In this article, we will explain the electric vehicle charging procedures defined in ISO/IEC 15118 and related standards.
When an electric vehicle is plugged into a charging station, the physical connection is first detected through the IEC 61851 Control Pilot (CP) mechanism. PLC-SLAC then establishes the power line communication link, followed by Service Discovery Protocol (SDP) for device discovery and the establishment of a secure TLS-encrypted communication channel.
At the application layer, ISO/IEC 15118 manages communication between the electric vehicle and the charging station, while IEC 61850 enables the charging station to exchange charging-related data with the power grid operator.
In simple terms, ISO/IEC 15118 governs vehicle-to-charger communication for charging and discharging, while IEC 61850 facilitates communication between the charging infrastructure and the power grid.
The complete communication session consists of three phases:
1. Setup – Session Establishment: Protocol handshake, service discovery, authentication, Plug & Charge (PnC) verification, and negotiation of charging voltage and current parameters.
2. Charging – Charging Execution: Cable check and pre-charge safety verification. The vehicle periodically sends current demand requests, supporting both conventional charging and reverse power flow through Vehicle-to-Grid (V2G) technology.
3. Finalize – Session Termination: A session stop command is issued, the high-voltage circuit is disconnected, and the charging session is terminated.
Throughout the vehicle-to-charger communication process, the EVSE simultaneously reports vehicle connection status, battery State of Charge (SOC), real-time power, and metering data to the grid operator via IEC 61850.
Based on this data, the grid operator can perform load monitoring and coordinate Vehicle-to-Grid (V2G) operations.
Standard Comparison
Standard Communication Between Core Functions ISO/IEC 15118 EV ↔ EVSE Authentication, Plug & Charge (PnC), and bidirectional charging sessions IEC 61850 EVSE ↔ Grid Operator Charging data reporting, grid monitoring, and load management
ISO/IEC 15118 enables bidirectional charging and discharging communication between electric vehicles and charging stations, while IEC 61850 establishes communication between charging stations and power grid management systems. Together, these two standards enable Vehicle-to-Grid (V2G) integration.
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