## 1 Introduction  
In recent years, distributed generation (DG) units under smart grid ambient and assisted by a cyber-physical system have been considered in microgrids (MGs) [1; 2; 3; 4] to attain some benefits such as supplying the local loads, increasing reliability, reducing greenhouse gases, and delivering power to low voltage networks. To overcome the technical problems of connecting the DGs to the upstream distribution network, the concept of MGs have come to the attention of researchers, which are several collections of DGs, energy storage systems (ESSs), and loads which are responsive or not, as shown in Figure 1. A MG may be operated in grid connected mode or islanding mode due to a fault occurrence, maintenance scheduling, or maybe normal condition [5; 6; 7]. The voltage/frequency stability and optimal power management of DGs are the two significant concerns while providing the demand loads. In order to make sure that the most stable situations are obtained, an applicable control approach should be employed to make the renewable energy sources (RESs) not be overloaded [8]. One of the common approaches of power sharing among DGs in an island MG is frequency-active power (f-P) and voltage-reactive power (E-Q) characteristics of the drop control method. The drop controllers improve the performance of the DGs by proportionally sharing the power for the resources and reducing the rotational current among them. Due to the universality of frequency quantity, the sharing of active power among the sources is done accurately, however for reasons such as the pairing between real and reactive power, the limitation of voltage variations, and the dependence of reactive power on grid parameters, such as feeder impedance, conventional drop control is unable to properly distribute reactive power among DGs, resulting in overload of some resources. In addition to sharing reactive power, adjusting the acceptable voltage profile for consumers is also a particular importance [9; 10; 11]. There are several techniques that have been proposed to improve the droop characteristic of parallel inverters such as semi-centralized control [12], adaptive voltage characteristic [13], virtual frame [14], signal injection [15], and virtual impedance [16]. In [16], in order to achieve proper load sharing and reduction of circulating current for different line impedances, the concept of virtual impedance along with single-cycle control has been utilized. The \"reactive power based on voltage derivation\" feature to improve the reactive power sharing is presented in [17]. Although the use of this method reduces the reactive power sharing errors, it does not guarantee the ideal reactive power sharing for sources. Furthermore, the improvement of reactive power sharing is not evaluated considering the local load. A method for modifying the E-Q characteristic is presented in [17] with the aim of achieving the ideal reactive power sharing in a MG with an arbitrary structure and DGs considering local control. The reactive power sharing error is eliminated at specific times and by performing a special process while correcting the bandwidth from the E-Q characteristics of various sources. In order to achieve the desired result, all the resources in the MG have to perform the process simultaneously, and a low-bandwidth communication channel is used among the sources. Although the proposed scheme is one of the few methods for which no special constraints are considered on the network, the characteristic correction process in this way is a procedure with inappropriate dynamics with severe fluctuations in the output of DGs. In [18], the real power can be controlled directly by the voltage variations and the reactive power is dependent to the frequency. Therefore, in resistive MGs, the inverse E-P and \(\omega\)-Q characteristics can be used to weaken the coupling between active and reactive powers to maintain system stability.