Abstract:
The power system network has constantly been growing at a higher rate than
the generation thereby compelling the power systems to operate at a lower security
margin. On the other hand, small-scale and large-scale industries whose major components
are induction motors (IM) are being put up at the same rate as the power
network gets bigger and complex. The effectiveness of aggregation of different sizes
of motor for power system analysis has not been extensively analyzed in the past. It
is also apparent that as the load demand grows, voltage stability is a major concern
worldwide. Further, it is important to note that, for reliable loads stability there is a
need to compare the aggregation methods of IM of various sizes under steady-state
and under fault condition. This is because IM load constitutes a larger percentage of
the power system loads. Consequently, this will result to reliable and stable running
of the integrated power system and thus optimizing the existing network.
This research therefore, presents the comparison of two aggregation methods of
small-scale and large-scale IM loads for power system analysis. The small-scale and
large-scale IM loads are aggregated under steady-state and dynamic operation of the
power system. The focus is to identify the parameters of various sizes of IM and
compare their accuracy under the above stated conditions.
The results show that method based on no-load and locked-rotor conditions
(method 2) gives accurate aggregate motor parameters for both small and largemotors
under voltage disturbance compared to the transformer-equivalent circuit
(method 1). Therefore, method 2 has good potential to be used in the voltage
stability analysis of small and large motors during the normal operation and under
system disturbance in any complex power system because of its high accuracy
compared to aggregation method 1.
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