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IMPACT OF VOLTAGE REGULATORS IN UNBALANCED RADIAL DISTRIBUTION SYSTEMS USING PARTICLE SWARM OPTIMIZATION

Authored by: Puthireddy Umapathi Reddy*, Sirigiri Sivanagaraju, Prabandhamkam Sangameswararaju

ABSTRACT
In rural power systems, the Automatic Voltage Regulators (AVRs) help to reduce energy loss and to improve the power quality of electric utilities, compensating the voltage drops through distribution lines. This paper presents selection of optimal location and selection of tap setting for voltage regulators in Unbalanced Radial Distribution Systems (URDS). PSO is used for selecting the voltage regulator tap position in an unbalanced radial distribution system. An algorithm makes the initial selection, installation and tap position setting of the voltage regulators to provide a good voltage profile and to minimize power loss along the distribution network. The effectiveness of the proposed method is illustrated on a test system of 25 bus unbalanced radial distribution systems.

INTRODUCTION
This paper describes a new approach for modelling of automatic voltage regulator in the forward/backward sweep-based algorithms for unbalanced radial distribution systems. A voltage regulator is a device that keeps a predetermined voltage in a distribution network despite of the load variations within its rated power. Since it is the utilities’ responsibility to keep the customer voltage with in specified tolerances, voltage regulation is an important subject in electrical distribution engineering. However, most equipment and appliances operate satisfactorily over some ‘reasonable’ range of voltages; hence, certain tolerances are allowed at the customers’ end. Thus, it is common practice among utilities to stay within preferred voltage levels and ranges of variations for satisfactory operation of apparatus as set by various standards. In distribution systems operation, shunt capacitor banks and feeder regulators are necessary for providing acceptable voltage profiles to all end-use customers and reducing power losses on large distribution systems . A voltage regulator is equipped with controls and accessories for its tap to be adjusted automatically under load conditions. Moreover, it can be controlled by the installation of devices such as fixed and controlled capacitors banks, transformers with On Load Tap Changers (OLTCs), and Automatic Voltage Regulators (AVRs) . Loss reduction and improvement of voltage profile have been also studied by using OLTCs . One of the most important devices to be utilized for the voltage.

CONCLUSIONS
This paper presents a simple method to determine optimal allocation and tap setting of voltage regulators in Unbalanced Radial Distribution Systems through voltage drop analysis and PSO algorithm respectively. The effectiveness of the PSO has been demonstrated and tested. The proposed PSO based methodology was applied to 25 bus URDS. The obtained solution has succeeded in reducing total active power losses 25.43% in 25 bus URDS. From the test results, it can be said that the proposed model is valid and reliable, and the performance of the algorithms is not significantly affected from the inclusion of regulator modelling. The power loss per phase of unbalanced distribution system can be reduced by proper placement of voltage regulator. In addition to power loss reduction, the voltage profile also improved by the proposed method. The time of execution is reduced from 73.7 to 66.20 seconds for the same configuration system.

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