Energy Storage Provides Grid Resilience During Severe Storm Conditions
By Praveen Kathpal, AES Energy
On Sept. 7, 2017, the Dominican Republic was in the path of Hurricane Irma, a Category 4 storm originating in the Atlantic Ocean with torrential rain and wind speeds of 155 mph. More than 5,500 people were evacuated from the island in anticipation of the hurricane that resulted in storm surges, flooding and destruction across the island.
AES Dominicana owns and operates power generation assets in the Dominican Republic, including two Advancion energy storage arrays deployed at its facilities, Andres and Los Mina Dominican Power Partner (DPP). The two arrays are each 10 MW, 30-minute duration energy storage installations providing frequency response to the grid. Advancion’s frequency control algorithm autonomously responds to deviations in grid frequency and either charges or discharges the batteries to counteract the deviation and achieve the target frequency.
figure 1 : ANDRES – Operation during typical weather conditions | August 31, 2017. One week prior to Hurricane Irma
In anticipation of Hurricane Irma’s arrival, the grid operator requested that both the Andres and Los Mina DPP energy storage arrays be kept online and operational during the storm. The two energy storage arrays are unmanned facilities co-located within or next to thermal operating plants. They are operated by the thermal plant control room and are remotely monitored by the AES Energy Storage Services Team to ensure proper operation and to provide the local operators with remote assistance if required.
As the storm struck, almost 40 percent of the generation assets on the island were forced to shut down and several transmission and distribution circuits were cut off, putting additional stress on the system. There were some periods during the storm when only a few power plants and the Advancion energy storage systems were online.
STORM RESILIENCE IN ACTION
During the storm, power lines were damaged, distribution lines were disconnected in zones that had risk of flood or high winds, and some power plants went offline. These events resulted in volatile fluctuations in grid frequency during the hurricane, and both energy storage arrays performed significantly more work than usual to stabilize the frequency.
The Andres array was installed in June 2017 in Santo Domingo and is housed in a building enclosure. Figure 1 shows the measured frequency and corresponding power output of the Andres energy storage array under typical operating conditions. The grid frequency in the Dominican Republic is maintained within its standard operating frequency band of approximately 59.8 to 60.2 Hz with the energy storage unit’s output ranging from 4.8 MW to -9.7 MW to counterbalance the changes in frequency.
Figure 2 shows that the measured frequency range increased significantly during the storm, moving from 59.3 to 60.8 Hz, and the energy storage system charged and discharged at maximum capacity (10 MW) on a number of occasions to quickly rebalance the system. The period of increased frequency disturbances lasted for more than 10 hours and the Andres energy storage array delivered 56.5 percent greater energy throughput than under typical operating conditions.
LOS MINA DPP ADVANCION ENERGY STORAGE ARRAY
Location: Santo Domingo, Dominican Republic ; Capacity: 10 MW Interconnected ; Duration: 30 minutes ; Key Application & Services Provided: Frequency Regulation
figure 2 : ANDRES – Operation during severe storm conditions | September 7, 2017. During Hurricane Irma
The Los Mina DPP array, housed in four container enclosures, was installed in April 2017 in Santo Domingo. Figure 3 shows the measured frequency and corresponding power output of the Los Mina DPP array under typical operating conditions. The grid frequency ranges from approximately 59.8 to 60.2 Hz with the energy storage unit’s output ranging 5.1 MW to -9.8 MW.
figure 3 : LOS MINA DPP – Operation during typical weather conditions | August 31, 2017 One week prior to Hurricane Irma
Figure 4 shows that the Los Mina DPP measured frequency range also increased significantly during the hurricane, from 59.3 to 60.8 with the power output ranging from 9.8 MW to -10 MW (full capacity is 10MW). The Los Mina DPP system delivered 59.8 percent greater energy throughput during the 10-plus hours of increased demand.
ANDRES ADVANCION ENERGY STORAGE ARRAY
Location: Santo Domingo, Dominican Republic; Capacity: 10 MW Interconnected; Duration: 30 minutes; Key Application and Services Provided: Frequency Regulation; Enclosure: Building
figure 4 : LOS MINA DPP – Operation during severe storm conditions | September 7, 2017 During Hurricane Irma
Severe storm conditions created significant deviations in grid frequency. The energy storage systems provided rapid response to counteract these deviations, maintain the target frequency and support grid resiliency and stability. No energy storage outages were experienced at either site and the arrays maintained a total combined capacity of over 20 MW for the entire duration of the storm, demonstrating the technology’s capability to perform continuously without issues and provide responsiveness under times of grid duress.
During the storm the arrays went from a typical operating range of approximately 5 MW to -9.8 MW each, to a wider range of 9.8 MW to -10 MW each, effectively requiring an additional +/-5 MW each, or 10 MW total to maintain a balanced frequency.
Energy storage has been found to be 2.9 times more effective than traditional power generation due to speed and accuracy, according to PJM regulation market benefits factor calculations. The additional power output delivered by the energy storage arrays during the storm is equivalent to instantaneously adding a thermal power plant of approximately 30 MW.