This paper proposes a proper hierarchical control strategy composed of a modified droop controller in primary level and a distributed finite-time average controller in secondary layer. The aim of this paper is to achieve precise active and reactive power sharing and frequency and voltage alignment in an islanded AC microgrid (MG). To do so, a typical AC MG is simulated in MATLAB/SIMULINK software, and the proposed method is modeled and implemented. In the simulated AC MG, the distributed generation (DG) units are photovoltaic (PV) systems. The obtained results illustrate that the proposed method appropriately shares active and reactive powers among presented DGs in various operational modes such as load change, increase or decrease in DGs’ output power as well as connection and disconnection of communication links. It also accurately  restores the frequency and voltages of DGs to their nominal values.

Today, in many control methods, neighboring system information is used for better control and synchronization between different units, and therefore, in the access and transmission of information through communication links, problems such as disruption, uncertainty, noise, delay, and cyber-attacks occur. In this paper, the effect of the Denial of Service (DoS) cyber-attack on the microgrid in island mode is investigated and a cooperative distributed hierarchical controller is designed with the presence of this cyber-attack. distributed Generations (DGs) have been analyzed with the help of multi-agent systems and the communication network between them using graph theory. The effects of the DoS cyber-attack on the model of DGs are mathematically formulated and in proving the stability and synchronization of frequency and voltage, the suitable Lyapunov function is presented and the stability analysis of DGs against these cyber-attacks is performed and the stability and synchronization conditions of DGs are proved. To confirm the proposed theoretical issues, a case study model is simulated despite the DoS attack on the communicative links in Matlab Simulink, and the results show the performance of the designed controller in different conditions.

Dedicating more attention to renewable energies and power electronic improvements results in increased direct current microgrids (DC MGs) application. However, DC MGs have some challenges with voltage adjustment and power sharing. To do so, a two-layer hierarchical control structure, including a new fully distributed secondary control strategy and conventional primary droop control method, is proposed and employed in this paper to share power and swiftly adjust the voltage accurately. Indeed, a distributed-averaging proportional-integral (DAPI) secondary control strategy is introduced. Another problem in DC MGs is the existence of constant power loads (CPLs), which may result in instability. To overcome the problems caused by CPLs, a term based on the output voltage of CPL is added to the proposed DAPI to prevent instability. The required control inputs are obtained using localized data of the DC bus and their neighbor’s secondary control inputs inspired by cooperative control. Besides, this strategy needs no knowledge of the microgrid topology, which enhances flexibility. For validating the proposed DAPI strategy in DC MGs, an islanded DC MG is simulated in the MATLAB/SIMULINK software. Comparing the results with those obtained from another existing method proves the performance of the proposed DAPI controller under different scenarios of plug-and-play, communication failure, and load changes.

Microgrid, as a new structure of power systems, has challenges that should be addressed; regulating the frequency and voltage and power sharing are among the most critical challenges of AC microgrids (MGs). This paper studied a novel two-level control strategy composed of a modified droop controller at the primary level and a distributed finite-time (DFT) average controller in the secondary layer to achieve more precise active and reactive power sharing along with frequency and voltage alignment by implementing this strategy in an islanded AC MG. Thus, a typical AC MG, including three distributed generation (DG) units, is simulated in MATLAB/SIMULINK software, and the proposed method is first formulated, modeled, and then simulated. For validation and better comparison, the results obtained by the proposed method were compared to the conventional droop and other distributed methods in case studies of load changes and plugging in/out of DG units. The results proved that the proposed method appropriately shared active and reactive powers among DG units. It also efficiently restored the frequency and voltages of DG units to their nominal values. Moreover, a mathematical stability analysis is obtained that proved the stability of the proposed DFT-based secondary controller.

distributed generations that are connected to the network via a converter, employ dq current control method to control their active and reactive power components in grid-connected mode. In this paper a simple lead-lag control strategy is proposed for a distributed generation (DG) unit in island mode. When it is connected to the utility grid, the DG is controlled by a conventional dq-current control strategy for active and reactive power components. Once the islanding occurs, the dq-current controller is disabled and the proposed controller is used in order to for control of the DG unit operating with its local load. The problem of tuning of controller parameters is converted to an optimization problem with a time-domain objective function which is solved by a genetic algorithm. To achieve a robust performance ITAE criterion is used as objective function. The robustness of controller is proved by zero-pole diagram and frequency domain analysis. Simulations results under different operating conditions verify robustness of controller in comparison with a classical d-q based controller. The results reveal that the proposed control strategy has an excellent capability in achieving good robust performance and greatly enhances the dynamic stability of the system against load parameter uncertainties.

In the family of Flexible AC Transmission Systems (FACTS) controllers, the distributed power flow controller (DPFC) can control powerfully all the system's parameters like bus voltages magnitude, transmission angle, and line impedances with high redundancy and a wide range of compensation. In this paper, IEEE-14 bus IEEE-30 bus, and IEEE-118 bus systems are taken for the testing of the proposed approach. The optimal placement of the series and shunt converters of the DPFC is decided by the most critical bus and most critical line associated with that bus respectively. The sizing of the DPFC is decided based on the minimization of active power losses of the systems. The loss function is considered an objective function and the limits of the bus voltages magnitudes, bus voltage angles, thermal limits of the lines, and level of compensation of the DPFC are taken as the system's constraints. To solve complex problems in various fields, meta-heuristic optimizations are more popular. Among the meta-heuristic optimizers, the jellyfish optimizer is one that is based on the behavior of jellyfish in the ocean. The optimization of the objective function with constraints has been solved by time-varying acceleration coefficients (TVAC) particle swarm optimization (PSO), artificial bee colony (ABC), genetic algorithm (GA), and metaheuristic optimizer jellyfish methods. Results show that all the optimization techniques provide solutions with minimum losses. Among these methods, the solution of the jellyfish optimizer has the lowest active power losses, highest convergence rate, less number of iterations, and also takes less computational time.

In this paper, a new hierarchical robust control approach based on the combination of decentralized and distributed control is proposed for voltage control and power sharing in islanded DC microgrids by considering uncertainties and disturbances in the primary control loops and communication channels in the secondary layer. Uncertainties and disturbances are the main factors that can affect the stability of a microgrid. Unlike the previous methods, first by using a decentralized robust PI control structure based on Kharitonov's theory, the primary voltage control loop is robustly designed considering uncertainties and disturbances. By anticipating these changes and preventing them from entering the communication channel in the secondary layer, we compensate for the voltage deviations in the primary layer by using the distributed PI robust control structure. In addition to being simple and robust, the proposed controller is based on a new consensus and robust decentralized protocol, which has a higher convergence rate than the previous protocols and its performance is completely satisfactory under the conditions of uncertainties and large disturbances. Different simulations are performed in MATLAB/SimPowerSystems toolbox on a standard DC microgrid including four distributed generations and under different disturbances. The simulation results show the effectiveness of the proposed controller. In general, the proposed controller increases the reliability of microgrid by sending low data in communication channels.

Musculoskeletal disorders caused by heavy workloads are very common in workers, which negatively affects workers' health and productivity. In this regard, the idea of designing an exoskeleton robot is proposed. This robot is similar to a dress which worn on the user's body and parallels the body, accompanying and helping the person. In this paper, the parallel distributed compensation control method is proposed to be applied to a four degrees of freedom exoskeleton waist robot. Initially, the dynamical equations governing the system are extracted. According to the nonlinear nature of the system, the parallel distributed compensator controller is designed with a Takagi-Sugeno linearization approach. The closed loop system response of this controller is investigated in the Simulink environment of the MATLAB software. The results show that the Takagi-Sugeno linearization approach accurately estimates the nonlinear system, and also the proposed controller perfectly intercepts the optimal closed loop response.

The ever-increasing of renewable distributed generation sources in distribution networks, as well as increasing network size, have faced agent-based protection schemes with a heavy communicational load. Accordingly, despite the fast and reliable nature of multi-agent systems, they have the possibility of improper performance, especially in centralized protection systems. This paper presents an intelligent self-healing method that has the ability to replace common multi-agent systems during fault conditions. Therefore, protection tasks are performed in a single control level, without dependence on higher communicational levels, to clear the fault. Decentralized operation of this structure is provided by using intelligent electronic devices and distributed communications. In this way, the proposed scheme is described with high-speed peer-to-peer communication capability using the IEC-61850 GOOSE protocol. Then, a penetration-free algorithm, without the help of a central controller, is provided by using GOOSE message capabilities, to prevent any electricity interruption due to insufficient protection settings. Finally, by planning different scenarios and simulating a practical distribution network via ETAP software, the accuracy of the proposed algorithm has been proven.

In recent years, a new generation of networks called software defined networks (SDN) has been introduced whose main focus is on separating control logic from hardware and concentrating it on a central software called the "controller". SDN improves the network efficiency and reduces the expenses. Despite numerous advantages, SDN faces a lot of challenges such as scalability and reliability that can be fixed through physical decentralization of the control level and introduction of distributed controllers. However, the distributed controllers also face challenges including scalability, stability, and coordination strategy. This research deals with the improvement of distributed controllers’ scalability using the concept of load balancing. For this purpose, we have suggested that a controller load detection function (CLDF) be placed on each of the related controllers, and if the load exceeds the threshold level, the new load be transferred to a controller with the least load. The suggested method is implemented on the Floodlight controller in a distributed manner, and implemented on Ubuntu 14. 04 operating system using the mininet simulation platform. The simulation results show that suggested method causes an average growth of 31. 6 percent on the transition rate.