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This paper presents a power sharing control method for use between paralleled three-phase inverters in an islanded microgrid. In this study, the mismatch of power sharing when the line impedances have significant differences for inverters connected to a microgrid has been solved, the accuracy of power sharing in an islanded microgrid is improved, the voltage droop slope is tuned to compensate for the mismatch in the voltage drops across line impedances by using communication links. The method will ensure in accurate power sharing even if the communication is interrupted. If the load changes while the communication is interrupted, the accuracy of power sharing is reduced but the proposed method is better than the conventional droop control method. In addition, the accuracy of power sharing base on the proposed method is not affected by the time delay in the communication channel and local loads at the output of the inverters. The control model has been simulated in Matlab/Simulink with two or three inverters are connected in parallel. Simulation results demonstrate the accuracy of the proposed control method. Futhermore, in order to validate the theoretical analysis and simulation results, an experimental setup was built in the laboratory. Results obtained from the experimental setup verify the effectiveness of the proposed method.

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In microgrid, non-linear or unbalanced loads will degrade the voltage quality at the output of the inverters, and the voltage of the load will be distorted or unbalanced. On the other hand, the inverters in microgrid are connected in parallel to improve efficiency, increase transmission capacity, and are easy to repair and maintain. When the microgrid is operating in standalone mode, inverters must be controlled to share power according to their rated power; this is to stabilize frequency and voltage in the microgrid. However, since non-linear or unbalanced loads will produce load currents containing harmonics, it will make the voltage of load unbalanced, which will affect the control of power-sharing for the inverters, and it also degrades the voltage quality at the output of the inverters. This paper has proposed an improved power-sharing control method combined with the sliding mode control (SMC) technique to improve the voltage quality and improve the accuracy of power-sharing for the inverters in the microgrid. The proposed method will ensure accurate power-sharing even if the communication is interrupted. If the load changes while the communication is interrupted, the accuracy of power-sharing is reduced but the proposed method is better than the conventional power-sharing method. In addition, the accuracy of the proposed power-sharing method is not affected by the time delay in the communication channel and local loads at the output of the inverters. Simulation and experimental results will prove the effectiveness of the proposed method.

In this article, a method is proposed to increase the accuracy of reactive power‐sharing for parallel‐connected inverters in Microgrid, this method is done by automatically adjusting the values of the virtual impedance to adjusting the output voltage of the inverters. The virtual impedances are automatically adjusted to compensate for the difference in the output voltage of the inverters due to the influence of the line impedances. The output voltage of the inverters will be adaptively adjusted according to the change of the load, this method greatly improves the accuracy in the reactive power sharing The correct power sharing for the inverters will ensure the stability of voltage and frequency in the Microgrid. The control method is simple and does not need to know the line impedance parameter. The feasibility and effectiveness of the proposed strategy are proven by simulation and experimental results.