Secondary Voltage Control in A Hybrid Microgrid

Compared to individual dc or ac microgrids, hybrid microgrids (hmgs) are more efficient and inexpensive due to the elimination of multiple dc-ac-dc conversions. in hmgs, where ac loads are supplied by a dc link, load demand disturbance has direct negative effects on the dc link voltage. in this study, primary and secondary controllers are applied to realize suitable operation conditions and control the microgrid converters. each converter has a primary controller to compensate for the demand power fluctuations. a secondary controller is also designed for extra demand varieties to send the proper control signals to the primary controllers. the expressed capability of the primary controllers can be obtained by designing a simple and robust secondary controller. hence, the effects of demand fluctuations are eliminated and the system is stabilized. the overall state space model of the system is conducted for stability analysis. to demonstrate the proposed controller efficiency, a prototype hmg is modeled and simulated. the stability analysis reveals that the system is stable when the secondary controller tracks the error signal of the dc link. simulation results show that the proposed method could efficiently manage the ac side voltage under load fluctuations.