**4. Intelligent Bidirectional V2G Systems**

For the widespread use of EVs, the battery needs to be charged quickly and effectively. The average modern electric car can travel 300–400 km without recharging. There are numerous difficulties to think about: the first is having charging stations available everywhere; the second is quick charging; and the third is improving power density and specific power [101]. There are four primary forms of charging in use today. The following charger types are described in Table 1 [102].


**Table 1.** Different charging level systems [102].

In level 1 and level 2 chargers, batteries are always plugged in on-board, whereas in level 3 converters they are usually off-board systems and have enough ability for a highpower charge. Moreover, it is also seen that level 1 and 2 are sluggish when it comes to their charging time, and therefore they are available commonly in public spaces, homes, and private setups. In most of the shopping centers one may find level 3 charging systems, which are DC power in nature and very fast in charging the system [101,102]. Regarding the level 2 charging systems, they produce approximately 20 kW of AC charging and take almost 2 h; using this system the EV may travel up to 200 km. In addition to this, one may cover 200 km by utilizing the 150 kW DC charging system that may lower down the time by 15 min compared to the conventional one. Similarly, the charging system of 350 kW takes 7 min [103,104].

Regarding the three-phase topologies compared to the front-end inverters, they may include rectifiers based on diodes, matrix rectifiers, as well as Vienna rectifiers [105]. The simplest and most effective tool for power conversion is a diode rectifier. However, the output fixed voltage is affected by the three-phase supply voltage. In terms of total harmonic distortion, it is unfavorable (THD). A three-phase active front-end (AFE) rectifier tackles the THD problem by generating three-phase sine shaped input current waveforms with an enhanced power factor and efficiency and offering variable DC output voltages. Even though it might not be as well known, the Vienna rectifier is becoming more and more widespread. Out of all the three-phase conversion techniques described so far [103,106], the AFE boost rectifier can be used for off-board fast-charging systems. As the number of battery electric vehicles has expanded, so too has the prevalence of grid-connected power electronic converters (PEC). If these PECs are bidirectional, the power kept in a car can be used to either supply peak power or temporarily store electricity (V2G, or vehicle-to-grid; grid-to-vehicle, G2V). Active switches now replace diodes in the existing PEC topologies to handle the bidirectional power flow. The system design for the multiphase-bidirectional on-board charger is depicted in Figure 5.

**Figure 5.** Architecture of the multiphase-bidirectional on-board charger system [107].
