# A Smart Approach to Electric Vehicle Optimization via IoT-Enabled Recommender Systems
## 3 Infra-Structure Analysis
### AC and DC Power Distribution  
Step-down transformers act as a conduit between the distribution network and three-phase AC buses in AC-connected systems. These buses operate between 250 and 480 volts line-to-line. Each charger at the station is powered by an AC bus and features its own independent AC/DC stage. The number of conversion stages between the DC port of a RES or an EV, like a battery or photovoltaic system, and the distribution network is significantly increased by this method [38]. In AC-connected systems, a higher number of conversion stages can lead to reduced system efficiency, increased system costs, and heightened system complexity [39]. Adopting the AC bus has numerous advantages, such as better and easier-to-access rectifier and inverter technologies, readily available switchgear and protective devices, established standards and protocols for AC power distribution systems, and much more. Figure 3 shows the block diagram of the AC charger where, AC to DC conversion happens in electric vehicles. Figure 4 shows a block diagram of a DC charging unit, where the conversion happens at the charger in which the DC-connected devices with energy storage and REs can operate more energy effectively since a DC bus can be built with just one central front-end AC/DC converter. A Solid-State Transformer (SST), sometimes called an LV (250 V-480 V) rectifier stage, comes after the low-frequency transformer at the front end. SSTs integrate isolation, voltage step-down, and rectification processes into a single device. To be compatible with the current battery voltage range of about 400 V, the DC bus voltage typically stays below 1000 V.  
The design requirements for EC stations with DC and AC buses should be the same at this voltage level. Connecting each charger to the DC bus via a DC/DC converter reduces the number of conversion steps compared to AC-connected systems [40]. It eliminates the need for separate AC/DC converters. The \"DC distribution\" approach may have the benefit of only requiring a single central front-end connection to the utility. Additionally, by using this technique, the nameplate rating of the grid connection and the AC/DC converter can be significantly lowered, which will ultimately result in a reduction in the overall cost of system installation. It is accomplished by taking advantage of the load diversification generated by varying EV battery capacity and SOC-adjusted variances in battery charge acceptance. Figure 3: Block diagram of AC charging unit. Furthermore, another advantage of DC systems is their reduced need for control, as they do not involve reactive power considerations. It is simpler to connect to an island system from the primary grid because of the single inverter's direct grid connection. Through partial power converters, DC distribution systems may make communication between the car and the DC bus easier. These partial power converters only process a portion of the power supplied to the vehicle, which lowers converter ratings and boosts conversion efficiency [41]. For instance, using several partial power DC/DC converters to communicate with the common DC bus of an EC station is recommended [25]. These converters prevent galvanic isolation between cars by sending a portion of their control power straight from the DC bus to the vehicle. Since \"each output circuit must be completely isolated from each other\" for an EV charging station, this technique must overcome several significant technological challenges to comply with current charging rules. DC-connected systems offer certain advantages but have unique challenges, including DC metering and protection issues. Various safety devices are available for low-voltage DC systems, including protective relays, solid-state circuit breakers, fuses, and circuit breakers. There are not any set criteria for protective coordination for DC-connected EV charging stations yet.