Southwest Research Institute (SwRI) has deployed the first vehicle-to-grid (V2G) aggregation system qualified by the Electric Reliability Council of Texas (ERCOT) to manage charging activities for a fleet of electric delivery trucks. The SwRI system suspends vehicle charging when the electric grid frequency drops too far below 60 Hertz, the normal operating frequency. This novel smart grid system demonstrates enabling technologies to support stable electric power delivery.
Electricity is difficult to store yet has to be available on demand. Because supply and demand across a grid vary continuously, organizations such as ERCOT coordinate power through various suppliers to maintain frequency levels and make rapid adjustments when the frequency falls outside the normal range. Alternative energy supplies, such as wind energy, can be especially variable, so the SwRI-developed technology is particularly useful for integrating these green technologies into the energy infrastructure.
The development is part of a Center for the Commercialization of Electric Technologies (CCET) smart grid demonstration project funded jointly by CCET partners and the US Department of Energy through an American Reinvestment and Recovery Act grant.
The SwRI aggregation system manages charging for a fleet of electric vehicles, while also analyzing grid frequency on a continual basis. When grid frequency drops below an ERCOT-determined set point, our system automatically stops charging some vehicles, removing load from the grid and allowing frequency to return to normal ranges.—Sean Mitchem, a principal analyst in SwRI’s Automation and Data Systems Division
SwRI developed this aggregation system as a part of an ERCOT pilot program for Fast Response Regulation Services (FRRS), with the goal of providing extremely quick response to grid frequency deviations. In normal frequency regulation services, generators and load resources respond to ERCOT requests to add or remove energy from the grid in seconds to minutes, depending on the resource. FRRS is designed for services that can respond nearly instantaneously to grid events, helping to slow frequency decay and ultimately reverse it sooner than current frequency regulation services can. Electric vehicle batteries can respond in milliseconds, making them an asset suited for FRRS services.
ERCOT qualification is an important step for this program. Being qualified means that the fleet owner can bid energy services regularly into the ERCOT market and get paid for those services. The fleet owner is now able to take advantage of the normal vehicle downtime to generate additional revenue by making stored energy available to the grid.—Sean Mitchem
One of the technical challenges in this project was developing a real-time embedded system that could monitor and log frequency and power and react to events in less than one second, according to SwRI Research Engineer Gerardo Trevino. The SwRI real-time system reacts in less than half a second, including all hardware and software delays.
When the system detects grid frequency dropping below the set point, it automatically suspends charging until grid frequency recovers, at which point it resumes vehicle charging. The system is unique in that it operates autonomously, saving valuable time normally lost in human intervention and communications. The SwRI system keeps ERCOT informed of its current power available and status through regular telemetry.