Improvement of active power sharing ratio of P/V droop controllers in low-voltage islanded microgrids

Microgrids provide a coordinated integration of distributed generation units in the electrical power system. By operating in islanded mode, they can increase the reliability of the system or electrify remote areas. For the power sharing and voltage control in low-voltage microgrids, active power/grid voltage droop control is highly suitable. In order to optimize the integration of renewable energy sources in the microgrid, a variant of this droop control, the voltage-based droop (VBD) control, has been presented. A well-known concern about droop controllers is the inherent trade-off between voltage control and power sharing. Therefore, in this paper, an additional control loop is included in the VBD control to improve the active power sharing ratio. In this way, accurate power sharing is achieved, i.e., the DG units respond to load changes exactly according to their droops. Although this modification relies on communication, it does not jeopardize the reliability of the microgrid as if the communication is lost, the basic VBD control still ensures a stable microgrid operation, while operating without the need for communication.