IEEE Power & Energy Magazine - March/April 2021 - 27

situation for the future grid operating conditions
and can effectively mitigate anticipated large netload ramp events.

Current Challenges and Work Planned
for the Nearest Future
Increasing numbers of IBRs and declining online synchronous generation lead to lower system strength and
higher voltage sensitivity. Frequent adjustments of voltage
profiles and reactive power devices are expected due to
the variation of renewable generation and load patterns.
To address this challenge, ERCOT identified the need
for a reactive power control tool in operations to improve
the control and coordination of various reactive devices,
including generator voltage profile, switchable shunts,
static var compensators, and static synchronous compensators, for both day-ahead and real-time operations. Currently, there is no commercial tool available to meet this
need, and ERCOT is in the process of developing and
implementing one.
ERCOT has already implemented a transient security assessment tool in operations to assess the system's
dynamic stability on an as-needed basis. However, due to
the increasing dynamic stability challenges in the evolving grid, ERCOT plans to implement a real-time transient
security assessment tool to assess real-time dynamic stability. Similar to the real-time voltage stability assessment,
the real-time transient stability assessment is expected to
run automatically at regular intervals, e.g., every 10 min, to
determine dynamic stability limits on defined transmission
interfaces. The identified limits will be managed through
generic transmission constraints enforced in security-constrained economic dispatch.

Conclusions and Recommendations
As more wind and solar generation is added to the system,
ERCOT and its market participants are introducing necessary changes to the market rules, ancillary services, and
operation practices as well as developing new situational
awareness tools and real-time studies to ensure continued
system reliability. Based on ERCOT's experience, the following practices are recommended to ensure operational
security with high IBRs:
✔ Granular unit commitment and economic dispatch must take into account the most up-to-date
load, renewable forecast, and generation unit status information.
✔ Essential reliability support needs to be regularly
reviewed and revised to account for evolving system characteristics. While some essential reliability
requirements may need to be implemented through
interconnection requirements or grid codes, market
solutions should also be considered where practical.
✔ Ancillary service products need to grow with the
evolving generation mix, and faster, more flexible
march/april 2021

✔

services may be required as the share of IBRs continues to increase. The continuous refinements of ancillary service methodology reflecting changing system
needs is recommended.
It is recommended that possibilities to supplement
diminishing inertial response from synchronous
generation with the use of emerging technologies
are explored.
Granular telemetry from all generation resources is
required to inform situational awareness tools and
studies conducted in operations as well as ex-post
analysis.
Conducting several studies and analyses in dayahead and real-time situations allows maintaining
reliable system operation. This simultaneously allows for more efficient operation under less conservative assumptions compared to predetermined
limits based on offline studies with worst-case scenario assumptions.
Real-time situational awareness tools in the control
room are essential for efficient and reliable operation.
Continuously improving existing tools and identifying
the need for new tools is paramount for adapting to the
rapidly evolving power system.

For Further Reading
" Inertia: Basic Concepts and Impacts on the ERCOT Grid, "
ERCOT, Taylor, TX, Apr. 2018. [Online]. Available: http://
www.ercot.com/content/wcm/key_documents_lists/141324/
Inertia_Basic_Concepts_Impacts_On_ERCOT_v0.pdf
" 2017 Responsive Reserve Service (RRS) study for determining 2018 ancillary service RRS requirements, " ERCOT,
Taylor, TX, Sept. 2017. [Online]. Available: http://www
.ercot.com/content/wcm/key_documents_lists/108744/05
._RRS_Study_2017_Methodology_11022017.docx
" Use of generic transmission constraints in ERCOT, "
ERCOT, Taylor, TX, July 2020. [Online]. Available: http://
www.ercot.com/content/wcm/lists/197392/The_Use_of
_GTCs_in_ERCOT_July_2020.pdf
" Nodal protocols and operating guides, " ERCOT,
Taylor, TX, Nov. 2020. [Online]. Available: http://www
.ercot.com/mktrules/nprotocols/current

Biographies
Julia Matevosyan is with the Electric Reliability Council of
Texas, Taylor, Texas, 76574, USA.
Shun Hsien Huang is with the Electric Reliability Council of Texas, Taylor, Texas, 76574, USA.
Pengwei Du is with the Electric Reliability Council of
Texas, Taylor, Texas, 76574, USA.
Nitika Mago is with the Electric Reliability Council of
Texas, Taylor, Texas, 76574, USA.
Rochie Guiyab is with the Electric Reliability Council of
Texas, Taylor, Texas, 76574, USA.
p&e

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http://www.ercot.com/content/wcm/key_documents_lists/141324/inertia_basic_concepts_impacts_on_ercot_vo.pdf http://www.ercot.com/content/wcm/key_documents_lists/141324/inertia_basic_concepts_impacts_on_ercot_vo.pdf http://www.ercot.com/content/wcm/key_documents_lists/141324/inertia_basic_concepts_impacts_on_ercot_vo.pdf http://www.ercot.com/content/wcm/key_documents_lists/108744/05_rrs_study_2017_methodology_11022017.docx http://www.ercot.com/content/wcm/key_documents_lists/108744/05_rrs_study_2017_methodology_11022017.docx http://www.ercot.com/content/wcm/key_documents_lists/108744/05_rrs_study_2017_methodology_11022017.docx http://www.ercot.com/content/wcm/lists/197392/The_Use_of_gtcs_in_ercot_july_2020.pdf http://www.ercot.com/content/wcm/lists/197392/The_Use_of_gtcs_in_ercot_july_2020.pdf http://www.ercot.com/content/wcm/lists/197392/The_Use_of_gtcs_in_ercot_july_2020.pdf http://www.ercot.com/mktrules/nprotocols/current http://www.ercot.com/mktrules/nprotocols/current

IEEE Power & Energy Magazine - March/April 2021

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