Investigating the Electric Power Distribution System (EPDS) Bus Voltage in the Presence of Distributed Generation (DG) Hasham Khan, Mohammad Ahmad Choudhry, Tahir Mahmood, and Aamir Hanif Electrical Engineering Department Department of Electrical Engineering, University of Engineering & Technology, Taxila PAKISTAN Abstract: - This paper investigates the Electric Power Distribution System (EPDS) bus voltage in the presence of Distributed Generation (DG). Distribution Company’s (Discos) planner endeavor to develop new planning strategies for their network in order to serve the load growth and provide their customers with a reliable electric supply. In this research work, five different cases including preplanned islanding and grid-connected mode has been discussed. The studies are performed based on well known software package PSCAD/EMTDC. The work shows that presence of DG provides a significant support to EPDS in term of power quality and voltage stability of bus voltage. Key-Words: - Electric Power Distribution System, power quality, islanding, distributed generation, PSCAD, voltage stability 1 Introduction The Distributed Generation (DG) technologies have an important role in the electric power distribution system (EPDS) structure, design, up gradation issues and power quality problems. In the era of deregulation, the competitive market forces drive the Discos planner to investigate the economical, flexible and technically feasible alternative for new capacity. Utilities have recognized the DG as an imperative tool that can partially replace the need to erect new generating stations in order to meet the increasing load demand. The Distributed Generation option is enjoying a global popularity to offset the future load growth [1]. The Discos / end-users can install DG units within their service area. Due to the availability of such a flexible option at the distribution voltage level, the distribution network is now being transformed from passive network to an active one. A recent study by the electric power research Institute (EPRI) indicates that by the year 2010, 25% of the new generation will be that of distributed generation type. Another study in the national Gas Foundation concludes that the figure may be as high as 30% [2]. 2 Why DG? The main reasons behind the expected wide spreads of DG are: • Deregulation in power market, which encourages public investment to sustain the development in power demand. • Emergence of new generation techniques with small ratings, ecological benefits, increased profitability and which can be combined with heat generation. • Saturation of existing networks and continuous growth demands. As DG system is of limited capacity and small in size, it can be installed easily near the load [3]. In this way it avoids the transmission and distribution line requirements. The other technical merits associated with the implementation of distributed generation are voltage support, energy loss reduction, release of system capacity, and improve utility system reliability [4]. Proceedings of the 5th WSEAS Int. Conf. on Instrumentation, Measurement, Circuits and Systems, Hangzhou, China, April 16-18, 2006 (pp207-212)