Interest in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs) technologies are growing due to their reduced usage of fuel and emissions of greenhouse gases. In terms of driving range PHEV has the advantage because fuel acts as a secondary resource while EVs only use power from the main battery and does not use fuel. Connecting EVs and PHEVs to the grid helps with load balance, reactive power support as well as tracking the output of renewable energy sources. IEEE, the infrastructure working council (IWC), and the society of automotive engineers (SAE) and more organizations are setting standards and codes for the customer interface due to the public policies that have been implemented by governments to encourage electrification at all levels. Even though great strides have been taken by governments and organizations alike to push toward electrification EVs and PHEVs have a long way to go towards becoming the preferred choice when it comes to transportation. The high cost and cycle life of batteries, complications of chargers, as well as the lack of charging infrastructure are the three most important walls facing EVs and PHEVs . There are three levels of charging: Level 1 (slow) charging where the EV is connected to a convenience outlet usually overnight, level 2 which is the usually the primary method for both public and private facilities which requires 240V outlet this level is semi-fast and can be implemented almost in every environment and provides high power, level 3 (fast) charging which is more suitable for public implementation like charging stations in gas stations, hotels, malls, etc. because it requires 415V which can also use level 2. Single-phase solutions can be used for all three levels while three-phase solutions are usually used for level 2 and level 3 for public use. Chargers can be either on-board or off-board where on-board chargers face problems with weight, space, and cost so high power is limited but such barriers can be overcome by integrating the charger with the drive itself and is usually limited to level 1 and level 2 while off-board chargers can be implemented by installing specialized hardware in both public and private uses where the public can be implemented in all levels but usually it is level 2 or 3 to provide fast charging and private uses are usually level 2. Furthermore, chargers can be classified as unidirectional and bidirectional where implementing unidirectional as a first step makes a lot of sense since it is less complicated and does not require a lot of hardware and reduces battery degradation. However bidirectional chargers support grid to vehicle (g2v) connection and energy injection back into the grid and power stabilization. Before discussing the types of chargers and their layouts the issue of isolation must be addressed for safety reasons regarding all aspects of an EV and especially the charger even though a non-isolated charger has simple structure, high efficiency, high reliability, low cost and many more advantages having isolation in the charger is essential for safety so galvanic isolation can be used through transformers, however, in low-frequency applications, the transformer will be costly and requires a large space to avoid that the operating frequency is increased which allows the use of small transformers which also provides voltage adjustment, reduced cost as well as the ability to use it in different applications but avoiding over-voltages on the passive rectifiers due to the high snubber loss is the main advantage of the high-frequency approach. Furthermore, isolation is needed to comply with safety standards for personnel protection.
On-board bidirectional chargers_MG2
Isolated off-board bidirectional chargers_MG2