Written by: Lin Franks, Senior Strategist RTO, FERC, and Compliance Initiatives
It is broadly known that to have reliable electricity
service means having enough energy to serve the needs of customers. It is also fairly well understood that for
that electricity service to be provided to all of us requires transmission and
distribution lines. However, most people are not aware of how utilities assure
that the transmission and distribution lines are operated to provide reliable
service. A key element of operating
these lines (the grid) reliably is maintaining frequency and voltage within North
American Reliability Corporation (NERC) standards. These industry-wide
standards were developed as part of a structure to assure reliable service
every hour of every day. Deviations from
the standards can cause outages in a localized area or even outages that
cascade to other areas of the interconnected system.
Historically, the functions of frequency and voltage control were part of the benefits of
traditional generators such as those that are fueled by coal. Today and for the foreseeable future, more
generators will be renewable resources.
These greener resources, while they have many benefits, do not have the
same capabilities as traditional generators and are not effective providers of
frequency and voltage control services. Devices used to control frequency and
voltage must be available and operating at all times. Wind and solar resources are available only
when the wind is blowing and the sun is shining, so they cannot provide
controls services at all times. As IPL
planned to provide reliable service with greener resources we also planned for
effective and efficient control of frequency and voltage to assure our
customers continued reliable electric service.
The change in generation resources in our service territory and
throughout the interconnected grid motivated us to seek newer more efficient
technologies designed specifically for frequency and voltage control. One of the devices we chose to provide
frequency control is a lithium ion battery.
We are pleased to announce that our 20 megawatt (MW) battery, the IPL Advancion® Energy Storage Array, more
commonly known as the Harding Street Battery Energy Storage System (HSS BESS)
went into service on May 20, 2016 and is automatically providing frequency
control far more efficiently than its predecessors of traditional
generation. Frequency deviates from the standard
any time the generation online and the load (demand for electricity) are not
equal. The HSS BESS reacts to frequency
deviations in milliseconds without human intervention. Traditional generation requires several
minutes or longer to sufficiently correcting a deviation. In reality, generation and load never match so system operators are continuously ramping generators up and down. Generators cannot move as fast as load
changes so it is a constant effort to maintain frequency in conformance with
The HSS BESS is the most efficient technology available
today and was designed specifically for frequency control. With its ability to
move in milliseconds, this device can very closely match changes in load. Variations between generation and load occur
in normal operations because the generation operating is planned around a
forecast of what load will be. The
forecast is never perfect because customers determine when they turn lights on,
watch TV, and run their appliances.
Weather, however is the largest impact on forecasts and we all know it
is volatile in Indiana. The forecast is
usually rather close to the ultimate load as it occurs because we humans have a
pattern to our consumption of electricity. There are other times when there is
a frequency deviation caused by a generator suddenly stopping due to a
mechanical problem or a transmission line going out of service due to a
mechanical or weather related problem.
These surprise events are usually much more problematic for frequency
control than the normal day to day imbalances and can impact IPL’s customer
reliability if they happen anywhere in the multi-state interconnected
transmission system. The HSS BESS senses
the change and reacts automatically in milliseconds preserving the reliable
service our customers deserve.
The HSS BESS is the first of its kind in Indiana. It also is the first of its kind in the area controlled
by the Midcontinent independent System Operator (MISO). MISO operates the transmission system for a
vast part of the interconnected transmission system. The MISO footprint extends to 15 states and a
Canadian province. Being the first of
its kind and having unique operating characteristics and benefits is one of the
reasons many utilities in MISO are watching us closely. While not all utilities have committed to the
percentage of renewables and natural gas fired generation as has IPL, they are
all seeking efficient solutions to the declining availability of essential
reliability service to control frequency.
Lithium Ion batteries like the HSS BESS are the leading solution now and
for the foreseeable future. As they
operate differently than generators, the industry is just beginning to
recognize the significant value and understand all the device can do. Over
the next several months, IPL will be working toward demonstrating other
benefits this amazing device can provide.
Initially it will quietly, automatically, and quickly control
frequency. Over time we will provide
additional services to support reliability while continuing to control frequency
as part of providing reliable service to our customers.