What are the different types of chargers?
Types of Chargers
Electric vehicle chargers can be divided into various types according to different classification standards, as shown in Table 11-5.
Table 11-5 Types of Electric Vehicle Chargers
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(1) On-board Charger (OBC) The on-board charger is installed in the electric vehicle and is connected to the AC outlet via a plug and cable. The advantage of the on-board charger is that the battery can be charged anytime it needs charging, provided there is an available power outlet. Figure 11-18 shows a 6.6kW on-board charger. Figure 11-19 shows commonly used on-board chargers.
(2) Ground Charger The ground charger is generally installed at a fixed location, connected to the AC input power supply, and its DC output is connected to the charging interface of the electric vehicle that needs charging. The ground charger can provide high-power current output, is not limited by the vehicle installation space, and can meet the requirements for high-power fast charging of electric vehicles.
(3) Conductive Charger and Inductive Charger The output of a conductive charger transmits electric energy directly to the electric vehicle via wires during charging. There is a physical connection between the two, and the electric vehicle is not equipped with power electronic circuits.
As shown in Figure 11-20, the inductive charger utilizes the principle of electromagnetic energy transfer, transmitting electrical energy to the electric vehicle through electromagnetic induction coupling. There is no direct mechanical connection between the power supply part and the receiving part; the energy transfer between the two relies solely on the conversion of electromagnetic energy. The structural design of this charging method is relatively complex; the receiving part is installed in the electric vehicle and is limited by the vehicle's installation space, thus restricting the power level. However, since charging personnel do not need to directly contact high-voltage components, its safety is high.
(4) Ordinary Charger and Multifunctional Charger An ordinary charger only provides the function of charging the power battery. Currently, the actual chargers used are basically AC-input, so the power conversion unit of the charger is essentially an AC/DC converter. A multifunctional charger not only provides the function of charging the power battery but can also offer functions such as capacity testing for the power battery, harmonic suppression for the power grid, reactive power compensation, and load balancing.
The high-power ground charger is mainly a conductive high-power charger, which typically uses three-phase AC power as the input, obtains DC bus voltage after passing through a diode rectifier bridge and an LC filter stage, and then uses an isolated full-bridge DC/DC converter for voltage conversion. Available isolated full-bridge DC/DC converter topologies include hard-switching PWM converters, series/parallel resonant converters, dual active bridge (DAB) converters, and phase-shifted full-bridge converters. Among them, the main circuit structure and control method of the hard-switching PWM converter are the simplest, and the magnetic components (including the isolation transformer, output filter inductor, etc.) are also the simplest to design and manufacture, making it the most mature and widely used topology for high-power chargers. However, it also has disadvantages such as low switching frequency, high noise, and large volume. More advanced high-power chargers are constantly emerging and being put into practical use.
(5) Bidirectional Charger A bidirectional charger, also known as a bidirectional topology, can charge the on-board battery in constant current or constant voltage mode, and at the same time can feed power back to the grid, realizing the leveling of active load peaks on the power grid. It can also perform capacitive or inductive reactive power compensation by outputting current with a phase lead or lag relative to the grid voltage. As a medium connecting the upper-level control system and the electric vehicle, it can perform charging and power feedback operations in combination with instructions from the grid dispatch center and the battery management system.
With the maturity of power battery technology and the improvement of electric vehicle intelligence, the number and power of charging stations continue to increase, and the impact of chargers on the power grid is gradually becoming prominent. At the same time, the improvement of the electric vehicle discharge function and the maturity of DC microgrid technology for energy storage provide feasible solutions for charging stations to reduce the impact from the grid and perform peak shavingand valley filling. In addition, with the reduction in the cost of solar power generation, installing photovoltaic power generation facilities in charging stations has also become the best choice to reduce the impact on the power grid. Charging modules in V2G (Vehicle to Grid), V2V (Vehicle to Vehicle), and PV optimizer microgrids have become new demands. V2G refers to the technology of two-way transmission of energy and information between the electric vehicle and the power grid. For V2G modules, the traditional AC/DC module is challenged by the need for reverse discharge, wide-range output, real-time bidirectional switching, and full-range high-efficiency output. In DC microgrid, V2V, and PV energy storage applications, the DC/DC module is required to not only meet DC charging but also have reverse discharge capability and maximum power point tracking capability for PV. The new bidirectional converters inject new vitality into the development of charger module technology and have become a direction for future technological innovation.
