Cyberphysical systems have achieved rapid development over the past decade due to their widespread applications in various domains, and are typically composed of sensing, communication, computing, and actuation capabilities. However, the communication network of physical security systems may be attacked by cyber attacks, which significantly destroys the performance of the system. Recently, DOS denial-of-service attacks (1) have attracted a lot of attention. In this article, a solution to deal with DoS attacks on the power sharing control system of the electrical energy distribution network, including distributed generation, is presented. So that a time-varying distributed estimator has been used. Based on the feature of service interruption communication duration, the convergent design conditions of observer parameters are obtained using Lebag2 integral theory and average dwell time method. It is also shown that the observer errors converge. Finally, the presented coping method is placed on the virtual impedance control line 3 of the power sharing control system and will neutralize service interruption attacks

Input-Parallel Output-Parallel DC-DC converters are convenient for high voltage and high current applications. One important goal of this type connection is to power-share and reduce circulating current between the converters. Therefore, control methods for power-sharing between converters should be used when the parameters mismatch. In this paper, a configuration comprising two DC-DC common grounded Z-source converters with Input-Parallel Output-Parallel connections is presented, which common grounded Z-source converter have advantages over similar converters. This study proposes two control strategies: (1) a decentralized inverse-droop control, (2) a general control strategy. Inverse-droop control is a simple method and does not need any communication between parallel converters. In the general control strategy, each converter is self-contained, and no external controller is required for achieving input/ Output Current Sharing, and a few wires are needed to create the entire system. The simulation results of an Input-Parallel Output-Parallel system comprising two common grounded Z-source converters are evaluated for investigating effectiveness of general control and inverse-droop control. It reported performance of the general control method to be better than the decentralized inverse-droop control method, which enhances the stability and dynamic characteristics of the system. The validity of the two control strategies has been studied through MATLAB simulation and the results were satisfactory.

With recent advances in power-electronics، inverter-based microgrids are gaining great attention. Droop control is one of the main methods to share the real and reactive power among distributed energy resources (DERs) in an islanded microgrids. Due to different characteristics of microgrid feeders، reactive power sharing is not fully accurate and consequently، some DERs may face overload. To address this problem، this paper presents a droop-based method using virtual impedance concept in the DER control system. The resultant voltage drop on the virtual impedance increases reactive power sharing accuracy. To adjust this virtual impedance، the local controllers of DERs exchange the required data with the microgrid management center using the low bandwidth communication links. Then، a virtual impedance? reactive power droop characteristic is proposed to calculate the value of virtual impedance. The slope of this characteristic is adaptively adjusted based on the microgrid load. To verify the effectiveness of the proposed method، various scenarios are tested on the benchmark low voltage microgrid network.

In this paper a repetitive control (RC) approach to improve current sharing between parallel-connected boost converters in DC microgrids is presented. The impact of changes in line impedance on current sharing is investigated. A repetitive controller is designed and connected in series with current controller of the boost converters to control the switching signals such that by regulating of the output voltage of each converter, the circulating current is minimized. The performance of the proposed control strategy is validated through simulation.

In this paper a new power sharing control method is proposed for islanding microgrids. With regard to low dynamic distributed generators like fuel cells, microgrid capability is enhanced to face the different load scenarios. In the new method there is not the need for energy storage devices like batteries and super capacitors in coordination with low dynamic energy resources. So the productivity of the installed capacity is enhanced. Any change in the load is automatically detected by the proposed method and the controller manages the dynamic distributed generator power in its transient time. Back to back voltage and current controllers are also embedded beside power controller to enhance the transient stability of the microgrid in sudden load changes. In order to evaluate the new method, a sample microgrid is considered. Simulation results show the proper power sharing among the generators while satisfying the frequency stability of the system. Technical and economical comparison show the effectiveness of the proposed power sharing method with respect to the conventional methods.

In this article, the control of interfaced converters of distributed generations (DGs) in order to improve microgrid power quality with emphasis on voltage unbalance is considered. The control scheme of these converters is coordinated so that the DGs contribute to voltage unbalance compensation proportional to their rated power and by considering the residual capacity of each DG. The control structures presented in this article are classified into two categories: voltage_controlled mode (VCM) control scheme and current_controlled mode (CCM) control scheme. VCM units using capacitive virtual impedance contribute to voltage unbalance compensation, while in the control scheme of CCM units, a virtual admittance is implemented in order to compensate voltage unbalance with considering the residual capacity of the inverter. Also, VCM and CCM units contribute to reactive power sharing by droop and reverse droop control methods, respectively. Droop coefficients are adjusted considering the limited capacity of these inverters and the unbalance power. Finally, the results were then presented to show the effectiveness of the proposed control structure at different stages.

In the islanded microgrids, distributed energy sources are responsible for power-sharing, and accurate power-sharing is essential among these microgrids. Due to the mismatch of the physical impedance of power lines, poor reactive power-sharing is observed. Therefore, in this paper, the use of virtual impedance in the form of two methods of virtual positive impedance and virtual negative impedance is proposed to improve the accuracy of reactive power-sharing in a conventional droop controlled islanded microgrid. In this paper, in addition to presenting a controller to properly adjust the virtual impedance, the concept of virtual negative impedance is used to correct the effective impedance of the power supply line and improve the common bus voltage, and increase the output power of energy sources. To evaluate the proposed control methods, a test islanded microgrid is simulated in PSCAD/EMTDC software. The results show that both proposed methods have a good effect on the proper reactive power-sharing in the microgrid. In addition, the results show that the virtual negative impedance method can improve the common bus voltage and increase the output power of the source by reducing the effective line impedance.

The increased penetration level of Distributed Generation (DG) units in microgrids that feed large loads in parallel connections has led to developing the concept of power sharing. A microgrid's voltage and frequency in the islanded mode are controlled using an inverter with high inertia. Therefore, the internal control loop is executed in such a manner as to avoid overloading of all the DGs in the microgrid. Consequently, reactive power sharing error is eliminated and the voltage is also kept constant within the permissible range. This paper presents a modified control method based on the sliding mode approach. The proposed control method is tested using several disturbances and three scenarios. Also, the fractional order calculus is applied to the proposed control strategy to increase the convergence speed and system accuracy. Finally, the proposed method is compared to other well-known controlling approaches and the achieved results confirm its superiority.

In this paper, a novel risk-based, two-objective (technical and economical) optimal reactive power dispatch method in a wind-integrated power system is proposed which is more consistent with operational criteria.  The technical objective includes the minimization of the new voltage instability risk index. The economical objective includes cost minimization of reactive power generation and active power loss. The proposed voltage instability risk employs a hybrid possibilistic (Delphi-Fuzzy)-probabilistic approach that takes into consideration the operator’s experience, the wind speed and demand forecast uncertainties when quantifying the risk index. The decision variables are the reactive power resources of the system. To solve the problem, the modified multi-objective particle swarm optimization algorithm with sine and cosine acceleration coefficients is utilized. The method is implemented on the modified IEEE 30-bus system. The proposed method is compared with those in the previously published literature, and the results confirm that the proposed risk index is better at estimating the voltage instability risk of the system, especially in cases with severe impact and low probability. In addition, according to the simulation results compared to typical security-based planning, the proposed risk-based planning may increase the security and economy of the system due to better utilization of system resources.

A single-phase distributed generation (DG) sources embedded in three-phase microgrids develop with a fast-paced trend, it is important to make use of suitable power sharing strategies among multiple DGs and utilizing the power generation of these units to the full capacity. This paper presents an innovative sliding mode-based power control strategy for microgrids. The multi-bus microgrid consists of three-phase DG units that are two photovoltaic (PV) array, and three single-phase DG units including PV, battery and fuel cell (FC). The dynamic modeling of all DGs is based on voltage source inverter (VSI). One of the three-phase DGs is responsible for frequency and voltage control, and the other one for current control. The single-phase DGs are controlled based on the three-phase DGs. Finally, the voltage and power control operations are implemented in a per-unit system. The proposed control strategy has a fast response and the ability to trace a reference signal with a low steady-state error compared with the PI controller; moreover, it provides the accurate active and reactive power sharing among energy units under various faults and loading conditions along with robustness against the microgrid parameters. Additionally, the ability to maintain the dc-link voltage and frequency constant is another feature of this controller.