By Dan Ware
To better understand the impact of increasing amounts of privately-owned renewable energy and energy storage on the electric grid, major advances in developing more accurate electricity distribution grid models have been created by researchers at Sandia, in conjunction with researchers at the Electric Power Research Institute (EPRI) in Palo Alto, California. These advances focus specifically on the power distribution secondary system, which provides customers their power through transformers and low-voltage wires onto their property. The results are published in an article in the journal IEEE Transactions on Sustainable Energy.
Increasing amounts of solar photovoltaics and other sources of energy termed distributed energy resources entering the nation’s energy grid have increased grid operators and planners’ need for more accurate distribution systems modeling. Residential solar power and energy storage are becoming an ever-larger part of energy generation. These energy and storage installations are connected to the distribution secondary system, making it vital to include those systems in distribution grid models for an accurate understanding of the impact of distributed energy resources to electric grid operations.
Before the rapid increase of distributed energy resources and smart meters on the grid, the secondary system lacked measurement data, making it difficult to create or validate models of those systems. Now, with increases in both automated metering infrastructure and inverters on the secondary system, distributed voltage and power measurements are available. This has created a growing interest in developing methods to improve distribution system modeling and allow for more accurate understanding of distributed energy resource impacts.
“Parameter and topology estimation leverage ubiquitous measurements across a distribution grid to enhance grid model accuracy by identifying and correcting errors in customer layouts and line impedances,” says lead author Matthew Lave. “Special focus is given to model correction on the secondary system which connects the distribution transformer to the customer, since many distributed energy resources such as rooftop solar are located at homes and businesses. While estimation methods have been previously proposed, they had not been demonstrated or tested on real utility distribution feeders with field measured data.”
In the article, written by Sandia researchers Matthew Lave and Matthew J. Reno and EPRI Technical Leader Jouni Peppanen, parameter and topology estimation methods are applied to data from real distribution feeders under normal operating conditions.
The article presents a new method to resolve the parameters for secondary systems with only a single customer by comparing their data to other secondary systems. The results reported in the article highlight the value of these highly-accurate newer methods based on ubiquitous measurements over the simple assumptions. Previously, utilities employed simple assumptions due to a lack of data, which resulted in high uncertainty.
Ongoing work focuses on implementing these parameter and topology estimation methods into distribution modeling software used by utilities. This will allow utilities to easily update their distribution grid models to accurately reflect the system. This will also allow utilities to quickly detect changes to the system, such as feeder reconfigurations or changes to customer connections.