Elimination of Circulating Currents in PV-Powered Charging Stations Through Dual Active Bridge Modulation

In many energy storage system applications, such as PV-powered charging stations (PVCS), a latent efficiency problem is the circulating currents in the DC ports of the Dual Active Bridge (DAB) converter which is in charge of charging/discharging batteries that support these systems. Specifically, the circulating currents may provoke that the charging/discharging frequency becomes twice the switching frequency, shortening the batteries’ lifetime. Also, these currents may cause high peak values in the DC currents, increasing the current through the inductor. To solve this, this paper advocates the use of a Proportional-Values Modulation (PVM) technique to generate the firing pulses of the DAB. The major advantages of this scheme are: (i) a complete elimination of circulating currents in both DAB ports; (ii) a reduction of the apparent power in the medium frequency transformer (MFT), remaining low the harmonic distortion. (iii) a lower output capacitance. To demonstrate the effectiveness of our proposal, this was successfully implemented through a real-time controller hardware-in-the-loop (C-HIL) simulation.