High-Frequency High-Density Bidirectional EV Charger

Hybrid Micro-Grids Exploiting Renewables Sources, Battery Energy Storages, and Bi-Directional Converters

“…it has been sized at 400 V in [3] in case of a 10 kW bidirectional EV charger and at 450 V in case of a 1.65 kW bidirectional EV charger in [71]. In [72][73][74], as special optimization case, a bidirectional EV charger is proposed where the value of the DC power bus can be sized from 500V to 840V. The AC grid is typically a 3-phase 380Vac one.…”

“…In the detailed circuit schematic of the EV bidirectional charger in Figure 7 the bidirectional 3-phase AC/DC converter and the boost DC/DC converter follow classic circuit solutions. For the isolated bi-directional DC/DC converter in Figure 7, instead of using a dual-active bridge topology as in [71][72][73][74] (see Figure 8B), a half-bridge series resonant LLC topology is proposed (that of Figure 8A). This approach allows reducing the number of active switches to be used and hence it makes more convenient the adoption of SiC power Mosfets (e.g., Cree C2M0040120D adopted in [3]) instead of classic Si power Mosfets (e.g.…”

“…As discussed in [72][73][74], by using wide bandgap power devices like SiC and GaN the typical frequencies of power Si devices of about 100 kHz can be increased above 300 kHz. For example, a 500 kHz switching frequency is used for a 6.6 kW CLLC DC/DC resonant converter in [72][73][74] where a bi-directional EV charger is proposed by cascading a first AC/DC stage (switching at 300 kHz) followed by the 500 kHz CLLC DC/DC converter stage. The higher the frequency, the lower the size and weight of the inductive passive devices (inductors, transformers).…”

“…From a switching frequency point of view, the solutions proposed in [3,71] for bidirectional DC/DC conversion are in the order of 100 kHz, more in detail up to 140 kHz in [71] and up to 150 kHz in [3]. As discussed in [72][73][74], by using wide bandgap power devices like SiC and GaN the typical frequencies of power Si devices of about 100 kHz can be increased above 300 kHz. For example, a 500 kHz switching frequency is used for a 6.6 kW CLLC DC/DC resonant converter in [72][73][74] where a bi-directional EV charger is proposed by cascading a first AC/DC stage (switching at 300 kHz) followed by the 500 kHz CLLC DC/DC converter stage.…”

“…As far as the selection of the active devices is concerned the work in [72][73][74] proposes a mix of 650 V GaN and 1.2 kV SiC power switch devices. Particularly, since in [72][73][74] the power DC Bus of the EV charger is sized for values ranging from 500 V DC to 840 V DC (when the battery on board the EV is 250 V DC to 420 V DC ) it is necessary to change the 650V GaN devices with 1.2 kV SiC Mosfets in the AC/DC stage and in the primary side of the DC/DC stage of the bidirectional EV charger. 650V GaN devices are used in [72][73][74] only for the secondary stage of the bidirectional DC/DC converter.…”