Using low bandwidth communication through power lines to enhance reactive power sharing for inverters-based microgrids

Active and reactive powers should be properly shared among sources to avoid instability problems and to improve reliability in inverter-based micro grids. This can be done using a number of control techniques including hierarchical, centralized and decentralized control. Decentralized control techniques offer extra reliability to the system in addition to the plug and play functionality of distributed generators . This control method is conventionally done using a droop controller. However, the droop control method has certain limitations, particularly in terms of the reactive power sharing. The improper reactive power sharing can lead to serious problems when reactive power surges occur, such as severe circulating reactive powers, instability issues and even a complete shutdown of inverters. The aim of this work is to present a new method for a proper sharing of reactive power by utilizing a low-bandwidth communication through power lines. Using these communication signals, the virtual impedances of the inverters are automatically adjusted to achieve accurate reactive power sharing. The method is described and analysed in detail, including stability analysis related to communication loss and delay effects. The same communication through power lines can be used to share additional information within the micro grid to achieve other control tasks such as secondary control. The proposed method is verified by simulations and using a hardware prototype. Results show that the proposed algorithm is able to accurately achieve reactive power sharing while maintaining the expected power quality at load buses.