Frequency Response (BAL-003-1) – What will we do when FERC approves the standard?
Frequency and voltage control provide the foundations for reliable, stable electric power system operation. Today, every utility and operating entity must abide by certain frequency and voltage control guidelines.
Frequency response is of paramount interest to the industry, especially due to the potential grid impact from integrating increasing levels of variable energy resources (VERs), including wind and solar PV. Utilities and stakeholders are exploring how energy storage can help support VER integration and frequency regulation applications.
The NERC Board of Trustees (BOT) has approved BAL-003-1 whose purpose is to “require sufficient Frequency Response from the Balancing Authority (BA) to maintain Interconnection Frequency within predefined bounds by arresting frequency deviations and supporting frequency until the frequency is restored to its scheduled value.“ FERC and NERC are now discussing via a NOPR and comments to the NOPR with the idea that BAL-003-1 will be implemented and enforceable to prevent some of the existing frequency response shortcomings. Why BAL-003-1?
There are a number of frequency response challenges we face, and BAL-003-1 is directed towards the requirements that will provide assistance to neighboring balancing areas experiencing a frequency excursion while inhibiting excess frequency deviations as the frequency excursion is being resolved. Relying on AGC to maintain frequency targets and interchange schedules to maintain flows between balancing areas during frequency excursion in another area are problematic. The current methods of determining Frequency Bias are varied and problematic. We will now discuss some of the proposed changes intended to resolve the issues including NERC determining our Frequency Bias Setting.
Summary of BAL-003-1 activities
NERC has established a target contingency protection criterion for each Interconnection called the Interconnection Frequency Response Obligation (IFRO). NERC will annually define each Balancing Authority’s Frequency Response Obligation (FRO) and Frequency Bias Setting (FBS). The Balancing Authority will calculate its Frequency Response Measure (FRM) from Single Event Frequency Response Data (SEFRD). Balancing Authorities will complete their frequency response sampling for all four quarters and their FBS calculation, returning the results to the ERO.
Below are the worst case scenarios that a Balancing Authority (BA) or Frequency Response Sharing Group can find themselves in, which I offer as a way of determining what we are actually being measured against.
- The summation of the Balancing Authorities’ FRM within an Interconnection did not meet its IFRO, and the BA’s, or Frequency Response Sharing Group’s, FRM was less negative than its FRO by more than 30% or by more than 15 MW/0.1 Hz, whichever is the greater deviation from its FRO.
- The BA is in a multiple BA Interconnection and not receiving Overlap Regulation Service and uses a fixed Frequency Bias Setting did not implement the validated Frequency Bias Setting value into its ACE calculation in more than 25 calendar days from the implementation period specified by the ERO
- The BA that is a multiple BA Interconnection and not receiving Overlap Regulation Service and uses a variable Frequency Bias Setting average Frequency Bias Setting during periods when the clock-minute average frequency was outside of the range 59.964 Hz to 60.036 Hz was less negative than its Frequency Response obligation by more than 30%
- The BA incorrectly changed the Frequency Bias Setting value used in its ACE calculation when providing Overlap Regulation Services with combined footprint setting-error more than 30% of the validated or calculated value or the BA failed to change the Frequency Bias Setting value used in its ACE calculation when providing Overlap Regulation Services.
Options to address frequency response
There are a number of options to address frequency regulation, including demand-side management, frequency response obligation, supplemental service, and overlap regulation service. These options can help a utility be prepared in advance for NERC frequency regulation standards on the horizon.
Demand-side management (DSM) – A growing number of utilities and independent system operators (ISOs) are employing DSM solutions to decrease load peaks by altering consumer load profiles. DSM is accomplished when the consumer voluntarily allows the utility to turn off specific appliances, such as hot water heaters, pool filters, and air conditioners, for a limited period of time.
Frequency response obligation – Today, the primary source of frequency response to meet a balancing authority’s (BA) obligation resides with generation companies. A second source comes from programs, such as Load Resources, or from load-shedding schemes. These solutions tend to work when the disturbance is within a utility’s area. However, they may be less effective when the disturbance is in a neighboring area.
Augmenting generation frequency response –Utilities can also obtain frequency response through supplemental service (SS) or overlap regulation service (ORS). ORS uses a reserve sharing group, which is a viable option as long as the sharing area is not experiencing the disturbance. For SS, utilities might look at DSM as an option. When experiencing significant frequency deviations, the duration of the impact might be lessened by augmenting the generator’s response with DSM, which can be calibrated and directed by the utility, controlling the impact.
By using DSM to shorten the period and stabilize the frequency, the BA lessens the impact on the frequency response measure (FRM) and decreases the potential of incurring NERC’s BAL-003-1 standard Violation Severity Level.
Designing a frequency response process
Designing and implementing an effective utility frequency response process is a key component of NERC BAL-003-1 compliance. A process to maintain the FRM within NERC’s assigned limits requires the ability to detect an external disturbance by monitoring tie line flows and frequencies, then activating DSM. The process might also require accumulating residual FRM from event-to-event to apply to subsequent events. This helps keep the utility’s annual frequency response within NERC’s guidelines and avoiding potential penalties.
In some cases, this process can be implemented as an application in the utility’s energy management system (EMS), if it can get a one-second periodicity. However, since EMS systems are typically not designed for a one-second resolution, this process might be better implemented external to the EMS by reading one-second frequency data and triggering DMS. Another consideration is if the one-second process isn’t reading frequency directly, the frequency data must be time stamped to prevent unknowingly reading the same frequency, creating false positives. There are other process design considerations to ensure customers are minimally inconvenienced and the annual FRM calculation is correct, which will arise as the technology evolves.
Let us know what you think
How will BAL-003-1 affect you when FERC approves the standard? What are your major concerns? Let us know in our brief survey. For additional insight into the use of DSM relative to frequency response solutions, contact firstname.lastname@example.org.
Raymond Gilby, a member of DNV GL’s NERC Compliance Group, has over 35 years of utility experience. Since 2007, Ray has been assisting generation, transmission and distribution entities with NERC registration; Operating and cyber security processes and procedures for NERC compliance; Defining and implementing NERC compliance programs; Serving as interim or startup NERC Compliance Manager to bridge a resource gap; Performing initial, annual or dry-run compliance assessments. When asked who he works for, his reply is “the client’s NERC compliance” and where does he live; “airline terminals, hotels, and client conference rooms.” Read more on our contributors page.