously ensure current sharing between the DGs and regulate the DC bus voltage. The proposed control scheme eliminates the voltage deviation and ensures balanced current sharing by combining the voltage and current errors in the designed secondary control loop. A new flight-based artificial bee colony optimization algorithm is proposed. This selects the parameters of the distributed secondary control scheme to achieve the objectives of the proposed controller. A state–space model of the DC microgrid is developed by using eigenvalue observation to test the impacts of the proposed optimized distributed secondary controller on the stability of the DC microgrid system. A real-time test system is developed in MATLAB/Simulink and used in a Speedgoat real-time simulator to verify the performance of the proposed control scheme for real-world applications. The results show the robustness of the proposed distributed secondary control scheme in achieving balance current sharing and voltage regulation in the DC microgrid with minimal oscillations and fast response time. [ABSTRACT FROM AUTHOR]

This paper proposes a learning-based finite control set model predictive control (FCS-MPC) to improve the performance of DC-DC buck converters interfaced with constant power loads in a DC microgrid (DC-MG). An approach based on deep reinforcement learning (DRL) is presented to address one of the ongoing challenges in FCS-MPC of the converters, i.e., optimal design of the weighting coefficients appearing in the FCS-MPC objective function for each converter. A deep deterministic policy gradient method is employed to learn the optimal weighting coefficient design policy. A Markov decision method formulates the DRL problem. The DRL agent is trained for each converter in the MG, and the weighting coefficients are obtained based on reward computation with the interactions between the MG and agent. The proposed strategy is wholly distributed, wherein agents exchange data with other agents, implying a multi-agent DRL problem. The proposed control scheme offers several advantages, including preventing the dependency of the converter control system on the operating point conditions, plug-and-play capability, and robustness against the MG uncertainties and unknown load dynamics. [ABSTRACT FROM AUTHOR]

Power buffers are power electronic converters, with large capacitors, that decouple volatile loads and a low-inertia distribution network in a DC microgrid. In this work, a set of distributed optimal control policies enable power buffers to reciprocally assist each other during abrupt load changes. While the majority of existing control paradigms are localized, enabling communication among buffers extends their effective range of assistance and helps them minimize a shared objective in a cooperative fashion. The control law's weights surfaces are learned for a mesh of reference loads of each power buffer. Hamilton-Jacobi-Bellman equation is solved by a continuous-time adaptive dynamic programming (ADP) approach with off-policy learning to directly provide a feedback controller, instead of existing approaches that obtain open-loop policies via Pontryagin's minimum principle. This paper presents the first attempt in using ADP techniques for the control of power buffers that respects their original nonlinear dynamics, overcoming the limitations of previous approaches based on small-signal analysis. Compared to the current literature, the proposed approach provides trained controllers that are known a priori, avoiding player-by-player solutions or real-time optimization procedures that could degrade performances or become computationally intensive. Hardware-in-the-loop emulations of a low-voltage DC microgrid validates the proposed approach. [ABSTRACT FROM AUTHOR]

Distributed energy storage systems (DESSs) play an important role in maintaining voltage stability in DC microgrids. In order to improve the inertia of DC microgrid and balance the charge/discharge power and the state-of-charge (SOC) of each energy storage unit (ESU), an SOC-based virtual DC machine (VDCM) control strategy for DESSs in DC microgrid is proposed in this paper. By adding SOC to the armature resistance, the improved virtual machine algorithm can dynamically balance power and SOC simultaneously. In this article, the transient stability of DC bus voltage is enhanced using the output inertia of VDCM, and the SOC differences between ESUs are rapidly reduced by introducing the average SOC of ESUs. Small-signal models of both each ESU-interfacing converter and DESS-inclusive DC microgrid with proposed control method are established. The impact of VDCM parameters on voltage stability is analyzed. Finally, a test DC microgrid is built to verify feasibility and effectiveness of the VDCM control strategy. [ABSTRACT FROM AUTHOR]

Line current differential relays (LCDRs) detect faults accurately and promptly, by comparing all currents flowing into the line. This type of relay has been identified in the literature as a reliable protection for lines in DC microgrids (MGs). LCDRs, however, lack the required resiliency against cyber intrusions, such as false data injection attacks (FDIAs) and time synchronization attacks (TSAs), due to their high dependence on communication infrastructure and/or the Global Positioning System (GPS). This paper first introduces coordinated attacks—i.e., several almost-simultaneous FDIAs or TSAs that are carried out independently to achieve a specific objective—as potential threats for MGs. Then, through a case study, it shows how coordinated FDIAs and TSAs can initiate a sequence of events that result in instability of an entire MG. Afterwards, an approach is presented to detect FDIAs and TSAs, and to distinguish them from real faults. The proposed method is comprised of passive oscillator circuits (POCs) installed in series with each converter. During faults, the resultant RLC circuit causes the POCs to resonate and generate a damped sinusoidal component with a specific frequency, i.e., $f_{d}$. However, $f_{d}$ is not generated during FDIAs and TSAs, since unlike faults, which are physical events that trigger the natural frequencies of a system, cyber-attacks happen in the cyber layer without provoking natural frequencies of the physical layer. Thus, an LCDR pickup without detecting $f_{d}$ denotes an FDIA or a TSA. Since $f_{d}$ is locally measured and analyzed by each LCDR, the proposed detection approach cannot be targeted by cyber-attacks. The proposed method is evaluated on a simulated ±2.5 kV DC MG. Numerical analysis confirms that the proposed method (i) is system-independent; (ii) detects FDIAs and TSAs in less than 1 ms; (iii) is sensitive to high-resistance faults; (iv) can determine fault types, and (v) reduces faults’ peak currents. [ABSTRACT FROM AUTHOR]

The increased usage of fossil fuels has caused a concern for the depletion of such fuels, and has a detrimental impact on the environment by producing greenhouse gases. These major concerns have turned worldwide focus towards performing innovative research in renewable energy resources so that these could readily replace the depleting fossil fuels. Recently, the research and the resulting developments in the field of power electronics has allowed the use of integrating multiple renewable resources, such as wind and solar, for efficient distributed generation. Commercially sold systems have separate inverters for each renewable resource, thus increasing the system complexity, cost and power losses. Replacing these separate inverters with one inverter will reduce the system complexity, cost and power losses. Therefore, this paper studies the modeling and simulation of grid connected DC microgrid with wind and solar resources. The study analyses the modeling of each module: permanent magnet synchronous generator (PMSG) wind energy systems with diode rectifier; PV panels; DC-DC boost converters; voltage source inverter (VSI). The entire system is simulated with Powersys library of Simulink-MATLAB. [ABSTRACT FROM AUTHOR]

Because of the low inertia of dc microgrids, system state variables are easily changed acutely after being disturbed. Hence, dc microgrids meet the serious transient stability issues especially for some stressed states. But the transient stability analysis is a very challenging problem since the dc microgrid system is high-order and nonlinear. To offer a new and more effective analysis framework, this paper proposes a nonlinear decoupling method to evaluate the transient stability of dc microgrids. The proposed nonlinear decoupling method takes full consideration of the nonlinearity of the dc microgrid system and approximately transforms the original nonlinear system into a series of decoupled first-order quadratic or second-order quadratic systems. For these decoupled low-order quadratic systems, their dynamics and stability can be analyzed easily, then the transient stability of the original system can be reflected indirectly. Also, the nonlinear decoupling based analysis framework can be extended to other power electronics dominated power systems to evaluate their transient stability. The accuracy of the proposed analysis method has been validated through related case studies. [ABSTRACT FROM AUTHOR]

For a distributed DC microgrid, the conventional voltage control highly relies on the accuracy of the voltage observer, and the observer will produce an estimation error under time delays. To address the problem brought by the voltage observer, this paper transforms the voltage control into an optimization problem and integrates it into the power sharing control based on the PI consensus algorithm. With the proposed optimal control, the DC bus voltage control and proportional power sharing of the energy storages can be realized in one controller, so that the controller structure is dramatically simplified and the control accuracy will not be affected by the time delay. In addition, to further improve the system stability to resist delay, scattering transformation is introduced in the distributed optimal controller. By constructing Lyapunov function, it has been proved that the stability of the controller under the time delay can be guaranteed. Simulations are conducted to verify the effectiveness of the proposed control strategy and the transformation with and without time delay. [ABSTRACT FROM AUTHOR]

The rapid development of electric vehicles (EVs) increases the power demand, which causes an extra burden on the public grid, increasing the load fluctuations and, therefore, hindering the high penetration of EVs. In this paper, a real-time rule-based algorithm for electric vehicle (EV) charging stations empowered by a direct current (DC) microgrid is proposed. Such a DC microgrid model consists of EVs, an electrochemical storage system, a public grid connection, and photovoltaic sources. The EV charging station model is based on data-driven modelling while its management model takes into account discrete events. This paper focuses on power management strategy of an EV charging station under power limitation and considers most of the drivers' choices. The EV charging system topology is presented and common problems during an EV charging process are discussed, e.g., disconnection operation, standby mode, shedding, and restoration operation. Furthermore, the proposed power management deals with the uncertainties of EV drivers' behavior considering arbitrary and random choices through the human–computer interface. The simulation results obtained under MATLAB/Simulink verify the feasibility of the proposed management strategy that presents a good performance in terms of precise control. [ABSTRACT FROM AUTHOR]

This paper investigates stability of a DC microgrid with integrated constant power loads (CPLs). The investigation is based on an interconnected model of the DC microgrid with two subsystems. One subsystem consists of a CPL under examination and the other subsystem is constituted by remainder of DC microgrid (ROM). Analysis is carried out to indicate when an oscillation mode of CPL subsystem is in the proximity of an oscillation mode of ROM subsystem on complex plane, stability of the DC microgrid decreases as caused by the CPL, leading to growing oscillations in the DC microgrid in the worst case. Hence, the investigation reveals the mechanism about why the CPL may cause instability of DC microgrid from a new perspective of modal proximity. An index is proposed to detect the instability risk by applying the modal analysis to subsystems. The proposed application extends the merit of widely used frequency‐domain analysis to the modal analysis, because instability danger can be detected by the proposed modal analysis in practice without having to establish parametric model of the DC microgrid. Two example DC microgrids with CPLs are presented to demonstrate and evaluate the analysis and conclusions made in the paper. [ABSTRACT FROM AUTHOR]

This paper presents a fault location method suitable for low-voltage DC line. To estimate the fault location of DC lines, a fault location module is designed, and it is connected to each end of the DC lines. When the DC lines fail, the DC circuit breaker gets tripped quickly, and the residual current of the DC line inductance still flows through the fault location module. Considering attenuation of the DC line inductance current, which is a function of the fault distance and fault resistance, the fault location algorithm is established. A simplified DC microgrid model is built by PSCAD/EMTDC, and the proposed method is simulated by MATLAB. The results show that the proposed method can accurately locate the fault point of DC lines. In addition, the proposed method is also verified on a small-scale hardware experiment platform. [ABSTRACT FROM AUTHOR]

The advent of distributed energy resources encourages the direct energy transaction among grid subscribers, who may play interchangeable roles as energy producers and consumers (prosumers). Since microgrids integrated with distributed energy resources (DERs) can offer diverse options, it is desirable to design a proper energy transaction protocol to minimize the cost of prosumers. This paper proposes a discrete biased min-consensus algorithm to discover the best supply candidate with minimum power loss. The proposed discrete approach is implemented based on the multi-energy-router system (MERS) by performing three types of consensus-based algorithms in a distributed manner. Major procedures include demand request broadcasting, transmission power loss calculation, and the optimal routing discovery. The convergence of the proposed discrete approach is proved by rigorous mathematical analysis. Simulations demonstrate the effectiveness of the proposed discrete approach for both small- and large-scale systems. [ABSTRACT FROM AUTHOR]

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This paper is initiated by considering an emerging practical issue that dc microgrids should be able to operate with a large-signal stability sense when feeding both resistive loads and constant power loads (CPLs). To be more specific, the stability should be ensured in the presence of large variations of integrated renewable sources and CPLs, system internal uncertainties, external disturbances, coupled interactions, and other adverse effects. From a control point of view, we intentionally propose a general solution to realize the exact decentralized tracking control task for interconnected systems. First, an alternative finite-time feedforward decoupling mechanism is presented, which is essentially different from existing design approaches via feedback domination or recursive cancellation processes. Second, a composite controller can be straightforwardly built from the system information since it is detached from stability analysis. One major advantage of the proposed design framework is that it reduces the design complexity and therefore facilitates the practical implementations. As a direct application, a simple decentralized composite controller is constructed for an autonomous dc microgrid system. Both numerical simulation and experimental comparison results show that a large-signal stability is achieved for dc microgrids under a range of different situations. [ABSTRACT FROM AUTHOR]

Integration of distributed generations units in distribution systems affects the amplitude and the direction of fault currents. On the other hand, dc fault currents have large amplitude and fast transients. Thus, the setting and coordination of overcurrent relays in dc microgrids will be a challenging issue. This paper proposes a new communication-assisted overcurrent protection scheme for photovoltaic (PV)-based dc microgrids. The proposed scheme has lower cost than the schemes based on the differential protection and also provides the backup protection for the relays. First, possibility of using the overcurrent-based protection is evaluated using a comprehensive strategy for every line section of the system. The strategy determines which relays have to be set for protection of the microgrid in the grid-connected and islanded operation modes. Then, the selectivity and coordination problems of the overcurrent relays in the presence of the PV units are solved by implementing blocking and intertripping schemes using communication infrastructures of the smart grids. Finally, the proposed protection scheme is validated by simulation results on a dc microgrid test system. [ABSTRACT FROM AUTHOR]

The load sharing in the DC microgrids is affected by the practical factors such as the cable resistances and changes in the system topology. This paper presents a new control algorithm for the application in the DC microgrids to achieve accurate load distribution between droop controlled converters. An identical steady state voltage feedback is used for all droop controlled converters to ensure accurate current sharing. The information about the common voltage is obtained by means of the proposed communication-less control strategy. The proposed strategy does not require prior information about the grid topology and parameters. Therefore, it is applicable to both single- and multi-bus microgrids. The conducted stability analysis demonstrates that the proposed approach and the conventional droop control deomstrate similiar dynamic performance. Furthermore, the proposed algorithm has a potential to enhance the operation of the Interlinking Converters in the hybrid AC/DC microgrids. A comprehensive nonlinear simulation study is conducted in the Matlab/Simulink environment. The simulation results verify the effectiveness of the proposed communication-less control scheme to enable proper load distribution between droop controlled converters as well as enhance the load sharing between AC and DC microgrids. Finally, the proposed control approach is verified using an OPAL-RT setup. [ABSTRACT FROM AUTHOR]

This paper proposes a new control algorithm for effective power management in the dc microgrid with renewable energy sources (RES) and energy storage system (ESS). This scheme overcomes the average power sharing and bus voltage regulation problems with maximum utilization of source power. In the source, the additional power available beyond its average rated value is treated as virtual generation. The new references are generated considering virtual generation. The novelty of the proposed algorithm is to bring the virtual generation effectively in operation. The virtual generation of the individual source is based on available power source. The proposed algorithm reduces the charging/discharging cycles of ESS and, hence, enhances the life span of ESS. It reduces the stress on interfaced converters, regulates the system bus voltage, reduces power fluctuations on the sources, and enhances stability. The proposed control algorithm is verified in MATLAB simulation and in real-time simulator. [ABSTRACT FROM AUTHOR]

This paper presents a battery control and monitoring strategy for a DC microgrid feed by a public utility (PU) photovoltaic (PV) including with multi-battery bank (BB). The BBs respond to the changes in a power imbalance between generation and demand within a DC micro-grid, to maintain the micro-grid voltage and reliability enhancement. The fuzzy model reference learning control (FMRLC) controller has been designed to power control of the battery bank. The proposed battery control and monitoring system (BCMS) strategy keep the battery charging and discharging power as per standard charging/discharging characteristics of the battery. The BCMS allows continuous monitoring and intelligent control of distribution system operations such as battery bank energy storage (BBES), the PV system and the electric load of the consumer. A power sharing between the sources has been controlled for smooth supply. A graphical user interface (GUI) in the MATLAB environment has been configured to demonstrate the control and monitoring of the DC micro-grid and the operation performance of the BCMS algorithm for various scenarios (i. e modes). The proposed BCMS shows better operational performance for various operating conditions in terms of monitoring and control of the batteries power in the grid-connected DC micro-grid. [ABSTRACT FROM AUTHOR]

Large disturbance scenarios, such as pulse power load operation and load switching are commonly seen in the operation of dc microgrids. The mixed potential theory-based large-signal stability (LSS) analysis is a simple and practical method for investigating the LSS of dc microgrids. However, this method is characterized by conservatism, and produces conservative stability criterion results. When they are applied to the parameter designs of dc microgrids, they create excessive control parameter redundancies; when used for running status estimations, they may cause the system to be misjudged as unstable, and trigger unnecessary protective actions when the system runs into the conservative region. This paper presents a comprehensive analysis of the conservatism, revealing its main causes to be the idealization of the load converter's response characteristics, and the lack of refined models. It then proposes a novel, improved analysis method for transient response characteristics of the load converter. Experimental and simulation results using the improved method have validated it by showing that the conservatism of the traditional method had been eliminated, and the stability criterion obtained was more accurate. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of dynamic stabilization of dc microgrids (MGs) through a robust non-fragile fuzzy control synthesis of power buffer. The suggested robust fuzzy controller is designed to quickly stabilize the MGs by circulating the power between the dc link and an energy storage system (ESS). By employing the exponential stability analysis and Takagi–Sugeno fuzzy modeling, sufficient controller design conditions are derived in terms of linear matrix inequalities, which bring about a simple, systematic, and effective controller. The proposed approach is resilient against the uncertainties of the dc MG and ESS parameters. To show the merits of the proposed approach, it is applied to a dc MG that feeds one constant power load. It is shown that the proposed approach is more robust against system and controller uncertainties compared to the existing results. Finally, experimental results are then presented that show the transient performance improvement of the closed-loop system compared to the state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Due to the private ownerships of various resource and equipment in a microgrid, it is essential to design a proper power trading strategy for a mutually satisfying partnership among suppliers and users. This paper proposes a novel discounted min-consensus algorithm to discover the optimal electrical power trading route with minimal power loss in dc microgrids. The proposed distributed algorithm only requires information exchange among neighbors based on a peer-to-peer communication protocol, which is robust to topology changes and enables parallel data processing to achieve fast decision-making. The convergence and optimality of the proposed discounted min-consensus algorithm are guaranteed by rigorous analysis. Simulation results of the 10-bus, 68-bus, and 1062-bus power systems demonstrate the effectiveness of the proposed distributed optimal routing strategy for electrical power trading. Moreover, the proposed novel distributed algorithm sheds light on applying distributed control and optimization approaches to solve problems arising in artificial intelligence. [ABSTRACT FROM AUTHOR]

DC microgrid is gaining attraction and a recent trend in distribution power generation system due to penetration of renewables (especially photovoltaic or fuel cell). In this paper, a new triple-switch-triple-mode high step-up converter (TSTM-HS converter) is presented for dc microgrid applications. In the proposed converter, voltage lift technique is employed and range of duty cycle is extended by incorporating an additional switch in converter circuitry. By doing this, high voltage conversion ratio is achieved without using a transformer, coupled inductor, and multiple stages of switched capacitors. Moreover, the TSTM-HS converter operated in three modes with two types of the duty cycles to achieve low to high voltage conversion without using high duty cycle for each switch. The effects of difference in the inductance values on the regulation and operating behavior of the TSTM-HS converter are discussed. The continuous conduction mode and discontinuous conduction mode characteristics of the TSTM-HS converter are discussed in detail with steady-state analysis and boundary condition. The comparison is provided to highlight the benefits of the TSTM-HS converter. The selection of semiconductor devices and the design of reactive components are discussed for the TSTM-HS converter. The experimental results of the proposed converter are provided which validate the theoretical approach, performance, and feasibility of converter. [ABSTRACT FROM AUTHOR]

Photovoltaic solar home systems (SHSs) provide a cost-effective solution for the limited electrification of remote off-grid communities. However, due to their standalone nature, the benefit of usage diversity cannot be extracted. In this paper, we present the power electronic interface along with the decentralized control scheme for the integration of standalone SHSs for driving community load applications. Power electronic interface consists of an isolated boost converter capable support dc bus integration, thereby it formulates a dc microgrid through the interconnection of multiple standalone SHSs. Power aggregation is achieved through decentralized controlled resource sharing based upon the resource availability and installed capacity in the individual solar home system. To ensure cost affordability and to avoid the deployment of any communication infrastructure, modified I–V droop control is designed for the intended application. Thereby, power aggregation through the proposed power electronic interface and its decentralized control allows us to extract the benefit of usage diversity and drive high power community power loads at a village scale. The overall schematic is simulated using MATLAB and scaled down model is implemented on hardware. Results of power aggregation from various resource sharing scenarios are illustrated. [ABSTRACT FROM AUTHOR]

This paper proposes a new load current sharing control strategy for dc microgrid (MG). It adopts the piecewise linear formation to adaptively assign droop gains to balance the load sharing accuracy with the deviation of bus voltage. Communication among the distributed units is unnecessary for the proposed operation. The approach is considered as a comprehensive solution to deal with the unbalanced performance in dc MG for different load levels. The balancing performance is shown by comparing with the traditional linear droop control and the latest nonlinear droop gain solution. The study is proceeded by the in-depth analysis of both steady state and system dynamics with simulation support. The claimed advantage is finally verified by both simulation and experimental evaluations. [ABSTRACT FROM AUTHOR]

Ensuring accurate current sharing and regulating output voltage is challenging in DC microgrids. Conventional droop control has limitations in achieving voltage regulation and accurate current sharing. Unequal transmission line resistances, local loads, and constant power load (CPL) add to the complexity. To tackle this issue, this paper presents a novel consensus based distributed secondary control that determines the resistance of transmission lines by injecting an external pulse to the reference voltage of each converter, and then measuring the resulting changes in output voltage and current. The proposed secondary control signal, denoted as ψi, enables simultaneous proportional current sharing and voltage restoration in the DC microgrid. To guarantee the stability of the proposed method, a comprehensive stability analysis of the system is performed. In contrast to similar methods, the proposed method enables achieving precise proportional current sharing and voltage restoration, even when faced with varying resistive loads and CPLs. Furthermore, the proposed method exhibits remarkable features including, high convergence speed, the capability to determine transmission line resistances instead of assuming them to be known, and robustness in plug-and-play scenarios and communication system failures. The proposed method is validated through simulations in MATLAB and experimental tests, affirming its effectiveness. [ABSTRACT FROM AUTHOR]

This paper addresses the mean-square quasi-consensus problem for a class of heterogeneous multi-agent systems (MASs) with cascade-type two-layer structure subject to discrete-time deception attacks. A two-layer distributed hybrid controller is proposed based on the structural characteristics of the considered MASs. The deception attacks are supposed to occur in the upper-layer communication channel and their occurrences are modeled by a Bernoulli process. The discrete-time deception signal is considered as a bounded external disturbance sequence, so the mean-square quasi-consensus problem can be reduced to a mean-square exponential input-to-state stability (MSEISS) problem. A novel MSEISS analysis method combined with the use of a weighted discontinuous Lyapunov function is developed to establish a MSEISS criterion of the consensus error system, where the robustness performance of the mean-square quasi-consensus with respect to the randomly occurring deception attacks is quantified by the MSEISS gain. The effectiveness of the proposed resilient distributed hybrid control algorithm is verified through numerical simulations. Specifically, the proposed resilient control algorithm is applied to the secondary control of DC microgrid with discrete interaction. Several case studies show that the resulting resilient distributed hybrid secondary control algorithm has a good robustness performance on resisting the deception attacks. • A hybrid control framework for heterogeneous multi-agent systems under discrete-time deception attacks is developed. • A separate principle is proposed to decouple the design of lower- and upper-layer controllers. • The effect of deception attacks on consensus performance is analyzed in terms of mean-square input-to-state stability. • A resilient secondary control algorithm is proposed for DC microgrids subject to deception attacks. [ABSTRACT FROM AUTHOR]

In the DC microgrid, aimed at the power flow problem of dual active bridge (DAB) converters and their connected energy storage systems, this paper proposed an accurate direct power control(ADPC)method. The introduced control approach ensured constant power transmission on both sides of the DAB converter and was characterized by high accuracy, fast dynamic response, and excellent stability. It overcame the limitations of traditional direct power control(DPC)methods, which were highly dependent on system parameters. The effectiveness of the ADPC method was verified through simulations using MATLAB/Simulink and real-world experimental platforms. When compared to traditional power PI control methods, the proposed ADPC method, according to simulation and experimental results, significantly improves the dynamic performance of output power, especially under conditions of abrupt changes in power setpoints, load shifts, and input voltage fluctuations. Moreover, the method is independent of system parameters, enhancing the control method's compatibility and portability. The proposed method shows promising application prospects in the field of electric energy dispatch control within DC power supply networks. [ABSTRACT FROM AUTHOR]

In DC microgrids, the utilization of renewable energy results in disruptions. This paper proposes coordinated control of multiple batteries using a fuzzy logic controller (FLC). The goal is to regulate the voltage and power on the DC microgrid. Method used with a modified DC coupling configuration. The proposed new DC coupling topology uses 2 photovoltaic (PV) arrays. Part of the PV array output will be stored in the battery, and part will be provided to the DC bus. Apart from being connected to the DC bus, PV array1 (PV-A1) and PV array2 (PV-A2) are also connected to battery 1 (B1) and battery 2 (B2) via a buck converter. Instead, battery 3 (B3) is connected to the public grid source. The results of the study show that with FLC the voltage deviation and DC bus power are lower when in comparison to the proportional integral (PI) controller. As well, voltage on the DC bus response time with FLC produces a settling time of 0.5 seconds and an overshoot of 0.5%, while the PI controller produces a settling time of 1.15 seconds with an overshoot of 27.6%. [ABSTRACT FROM AUTHOR]

Virtual inertia and damping control (VIDC) improves the stability of DC microgrid (DC-MG). However, the potential positive feedback aggravates low-frequency oscillation induced by the interaction insides control loops, which is explained and solved in this paper. The multi-timescale impedance modelling framework is established to clarify stability mechanism of VIDC and the low-frequency oscillation of VIDC controlled DC-MG. Control loops of different timescales are visualized as independent loop virtual impedance (LVI) elements to form an impedance circuit considering the constant power load (CPL), rather than an all-in-one impedance as the external dynamic representation of power converters. Concrete impedance analysis is performed on LVI to reveal the impedance-shaping effect of control loops intuitively, the physical impedance nature of control parameters and the interaction among different timescale, which illustrates the stability mechanism of VIDC. The low-frequency oscillation (LC impedance interaction) in voltage- and inertia-loop is elaborated by RLC circuits of LVIs. The potential instability factors, resulting in poor damping against voltage oscillation, are also revealed. Thus, dynamic stability enhancement method is further proposed to compensate for the negative damping caused by positive feedbacks of VIDC and CPL, and super-capacitor is added to alleviate rapid voltage changes. Accordingly, the passivity property of system impedance is strengthened and the stability can be evaluated by Nyquist plot. Finally, the simulation and experiment results have validated the low-frequency oscillation analysis and stability enhancement method. [ABSTRACT FROM AUTHOR]

In this paper, an integral terminal sliding mode controller (ITSMC) based on a modified exponential reaching law (MERL) is developed for providing large-signal DC-bus voltage stability while smoothing power flow in DC microgrids (DCMGs). It is worth mentioning that this control approach is not employed in DCMG applications yet to adjust the DC-bus voltage while preserving power balance. The proposed DCMG is made up of a solar photovoltaic (PV) unit, a battery energy storage system (BESS), and DC loads. A DC-DC boost converter (DDBC) and a bidirectional DC-DC converter (BDDC) are employed to connect the solar PV and BESS, respectively, with the DC-bus, which not only controls the output power of these units but also regulates the DC-bus voltage. First, a detailed dynamical model including external disturbances is developed for each component, i.e., the solar PV and BESS. Then, the proposed control approach is employed on these units to get their corresponding control signals. Afterward, the overall stability of each unit is ensured using the Lyapunov stability theory. Moreover, to ensure the robustness of the proposed controller, external disturbances are also bounded based on the value of user-defined constants. Finally, simulation results are used to evaluate the effectiveness of the proposed control approach in a variety of operational scenarios. Additionally, simulation results of the proposed control strategy are compared to those of existing controllers to demonstrate its superiority. [ABSTRACT FROM AUTHOR]

A DC microgrid has many advantageous features, such as low power losses, zero reactive power, and a simple interface with renewable energy sources (RESs). A bipolar DC microgrid is also highlighted due to its high-power quality, improved reliability, and enhanced system efficiency. However, the bipolar DC microgrid has high DC bus voltage fluctuation due to the load power unbalance between the poles. Therefore, this paper analyzes the DC bus voltage fluctuation that can occur in the bipolar DC microgrid. An autonomous grid voltage regulation method is introduced to regulate the DC bus voltage of a bipolar DC microgrid using distributed energy storage systems (ESSs). The proposed grid voltage regulation scheme using the distributed ESSs could regulate DC bus voltage in real time, regardless of the structure of the DC microgrid without external communication. Lastly, experimental results using a lab-scale bipolar DC microgrid prototype verified the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a single-objective model predictive control for a bidirectional DC-DC flying capacitor (FC) converter, which integrates a battery to the microgrid. The presence of multiple FCs facilitates the converter to interface a low-voltage battery to a high-voltage DC bus at reduced voltage stress on its power switches. However, such converter requires a controller that fulfils multiple objectives, namely DC bus and FC voltage regulations, and bidirectional power flow. The key feature of the proposed controller is that it utilizes a model predictive control with a single-objective cost function based on battery current and a redundant state selection scheme to attain these multiple objectives. Adopting such a strategy not only reduces computational burden but also eliminates the need for weighting factors and requirement of complex numerical models for its estimation. Another notable aspect is that the controller employs an improved dynamic reference model to generate appropriate battery current reference for the DC bus voltage regulation, without necessitating a secondary control loop and additional current sensors. Finally, experimental results of the proposed system for a step-response of the DC bus voltage, varying PV power, and loads are validated and compared against finite control set model predictive control. [ABSTRACT FROM AUTHOR]

Distributed energy resources have been broadly developed in recent years for supporting DC and AC microgrids. Unfortunately, most of them produce low output DC or AC voltages, and interfacing converters are required. These are implemented either in single‐stage or dual‐stage configurations. Step‐up converters are the essential section in dual‐stage designs, which their producing gain is important. Improving the boost factor and efficiency as well as decreasing the number of required components and electrical stresses on power components are the most critical challenges in designing such topologies. Continuing past efforts, this paper proposes a new non‐isolated step‐up DC/DC converter that can be used in low‐voltage distributed power systems and many other applications requiring step‐up DC/DC conversion. The topology requires only one power switch located on the converter's low voltage (LV) side. Hence, it can be easily selected from LV ratings, low on‐resistance power semiconductors. Besides, the converter operates with a continuous input current, which is a valuable feature in connection with current‐sensitive voltage resources. Compared with the recently proposed topologies, the topology provides better conversion gain and efficiency. In this article, the operating principle of the introduced converter is comprehensively investigated. Also, in order to examine the converter performance, experimental results will be presented and analyzed. For this purpose, a 400 V/400 W prototype has been designed and built. Results confirm the above claims and show that the converter efficiency equals 96.1%, and it produces high output voltage gain about 12 times. [ABSTRACT FROM AUTHOR]

The superior access to renewable sources in modern power systems increases the fluctuations in system voltage and power. Additionally, the central dilemmas in using renewable energy sources (RESs) are the intermittent nature of and dependence on wind speed and solar irradiance for wind and photovoltaic (PV) systems, respectively. Therefore, utilizing a vigorous and effective energy storage system (ESS) with RESs is crucial to overcoming such challenges and dilemmas. This paper describes the impacts of using a battery storage system (BSS) and superconducting magnetic energy storage (SMES) system on a DC bus microgrid-integrated hybrid solar–wind system. The proposed method employs a combination of BSS and SMES to improve the microgrid stability during different events, such as wind variation, shadow, wind turbine (WT) connection, and sudden PV outage events. Distinct control approaches are proposed to control the system's different components in order to increase overall system stability and power exchange. Both the PV and wind systems are further equipped with unique maximum power point tracking (MPPT) controllers. Additionally, each of the ESSs is controlled using a proposed control method to supervise the interchange of the active power within the system and to keep the DC bus voltage constant during the different examined instabilities. Furthermore, to maintain the load voltage /frequency constant, the prime inverter is controlled using the proposed inverter control unit. The simulation results performed with Matlab/Simulink show that the hybrid BSS + SMES system successfully achieves the main targets, i.e., DC voltage, interchange power, and load voltage/frequency are improved and smoothed out. Moreover, a comparison among three case studies is presented, namely without using ESSs, using the BSS only, and once more using both BSS and SMES systems. The findings prove the efficacy of the proposed control method based on the hybrid BSS + SMES approach over BSS only in preserving the modern power system's stability and reliability during the variable events. [ABSTRACT FROM AUTHOR]

Dual active bridge converters (DAB) are used to interconnect photovoltaic (PV) generators with AC and DC buses or isolated loads. However, a controller is needed to provide a stable and efficient operation of the DAB converter when the PV generator must be interconnected with a DC bus, which is particularly important in microinverter applications. Therefore, this paper proposes the design of a cascade controller for a PV system based on a DAB converter. The converter is controlled using a peak current control and an adaptive PI voltage control; thus the methodology to design the cascade controller is developed in two steps; first, the PV system formed by a PV generator, a DAB converter, and an inverter or load is introduced, including the description of the leakage current; as a second step, the model of the PV system to design the cascade controller is presented. Then, a relationship between the phase shift factor and the peak current of the leakage inductor is derived, which is used to design the peak current controller to ensure the DAB converter operation at the most efficient operating condition. On the other hand, an adaptive PI controller for the PV voltage is designed to ensure the reference tracking provided by a maximum power point (MPP) algorithm. The effectiveness of the proposed cascade controller is demonstrated through realistic examples simulated in PSIM. The power and control circuits implemented in PSIM are presented to encourage the use of the proposed solution. The simulation results confirm the correct operation of the control system, which mitigates the oscillatory perturbation produced by an inverter connected to the PV system, and also ensures the maximum power extraction from the PV panel by following the MPP reference. [ABSTRACT FROM AUTHOR]

The standalone microgrids with renewable energy resources (RERs) such as a photovoltaic (PV) system and fast changing loads face major challenges in terms of reliability and power management due to a lack of inherent inertial support from RERs and their intermittent nature. Thus, energy storage technologies such as battery energy storage (BES) are typically used to mitigate the power fluctuations and maintain a power balance in the system. This paper presents a model predictive control (MPC) based power management strategy (PMS) for such standalone PV/battery systems. The proposed method is equipped with an autoregressive integrated moving average (ARIMA) prediction method to forecast the load and environmental parameters. The proposed controller has the capabilities of (1) effective power management, (2) minimization of transients during disturbances, and (3) automatic switching of the operation of the PV between the maximum power point tracking (MPPT) mode and power-curtailed mode that prevents the overcharging of the battery and at the same time maximize the PV utilization. The effectiveness of the proposed method has been verified through a comprehensive simulation-based analysis. [ABSTRACT FROM AUTHOR]

In an islanded DC microgrid with multiple distributed generators (DGs), the droop control is employed to realize proportional current sharing among the DGs in the microgrid. The action of the droop control causes a deviation in the DC bus voltage which is exacerbated by the line impedance between the DG and the DC bus. In this paper, an advanced distributed secondary control scheme is proposed to simultaneously achieve accurate voltage regulation and cooperative current sharing in the islanded DC microgrid system. The proposed distributed secondary controller is introduced in the cyber layer of the system, and each controller shares information with neighbouring controllers via a communication network. The distributed technique maintains the reliability of the overall system if some part of the communication link fails. The proposed controller uses the type-II fuzzy logic scheme to adaptively select the secondary control parameters for an improved response of the controller. The sufficient conditions to guarantee the stability of the proposed controller are derived using the Lyapunov method. Comprehensive tests under different operating scenarios are conducted to demonstrate the robustness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Despite its advantages over its AC counterparts, DC microgrids present a lot of challenges. One of these challenges is the instability issues caused by constant power loads (CPLs). CPLs deteriorate the system's performance due to their incremental negative impedance characteristics. In this paper, a DC microgrid composed of a PV/battery system feeding a pure CPL was considered. A continuous-time model predictive control combined with a disturbance observer was applied to the DC–DC bidirectional converter. The purpose of the composite controller is to address the nonlinearity of the CPL and to maintain the stability of the system in a large operating region under load and PV generation variations. To show the performance of the system, several tests were performed under PV power and CPL power variations. Simulation results show good performance in terms of transient response, optimal tracking, and stability in a large operating region. [ABSTRACT FROM AUTHOR]

The state-of-the-art dynamic consensus-based microgrid (MG) secondary controls suffer from the communication delay effect. Specifically, the system could not converge to the desired operating points with time-delayed communications. Such deviations are hard to detect in a decentralized manner and could destabilize the system. This paper proposes an accurate distributed secondary controller for DC MGs based on the surplus consensus algorithm. The proposed controller achieves accurate proportional power sharing and average voltage regulation among distributed generators (DGs) with the presence of variable and bounded communication delays. A surplus consensus-based observer is developed. The developed observer is proved robust against variable and bounded communication delays; it tracks the average of a group of dynamic states with zero steady-state deviations, which cannot be done using the conventional dynamic consensus-based observer. The convergence speed of the developed observer is analyzed and a parameter design procedure is presented. Moreover, the delay-dependent stability analysis of DC MG operation with the proposed secondary controller is derived. The marginal delay that leads the system to instability is calculated. At last, the performance of the proposed secondary controller and the developed stability analysis are validated under various scenarios using MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

This paper proposes a nonunit protection scheme for DC microgrids (DC MGs) utilizing only local measurements. This scheme is developed based on the natural characteristics of DC current and its first and second derivatives under fault transients. Since it is based on local measurements, the problems associated with the communication delay are avoided. The selected protection scheme detects and discriminates the faults within a few microseconds of its inception. In this paper, a method to calculate the thresholds, used for the protection scheme, is also discussed. The proposed scheme is validated on a ring-type DC MG architecture under different fault scenarios and tested through MATLAB/Simulink simulations. [ABSTRACT FROM AUTHOR]

There are difficulties in analyzing the stability of microgrids since they are located on various network structures. However, considering that the network often consists of passive elements, the passivity theory is applied in this paper to solve the above-mentioned problem. It has been formerly shown that when the network is weakly strictly positive real (WSPR), the DC microgrid is stable if all interfaces between the microgrid and converters are made to be passive, which is called interface passivity. Then, the feedback passivation method is proposed for the controller design of various DC-DC converters to achieve the interface passivity. The interface passivity is different from the passivity of closed-loop systems on which the passivity based control (PBC) concentrates. The feedback passivation design is detailed for typical buck converters and boost converters in terms of conditions that the controller parameters should satisfy. The theoretical results are verified by a hardware-in-loop real-time laboratory (RTLab) simulation of a DC microgrid with four generators. [ABSTRACT FROM AUTHOR]

This research paper presents a novel long-horizon move-blocking based direct power model predictive control (DPMPC) strategy, uniquely designed to enhance the dynamic performance of boost converters in the grid-connected mode within DC microgrids. A precise dynamic model is developed considering a boost converter connected to a DC-link supplying constant power and resistive loads. To predict the system's dynamic behavior over an extended interval and enhance its performance in the presence of constant power loads, the long-horizon based finite control set model predictive control (FCS-MPC) method is introduced. To address the computational complexity associated with the conventional long-horizon DPMPC approach, a move-blocking (MB) strategy is incorporated into FCS-MPC, reducing the computational burden while improving the dynamic performance of the boost converter. Unlike recent studies that utilize DPMPC with short prediction interval, this paper presents evidence that a longer prediction interval is crucial for maintaining system stable and enhancing the dynamic response and also utilizing MB to make the control implementable in the real-time. The simulation results conducted using MATLAB/Simulink demonstrate the effective performance of the proposed strategy across various operating conditions of the boost converter. Experimental results further validate the strategy's capability to enhance the dynamic performance of the boost converter. Importantly, the experimental findings confirm the feasibility of implementing the proposed long-horizon move-blocking DPMPC strategy in real-time applications. • Developing an accurate dynamic model for a boost converter. • Proposing a long-horizon direct power model predictive control strategy. • Limiting the number of calculations and the execution time of the proposed strategy using move-blocking approach. [ABSTRACT FROM AUTHOR]

The coordination of clustered microgrids (MGs) needs to be achieved in a seamless manner to tackle generation-load mismatch among MGs. A hierarchical control strategy based on PI controllers for local and global layers has been proposed in the literature to coordinate DC MGs in a cluster. However, this control strategy may not be able to resist significant load disturbances and unexpected generated powers due to the sporadic nature of the renewable energy resources. These issues are inevitable because both layers are highly dependent on PI controllers who cannot fully overcome the abovementioned obstacles. Therefore, Grey Wolf Optimizer (GWO) is proposed to enhance the performance of the global layer by optimizing its PI controller parameters. The simulation studies were conducted using the well-established MATLAB Simulink, and the results reveal that the optimized global layer performs better than the conventional ones. It is noticed that not only accurate power-sharing and proper voltage regulation within ±1% along with fewer power losses are achieved by adopting the modified consensus algorithm for the clustered DC MGs, but also the settling time and overshoot/undershoot are reduced even with the enormous load and generation changes which indicates the effectiveness of the proposed method used in the paper. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of false data injection attack (FDIA) detection in microgrids. The grid under study is a DC microgrid with distributed boost converters, where the false data are injected into the voltage data so as to investigate the effect of attacks. The proposed algorithm uses a bank of sliding mode observers that estimates the states of the neighbor agents. Each agent estimates the neighboring states and, according to the estimation and communication data, the detection mechanism reveals the presence of FDIA. The proposed control scheme provides resiliency to the system by replacing the conventional consensus rule with attack-resilient ones. In order to evaluate the efficiency of the proposed method, a real-time simulation with eight agents has been performed. Moreover, a verification experimental test with three boost converters has been utilized to confirm the simulation results. It is shown that the proposed algorithm is able to detect FDI attacks and it protects the consensus deviation against FDI attacks. [ABSTRACT FROM AUTHOR]