A decentralized control for Non-error frequency regulation in an islanded microgrid containing multiple VSGs

Abstract

Secondary control in the hierarchical control of microgrids can achieve frequency restoration and accurate proportional power sharing among distributed generators (DGs) but depends on complicated communication systems. The flexibility and reliability of microgrids can be significantly improved by reducing the dependence on the communication system. Therefore, in this paper, a new decentralized control strategy for non-error frequency regulation with no intercommunication is proposed in an islanded microgrid containing multiple virtual synchronous generators (VSGs). In the proposed strategy, the frequency recovery link of the VSG, i.e., Proportional Integral (PI) controller, is split into an integral link and a proportional link that are connected in series. The integral link rapidly regulates the microgrid frequency to its rated value, while the proportional link achieves accurate proportional power sharing among VSGs. The whole process can be completed only by local measured signals by each VSG and through local frequency feedback instead of relying on the microgrid central controller (MGCC) and the information interaction between the adjacent VSG. The proposed control strategy enables multiple VSGs to collectively achieve frequency restoration, thus avoiding the problem of frequency regulation overload of a single VSG. The impact of VSG control parameters over the control system is also analyzed by the root locus. Finally, the simulation and experimental results verify the effectiveness of the proposed control strategy in this paper. The results show that the proposed control strategy can achieve frequency restoration and accurate proportional power sharing among VSGs simultaneously with no intercommunication.