Power balancing in islanded microgrids by using a dc-bus voltage reference

Recently, there has been a considerable increase of distributed generators (DGs) connected to the distribution network. Therefore, the concept of the microgrid has been developed. A microgrid is a cluster of DGs, loads and power storage devices that is typically connected to the distribution network via a single point of connection. Most DGs are connected to the microgrid via a power-electronic inverter with dc-bus. In order to exploit the DGs in an islanded microgrid effectively, new control methods for these inverters have to be developed. In this paper, a control strategy based on the specific characteristics of the distribution grid is proposed. The microgrid power is balanced by modifying the set-value of the grid voltage amplitude at the inverter ac-side according to changes of the dc-bus voltage of the DGs. In this way, straight-forward power balancing and voltage control are achieved and frequent changes of the generated power are avoided.