The North American Electric Reliability Corporation recently published a white paper to help inform electric vehicle stakeholders and policymakers about the need for greater cross-sector collaboration regarding the potential effects of the rapid growth of EV charging on bulk power system reliability.
“As EVs become more numerous, their charging characteristics (i.e., where and how they charge) will have an increasing effect on the grid,” NERC said in the white paper.
Various studies have indicated that there will be significant EV growth through 2050. Current projections and forecasts show that EV charging load can be dispersed throughout the BPS or at single points of interconnection.
The white paper provides an overview of the potential adverse impacts of this growth on BPS reliability if not properly mitigated.
NERC noted that EV charging falls into one of four classification levels based on rate of charging.
NERC’s initial study focus was primarily on Levels 1 and 2 based upon available data and projected near-term growth in these categories.
“However, it is important that future studies also address Level 3 and 4 chargers since the loads associated with these chargers (e.g., truck fleet charging) can be very significant.”
The ability of EV owners to charge with their home charging systems as well as with public charging stations adds an element of uncertainty in electric load forecasting for given parts of the electric grid, potentially complicating BPS operations and planning, NERC said.
NERC, the National Laboratories, and others have conducted preliminary studies and concluded that EV charging can operate in either a grid-friendly or a grid-unfriendly manner.
“However, if too many EV charging locations impact the grid in the unfriendly manner, BPS reliability could potentially be impacted.”
State of Industry Readiness
NERC has determined that there are significant gaps in both the electric utility and EV charging community’s technical understanding, planning, and modeling of EV charging characteristics.
“While NERC has made efforts to address these knowledge gaps by working directly with EV manufacturers and other EV stakeholders, increased EV stakeholder awareness, engagement, and cross-sector collaboration is essential.”
NERC said the following deficiencies are the most prevalent in modeling, standardization, and studies:
- Modeling: As it currently stands, there is only a single, generic electrical model to represent EV charging. More work is needed to ensure that the electric system planners and operators have the quality of models needed.
- Standardization: Currently, EVs and their charging systems do not follow consistent control philosophies or performance. Simply put, two different EVs that use Level 2 chargers do not necessarily interact with the grid in the same way. This lack of standardization makes grid planning difficult. Efforts are under way within the electric industry to address this issue.
- Studies: EVs and the effect of their charging systems on the grid have not been sufficiently studied.
To help address knowledge gaps about EVs and their charging systems, NERC undertook a study -- based on the only model currently available on the subject -- to determine how EV chargers interact with the electric grid and developed recommendations.
NERC determined that EV chargers can negatively impact BPS reliability depending on the way they draw current from the BPS (i.e., grid-friendly vs. grid-unfriendly).
“To avoid reliability issues, EV and charging system manufacturers must increase their collaboration with electric utilities and establish performance criteria and standards regarding grid-friendly EV charging methods. Without greater collaboration, policymakers may need to act,” NERC recommended.
NERC also found that reliability implications vary depending on the characteristics of the grid in specific locations and the number of EVs present. As a result, performance criteria are likely to vary based on location.
Transmission planners “will need to modify their planning criteria to indicate the types of charger performance criteria that are grid-friendly for their planning area. Different parts of North America will likely have different criteria for this, and it may be possible to address these criteria with EV charging software updates.”
NERC also found that knowledge gaps about EV charging behaviors create uncertainty in planning and understanding of the electrical impact that these devices may have on the BPS as well as associated policymaking.
Vehicle manufacturers, the electric industry, and policymakers must increase collaboration to close knowledge gaps and address reliability concerns and benefits, it said.