  The electric power grid has evolved significantly over the past two decades
in response to climate change. Increased levels of renewable energy generation,
as a prominent feature of this evolution, have led to new congestion patterns
in the transmission network. The transmission system is originally designed for
conventional energy sources, with predictable flow patterns. Insufficient
transfer capability in congested transmission systems results in commitment of
more expensive power plants and higher levels of renewable energy curtailment.
One way to mitigate congestion is adoption of power flow control through
variable-impedance flexible ac transmission system (FACTS) devices. In this
paper the impacts of power flow control on generation cost, carbon emissions
and renewable energy curtailment are studied under a wide range of scenarios,
including generation mix from major US regional transmission organizations, and
different load curves, representing seasonal variations. A two-stage stochastic
unit commitment, including FACTS adjustment, is used to evaluate the impacts of
FACTS devices on various types and penetration levels of renewable energy. The
results show that FACTS installation effectively reduces generation cost,
carbon emissions, and renewable energy curtailment. Location of renewable
energy resources, peak-hour demand and the system's generation mix are among
the influential factors.
