A voltage and frequency droop control method for microsources

This paper focuses on a control method for microsources which can work as AC voltage sources, instead of AC current sources. The microsources can not only provide AC power in grid-connected mode, but also control the frequency and voltage for the microgrid load in island mode. By using the voltage and frequency droop control method, the microsources can realize the “plug-and-play” concept: share the load automatically by using only the local information, i.e. the voltage, frequency, instead of the communications with the other microsources or the microgrid central control system. The microsources can work in parallel to the grid or as an island. When the microgrid system disconnects from the grid, caused by the grid´s short current or power failure, the microsources can keep on working for the microgrid loads, without restart process. Detailed analysis is shown in this paper, and experimentations on a 25kVA three phase inverter have been done to prove the performance of this method.