International Journal For Technological Research In Engineering Volume 1, Issue 9, April-2014 ISSN (Online): 2347 - 4718 www.ijtre.com Copyright 2013.All rights reserved. 681 IMPROVE POWER QUALITY THROUGH SERIES COMPENSATION IN ISOLATED POWER SYSTEM Sachin A. Jalit 1 , Dr. N. J. Phadkule 2 1 M.tech student, 2 Assistant Professor G. C. O. E., Amravati, India Abstract: The power quality requirement is one of the most important issues especially with the introduction of sophisticated device whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in failure of end user equipment. One of the major problem deal with sag and harmonics .To solve this problem series compensation is used to improve power quality of an isolated power system is considered. The role of compensator not only mitigates voltage sag but also reduces harmonics due to presence of nonlinear load in the network. In this paper series compensation is proposed and principle of harmonics mitigation is explained and the compensation strategies and control philosophy used in series compensation is explain. The isolated power system model is simulated in mat lab Simulink software and simulation result shows the reduce harmonics and thus improve power quality of the isolated power system Keywords: Harmonics, Power quality problem, injection transformer, ESS, VSI, I. INTRODUCTION Power quality problems encompass a wide range of disturbances such as voltage sags/swells, flickers, harmonics distortion, impulse transient, and interruptions. Sag is a decrease of R.M.S voltage to a value between 0.1to 0.9 p.u and lasting for a duration 0.5cycle to 1minute .voltage sag as a voltage dip. Voltage sag is mainly due to system fault. Harmonics are sinusoidal voltage or current having frequencies that are integer multiple of the frequency at which supply system are designed to operate (termed the fundamental frequency for usually 50or 60 Hz. Isolated power systems are commonly found in rural and remote areas of the world. Isolated power systems are characterized by limiting generating capacity. The sensitive loads which are present in the isolated power systems are much more affected by the power quality problems. Power Electronics and Advanced Control technologies have made it possible to mitigate power quality problems and maintain the operation of sensitive loads. Among power system disturbances, voltage sags, swells and harmonics are some of the severe problems to the sensitive loads, because  The occurrence of voltage sag in the system can cause devices/process down time, effect on product quality failure/malfunction of equipment etc.  The occurrence of harmonics in the system can cause excessive losses and heating in motors, capacitors and transformers connected to the system. To avoid those undesirable affects the proposed method mitigates the problems caused by voltage sag and harmonics. In the proposed system Voltage sag occurs due to the three phase fault in the transmission line and harmonics occurs due to the connection of controlled six pulse converter to the main drive load (nonlinear load). All these factors affect the sensitive load which is connected in parallel to the main drive load. So the proposed system protects the sensitive load by mitigating the voltage sags and harmonics using series compensation technique. A. Main sources, causes of electrical power quality problem- Power quality problem is an occur as a non-standard voltage, current and frequency. The power quality has serious economic implications for customers, utilities and electrical equipment manufacturers. However, in practice, power systems, especially the isolated systems are some of the source of distortion. Causes of dips, sags and surges: 1. Rural location remote from power source 2. Unbalanced load on a three phase system 3. Switching of heavy loads 4. Long distance from a distribution transformer with interposed loads 5. Unreliable grid systems 6. Equipment’s not suitable for local supply B. Major problems that arise from harmonic distortion are: a) Extra losses and heating in rotating machines and capacitors b) Over voltages due to resonance c) Interference with ripple control systems used in Demand Side Management (DSM) d) Telephone interference caused by noise on telephone lines II. SYSTEMMODEL Among the power quality problems (sags, swells, harmonics…), voltage sags are the most severe disturbances. In order to overcome these problems the concept of. Series compensator which is used in power distribution network, the function of s.c. will be to inject the missing voltage in order to regulate the load voltage from any disturbance due to immediate distort of source voltage. The DC side of SC is connected to an energy source or an energy storage device, while its ac side is connected to the three-phase inter facing injection transformer. Typical isolated power system model