04-12-2012, 12:43 PM
Application of Interline Power Flow Controller to Increase Transient Stability of Power System
Application of Interline Power.pdf (Size: 95.45 KB / Downloads: 53)
Abstract:
Problem statement: The Interline Power Flow Controller (IPFC) is a novel device which
can increase transient stability of power system. To verify the capability of the effect of IPFC on
stability improvement of power system, the suitable mathematical model and control strategy of IPFC
are needed to be presented. Approach: This study presented the mathematical model and control
strategy of IPFC. The multi-series converters of IPFC are represented by multi-series voltage sources
with associate transformer leakage reactance. The parameters of IPFC are modeled into power flow
equation and thus it is used to determine control strategy. This study used Bang-Bang control strategy.
The swing curves of the three phase faulted power system without and with an IPFC are tested and
compared in various cases. Results: The swing curve of system without an IPFC get increased
monotonically and thus the system can be considered as unstable whereas the swing curves of system
with an IPFC can return to stable equilibrium point. Conclusion: The presented model of IPFC can
help us to comprehend the effect of IPFC on transient stability improvement of power system. From
simulation results, the IPFC can increase transient stability of power system.
INTRODUCTION
Transient stability improvement is one of the
important aspects in modern power system. The
innovative Flexible AC Transmission System (FACTS)
devices have been proposed during the last three
decades and provide better utilization of existing
systems. There are various forms of FACTS devices
such as Static Synchronous Series Compensator
(SSSC), Static Synchronous Compensator
(STATCOM) and Unified Power Flow Controller
(UPFC) (Kumkratug, 2003; Kumkratug and Haque,
2003a; 2003b; Ravichandran et al., 2007; Shayeghi and
Abdolalipour, 2009; Nazarpour et al., 2006; Nayeripour
and Niknam, 2008).
Interline Power Flow Controller (IPFC) is the
newest FACTS devices. It is the innovative
combination of two or more series converters which are
coupled via DC link. The applications of IPFC to
improve damping of the system are reported in (Zhang,
2003; Vasquez-Arnez and Zanetta, 2008). A few
researches have applied IPFC to improve transient
stability of power system (Parimi et al., 2008; Azbe and
Mihalic, 2008; Bhownick et al., 2009). Thus it is
needed to further investigate the effect of IPFC on
transient stability of power system.
MATERIALS AND METHODS
Interline Power Controllers: Consider IPFC for n
converters as shown in Fig. 1. IPFC is the combination
of the multi-series converters. The multi series
converters are coupled by a common DC link as shown
in Fig. 1. The DC link provides a path to exchanges
active power between multi-series converters. The
series converters inject the series voltages into the
transmission lines through transformers.
The power flow through the line can be regulated
by controlling the magnitudes and the angles of the
converters. The injected voltage magnitudes and angles
determine the active and the reactive power into the
transmission lines. The converters have a capability of
electromechanically generating and absorbing the
reactive power. However, without losses of converters,
the injected active power must be supplied by the DC
link from the AC system.
RESULTS
The presented mathematical model and control
strategy of IPFC is used to study the effect of IPFC on
transient stability improvement of the system of Fig. 3.
In all cases, it is considered that a three phase self
clearing fault appears at bus m and the fault is cleared
without changing the network configuration. Figure 4
shows the swing curve of the system without an IPFC
for clearing time (tcl) = 144 m sec. Fig. 5 shows the
swings curve of the system with and without an IPFC
for tcl = 145 m sec.
DISCUSSION
From the results in Fig. 4 and 5, we found that the
critical clearing time of the system without an IPFC is
144-145 m sec. It can be seen from the Fig. 4 that with
fault clearing time (tcl) = 144, the system is considered
as stable and the system is considered as unstable with
tcl = 145 m sec as can been in Fig. 5. However, the
system with an IPFC control can stabilize the system
with tcl = 145 m sec. The simulation results indicate
that an IPFC can improve stability of the system.
CONCLUSION
This study investigates the capability of the
Interline Power Flow Controller (IPFC) on transient
stability improvement of the system. The mathematical
model is systematically derived. The presented
mathematical model has shown that power flow and
stability of system can be regulated by IPFC. This study
uses the Bang Bang control to derive its control
strategy. The speed deviation is the main factor to
decrease and increase power flow of the system. The
simulation results are tested on Single Machine Infinite
Bus (SMIB) system. From the simulation results, it
indicates that an IPFC can improve transient stability of
the system.