A novel control strategy for parallel operation of multi-inverters in low-voltage microgrids

Droop control is an effective method for the parallel operation of voltage sources without any communication among modules. However, in low-voltage microgrids (MGs) the line impedance is predominantly resistive that causes the control of active and reactive power can be no longer decoupling, and then finally influences the power sharing accuracy among inverters. It has been demonstrated that adding a virtual output impedance (VOI) in control loops can regulate the Total Equivalent Impedance (TEI) between module and common bus to be predominantly inductive, thus improves the power sharing accuracy. However, this method causes another problem that the common bus voltage will fall because of the voltage loss on the VOI. In this paper, the theories of power sharing and traditional droop control are studied in-depth. VOI is applied to make the TEI predominantly inductive, and a novel strategy aiming at regulating the bus voltage into reasonable range is proposed, which is based on the Real-time Estimation of Load Power (RELP). The proposed method is verified through a MG experimental platform composed of two 100 kVA inverters. (C) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 7th International Conference on Power and Energy Systems Engineering, CPESE 2020.