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:
SIMULINK BLOCK DIAGRAM:
EXPECTED SIMULATION RESULTS:
CONCLUSION:
A
FACTS 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 multimachine 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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