POWER March 2014 - 31

GRID SUPPORT
1. Second life. Two retired generators at the AES Huntington Beach plant were recently
converted to synchronous condensers to provide voltage support to the Southern California
grid after the unexpected retirement of the San Onofre Nuclear Generating Station. A planned
redesign will conceal a new plant behind giant surfboards, in keeping with the city's history as
a surfing destination. Courtesy: Siemens Energy and Chet Williams Photography
questions from regulators and policymakers
regarding cost and schedule. Both AES and
Siemens were very effective at coming back to
us and telling us exactly what we needed and
how they could meet the evolving timeline. "
Maintaining a Balance
The innovation behind the customized approach
was an easy sell to the stakeholders.
AES, the CEC, the South Coast Air Quality
Management District (SCAQMD), and
CAISO all quickly realized that the proposed
approach was the only one that could fulfill
all of the stringent requirements of the project,
particularly the looming summer deadline.
The application was filed with the CEC
on Oct. 5, 2012, and the synchronous condensers
needed to be fully functional no later
than June 28, 2013.
Work began immediately after project apAssessing
the Technology
There are a number of different ways to provide
voltage support to a transmission grid.
Though generation provides support, reactive
power is needed to move the power across
the grid to serve load.
Static var compensators (SVCs) are a popular
method for reactive power compensation
to improve and balance a network. An SVC
is made up of capacitive and inductive components
that inject reactive power and deliver
dynamic performance during periods of high
demand. However, SVCs may have limited absorption
levels and fault current performance.
Synchronous condensers, like SVCs, are
another means of power compensation, but
unlike SVCs, synchronous condensers are
single-component rotating machines-also
known as flywheels-which positively or
negatively alter the field of the generator
to distribute or absorb reactive power. The
single component design allows for smooth
waveform and a quicker, more reliable startstop
in a way that does not negatively affect
the system load. Synchronous condensers
also have a higher capacity to handle fault
currents, making them ideal in applications
such as this one.
Facing Challenges
Unfortunately, AES's generators presented
three challenges for conversion to synchronous
condensers:
■ Multiple Original Equipment Manufacturers.
The plant consists of two different
brands of generators, General Electric and
Westinghouse, in a cross-compound system.
Finding a conversion solution that
would work equally well for both generators
was necessary. This type of situation
would normally require all new equipment
March 2014 | POWER
to be installed for the conversion, which
would have inflated both the timeline and
budget for the project.
■ Size. Though the generators at AES aren't
abnormally sized compared to plants of
this capacity, they are still physically large.
A conversion solution for equipment this
size generally requires substantial electrical
modification to assist in controlling
the unit's speed and a significant amount
of system analysis and adjustment.
■ Age. As an added complication, the turbines
at AES were nearly 50 years old, so
the issue of potential replacement or repair
of the existing equipment was a concern.
Most modern generators are converted to
motors to turn themselves on and bring
themselves up to speed, serving dual electrical
purpose. The generators at AES were
not designed for that type of functionality.
With each of these challenges came added
stress in identifying a solution that could be completed
on time and within the allotted budget.
The team at AES partnered with Siemens
Energy to review their options. With the tight
timeline being the most critical factor, a moment
of clarity brought a solution that took
repair or replacement of the AES turbines
out of the equation. After nearly a month of
comprehensive evaluation, the team was able
to retain most of AES's existing infrastructure
without requiring new equipment or significant
upgrades. The only new equipment
investments made were those pieces that
immediately supported the conversion: pony
motors, thrust bearings, variable frequency
drives (VFDs), and new distributed control
system (DCS) panels.
" Timing was a critical issue, " said Phil
Pettingill, director of regulatory strategy at
CAISO. " There was a constant stream of
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provals were granted in late 2012. AES employed
Siemens to lead a team of contractors
in the installation. With the tight timeline
constantly in mind, the Siemens team made
the decision to adapt to the situation and materials
at hand, rather than bring in a slew of
new equipment.
The Huntington Beach plant operated as
a cross-compound system. There were four
generators onsite, but only two acceleration
models were needed to bring the system to life.
Essentially, the two small pony motors were
used as prime movers, which replaced the existing
boilers and steam turbines. Original plans
called for one power source to control the motors,
but after careful consideration, the team
decided to install a second source to provide a
redundant source of power should any unforeseen
circumstances affect drive functionality.
The VFDs were installed to drive the strategically
located pony motors (Figure 2) and keep
the motors' size, horsepower, and costs down
thanks to the way the units were configured
with the two tandem generators. The drives
allow the generators to be brought up slowly
and simultaneously while keeping them in an
electrical lock. Though adding the additional
power source was not part of the original plan
and required additional time to implement, the
team had been prepared by building a buffer
into the schedule for minor delays.
Along the way, the team faced additional
challenges that could have potentially affected
the timeline. At one point in the installation,
an overhead crane failed. Ultimately, the crane
was repaired and the project stayed on track.
Despite a few minor setbacks, the converted
system was successfully started up on
June 28, 2013-the exact date that the project
was slated for completion-and has been
a reliable resource ever since.
The generators can be automatically excited
when needed and as a result do not need
31

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POWER March 2014

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