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Please note this is a comparison between Version 1 by Aziz RACHID and Version 3 by Lindsay Dong.
The high-voltage battery is a crucial element for electric vehicles (EVs) traction systems. It is the primary energy source that must be regularly recharged to reach the autonomy declared by the manufacturer. Therefore, an EV charging system is required to ensure the battery charging process.
- EV charging system
- EV charger standards
- bidirectional EV charger topologies
12. Classification and Topologies of EV Charger
1.1. EV Chargers Classification
2.1. EV Chargers Classification
The high-voltage battery (HVB) is vital for electric vehicles (EVs) traction systems. It is the primary energy source that must be regularly recharged to reach the autonomy declared by the manufacturer. Thus, an EV charging system is required to ensure the battery charging process. This vital component, based principally on power conversion stages, allows the electrical energy transfer between the power grid and EV batteries. Therefore, these EV chargers can be classified according to several criteria, including the charger location, the energy transfer direction, the charger structure, the connection type, and the number of power conversion stages [1][2][30,31]. Accordingly, the options for each classification type are described in Table 1 (Figure 1).
Table 1.
EV charging systems classification.
| EV Chargers | Description | |
|---|---|---|
| Offboard chargers | All the components required for the EV charging and discharging process are inside the public EV charging station [3][4]. | All the components required for the EV charging and discharging process are inside the public EV charging station [32,33]. |
| On-board chargers | Some components required for the battery-charging process are embedded inside the EV. |
Figure 38. The electrical schematics of the commonly used bidirectional ac-dc power conversion stage in EV chargers: (a) Bidirectional half-bridge single-phase ac-dc power converter; (b) Bidirectional full-bridge single-phase ac-dc power converter; (c) Bidirectional three-phase ac-dc power converter; (d) Bidirectional three-level diode-clamped ac-dc power converter.
Figure 49 shows the most used dc-dc power circuitry for EV charging applications with V2X technology. However, Figure 49a illustrates a non-isolated bidirectional half-bridge dc-dc power converter, while Figure 49b presents its interleaved version. Figure 49c illustrates an isolated bidirectional dual-active bridge (DAB) dc-dc power converter, while Figure 49d shows its contactless version. It is a structure used for bidirectional inductive EV chargers; the left bridge is situated in the EV charging station, while the right one is embedded into the vehicle [25][60].
Figure 49. The electrical schematics of the most used dc-dc power conversion stage in EV chargers with V2X technology: (a) non-isolate bidirectional half-bridge dc-dc power converter; (b) Bidirectional interleave dc-dc power converter; (c) Isolated bidirectional dual-active bridge dc-dc power converter; (d) Inductive bidirectional dual-active bridge dc-dc power converter.
3. EV Charging Standards
3.1. SAE J1772 Standard
SAE J1772 is a standard published by SAE International that encompasses the general physical, electrical, functional, and quality criteria for EVs’ conductive charging process in North America [26][69]. This standard provides available conductive charging methods for EVs and electric vehicle supply equipment (EVSE), including the operational, functional, and dimensional requirements for the vehicle inlet and mating connector [27][70]. In addition, the SAE International terminology “Charging Levels” is utilized to classify the rated currents, voltages, and powers of the charging systems currently offered in North American markets [28][29][71,72]. Accordingly, the October 2017 revision of the SAE J1772 standard outlines four charging levels: AC Level 1, AC Level 2, DC Level 1, and DC Level 2 [30][65]. Table 2 lists and describes their charging configuration settings and ratings [31][73].
Table 2.
Levels charging available in SAE J1772 (2017) configuration.
| Charging Level | Specifications | ||||
|---|---|---|---|---|---|
| AC Level 1 |
| ||||
| AC Level 2 |
| ||||
| Unidirectional chargers | The electrical energy transfer is one-way from the EV charging station to the EV battery. Therefore, only the G2V operation mode is possible. | ||||
| Bidirectional chargers | The electrical energy flow can be from or to the EV battery. Thus, V2X technology can be ensured by this type of charger [5]. | The electrical energy flow can be from or to the EV battery. Thus, V2X technology can be ensured by this type of charger [34]. | |||
| Dedicated chargers | All equipment making up the charger is exclusively utilized to guarantee the EV charging or discharging process. | ||||
| Integrated chargers | When the EV is linked to the electricity network, the traction system constituents (Motors, inverters, etc.) are used to guarantee the EV charging or discharging process [6]. | When the EV is linked to the electricity network, the traction system constituents (Motors, inverters, etc.) are used to guarantee the EV charging or discharging process [35]. | |||
| Conductive chargers | A dedicated electrical cable links the EV to the electricity network. | ||||
| Wireless Power Transfer Chargers [7] | Wireless Power Transfer Chargers [36] |
It is a contactless charging technology. No cables are utilized between the EV and the electricity network [8]. Instead, the electrical energy transfer is based on electromagnetic induction [9]. | It is a contactless charging technology. No cables are utilized between the EV and the electricity network [37]. Instead, the electrical energy transfer is based on electromagnetic induction [38]. | Figure 6 illustrates the concept of this EV charger type [10]. Compared with conductive chargers, these inductive chargers present various advantages [11]. Especially the convenience for the user and the intrinsic galvanic insulation, while the cost and the need for custom hardware inside the EV are the main drawbacks [12][13]. | illustrates the concept of this EV charger type [39]. Compared with conductive chargers, these inductive chargers present various advantages [40]. Especially the convenience for the user and the intrinsic galvanic insulation, while the cost and the need for custom hardware inside the EV are the main drawbacks [41,42]. |
| Single-stage & Dual-stage chargers |
The first one consists of a single power conversion: only one ac-dc or one dc-dc power converter. The second one involves double power stages: ac-dc and dc-dc power conversions. |
Figure 16.
EV wireless charger overview diagram.
1.2. EV Charger Topologies
2.2. EV Charger Topologies
Figure 27 illustrates available structures which can be implemented for EV charger applications [14][15][50,51].
Figure 27.
Possible structures for EV charger solutions.
In the dual-stage case, a bidirectional EV charger includes a dc-dc power stage following an ac-dc one. The first performs a power factor control (PFC) function and provides a regulated high dc-bus output voltage. In contrast, the second connects the EV battery to the high dc-bus voltage and ensures the energy exchange during G2V and V2G modes. In the G2V mode, the reversible ac-dc stage functions as a boost power rectifier with a unity power factor (UPF), whereas the bidirectional dc-dc converter works in buck mode to ensure the EV charge operation [16][52]. In V2G mode, the reversible ac-dc stage functions as a power inverter with a possible reactive energy injection into the electricity network, whereas the bidirectional dc-dc stage starts operating in a boost converter to ensure the energy exchange from the EV battery to the dc-bus [17][18][23,53]. In the single-stage case, the EV charger has only one ac-dc or one dc-dc stage [19][20][19,54].
Figure 38 shows the electrical schematics of the commonly used bidirectional ac-dc power conversion stage in EV chargers. Figure 38a shows a bidirectional half-bridge single-phase ac-dc power converter. Figure 38b shows a bidirectional full-bridge single-phase ac-dc power converter [20][21][54,56]. Figure 38c shows a bidirectional three-phase ac-dc power converter. Finally, Figure 38d shows a bidirectional three-level diode-clamped ac-dc power converter [22][57]. It is worth noting that bidirectional multilevel three-phase ac-dc power converters are recommended for high-power EV chargers [23][58]. These converters afford a high level of energy quality with a high-power factor, low total harmonic distortion (THD) rate, and lessened electromagnetic interference noise on the grid side. Besides, they offer a high level of dc voltage that is ripple-free, tightly regulated, and impervious to load and source disturbances on the dc-side [24][59].
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| ||
|
1 BEV battery capacity is presumed to be 25 KWh, while that of PHEV is 5–15 KWh.
3.2. IEC 61851 Standard
In Europe and other countries, the IEC uses the terminology “Charging modes” to classify the methods of power distribution and protection installation, as well as the communication and management of the EV charging system [32][77]. Accordingly, as illustrated in Figure 510, the international standard IEC 61851-1 published in 2017 describes four distinct EV charging modes [33][78].Figure 510.
IEC 61851-1 Charging Modes: (
a
) Mode 1; (
b
) Mode 2; (
c
) Mode 3; (
d) Mode 4.
3.3. China GB Standards
The China GB (Guo Biao) standards are mandatory or recommended. Mandatory standards, like other technical regulations in China, have legal force. They are regulated by legislation and authoritative rules to protect public health, private property, and safety. All standards that do not meet these criteria are deemed recommended (i.e., Quasi-Mandatory standards). GB standards are classified as Mandatory or Recommended based on their prefix code. GB is a mandatory standard, whereas GB/T is a recommended standard [34].
) Mode 4.
3.3. China GB Standards
The China GB (Guo Biao) standards are mandatory or recommended. Mandatory standards, like other technical regulations in China, have legal force. They are regulated by legislation and authoritative rules to protect public health, private property, and safety. All standards that do not meet these criteria are deemed recommended (i.e., Quasi-Mandatory standards). GB standards are classified as Mandatory or Recommended based on their prefix code. GB is a mandatory standard, whereas GB/T is a recommended standard [80].
Table 3 summarizes the GB/T standards concerning the EV charging systems implemented in China.
4 summarizes the GB/T standards concerning the EV charging systems implemented in China.
Table 34. Overview of GB/T standards for EV charging system.
| Standard Code | GB Standard Title | ||||
|---|---|---|---|---|---|
| GB/T 20234.1-2015 |
| ||||
| GB/T 20234.2-2015 |
| ||||
| DC Level 1 |
| ||||
| GB/T 20234.3-2015 | |||||
| DC Level 2 |
| |||
| GB/T 27930-2015 |
|
| |||
| GB/T 28569-2012 |
| ||||
| GB/T 29317-2012 |
| ||||
| GB/T 29318-2012 |
| ||||
| GB/T 38775-2020 |
|
4. EV Charging Couplers
4.1. SAE J1772 Coupler
The Yazaki manufacturer produced the SAE J1772 coupler in 2009 with full respect to the SAE J1772-2009 standard. Its specifications were later stated to the IEC 62196-2 standard in May 2011 (i.e., IEC Type 1 coupler). It’s widely utilized for AC charging systems in the United States, Canada, and Japan. It accepts a single-phase AC power supply and can charge up to 19.2 kW (240 V @ 80 A). 11 shows the EV J-plug and its corresponding EV Inlet [86].Figure 611. The SAE J1772 EV charging coupler: EV Plug (Left) and Inlet (Right).
4.2. IEC Type 2 Coupler
The type 2 coupler had first been proposed by the German manufacturer “Mennekes” in 2009, and it is still commonly referred to as such (i.e., Mennekes Type 2). In January 2013, the European Commission designated it as an official charging coupler in the EU. Some other countries outside the EU, including Australia and New Zealand, are adopting the same coupler, while the Chinese standard GB/T 20234-2 outlines a similar but unique design. As is described in the IEC 62196-2 standard, this coupler was initially designed for AC charging systems. That means it can support a power-charging up to 7.4 kW (230 V @ 32 A) or 43 kW (400 V @ 63 A) from a single-phase or three-phase AC power supply, respectively [36][37][38].
4.3. CCS Combo Coupler
The type 2 coupler had first been proposed by the German manufacturer “Mennekes” in 2009, and it is still commonly referred to as such (i.e., Mennekes Type 2). In January 2013, the European Commission designated it as an official charging coupler in the EU. Some other countries outside the EU, including Australia and New Zealand, are adopting the same coupler, while the Chinese standard GB/T 20234-2 outlines a similar but unique design. As is described in the IEC 62196-2 standard, this coupler was initially designed for AC charging systems. That means it can support a power-charging up to 7.4 kW (230 V @ 32 A) or 43 kW (400 V @ 63 A) from a single-phase or three-phase AC power supply, respectively [82,88,89].
4.3. CCS Combo Coupler
DC fast charging is also available in Europe, as it is in North America, where CCS Combo 2 is the standard utilized by almost all manufacturers except for Nissan and Mitsubishi [39][85]. It combines two DC-fast charging pins with the Type 2 connector in the same way that the CCS Combo 1 system (J1772 connector) does in the United States and Canada.4.4. CHAdeMO Coupler
CHAdeMO is a DC fast-charging coupler for electric vehicles with a charging power ranging from 6 KW to 400 KW. Its coupler is shown in Figure 17, while Figure 18 illustrates its sequence circuit and pin layout [40][96]. There are ten (10) pins, and one of them is not connected (Pin #3). The sequence circuit establishes the exchanged parameters necessary during charging control. In addition, the EV and the DC fast-charging EVSE are equipped with terminating resistors for communications.Figure 17.
The CHAdeMO coupler: EV Plug (
Left
) and Inlet (
Right
).
Figure 18.
CHAdeMO sequence circuit and pin layout.
4.5. GB/T Coupler
With the support of the governments of China and Japan, the CHAdeMO Organization and the China electricity council (CEC) have lately been working on a new international high-power DC charging standard that is backward compatible with existing CHAdeMO and GB/T standards. Figure 925 shows the new GB/T- CHAdeMO coupler prototype, which was revealed during the CHAdeMO general assembly with a charging power of up to 900 kW (1500 V @ 600 A) [41][42][43][101,108,109].
Figure 925.
The ChaoJi coupler: EV Plug (
Left
), Inlet (
Middle
), and Inlet pinout (
Right
).
4.6. Tesla Coupler
Founded in 2003, Tesla is a California brand specializing in EVs and energy. After its first EV, the Roadster 2008, the manufacturer has four models within its range: The Model S, the Model 3, the Model X, the Model Y, and the new Roadster 2020. The type of the Tesla EV inlet depends on the region in which the vehicle is sold. Thus, the US version is also sold in Canada, Mexico, Japan, and Taiwan and is equipped with the proprietary Tesla inlet, as shown in
Figure 10. In contrast,
27a. In contrast,
Figure 10b illustrates that the Tesla vehicle sold in Europe is fitted with a Type 2 inlet or, more recently, a CCS Combo 2 inlet, as presented in
27b illustrates that the Tesla vehicle sold in Europe is fitted with a Type 2 inlet or, more recently, a CCS Combo 2 inlet, as presented in
Figure 10c. Finally, the Tesla vehicle in China is equipped with a dual inlet: AC GB/T and DC GB/T inlets, as shown in
27c. Finally, the Tesla vehicle in China is equipped with a dual inlet: AC GB/T and DC GB/T inlets, as shown in
Figure 10d [44].
27d [81].
Figure 1027. The Tesla EV inlet according to the region of sale: (a) US; (b) and (c) EU; (d) China.
5. EV Batteries
Commonly, an EV is equipped with two types of batteries: a high-voltage battery called a traction battery and a low-voltage battery. The first is the principal energy source that supplies the electric traction motor via a three-phase power inverter. It is generally Lithium-ion based and can be charged using the ac-current through an on-board charger or directly using the dc-current provided by the dc fast-charging stations. However, a third charging technique called battery swapping makes it possible to exchange the drained battery with a charged one [45][46][47]. The second is a 12 V lead-acid battery that supplies the vehicle’s auxiliary loads [48]. It is charged from the high-voltage battery through a dc-dc converter [49].
Commonly, an EV is equipped with two types of batteries: a high-voltage battery called a traction battery and a low-voltage battery. The first is the principal energy source that supplies the electric traction motor via a three-phase power inverter. It is generally Lithium-ion based and can be charged using the ac-current through an on-board charger or directly using the dc-current provided by the dc fast-charging stations. However, a third charging technique called battery swapping makes it possible to exchange the drained battery with a charged one [66,116,117]. The second is a 12 V lead-acid battery that supplies the vehicle’s auxiliary loads [118]. It is charged from the high-voltage battery through a dc-dc converter [119].
The high-voltage battery is made up of several individual cells that are grouped into modules. These are added to each other to form the final traction battery, as shown in
Figure 11. The design of the battery cells varies depending on the vehicle manufacturer. In this case, the deciding factors are, e.g., energy density, heat dissipation, manufacturing cost, weight, modular adaptability, or mechanical stability. An anode (the negative pole), a cathode (the positive pole), and an electrolyte make up a battery cell [50]. The electrolyte is a conductive (liquid or solid) element that allows current flow between poles. Battery operation is based on using a pair of metals capable of exchanging electrons. Based on these metals, EV batteries will be classified in the next section.
29. The design of the battery cells varies depending on the vehicle manufacturer. In this case, the deciding factors are, e.g., energy density, heat dissipation, manufacturing cost, weight, modular adaptability, or mechanical stability. An anode (the negative pole), a cathode (the positive pole), and an electrolyte make up a battery cell [120]. The electrolyte is a conductive (liquid or solid) element that allows current flow between poles. Battery operation is based on using a pair of metals capable of exchanging electrons. Based on these metals, EV batteries will be classified in the next section.
Figure 1129. The high-voltage battery components.
