14-08-2012, 04:31 PM
Computer Aided Transient Stability Analysis
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Abstract:
A program for handling and improving the transient stability of the Iraqi Super Grid
electrical network was developed. The idea was demonstrated by applying it to the outages of the main
generating units. The methodology was built upon a state of increasing power transfer through the
healthy portion of network during disturbances. There were three parts concerned; the first part was the
developing of the load flow program using fast decoupled method and the transient stability program
using Modified Euler’s method in the step by step solution, the second part was the engagement
between the two programs, the third part was the application of the new program on the Iraqi supper
grid network (400 kV).
INTRODUCTION
Due to increased power transactions between
various power systems and due to continuing
postponement of transmission reinforcements, power
systems are being operated closer to their lower secure
limits. This has exacerbated the traditional conflict
between the two major objectives of power system
operation, economics and security[1].
Several methods for off line transient stability
analysis are under research and development. They
contain efficient step-by-step integration of the
differential equations, direct method of stability
analysis, pattern recognition techniques, expert systems
and neural networks. In multi-machine stability studies,
the only method that gives satisfactory results is step by
step integration method. The step by step time
simulation is a conventional method, which is the most
reliable one. It gives an accurate result and can handle
the complicated system models. The step by step
integration method has the advantage that voltages,
currents and apparent powers at various buses could be
monitored as a function of time during the disturbances.
Enhancement the transient stability of Iraqi grid:
Stability is an important constraint in power system
operation. A new methodology that reduces the
consuming time of the operator to determine a
transiently secure operating point is presented. From the
obtained results, it is obviously that the network is
suffering from serious problems. The outage of the
generating bus bars BAJ4 and HAD4, will lead SDM4
bus to swing away from the stability region and will
cause the instability of the whole system. While the
outages of the rest of the generating buses will not
affect the stability of the system.
CONCLUSION
This study was presented to ensure that transient
stability can be maintained by searching an operating
point that respects appropriate stability limits. Such a
search using power generation increment has to be
investigated. From the obtained results one realizes that
there are two dangerous regions in the network under
consideration, those are the north region (BAJ4
generating unit) and the west region (HAD4 generating
unit).
Rising the generation of the generated bus bar in
steps (50MW in each step) affects the stability of
network. From results obtained by a new program it
was clear that after the 3rd step of increasing the
generated power led to the stability of the network in all
the situations. This increment causes the reduction of
the high swing of SDM4.