PJM has joined forces with the U.S. Department of Energy’s Argonne National Laboratory to support the integration of distributed energy resources such as residential and commercial solar into the region it serves.
Under a Cooperative Research and Development Agreement, Argonne is supporting PJM’s Distributed Energy Resource Ride-Through Task Force, which is developing guidelines for “ride through” and “trip” requirements. These guidelines are important for PJM to be able to integrate the increasing number of solar installations into its footprint.
This trend is an energy boon, but it also creates challenges to safeguarding the electric grid. Argonne and PJM are analyzing ways to maintain system reliability as the share of distributed solar and other distributed energy resources in the fuel mix increases.
Two states within the PJM footprint, New Jersey and North Carolina, are among the country’s top 10 for solar capacity per capita. While useful as a clean energy resource, the increasing number of solar panels changes the calculus for what should happen when there’s an anomaly in the system.
“Our primary mission is reliability, and we are preparing our system for the advent of more distributed energy resources so that we can seamlessly operate and understand DER behavior, both during normal operations and times of system stress,” said Chantal Hendrzak, executive director – Applied Innovation & Market Evolution for PJM.
Solar as a Distributed Energy Resource
Much solar energy is considered a distributed energy resource, often called DER in the industry. These resources can also include battery storage, wind turbines and combined heat and power plants, and are located on the distribution side of the grid – which in the case of solar, could mean a customer’s rooftop.
Prior to the arrival of DERs, the distribution system was designed for one-way power flow. Electricity moved from power plants, through a transmission network, stepped down to a distribution system, and finally to customers. The fact that generation now also comes from the distribution level creates a new set of design considerations.
When an unexpected occurrence like storm damage for malfunctioning equipment disrupts power flow, the system is designed to respond while maintaining the delicate balance between electricity generation and electricity demand. DER settings determine whether a resource rides through, meaning stays connected, or trips offline when there is a disruption on either the transmission or distribution side of the system. Riding through an event helps keep power flowing reliably, while tripping offline protects against damage and safety concerns.
With more than 80 researchers who study the grid, Argonne National Laboratory has long developed modeling and analytics to help inform decision makers about issues related to electricity systems.
“Our team has directly relevant experience in modeling and usage of simulation tools, and it has conducted similar analyses for the DOE and the North American Electric Reliability Corporation that can contribute to this joint effort,” said Ning Kang, an Argonne staff scientist who is leading the project with PJM.
Argonne sent Rojan Bhattarai, another scientist from the lab, to work onsite at PJM to support the PJM task force. Bhattarai will analyze regional data, develop power system models with DERs and help PJM stakeholders fine-tune DER operational settings to maintain optimum system reliability.
The current challenge lies in the emerging dynamic between the transmission side of the grid (that PJM oversees) and the distribution side, where solar resources and other DERs outside of PJM’s jurisdiction now offset customer demand.
If a disturbance happens on the transmission side and DERs are unable to ride through, there could be a cascading effect where the system becomes overstressed. For example, in 2016 protection settings caused wind farms in Australia to trip offline during a storm, resulting in a major blackout. However, on the distribution side, in an emergency, a utility may want DERs to trip offline in order to maintain safety and protect against damaging facilities and equipment.
“For transmission system faults, DERs should stay connected to maintain reliability, while for distribution system faults, DERs should stop producing as fast as possible to ensure safety and protection,” said Bhattarai.
But a distributed resource doesn’t know whether the fault occurred on the transmission or distribution side.
“So the challenge for PJM and others is to find a middle ground and come up with one set of operating rules that can ensure DERs function properly for faults on both the transmission and distribution side,” he said.
PJM has the platform to reliably integrate and support new technologies connecting to the grid and allow those that want to compete to supply wholesale power and services. PJM’s stakeholders also represent a broad swath of the electricity industry that work together to find solutions that enable the benefits of DERs while maintaining a reliable grid.
In 2018, the Institute of Electrical and Electronics Engineers (IEEE) updated its standard for voluntary DER interconnection. The standard (IEEE 1547-2018), which is widely mandated in state and federal laws and regulations, guides trip and ride-through settings, but offers a fair amount of leeway. Different utilities might have different required settings for DERs, leading to uncertainty in the system’s response following a disturbance. The combined PJM-Argonne team will study the impact of DER trip and ride-through timing in the current IEEE standard to help PJM stakeholders reach a consensus on DER integration. It will also inform the technical guidance that utilities and states can use to implement DERs across the region PJM serves.