To overcome the abovementioned problems, different improved droop control methods have been proposed [14]. In order to solve the problem of resistive networks, the reverse droop control method using the P-V and Q-f droop characteristics is proposed. The control approach proposed in [10] provide a reverse control method that allows multiple voltage source converters to operate in parallel in a MG. The proposed algorithm works well in  
Figure 1: A smart microgrid (MG) considering smart equipment. both grid connected and islanding modes. In order to prevent the coupling of real and reactive power in low voltage networks, more strategies have been proposed [15]. This method, despite the proper operation in grid connected mode, but is not able to directly shares the active and reactive power in islanding status. The conventional droop control method is determined due to the dependence of system dynamics on droop coefficients, source output impedance, line frequency and the maximum allowable value of frequency and voltage deviation, as well as the rated output power. Accordingly, it is not possible to have much control over the dynamics of the inverters independently. A complete small signal model of an islanding MG is presented, in which the dynamic analysis represents that by changing the power demand by the consumers, the low frequency modes of the power distribution system are displaced and can lead to instability [16]. To solve this problem, a simplified linear model of the system and based on it, a modified droop control strategy has been proposed to optimally achieve the power sharing while maintaining the stability [17]. Similarly, the use of inductive and virtual impedance loops is presented to improve the performance of the power sharing accuracy in MGs considering the variations in impedance of cables, however, this method is not applicable with complex MGs and it is hard to program the DG controllers [18]. In general, reactive power sharing according to the droop control method is considered a problem due to the unequal feeder impedance, while the nonlinear and unbalanced loads also affect this issue [19]. As a complement to the droop method, virtual impedance loops were provided in [20] to improve reactive power sharing. However, induced virtual impedance can increase the reactive power capacity in the feeder unequal impedance mode, which is even more difficult in island conditions with nonlinear and unbalanced loads, and the reactive power sharing is not done accurately. Energy management systems (EMS) usually determine which DGs are arranged to be located in which parts of the network. This is based on the network capacity, customer demand and adaptive coefficients of the controller [21]. However, the main problem is in calculating the adaptive controller coefficients. A control method based on virtual impedance is presented to share the reactive power in island operation conditions with unequal feeder impedance [22]. This technique is used in virtual impedance with power frequency and its harmonics. Nonetheless when the load is nonlinear, the reactive power distribution does not work well. Then a robust control method for reactive power distribution in island conditions with unequal feeder impedance and nonlinear load. However, if the feeder or load is disconnected from the network, the MG becomes unstable. This will be one of the drawbacks of the proposed method [23]. The main contributions of this study are briefly summarized below:  
* This paper is aimed to improve the droop control method performance based on the sliding mode control (SMC) approach. This is because the droop control method is easy to implement, however, in order to minimize the reactive power sharing errors appeared in conventional ways, the authors contrive to apply a modern control approach to it.