(R) Interconnection Requirements for Onboard, Grid Support Inverter Systems
|Publication Date:||1 March 2021|
This SAE J3072 Standard establishes requirements for a grid support inverter system function which is integrated into a plug-in electric vehicle (PEV) which connects in parallel with an electric power system (EPS) by way of conductively coupled, electric vehicle supply equipment (EVSE). This standard also defines the communication between the PEV and the EVSE required for the PEV onboard inverter function to be configured and authorized by the EVSE for discharging at a site. The requirements herein are intended to be used in conjunction with IEEE 1547 and IEEE 1547.1. This standard shall also support interactive inverters which conform to the requirements of IEEE 1547-2003 and IEEE 1547.1-2005, recognizing that many utility jurisdictions may not authorize interconnection.
Utilities or local jurisdictions will establish procedures by which a site could be approved for the interconnection of PEVs with onboard inverters based partially on testing and certification to SAE J3072 and other required standards.
The vehicle manufacturer (VM) or their designated agents will perform the analyses, inspections, and tests to ensure that each inverter system model that is installed in one of their PEV models conforms to the requirements of SAE J3072. The VM or third party testing body will issue a certificate of conformance to SAE J3072 for each authorized inverter system model.
The EVSE manufacturer (EVSE OEM) or a Nationally Recognized Testing Laboratory (NRTL) will perform the analyses, inspections, and tests to ensure that each EVSE model to be used with a PEV with an onboard inverter system conforms to the requirements of SAE J3072 or to an EVSE standard which calls out conformance to SAE J3072, as well as other required and applicable United Laboratory (UL) standards. The EVSE OEM or NRTL will issue a certificate of conformance to SAE J3072 or other EVSE standard for each authorized EVSE model.
Two approvals are needed before a photovoltaic system can be used. A building permit must be secured from the municipality and their code enforcers inspect the installation to ensure that it meets the appropriate National Electrical Code requirements. An application to interconnect to the grid must also be made with the electric utility for both business reasons (such as net metering) and grid safety (which is based on meeting IEEE 1547). If the inverter unit is listed by a NRTL as conforming to UL 1741, this generally satisfies both the local code enforcement and utility technical requirements. The application forms request the model number of the inverter unit and many states maintain a data base of listed and state approved models. Because the PV system is fixed to the site, site-specific settings (such as the reference voltage) can be directly entered into the inverter unit. For a V2G-DC application where the inverter is installed in the EVSE, the same process used with PV systems can be followed.
However, a roaming V2G-AC PEV inverter creates some unique technical and interconnection approval issues. The PEV can easily cross utility service areas and state lines and connect at locations with different site settings. For example, one EVSE could be connected to 208 VAC service and another EVSE could use 240 VAC service. For an onboard inverter that needs to meet an IEEE 1547 requirement to stop discharging if the grid voltage drops below 88% of the reference voltage, the inverter needs to know the reference voltage for the specific EVSE. It is not practicable to allow this to be an explicit inverter setting in the PEV. SAE J3072 defines requirements for these settings to be made in the EVSE and transferred to the PEV when it connects to the EVSE.
There are no established procedures in the electric power industry for handling a DER interconnection application without providing the actual inverter model to be used on the form. The inverters are always fixed to the site and exactly known. PEVs roam and there could be many different PEV models that could possibly connect to a site EVSE, particularly at public sites. Utility DER interconnection application and approval procedures will need to be modified to allow for roaming V2G-AC PEVs with onboard inverters. The utility would approve the site for interconnecting the PEVs based on the EVSE serving as the gatekeeper and only allowing PEV inverter system models that have been certified to conform to SAE J3072 to discharge.