Improvement in Proportional Energy Sharing and DC Bus Voltage Restoring for DC Microgrid in the Islanded Operation Mode

Abstract

This article proposes a distributed consensus-based control algorithm based on the voltage shifting method for the secondary control layer of the hierarchical control structure in DC microgrids to attain both precise proportional power sharing and DC bus voltage restoration when the microgrid is isolated from the utility grid. The proposed algorithm implemented two unity gain integrators for each distributed controller, one is for ensuring proportional power sharing and the other is for restoring local DC bus voltage, and a low-bandwidth communication network to transfer information between converters. For the proposed strategy, each converter only needs to broadcast its p.u value, which is characterized by the relation between the current output power and the converter rated output power, and receive the voltage measurement from the nearest measure station on the DC bus. Voltage shifting terms will be calculated locally by distributed controllers, reducing the risk of having a single point of failure in the system as opposed to a centralized algorithm. When all converter p.u values converged to a universal value, proportional power sharing will be attained. The stability and effectiveness of the proposed algorithm will be evaluated using PLECS simulations and tested with an experimental DC microgrid setup.