ASSESSING THE IMPACT OF FLEXIBLE RAMP CAPABILITY PRODUCTS IN THE MIDCONTINENT ISO
Date
2014-04-25
Author
Advisor
Patino Echeverri, Dalia
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Abstract
In electric power systems, balancing authorities adjust the output of dispatchable
coal and natural gas generators in response to changes in net load (electricity demand
minus variable generation such as wind). As penetration of renewable energy increases,
so do the variability and uncertainty surrounding net load, making balancing more
difficult. The flexibility of the system to ramp power output up and down (i.e. ramping
capability) may be insufficient to accommodate large changes in net load, potentially
leading to scarcity events and threatening system security. The Midcontinent Independent
System Operator (MISO) has proposed ancillary service products called up-ramp capability
(URC) and down-ramp capability (DRC) intended to increase system flexibility.
The purpose of this study is to explore the economic, environmental, and reliability
impacts of MISO’s proposed ramp capability products. Two versions of the unit commitment
and economic dispatch processes used by MISO to optimally schedule generators were
modeled: (1) a baseline model representing current MISO practices, and (2) a ramp
capability model that includes the proposed products. These models were applied to
a small power system representative of MISO’s mix of generators under low and high
wind penetration levels.
In this model the DRC product had no impact, indicating that the representative power
system was more flexible in the downward direction than MISO’s actual system, perhaps
due to model simplifications or inaccurate assumptions. The URC product, however,
did benefit the system. Results show a reduction in the frequency of energy and operating
reserve shortages when compared to the baseline model, particularly with high wind
penetration, thereby indicating improved reliability. While there was a small price
increase in non-shortage intervals due to procurement of URC, this was outweighed
by the avoidance of high penalty prices incurred in shortage intervals; the overall
average market clearing price was significantly reduced. The URC product also caused
a small amount of fuel switching from coal to the more flexible natural gas, slightly
reducing the system’s CO2 emissions. However, the more pronounced environmental benefit
was the URC product’s ability to help the system absorb increased wind penetration
while avoiding most of the corresponding increase in reliability problems.
Type
Master's projectPermalink
https://hdl.handle.net/10161/8593Published Version (Please cite this version)
10.1016/j.rser.2017.06.037Collections
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