DC/DC Buck Converter

The DC/DC buck converter is supplied by the TDK-Lambda GEN600-5.5 DC power supply because, with this solution, the maximum deliverable current can be elec­tronically limited and the PV emulator is galvanically isolated from the power grid.

As an alternative, an isolation transformer and a bridge rectifier can be used to obtain the supply voltage for the PV emulator.

The DC/DC converter employs the SKM50GB123D power IGBT whose rated current is equal to 40 A at 80° C. This high current value allows to manage powers up to 10 kW.

Fig. 8.32 REO load 302 three-phase resistive load bank

image946The used driver circuit is the hybrid dual MOSFET driver SKHI22AR.

A snubber circuit is realized by using a 0.22 pF polypropylene capacitor, i. e., the MKPC4BS, suitable for high-frequency applications.

As previously indicated, the output filter of the buck converter is composed of a 3.7 mH inductor and a 33 pF capacitor. The corresponding parasitic components, experimentally evaluated, are, respectively, rL = 0.4 X and rc = 2.06 X.

The output voltage is sensed by a LEM LV25-P transducer, while the output current is measured by a closed-loop current sensor, i. e., the Honeywell CSNP661. Both these sensors exhibit a wide bandwidth and their range can be varied by a suitable setting of an external precision resistor.

As for the current transducer, its maximum range is equal to 50 A, coherently with the chosen IGBT. For the emulation of the considered plant this value has been lowered to 10 A by winding five turns around the sensor core.

Finally, the resistive load is realized by a REO load 302 three-phase resistive load bank.

A view of the resistive load is given in Fig. 8.32.

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