Architecture Design of V2G European Standard DC Charging Pile

(1) Topology: Three level Vienna rectifier (commonly used in unidirectional applications, but in V2G scenarios, bidirectional three-level topology is generally chosen, such as three-phase voltage type AC/DC with SiC MOSFET to achieve bidirectional power flow, or T-shaped three-level bridge)

(2) Device: SiC MOSFET (650V/1200V) is commonly used for power levels above 30kW, with a switching frequency of 20-50kHz to balance efficiency and magnetic component volume

(3) Function: AC/DC rectification (G2V)+DC/AC inverter (V2G)+active/reactive power decoupling control (used for power grid support/frequency and voltage regulation scenarios)

(4) Power quality: It needs to meet standards such as IEC 61000-3-12 (harmonics) and EN 50549 (grid protection), and the THD requirement during V2G discharge is usually less than 5%

(1) Topology preference: CLLC resonant converter (bidirectional symmetry, high soft switching efficiency, suitable for fixed/narrow range voltage gain occasions) or dual active bridge DAB (better dynamic response under wide voltage range, suitable for different vehicle battery voltage platforms of 150-1000V)

(2) Isolation transformers should be designed according to the highest insulation level (vehicle pile isolation to prevent coupling between vehicle potential and grid potential)

(3) This level is also an electrical isolation point required by the CCS2 standard (both GB/T 27930 and IEC 61851-23 require electrical isolation between vehicle and pile)

(1) Bus capacitor+bus voltage/current sensing (for V2G power loop control)

(2) DC contactor (one positive and one negative pole each, partially designed with pre charging resistor+pre charging contactor, used for CCS2 gun insertion and bus soft start)

(3) HVIL (High Voltage Interlock Circuit): runs through the entire process of the gun head bus converter, and any link that is disconnected will cut off the output

(4) Insulation monitoring IMD: Real time monitoring of the insulation resistance of positive and negative busbars to ground, triggering protection in case of faults

The key point added to ISO 15118-20 compared to 15118-2 is the Bidirectional Power Transfer (BPT) service, where vehicles report their discharge capacity and SOC limits through messages such as Schedule Exchange, and the pile end issues power curves based on this – this is the core difference between V2G and ordinary DC fast charging at the protocol level. If we want to be compatible with the GB/T standard system domestically, we also need to consider the compatibility layer between GB/T 27930 (current) and GB/T 27930-202x (V2G revised version, currently in progress).

(1) Usually using CAN 2.0B or CAN FD, the main control sends voltage/current commands to the power module, and the module reports status and fault codes

(2) If a modular power architecture is adopted (multiple power modules connected in parallel), master-slave arbitration/current sharing protocol is also required

(1) OCPP 2.0.1 is currently the mainstream choice, with its Bidirectional Power Transfer module specifically supporting power curve issuance and energy metering reporting in V2G scenarios

(2) If it involves participating in grid frequency regulation/demand response, some projects will use IEEE 2030.5 (CSIP) or OpenADR to interface with the DERMS/VPP platform, and SECC needs to do protocol bridging at this time