Harmonic modelling and control of dual active bridge converter for DC microgrid applications

Due to the intermittent power availability from renewable sources, the bidirectional DC-DC converter (BDC) must integrate with the energy storage system for bidirectional power flow. Among many BDCs, the Dual Active Bridge (DAB) converter is the most promising because of the system's power handling capacity and efficiency. DAB bidirectional DC-DC converter is a topology with the advantages of a decreased number of devices, softswitching commutations, low cost, and high efficiency. This work describes the guidelines for designing a DAB converter for small DC microgrid applications. It is shown that the judicial selection of reactive elements leads to soft switching for all the switches in the converter in varying load conditions. A guideline for the controller design is given and the operations are validated through the simulation. A harmonic modelling technique has been implemented to model the DAB converter based on an efficient closed-loop regulator. A solar PV system has also been implemented here with a SEPIC converter that is used as an interfacing element between the PV system and the load bus. At last, a DC Microgrid is simulated in a PSIM environment to showcase its various modes of operation. It is shown that the battery bank can support variable loads independently through the DAB converter. In inadequate solar power generation, load power demand is shared between the battery and PV system. In case of deep discharge of the battery, the PV system can charge the battery through a DAB converter.