Introducing V2G Control

Now that we know how V2G works electrically and the hardware components required, we can start to think about how a V2G eco-system is operated by discussing some of the key standards, protocols and stakeholders. We are really getting into the detail now so there are a lot of acronyms to understand!

A V2G eco-system, like with conventional charging systems, comprises three key sub-systems. These sub-systems, which must work together in order to create a useable V2G system are as follows:

The Electric Vehicle (EV). When parked, the EV essentially acts as a stationary battery. The EV contains the following components:

• EV Charge Controller (EVCC) – communicates with the chargepoint to control the charging and discharging processes.
• On-board Charger (OBC) – converts AC electricity supplied by the chargepoint in an AC charging process to DC to charge the battery.
• Battery Management System (BMS) – manages and protects the battery for charging and discharging.
• Battery Energy Storage System (BESS) – stores energy chemically in battery cells arranged in modules and packs. This energy is then available for later use, either for driving purposes or potentially for V2G.

The Chargepoint. Also known as Electric Vehicle Supply Equipment (EVSE), this includes a Supply Equipment Charge Controller (SECC) which communicates with the vehicle EVCC and supplies and receives power from the vehicle during charging and discharging.

The Chargepoint Operator (CPO). Often referred to as a Chargepoint Network Operator (CPNO), this entity will operate software that communicates with the EVSE to instruct charges and discharges and receive information in return.

Figure 1 shows how these sub-systems interface with one another. Also shown are other stakeholders that may interface with the eco-system via the CPO, such as Distribution System Operators (DSOs), e-Mobility Service Providers (eMSPs) and Fleet Management systems.

Figure 1: The V2G Control Eco-System

In the next two steps we will focus on the communication and control for V2G that occurs between:

• The vehicle and the chargepoint. This local interface is between the SECC (in the chargepoint) and the EVCC (on the vehicle).
• The chargepoint and the CPO. This is a remote interface.

Key Takeaways

There are three key sub-systems within the V2G eco-system; the vehicle, the chargepoint and the chargepoint operator (CPO). There are two interfaces used for V2G control. The first is a local interface between the chargepoint and vehicle’s charge controllers and the second a remote interface between the chargepoint and the CPO.