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On-Board Charger

Oct 25,2022 | TCcharger

EV battery chargers are broadly classified as on-board and off-board chargers. An off-board charger is installed only at the fixed location, whereas on-board charger is located inside the vehicle. Size, weight, space and cost are some of the constraints related to the on-board charger. To eliminate these constraints, this charger can be integrated with the motor drives in EV, in which, the motor winding itself can be used as the filter inductors or isolated transformer . On-board charging system can be either a conductive system which has the direct contact between the charger inlet and EV connector or an inductive system in which the power transfers magnetically . Inductive chargers are used in level 1 and level 2 AC charging methods and it can be either static or dynamic . Static charger refers to a stationary inductive charger which employs a primary inductor in the charging station and secondary inductor in the vehicle. When the primary paddle is inserted to the charge port in the vehicle, a magnetic circuit is formed and the power is transferred. Dynamic charger refers to a contactless roadway EV charging system in which the power is transferred from the stationary primary inductor embedded below the pavement surface to the secondary inductor installed in the moving vehicle. Also in EV chargers, unidirectional or bidirectional power flow is adopted.

In unidirectional power flow system, power is transferred from grid to the vehicle (G2V) whereas in bidirectional charger, power is fed from the battery to the grid (V2G) in addition to G2V power flow . During peak demand duration, G2V charging adds burden to the electrical grid which requires the increase in the power generation capacity or the usage of alternate source to meet the demand . Renewable Energy Sources (RES) can be used as an auxiliary source due to its inexhaustible and pollution free nature. Out of various RES, wind and solar energy are the most promising energy sources . The applications of RES are enriched by the improved installation process, advanced power electronic converter topologies and energy management systems . One such system used for charging EV is PV roofed / Wind generator installed parking system. This kind of EV battery charging system reduces the electricity traffic during the peak demand time .

AC level 1 charging is designed for slow charging from a 120 VAC single-phase power network and suitable for overnight charging. The estimated charging time is up to 17 h to charge a BEV from SOC of 20% to fully charged. The rating terminology of AC level 2 charging is 240 VAC with charging current up to 80 A and charging power up to 19.2 kW. The estimated charging time is as short as 22 min to fully charge a fully depleted PHEV by using the 20 kW charger. On the other hand, DC level 1 charging and DC level 2 charging are used to charge an EV though DC power. An off-board EV supply equipment is used to rectify the supply from power grid into DC output before charging the EV battery. DC level 1 charging has charging power up to 36 kW with 200–450 VDC and charging current up to 80 A. Meanwhile, DC level 2 charging has charging power up to 90 kW with 200–450 VDC and charging current up to 200 A. As shown in Table 3, DC charging can charge up an EV to SOC of 80% within half an hour. Both AC level 3 and DC level 3 charging levels are not finalized yet. The proposed charging power for AC level 3 is more than 20 kW and up to 240 kW for DC level 3.