Hybrid Distributed and Decentralized Secondary Control Strategy to Attain Accurate Power Sharing and Improved Voltage Restoration in DC Microgrids

This article proposes a secondary level control technique for dc microgrids, which achieves accurate power sharing through a distributed strategy while performing dc bus voltage restoration in a decentralized fashion. In order to attain proper power sharing, each power converter exchanges its output power information with neighboring converters through a low-bandwidth network at defined time intervals. A consensus-based algorithm is employed to process this information and modify the converter's droop coefficient, compensating droop mismatches and cable resistances and enabling power sharing. Restoration of the average dc bus voltage is realized locally with each converter compensating its own output voltage drop through an integrator. A comprehensive design procedure and performance and stability analysis, including communication loss and substantial time delays, are also provided. The strategy has shown to be robust to some communication failure scenarios and moderate communication delays. The proposed method is evaluated through simulation in the software PLECS and it is experimentally validated in a 4.5-kW dc microgrid setup.