STUDY AND IMPLEMENTATION OF “DROOP CONTROL” METHODS FOR INTERFACING VOLTAGE SOURCE INVERTERS TO MINIGRID

This contribution presents control methods for the regulation of the voltage and the frequency on AC minigrids, fed by voltage source inverters (VSI). In order to avoid a complex communication network for the synchronization of the various VSI on a minigrid, a conventional method called “Droop Control” consists in the emulation of rotating alternators for each VSI. Then the VSIs generate AC voltages with an active power dependent frequency, and a reactive power dependent voltage. Such a method is presented and simulated on a given minigrid. A second less-conventional method is introduced, where the characteristics on the minigrid line impedances are taken into account. This is obtained the projection of the active and the reactive power in a new referential depending on the line characteristics. By maintaining a “Droop Voltage” control on the new parameters, it is shown that the global stability is increased.