Compensation Alternatives for Power Sharing Mismatch in Multiport DC–DC–AC Converters

This article proposes several alternatives for the compensation of power sharing errors in the coupling dc bus of multiport dc–dc–ac converters. The case of study consists in a multiport converter used for the interconnection of an ac grid-tied converter, a battery, a supercapacitor, and a regenerative dc load. A distributed control system, where the central controller computes the load power sharing between the battery and the supercapacitor modules and local controllers for the power control at each converter port, is implemented. The sharing mechanism requires a precise measurement or estimation for the required load and port power. However, due to measurements errors or control action deviations, the real power share can differ from the estimated one, and hence, a power mismatch is produced. Those mismatches are absorbed by the dc-link voltage, which is assumed to be controlled by the grid-tied converter. However, considering power restrictions in the grid-tied converter, the differences in the power sharing can compromise the system operation and stability. This article includes an analytical study for the converter operation under saturation conditions and proposes three compensation methods, which are compared by simulation and experimental results. The proposed methods allow for the stable operation of the system, even when large errors in the power sharing are considered.