3.3.1. Hardware Design

The AC/DC converter, used to exchange power with the electric grid, has been designed and manufactured with a three-level Neutral Point Clamped (NPC) topology with SEMIKRON SK150MLI066T IGBTs, as shown in Figure 7. In comparison with the two level converter, this topology reduces the voltage stress on the IGBTs and their switching losses, increasing the output voltage waveform quality.The attenuation of the current switching ripple is done by a third-order LCL grid filter, which is smaller and lower-priced than the first order L filter [23]. Furthermore, the AC/DC converter can operate in the four quadrants, compensating reactive power if needed, even when the DC/DC converter is not working. This functionality makes it possible to perform the complete set of tests in facilities consuming only the active power losses of the whole testbench. This is because the EVE can compensate whenever the power factor of the charger diverges from 1, especially at low charging levels.

**Figure 7.** Topology of the AC/DC converter of the proposed EVE: a three-phase three-level NPC power converter.
