16-08-2012, 02:50 PM
An Improved UPFC Control for Oscillation Damping
[attachment=31692]
INTRODUCTION
ONE of the most promising network controllers for the
bulk power system is the family of power electronicsbased
controllers, known as “flexible ac transmission system”
(FACTS) devices. FACTS devices work by modifying power
flow in individual lines of the power grid, maintaining voltage
stability, and damping oscillations. The DOE National Transmission
Grid Study released in May 2002 identified FACTS
devices as playing a significant role in the “Intelligent Energy
System” of the future. This rapid control has been shown to
be effective in achieving voltage support and stability improvement,
thus allowing the transmission system to be operated more
efficiently with a smaller stability margin. The rapid development
of the power electronics industry has made FACTS devices
increasingly attractive for utility deployment due to their flexibility
and ability to effectively control power system dynamics.
The primary function of the FACTS is to control the transmission
line power flow; the secondary functions of the FACTS can
be voltage control, transient stability improvement and oscillation
damping. The unified power flow controller (UPFC) is the
most versatile FACTS device. The UPFC is able to simultaneously
provide both series and shunt compensation to a transmission
line providing separate control of the active and reactive
powers on the transmission line.
UPFC STATE MODEL
The unified power flow controller, or UPFC, is the most
versatile FACTS device. It consists of a combination of a shunt
and series branches connected through the dc capacitor as
shown in Fig. 2. The series connected inverter injects a voltage
with controllable magnitude and phase angle in series with the
transmission line, therefore providing real and reactive power
to the transmission line. The shunt-connected inverter provides
the real power drawn by the series branch and the losses
and can independently provide reactive compensation to the
system. The UPFC model is a combination of the synchronous
static compensator (STATCOM) and static series synchronous
compensator (SSSC) models [8] as follows:
CONCLUSION
In this paper, a new control for the UPFC was proposed. The
proposed control exhibited very good performance in damping
active power oscillations and maintaining the UPFC shunt bus
voltage. It exhibited favorable performance when compared
with a PI controller under several operating conditions. The
proposed control works well in both large and small systems
with rapid dynamic response and independent control. The
primary advantages of the proposed control are 1) it works over
a wide range of operating conditions, 2) requires only three
parameters, and 3) the parameters a
[attachment=31692]
INTRODUCTION
ONE of the most promising network controllers for the
bulk power system is the family of power electronicsbased
controllers, known as “flexible ac transmission system”
(FACTS) devices. FACTS devices work by modifying power
flow in individual lines of the power grid, maintaining voltage
stability, and damping oscillations. The DOE National Transmission
Grid Study released in May 2002 identified FACTS
devices as playing a significant role in the “Intelligent Energy
System” of the future. This rapid control has been shown to
be effective in achieving voltage support and stability improvement,
thus allowing the transmission system to be operated more
efficiently with a smaller stability margin. The rapid development
of the power electronics industry has made FACTS devices
increasingly attractive for utility deployment due to their flexibility
and ability to effectively control power system dynamics.
The primary function of the FACTS is to control the transmission
line power flow; the secondary functions of the FACTS can
be voltage control, transient stability improvement and oscillation
damping. The unified power flow controller (UPFC) is the
most versatile FACTS device. The UPFC is able to simultaneously
provide both series and shunt compensation to a transmission
line providing separate control of the active and reactive
powers on the transmission line.
UPFC STATE MODEL
The unified power flow controller, or UPFC, is the most
versatile FACTS device. It consists of a combination of a shunt
and series branches connected through the dc capacitor as
shown in Fig. 2. The series connected inverter injects a voltage
with controllable magnitude and phase angle in series with the
transmission line, therefore providing real and reactive power
to the transmission line. The shunt-connected inverter provides
the real power drawn by the series branch and the losses
and can independently provide reactive compensation to the
system. The UPFC model is a combination of the synchronous
static compensator (STATCOM) and static series synchronous
compensator (SSSC) models [8] as follows:
CONCLUSION
In this paper, a new control for the UPFC was proposed. The
proposed control exhibited very good performance in damping
active power oscillations and maintaining the UPFC shunt bus
voltage. It exhibited favorable performance when compared
with a PI controller under several operating conditions. The
proposed control works well in both large and small systems
with rapid dynamic response and independent control. The
primary advantages of the proposed control are 1) it works over
a wide range of operating conditions, 2) requires only three
parameters, and 3) the parameters a