Compensation Alternatives for Power Sharing Errors in Multi-Port Converters for Hybrid DC/AC Microgrids

This paper proposes several alternatives for the compensation of power sharing errors in the DC bus of hybrid DC/AC microgrids. The case of study consists in a multi-port converter used for the interconnection of a AC grid-tied converter, a battery, a supercapacitor and a regenerative DC load that has to be supplied. The storage elements and the load are connected by means of DC/DC converters. The power sharing between the battery and the supercapacitor is determined by using an estimation of the load power. However, due to errors in sensors or control actions of the converters, the real load power is not exactly equal to the estimated one and hence a power mismatch is produced. Those mismatches are absorbed by the DC-link voltage, which is controlled by the grid-tied converter. However, considering restrictions in the grid-tied converter, the differences in the power sharing can compromise the operation and the stability of the system. In this paper, three compensation methods are proposed and compared. The proposed methods allow for the stable operation of the system, even with noticeable errors in the power sharing.