ABSTRACT:
This paper presents a novel development of a
fuzzy logic controlled power system using UPFCs to damp the oscillations in a
FACTS based integrated multi-machine power system consisting of 3 generators, 3
transformers, 9 buses, 4 loads & 2 UPFCs. Oscillations in power systems
have to be taken a serious note of when the fault takes place in any part of
the system, else this might lead to the instability mode & shutting down of
the power system. UPFC based POD controllers can be used to suppress the
oscillations upon the occurrence of a fault at the generator side or near the
bus side. In order to improve the dynamic performance of the multi-machine
power system, the behavior of the UPFC based POD controller should be coordinated,
otherwise the power system performance might be deteriorated. In order to keep
the advantages of the existing POD controller and to improve the UPFC-POD
performance, a hybrid fuzzy coordination based controller can be used ahead of
a UPFC based POD controller to increase the system dynamical performance &
to coordinate the UPFC-POD combination. This paper depicts about this hybrid combination
of a fuzzy with a UPFC & POD control strategy to damp the
electro-mechanical oscillations. The amplification part of the conventional
controller is modified by the fuzzy coordination controller. Simulink models
are developed with & without the hybrid controller. The 3 phase to ground symmetrical
fault is made to occur near the first generator for 200 ms. Simulations are
performed with & without the controller. The digital simulation results
show the effectiveness of the method presented in this paper.
KEYWORDS:
1. UPFC
2. POD
3. Fuzzy logic
4. Coordination
5. Controller
6. Oscillations
7. Damping
8. Stability
9.
SIMULINK
10. State space model
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1 : A 3-machine, 9-bus interconnected power system model with
4-loads without the controllers
Fig.
2: A 3-machine, 9-bus interconnected power system model with 4-loads & 2
POD-UPFC & the fuzzy controller
EXPECTED SIMULATION RESULTS:
Fig.
4 : Simulation result of power angle v/s time (with UPFC & fuzzy control)
Fig.
5 : Comparison of the simulation results of power angle v/s time (without UPFC
& with UPFC & fuzzy control)
CONCLUSION:
AFACTS
based multi-machine power system comprising of 3 generators, 9 buses, 3 loads
with and without the 2 Fuzzy-POD-UPFC controllers was considered in this paper.
SIMULINK models were developed in MATLAB 7 with & without the Fuzzy- POD-UPFC
controllers for the considered multi machine model in order to damp out the
oscillations. The control strategy was also developed by writing a set of fuzzy
rules. The fuzzy control strategy was designed based on the conventional
POD-UPFC controller & put before the POD-UPFC in the modeling.
The main advantage of putting the
fuzzy coordination controller before the POD-UPFC in modeling is the
amplification part of the conventional controller being modified by the fuzzy coordination
unit, thus increasing the power system stability. Simulations were run in
Matlab 7 & the results were observed on the scope. Graphs of power angle
vs. time were observed with and without the controller. From the simulation
results, it was observed that without the Fuzzy-POD-UPFC controller, the nine
bus system will be having more disturbances, while we check the power angle on
the first generator.
There are lot of ringing
oscillations (overshoots / undershoots) & the output takes a lot of time to
stabilize, which can be observed from the simulation results. But, from the
incorporation of the Fuzzy- POD-UPFC coordination system in loop with the plant
gave better results there by reducing the disturbances in the power angle and
also the post fault settling time also got reduced a lot. The system stabilizes
quickly, thus damping the local mode oscillations and reducing the settling
time immediately after the occurrence of the fault.
The developed control strategy is
not only simple, reliable, and may be easy to implement in real time
applications. The performance of the developed method in this paper thus
demonstrates the damping of the power system oscillations using the
effectiveness of Fuzzy-POD-UPFC coordination concepts over the damping of power
system oscillations without the Fuzzy-POD-UPFC coordination scheme.
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