A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

Conventional droop-based techniques have widely been used in controlling Voltage Source Inverter (VSI) based on distributed generation units within a Micro-Grid (MG). Despite the simplicity and high reliability of the controller, the low-inertia nature of VSIs threatens the system stability against probable disturbances. Thus, from the stability viewpoint, it is essential to carefully monitor the system operating point to determine the stable region of the parameters affecting the micro-grid stability. To this end, a complete dynamic model for an inverter-based micro-grid has been derived. According to this model, states affecting the dominant eigenvalues of the system are identified using eigenvalues analysis and modal analysis. Then, bifurcation theory is used to predict the parameter stability margin and identify the type of bifurcation. In this paper, by introducing a bifurcation index, the appropriate virtual impedance X/R ratio is selected from the viewpoint of both small-signal analysis and bifurcation analysis. Finally, a multi-objective optimization framework is presented to prevent such a problem in parallel to other operational goals.

The presence of the inverter distributed generations in the power systems can bring about incoord-ination in the protection system performance while enjoying various advantages. In this paper, a suit-able solution, independent of relay settings, is presented in order to solve the protection problems of inverter island microgrids with circular arrangement. The presence of distributed inverter generation sources causes a change in the direction and amplitude of the fault current at the microgrid level. This problem is more visible in microgrids with circular arrangement. Therefore, conventional protection schemes that consider a single path and a high fault current level compared to load current may be problematic. An important factor for the proper design of a protective system for microgrids is the contribution of the injecting fault current of the inverter sources. In this paper, a protection strategy based on the inverter control of sources is presented and ordinary overcurrent relays with the same characteristic curve are used. When a short circuit fault occurs in the microgrid, an adaptive current limiting strategy is applied using the virtual impedance loop. In this case, the share of fault current of each source is controlled according to the position of the fault, and sources closer to the fault produce a larger fault current. Therefore, the current passing through the protective equipment is closer to the fault than other equipment in the micro grid. And without the need for making connection between protective equipment, the protective coordination is guaranteed.

Grid-connected inverters are crucial in transmitting power from distributed production systems and renewable sources to the grid. However, these inverters often generate current harmonics due to high-frequency switching and DC link ripple. To address these issues, various filters, including the LCL filter, are employed. This paper focuses on improving the power quality of grid-connected photovoltaic arrays using LCL filters, primarily through a current sensor and virtual impedance shaping. The paper divides the output impedance of the photovoltaic array power optimization system into an active and passive part. It neutralizes the active component by introducing a series of virtual impedances and counteracts its adverse effects with parallel virtual impedance. The design process for both series and parallel virtual impedance is elaborated, and the system's sensitivity is thoroughly analyzed. To validate the proposed approach, extensive simulations have been carried out using MATLAB software. The simulations demonstrate the robust and precise performance of the control system in effectively injecting the maximum power generated by the photovoltaic array into the grid. Additionally, they showcase the high-quality current being injected into the grid and the system's capacity to maintain stability, even in a weak network environment.

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.

With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and the converter may be unstable during the fault. Converters use phase locked loop (PLL) to synchronize with the grid. PLL is not able to be stable during severe voltage drop, so converters cannot ride through the fault and should be disconnected. In this paper a novel method based on virtual impedance is proposed to maintain the synchronization during severe voltage drop. This method needs grid impedance estimation and virtually connects the converter to a point that has a stronger connection. By this novel method, during voltage drop, the converter stays connected to the grid and injects reactive power. Simulation results in MATLAB verify the ability of proposed method in improving the transient stability of converter.

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.

Deep-sea vessels use various navigational aids like AIS (automatic identification system), ECDIS (electronic chart display and information system), radar, GPS (global positioning system), and etc. vessels use AIS to communicate their navigational characteristics, destinations, and load information. Such data are very helpful for vessel officers; therefore, AIS can be used for communicating the name and position of the vessel as well as navigational signs in the port area. So, this system is very helpful in improving the quality of pilotage as well as improving the safety of navigation in canals like Khur Musa.

Due to the different distances and complexity of micro-grids, the lines impedance varies between the feeders of the distributed generation and the loads. Therefore, conventional droop control method does not have good efficiency in power distribution between distributed generation (DG) units. Generally, due to simplification, the impedance of the lines is not considered in a complex. The stated conditions greatly reduce the accuracy and speed of the dynamic response of the control system. In this paper, harmonic compensation, voltage and frequency control of micro-grid with adaptive virtual impedance method based on proportional power distribution are presented. In the proposed method, reducing the error coefficient of active power and reactive power, control of voltage and currents’,harmonic in two modes of connection to the main grid and islanded, as well as voltage and frequency control for optimal operation of the micro-grid is presented. The proposed method, without the need to update the impedance information of the feeders, has the capability of optimal operation and power distribution under different operating conditions, taking into account the complex impedance. To validate, the proposed method is simulated in MATLAB/Simulink software environment and the results are presented along with stability and sensitivity analysis.