1. Introduction to DC charging pile
In recent years, the rapid growth of electric vehicles (EVs) has driven the demand for more efficient and intelligent charging solutions. DC charging piles, known for their fast charging capabilities, are at the forefront of this transformation. With advancements in technology, efficient DC chargers are now designed to optimize charging time, improve energy utilization, and offer seamless integration with smart grids.
With the continuous increase in market volume, the implementation of bidirectional OBC (On-Board Chargers) not only helps alleviate consumer concerns about range and charging anxiety by enabling fast charging but also allows electric vehicles to function as distributed energy storage stations. These vehicles can return power to the grid, assisting in peak shaving and valley filling. Efficient charging of electric vehicles via DC fast chargers (DCFC) is a major trend in promoting renewable energy transitions. Ultra-fast charging stations integrate various components such as auxiliary power supplies, sensors, power management, and communication devices. At the same time, flexible manufacturing methods are required to meet the evolving charging demands of different electric vehicles, adding complexity to the design of DCFC and ultra-fast charging stations.
The difference between AC charging and DC charging, for AC charging (left side of Figure 2), plug the OBC into a standard AC outlet, and the OBC converts AC to the appropriate DC to charge the battery. For DC charging (right side of Figure 2), the charging post charges the battery directly.
2. DC charging pile system composition
(1) Complete machine components
(2) System components
(3) Functional block diagram
(4) Charging pile subsystem
Level 3 (L3) DC fast chargers bypass the on-board charger (OBC) of an electric vehicle by charging the battery directly via the EV’s Battery Management System (BMS). This bypass leads to a significant increase in charging speed, with charger output power ranging from 50 kW to 350 kW. The output voltage typically varies between 400V and 800V, with newer EVs trending toward 800V battery systems. Since L3 DC fast chargers convert three-phase AC input voltage into DC, they use an AC-DC power factor correction (PFC) front-end, which includes an isolated DC-DC converter. This PFC output is then linked to the vehicle's battery. To achieve higher power output, multiple power modules are often connected in parallel. The main benefit of L3 DC fast chargers is the considerable reduction in charging time for electric vehicles
The charging pile core is a basic AC-DC converter. It consists of PFC stage, DC bus and DC-DC module
PFC Stage Block Diagram
DC-DC module functional block diagram