The 5th International Power Engineering and Optimization Conference (PEOCO2011), Shah Alam, Selangor, Malaysia : 6-7 June
2011
Rotary Power Flow Controller (RPFC) Characteristics Analysis
Mohamad Hosseini Abardeh and Reza Ghazi, Member, IEEE
Abstract—FACTS devices are used to increase the capacity,
flexibility and controllability of the transmission networks. Utilizing high power switches for implementing these devices will
raise their cost. On the other hand, continuous switching process
may cause power quality problems. Rotary power flow controller
(RPFC) is one of the FACTS devices based on rotary phase
shifting transformer (RPST) configuration. In this paper, steady
state operational specification of this device is analyzed using a
new formulation. Its ability to control active and reactive power
of transmission lines is studied and the equations for calculating
the operational limitations are presented. In addition, the effects
of the series transformer connection type and the angle between
stator and rotor of two RPSTs on the power flow are also
analyzed.
Index Terms—Rotary power flow controller (RPFC), rotary
phase shifting transformer, active power control, reactive power
control, transmission system, FACTS.
I. I NTRODUCTION
Power transfer capacity of the transmission networks can be
increased by, 1) building new transmission lines, and 2) using
FACTS devices such as unified power flow controller (UPFC),
thyristor controlled series capacitor (TCSC) and rotary power
flow controller (RPFC). Application FACTS devices is preferred from economical point of view. Furthermore, use of
these devices results in flexibility and controllability of the
network.
The concept of the RPFC was first presented in 1998 based
on rotary phase shifting transformer (RPST) [1], [2]. The first
experimental RPFC system was reported by Chubu electric
utility company of Japan [3]. The primary purpose of RPFC is
to balance active power flow in a parallel transmission corridor
in normal and emergency conditions [3] , [4].
The RPFC operation is comparable with UPFC. The high
power semiconductor switches of the UPFC necessitate high
investment cost and lower reliability while RPFC consists
of two induction machines and two transformers. So having
significant reliability, the cost of the RPFC is about one third
of the UPFC. Operation and maintenance costs of RPFC are
lower than UPFC. Hence, using RPFC for expanding the
transmission line capability and power flow control is more
economical compared with either installation of UPFC or
building new lines [5].
There are two types of RPFC, 1) single shaft and 2)
double shaft. A dynamic model for a double shaft RPFC
is presented in [3] , [4]. Based on this model, the voltage
control region and the device operation for active power flow
M. Hosseini Abardeh is a Phd student in Department of Electrical Engineering, Ferdowsi University of Mashhad, Iran, P. O. Box 9177948974 (e-mail:
mohamad.hosseini1@gmail.com)
R. Ghazi is a professor in Department of Electrical Engineering, Ferdowsi
University of Mashhad, Iran, P. O. Box 9177948974 (e-mail: rghazi@um.ac.ir)
978-1-4577-0354-6/11/$26.00 ©2011 IEEE
978-1-4577-0353-9/11/$26.00 ©2011 IEEE
Fig. 1.
RPFC configuration.
control in a transmission corridor with two parallel lines is
simulated. However, the operational limitations for active and
reactive power control and the effect of the series and shunt
transformers have not considered so far. Remaining papers are
concerned with single shaft RPFC. In [6] and [7] a steady state
and dynamic approximative model for single shaft RPFC is
presented and the effects of transformers turn ratio and the
angle between the rotor and the stator of RPSTs are studied.
Reviewing the relevant papers itcan be concluded that there
is no discussion about the effects of the device on reactive
power flow and the coupling between active and reactive power
control.
In this paper, the operational specification and the working
region of the double shaft RPFC for active and reactive power
flow control of a transmission line are studied. The effects of
the RPST angles and the type of the series transformer on the
power flow of the line are analyzed.
Lossless RPFC model using steady state relations is represented in the next section. The relation between two RPSTs
and injected voltage is calculated. Finally, operational limitations of the device are analyzed and the effect of different
parameters on its operation is studied.
II. RPFC C ONFIGURATION
As shown in Fig. 1, RPFC consists of a series and a shunt
transformer. Rotor windings of two RPSTs are connected in
series and stator windings is parallel. The angles α1 and α2
between stator and rotor voltages are varied by changing the
position of the rotary transformers (RT) rotor. Consequently,
the injected voltage Vser changes. So RPFC is a series
compensator which controls the line power flow by injecting
the proper voltage.
Generally, there are two distinct configurations for RPFC:
1) Single shaft RPFC: two RPSTs have a same shaft but
different voltage phase sequence (so α1 = α2 , where
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