APPLICATION OF AN OPTIMAL TUNING TECHNIQUE OF ON-LOAD TAPCHANGING TRANSFORMER FOR POWER QUALITY IMPROVEMENT IN TRANSMISSION LINE NETWORK
APPLICATION OF AN OPTIMAL TUNING TECHNIQUE OF ON-LOAD TAPCHANGING TRANSFORMER FOR POWER QUALITY IMPROVEMENT IN TRANSMISSION LINE NETWORK
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Date
2021
Authors
LAWAL, RABE
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Abstract
For reliable and efficient operation of power system, voltage level and reactive power flow along
transmission lines has to be adequately regulated. To control reactive power flow over transmission
lines and compensate for varying voltage drops, tap changing transformers are required. By altering the
voltage magnitudes at the windings of the transformers through winding tap adjustment, reactive
power flow can be controlled. The transformers can be off-loaded or on-line tap changer. In the latter,
the transformers are disconnected from the system when the tap setting is to be adjusted, while in the
former, the tap adjustment is carried out with the transformers connected. In this research work, Grey
Wolf Optimization (GWO) algorithm is applied to determine the optimal On-Line Tap Changer (OLTC) of
the available transformers in the system in order to improve the voltage profile and regulate reactive
power. The constraints considered in the formulation of the problem are demand-generation balance,
bus voltage limits, line thermal overloading limits and tap-changer adjustment limits according to IEEE
C57.131 2012 requirement. To verify the effectiveness of the developed technique, it is implemented
on IEEE 14-bus, IEEE 30-bus and 57-bus Nigerian Transmission systems. The performances of the
proposed technique is compared with those obtained using Particle Swarm Optimization (PSO). From
the simulation carried out in MATLAB environment, it is observed there is significant reductions in the
overall voltage deviation (VD) as well as the reactive power loss (RPL) when the OLTCs are optimized.
For instance, in the IEEE 14-bus system, the VD was reduced from 2.0892pu (base case) to 1.0153pu
due to the optimal tuning of the OLCTs using GWO and 1.4783pu when PSO was applied. This
represents 51.40% improvement in the case of the developed GWO over that of the base case and
31.32% improvement over the case of the PSO. Similarly, the RPL was reduced from 277.298MVar of
the base case value to 156.542MVar due to the optimal tuning of the OLCTs using GWO and
206.591MVar when PSO was applied representing 43.54% and 25.49% improvements respectively.
These have demonstrated the applicability of the GWO and its superiority over PSO in optimizing the
OLTCs in the IEEE 14-bus and 30-bus systems. In the Nigerian 57-bus system, by applying the GWO, the
total VD was reduced from 6.7808pu (base case) to 4.4519pu representing 34.35% improvement.
Finally, the value of RPL was reduced by 36.56% from its original value of 185.4685Mvar.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE AWARD OF MASTER OF SCIENCE (MSc) DEGREE IN ELECTRICAL
ENGINEERING
DEPARTMENT OF ELECTRICAL ENGINEERING,
FACULTY OF ENGINEERING,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA