Regulation Characteristic Formulas for Scalable CF-MAB converter, operating with DPS modulation

Description

The equations in the file represent the regulation characteristics for the isolated ports of the CF-MAB converter, operating with a dual phase shift (DPS) modulation. The power delivered to the isolated EV outputs depends on the converter operating mode, which, in turn, depends on the primary side duty cycle D1, the mismatch factor between the BT and EV ports (G=VBT·n/VEV), as well as the phase shift between the primary and secondary transformer voltages. This converter is applied in the field of bidirectional EV chargers powered by DC grids. The use of dual-phase shift modulation (DPS) modulation instead of single-phase shift (SPS) modulation allows for reduced RMS currents in the transformer, leading to lower losses. To implement DPS modulation for the studied converter, auxiliary phase shifts were introduced, both of which also depend on converter operating mode. Overall, there are eight operating modes, half of which are unique, while the other half duplicate the first four, due to symmetrical converter operation over D1=0.5. This symmetry means that the waveforms and equations for D1=m and D1=1-m are identical. To derive the equations, one converter port is represented by an equivalent circuit, consisting of two controlled voltage sources (whose waveforms are shown in Fig. 1), connected across an inductor (typical equivalent circuit for a classical DAB converter). The current through the inductor is then determined and averaged over the time when d2 has a nonzero value. When the transformer current and output voltage have the same sign, the value was added to the total EV port current and if the signs are opposite, the current is subtracted from the average current. The formulas were verified through simulations of the studied converter. As a result, the experimental regulation curves and the theoretical ones described here fully coincide.

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