31-07-2012, 11:30 AM
Comparison of shunt capacitor
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Abstract
This paper compares the shunt capacitor, SVC and STATCOM in static voltage stability
improvement. Various performance measures are compared under different operating system
conditions for the IEEE 14 bus test system. Important issues related to shunt compensation, namely
sizing and installation location, for exclusive load margin improvement are addressed. A methodology is
also proposed to alleviate voltage control problems due to shunt capacitor compensation during lightly
and heavily loaded conditions.
Static voltage stability
Static voltage instability is mainly associated with reactive power imbalance. Thus,
the loadability of a bus in a system depends on the reactive power support that the
bus can receive from the system. As the system approaches the maximum loading
point or voltage collapse point, both real and reactive power losses increase rapidly.
Therefore, the reactive power supports have to be locally adequate. With static
voltage stability, slowly developing changes in the power system occur that eventually
lead to a shortage of reactive power and declining voltage. This phenomenon
can be seen from a plot of power transferred versus voltage at the receiving end.
These plots are popularly referred to as P–V curves or ‘Nose’ curves. As power transfer
increases, the voltage at the receiving end decreases.
Shunt capacitor, SVC and STATCOM
It is a well-known fact that shunt compensation can be used to provide reactive
power compensation. Traditional shunt capacitors or newly introduced FACTS controllers
can be used for this purpose. FACTS controllers are very expensive; Table
1 gives an idea of the cost of various shunt controllers.12,13 Descriptions of each of
these controllers, along with their terminal characteristics, are given in the next
subsections.
Results and discussion
The best location for reactive power compensation as far as the improvement of
static voltage stability margin is concerned, is the ‘weakest bus’ of the system. The
weakest bus of the system can be identified using tangent vector analysis, as
explained in the previous section. Table 2 shows the first four weakest buses. Table
2 indicates that bus 14 could be considered the best location for a reactive power
support.