SMART CHARGING 102: What are V1G, V2G and V2H / V2B / V2X smart charging? | Integrating electric vehicles into power grid

Increasing electric vehicle transportation, thus the burden they can bring to power grids and transmission infrastructure are inevitable! (read also: Increasing electric vehicles would destroy power grids & infrastructure: Is it true?). 

However, the extent of negative impacts on peak demand & grid infrastructure can be mitigated by integrating EVs into the grid via smart charging. If charged smartly, electric vehicles can not only avoid adding stress to the local grid but also provide services to fill flexibility gaps both on the local level and on the system level. 

This article may give an overview of how these smart charging implementations work and how the EVs could help to improve local load curve, avoid investment in peaking generation capacity, as well as mitigate grid reinforcement needs. 

Levels of Vehicle-to-grid integration:

Different forms of vehicle-to grid integration smart charging implementation are possible – based on charging infrastructure and customer’s willingness. In a broad sense, the smart charging of electric vehicles can be divided into five forms: Uncontrolled smart charging, Basic control, V1G – Unidirectional control, V2G- Vehicle to Grid, and V2H/V2B/V2X bidirectional charging. 

Note: Local load management (LLM) and active/static load balancing of charging stations are different; this article focuses on smart charging scenarios when the charging cycle can be altered by external events, and the EV effectively integrates with the whole power system in a grid. 

Source: IRENA - International Renewable Energy Agency

1. Uncontrolled but with time-of-use smart charging:

The simplest form of smart charging is the time-of-use optimization – that encourages consumers to defer their charging from peak to off-peak periods.

This time-optimized smart charging implementation is relatively simple, does not need any control from external stakeholders. However, it proves to be relatively effective at delaying EV charging until off-peak hours at low EV penetration levels.

Below experiment conducted by Mckinsey in the US shows that mid-night time-of-use smart charging optimization reduced peak grid demand close to 50%. (from +30% peak demand to +16%).

2. Unidirectional controlled charging (V1G):

V1G refers to unidirectional controlled charging where electric vehicles or charging infrastructure adjust their rate of charging based on control signals from the grid operator.

Open Smart Charging Protocol (OSCP) in combination with OCPP facilities a 24-hour prediction of the local available capacity of every region to the Charge Spot Operator. The CPO will then fit the charging profiles of the electrical vehicles within the boundaries of the available capacity.

3. Bidirectional V2H / V2B / V2X smart charging:

Vehicle-to-home (V2H) or vehicle-to-building (V2B) or vehicle-to-everything (V2X) do not typically directly affect grid performance. but creates a balance within the local environment.

The EV is used as a residential back-up power supply during periods of power outage or for increasing self-consumption of energy produced on-site (demand charge avoidance).

Unlike more mature V1G solutions, V2X has not yet reached market deployment, apart from Japan where commercial V2H solutions have been available since 2012 as back-up a solution in case of electricity black-out. (especially after the Fukushima tragedy).

4. Bidirectional Vehicle-to-grid (V2G):

Vehicle-to-grid (V2G) is one step further than controlling their demand for electricity (V1G) and using the bidirectional (dis-)charging for self-consumption (V2H/B.X). With V2G, the electric vehicles could be equipped to actually provide electricity to the grid.

The utility / transmission system operator may be willing to purchase energy from customers during periods of peak demand, and/or to use the EV battery capacity for providing ancillary services, such as balancing and frequency control, including primary frequency regulation and secondary reserve. Thus, V2G is in most applications deemed to have higher potential commercial value than V2B or V2H. 

Below is a summary of all the above explained smart charging implementations:

Type of V-G-integration	What is it?	What problem does it solve?
Uncontrolled, but with time-of-use optimization	Change charging pattern from peak to off-peak periods. Uncontrolled (simple on/off charging based on time)	Peak shaving; reduces peak use demand.
Unidirectional controlled (V1G)	Increase and decrease charging speed (current) based on real-time demand forecasts from DSOs	Helps in grid congestion management
Bidirectional vehicle to- home/building/anything (V2H/V2B/V2X)	EV is used as a residential power during periods of power outage; and/or enables increased self-consumption of home/building.	Reduces not only peak use demand, but eases of the overall grid capacity demand for a home/building.
Bidirectional vehicle-to-grid (V2G) and grid-to-vehicle (G2V)	EV is equipped to feed-back electricity to the grid	Provides flexibility on power capacity and peak demand on large-scale.