POWER January 2021 - 32

TRANSMISSION & DISTRIBUTION
A Reactive Solution to
Renewables' Growth on the Grid
Electricity transmission network operators are being tasked with adding more
renewable energy resources to the power grid. The use of static VAR compensators
(SVCs) is growing as a means to control voltage fluctuations and improve power
quality and efficiency.
Darrell Proctor
T
he power grid continues to evolve,
particularly as transmission system
operators look to integrate more intermittent
renewable resources into the
electricity supply.
The use of static VAR compensators
(VAR stands for volt-ampere reactive),
known as SVCs, is growing as a means to
suppress voltage fluctuations. SVCs provide
dynamic voltage support, and help
maintain the reliability and efficiency of the
power supply. The technology is being integrated
into both existing and new power
infrastructure (Figure 1), helping reduce
the investment that would be required to
build new network extensions.
The importance of SVCs grows as more
renewable energy resources come online,
and more conventional power sources
such as coal-fired and natural gas-fired
generation are retired. Renewable resources
lack any automatic frequency response
mechanism, such as those found in large
rotating thermal turbine-generators. SVCs
mimic the action of rotating thermal turbines,
and provide the ability to respond
quickly, usually within milliseconds, to reactive
power transients on high-voltage
electrical transmission lines.
The technology includes a static synchronous
compensator (STATCOM), or
static synchronous condenser (STATCON),
a regulating device used on
alternating current (AC) electricity transmission
networks. It is based on a power
electronics voltage-source converter and
can act as either a source or sink of reactive
AC power to an electricity network.
If connected to a source of power, it can
also provide active AC power. SVCs are
part of the flexible AC transmission system
(FACTS) device family.
" In today's environment, thermal power
plants are being decommissioned and
replaced by wind and solar, " said Fabrice
Jullien, Global FACTS Business Leader for
Grid Integration Solutions, in GE Renewable
Energy's Grid Solutions business.
32
Jullien told POWER, " When this happens,
the grid can become 'weaker' ... meaning
that it is not as stable and is prone to larger
voltage swings based on changes in both
generation and load. SVCs can be helpful
in these scenarios to stabilize the voltage
on the network. "
Jullien said the " SVC is a reactive power
source that uses complex control systems
and thyristor switches to dynamically control
reactive power output, " which he noted
is measured in mega-VAR, or Mvar. " SVCs
can either generate or absorb reactive
power, which helps maintain the voltage
level on the local grid, thereby improving
the stability and reliability. "
Reactive Power Compensation
The differing types of technology that
provide
reactive power compensation
include both the SVC and the STATCOM,
said both Jullien and Dmitriy Anichkov,
chief technology officer for Merit Controls
and Merit SI, groups that provide
power control systems and grid integration
solutions for renewable energy
installations. Anichkov told POWER,
" STATCOM is a power-electronics device
typically used for reactive power
control supporting electrical networks
with a poor power factor or inadequate
voltage regulation. "
Anichkov said SVC " has become an
important technical means of overcoming
the bottleneck of power transmission, "
and said that in his company's
opinion, " STATCOM has better operational
characteristics than SVC. "
Anichkov said, " SVC and STATCOM
are expensive since they are proprietary
and unique. Replacing expensive proprietary
SVC and STATCOMs with a singlecycle
phasor-based control system and
off-the-shelf inverters is a viable and appealing
alternative. Modern grid benefits
of a phasor-based control combined with
inverters delivers full value stack optimization
of energy storage, " which he said
includes the following benefits:
www.powermag.com
1. Static VAR compensators (SVCs) can be
integrated into existing power infrastructure,
such as at this substation. SVCs are a key
component of facilitating the addition of renewable
energy resources to the power grid,
helping control voltage fluctuations. Courtesy:
Siemens Energy
■ Demand charge and energy cost reduction
through real-time optimization
of energy storage.
■ Time-of-use (TOU) energy shifting.
■ Power factor management within utility
requirements, and voltage and frequency
stability improvements.
■ Seamless islanding and reconnection
to a main grid with multiple distributed
energy resources, such as solar and
wind power.
" Phasor-based control, in our opinion,
should be applied wider, bringing abovementioned
and other benefits to the
whole range of renewable generators
such as wind, solar, and their hybrids
with the battery storage, " Anichkov said.
" Besides, phasor-based control should
be used not only for distributed energy
resources, small-scale power generation,
or storage technologies typically in
the range of 1 kW to 10,000 kW, but also
for large utility-scale generating assets. "
SVC Applications
There are many players in the global SVC
market. Along with GE and Merit, they include
well-known names such as Hitachi
ABB Power Grids, Siemens Energy, Mitsubishi
Electric, and S&C Electric. Other
companies in the market include AMSC,
Ingeteam, Comsys AB, and Merus Power.
POWER | January 2021
http://www.powermag.com
POWER January 2021

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