T&D World Magazine

Putting DERs to Work

What does the future hold for utilities in regards to the various distributed energy resources? 

Most people believe utilities in the future will contend with numerous distributed energy resources (DERs) such as microgrids, electric storage, solar photovoltaic, electric vehicles and demand response. How will utilities make all this work? Here’s a glimpse into a possible future.

As he scanned the control room, Miguel saw the March day was shaping up as a typical “hi-lo” day that would test system resources. He called these days hi-lo because moderate temperatures would keep overall demand low, but the clear skies would mean that the many connected solar PV arrays would be producing electricity at near peak capacity. Sunrise was just an hour away and that’s when things would start hopping. As the director of system operations for his utility, it was his job to ensure hopping did not become popping.

Miguel turned to the two large ultrahigh-definition flat screen displays on his desk and pulled up the net load forecast for the day. At this time of year when the total distributed solar production was subtracted from the total electric load it produced a net load profile that had a noticeable valley during daylight hours due to all the solar production.

When it was first experienced in California several years back, it had been labeled a “duck curve” because of its shape. Now Miguel simply viewed it as the net load forecast for a typical cloudless spring day.

Next, Miguel called up the summary page of his distributed energy resource management (DERM) system. He first glanced at the independent system operator (ISO) resource table for his utility. This table displayed the DER calls that the ISO would be making that day. The columns represented the system requirements of each call such as ramp-up, ramp-down, frequency regulation, standby reserve, load shaping and other services. Some of the DER represented on the table was installed on the utility’s grid, some on customer’s premises and other resources were embedded in hybrid microgrids.

Rows in the table indicated the types of resources used to meet each need. These included batteries and other storage, positive demand response and negative demand response. The last two resources were particularly prevalent in the load-shaping column. These resources along with some of the storage would be used to limit load excursions. Positive demand response had been routinely used to limit peak demand but recently Miguel had watched the amount negative demand response grow. This basically consisted of discretionary loads that could be added to the system to fill in the valleys in the load profile.

Miguel then called up the System Visualization App. Immediately, his left screen was filled with a one-line map of the distribution grid. He was glad to see that most lines were colored green, indicating that no operational issues were foreseen. He did notice that feeder number three out of the Fall River substation was colored yellow, indicating a potential problem, and three of the five feeders out of the Pine Ridge substation were colored orange, indicating a higher probability for a service interruption.

Miguel glanced at his right hand display and saw the Line and Equipment status table. During a routine aerial patrol of the Fall River circuits, one of the utility’s drones had detected a hot splice with its infrared camera. A note indicated that the splice was scheduled for priority replacement. Until then, he saw that the community storage along that feeder had been reserved for reliability support. This meant it was not available for an ISO DER call. All storage devices in the affected area were fully charged and ready to provide uninterrupted service if the line splice failed.

The orange-colored Pine Ridge feeders were no surprise. Serving an affluent residential area, these feeders hosted a high concentration of solar PV. On hi-lo days the area always produced more electricity than it consumed resulting in reverse power flows that can threaten line stability. Fortunately, this area also had a high concentration of energy storage. Like the Fall River storage, it had been reserved for reliability support; near empty, this storage was ready to receive the expected surplus solar production. If everything worked according to plan, the “Ridge” would be ready to go.

Lastly, Miguel looked at the weather forecast for the next day. With overcast conditions expected all day, he knew the low solar production would present an entirely different set of problems. Sometimes Miguel missed the simpler days of the past, but he reminded himself that today his utility had many more options to keep customers happy, and that was a good thing.

Too futuristic? Maybe not. New York, California and other states are pushing hard to expand DER use. New Brunswick Power is currently working with an early stage DERM to help meet a 40% renewable energy goal, and Oncor is piloting customer colocated storage designed to provide backup power in outages. The Electric Power Research Institute and National Renewable Energy Laboratory are working on DER communications standards. Will it all work or will it just crash and burn? We will see.

Do you have a different perspective? If so, I would like to hear from you.


TAGS: Renewables
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