Widespread use of
conventional FACTS controllers has not extensively occurred due in part to
size, expense, and installation effort. Technology improvements since the
inception of FACTS allow the genre of power flow control concepts to be
revisited. The use of distributed flexible AC transmission system (D-FACTS)
devices may facilitate the realization of a comprehensively controllable power
system. Large-scale power flow control may finally be achievable.
DSSCs are series power flow
control D-FACTS devices which change the effective impedance of transmission
lines through the use of active impedance injection with a synchronous voltage
source (SVS) . DSSCs are comprised of a low-rated single phase inverter and
a single turn transformer and provide control similar to the SSSC, but are
smaller and will be less expensive. Hereafter, DSSCs will only be referred to
as D-FACTS devices.
A
D-FACTS device changes the effective line impedance actively by producing a
voltage drop across the line which is in quadrature with the line current. Thus, a D-FACTS device provides either purely reactive
or purely capacitive compensation. D-FACTS devices do not change the line’s
resistance at all since doing so would imply the ability of the device to
create real power. Hereafter, when we refer to the ability of D-FACTS devices
to change line impedances, we are only referring to the reactive line
impedance, As line impedance-changing devices D-FACTS devices have an impact on
states, power flows, losses, and more. One attractive feature of D-FACTS
devices is their potential capability to send and receive signals wirelessly
through a built-in wireless transceiver. D-FACTS may receive commands for
desired impedance injection changes. The impact on the system caused by D-FACTS
devices on different lines working together can be coordinated to achieve some
desired control objective. Although communication is desirable in order to
achieve advanced control objectives, D-FACTS devices may be configured to
operate autonomously in certain situations such as during transients,
faults, or when communications are lost.
Ref. - D.
M. Divan, W. E. Brumsickle, R. S. Schneider, B. Kranz, R. W. Gascoigne, D. T.
Bradshaw, M. R. Ingram, and I. S. Grant, “A
distributed static series compensator system for realizing active power flow
control on existing power lines,” IEEE Transactions on Power Delivery, vol.
22, no. 1, pp. 642-649, Jan 2007
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