الفهرس 
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Abstract
In this thesis the main issue investigated is how to achieve voltage stability
of the system with high penetration level of wind farms. Steady state stability
and dynamic stability issues are studied in details to achieve reliable and
stable electrical network.
The study area in this thesis is the Canal Zone where the wind farm plants
exist. Voltage stability analyses of the Canal Zone grid are performed in both
steady state and dynamic cases.
The steady state investigation uses the techniques PV and QV analyses by
PSS®E program. These analyses require the load flow analysis. from PV
results bus voltages are monitored versus active power transfer and the
voltage stability sensitivity factors are obtained. Hence voltage collapse point
can be determined to each case. Based on the QV results, the needed sizes of
reactive power can be determined to maintain 1 p.u voltage at weak buses.
This can be performed in base cases and under contingency cases for the
2013 and 2017 systems.
The effects of (N-1) contingency analyses are also presented for the study
system. These analyses include different cases of trip transmission line or a
generation station as follows:
1. Disconnecting one circuit of double circuit transmission line between
Ghard and Italgen buses or between Italgen and Elzait buses.
2. Trip of a generation station like North West Suez Generation
(N.W.S .G).
It is found from the base case and (N-1) steady state analyses that there are
an extremely need to inject reactive power at the weakest buses Ghard and
Italgen in Canal Zone due to:
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1. Existing loads in the area and some types of wind farms (type 1 and 2)
which all absorb reactive power from the grid.
2. The radial configuration of the Canal Zone with few numbers of
generating units in the area.
This can be achieved by using either capacitors or STATCOM.
The dynamic simulation is used to ensure the dynamic performance of the
system under a wide range of conditions, and to identify any problems and
scope measures needed for improvement. This can be achieved by using
either capacitors or STATCOM.
from this purpose, several types of faults were simulated for the 2013 and
2017 systems. In all case studies, the applied fault is a symmetrical threephase
applied one second after the start of the simulation and the simulation
time lasted for 10 sec. The most severe fault types considered are:
i. Non sustained fault at Italgen bus. This fault duration is assumed to be
50 msec.
ii. The fault in the middle of one line of the two lines connected Ghard
and Italgen buses. This line is tripped after 50 msec from the incidence
of the fault.
5.2. Conclusion
Based on the results of this thesis the following can be concluded for the
2013 and 2017 systems:
1. Ghard and Italgen buses are the weakest buses in the system under
study as these buses have the highest voltage sensitivity and the lowest
voltage profile. Therefore, both voltage profiles and voltage sensitivity
factors in voltage stability analysis should be considered.
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2. Voltage profile results depict that buses close to generating units have
better voltage characteristics than other buses. The buses in the North
region of Canal Zone are the strongest buses in the zone. Smaller
voltage sensitivity factors at Sokhna, Ras Grb, Elzait and Zafarana
buses support this claim.
3. The voltage profiles of the buses in South region like Ghard, and
Italgen buses show that they may face voltage stability problems under
heavy loading situations. In South region of Canal Zone, bus voltages
start to decrease in great amounts even before critical point is reached
which proves the weakness of the buses in this region from the voltage
stability point of view.
4. The most severe cases under the (N-1) contingency analyses occur
when:
i. Tripping all units in N.W.S.G station i.e. in case of tripping the
whole station or
ii. Tripping the 220 KV transmission line between Ghard and Italgen
buses (highest voltage sensitivity and the lowest voltage profile).
5. Reactive power mitigation enhances the voltage stability of the whole
buses of the Canal Zone and in case of addition of STATCOM more
reactive power are supplied to system. As the voltage support of the
STATCOM is fair as its reactive power injection drops with the
voltage (V).
6. On the other hand, the voltage support from the shunt capacitor bank is
relatively poor as its reactive power injection drops with the square of
voltage (V2).
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7. The reactive power mitigation decreases both the sensitivity factors
and power losses decreased after reactive power mitigation. Thus,
critical point occurs in higher loading levels and the magnitudes of bus
voltages increase.
8. Under transient analyses, both voltage limit and frequency limit are
violated more than the criteria limit whereas the frequencies are less
than 50 Hz ± 0.5 and voltages values decrease less than value (0.95
p.u.). This can be attributed to the lack of reactive power support. So,
STATCOM is used to enhance the dynamic performance of the system
following the occurrence of the fault types listed above. The dynamic
analysis reveals that reactive compensator rating can be determined at
0.95 p.u voltage instead of 1 p.u in the steady state analysis at the weak
buses. This reduces the size of installed STATCOM which will be
more economic. Also, the system performance is still strong as voltage
values and the oscillations occurred in frequency are within the criteria
limit.
9. It is recommended to use new types of wind turbines (WT3, WT4) as
used in Ras Grb and Elzait buses which are strong buses. These new
turbines can be controlled to supply the system with reactive power
and improve the steady state and dynamic performance.