International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 04 | Apr -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 3108 A Review on UPQC Allocation to Improve Power Quality Simrankaur Digwa 1 , Sneha Tibude 2 1 Student M-Tech IPS, Department of Electrical Engineering, AGPCE, Nagpur, India s.j.digwa@gmail.com 2 Assistant Professor, Department of Electrical Engineering, AGPCE, Nagpur, India sneha.electrical@agpce.com ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Flexible AC Transmission Systems (FACTS) devices are used to develop and improve the dynamic performance of the modern power system. The quality of the Electrical power is affected by many factors like the presence of harmonic, voltage swell and voltage sag due to switching of loads, current flickering etc. Unified Power Quality Conditioner (UPQC) is one of the FACTS devices that can provide controllable compensating voltage and current simultaneously. UPQC, which is composed of the DC/DC converter and the storage device connected to the DC link of UPQC, is proposed to balance the voltage. Key Words: Harmonic, SPWM, Voltage sag, Voltage swell, UPQC. 1.INTRODUCTION There are many nonlinear loads in the distribution system due to which harmonic distortion occurs. The quality of the power gets affected by the loads like thyristor power convertors, arc furnace, etc. The current and voltage flickering occurs due to EAF. The sag and swell voltage quality issues occurs due to switching ON and OFF of loads. LC filters can solve this power quality issues but random variations in load current canǯt be solved by LC filters. Active filters may help in reducing flickers but those are very costly. They are also difficult to install on large scale. So for overcoming it, the UPQC can compensate the power quality issues in distribution system. UPQC is a combination of filters, series and shunt, connected through common DC link capacitor. UPQC can compensate power quality issues such as voltage sag, voltage swell, power unbalance, flickers, harmonics, and reactive power demand. 2. POWER QUALITY ISSUES Power quality problem embodies deviation in voltage, current or frequency that culminates into a failure of equipment. Power quality problems often accompany loss of production, damage to appliances, higher power losses, communication interference and so on. It is, therefore, significant to establish and maintain higher standards of power quality. The frequently encountered problems related to power quality are voltage sags, voltage swells, interruption, harmonics and distortion. 2.1 Voltage Sags: Voltage sag is defined as a decrease in voltage between 0.1 and 0.9 pu at a power frequency for duration from 0.5 cycle to 1 min. These problems are usually associated with system faults, but may also be caused due to the heavy loads. Fig . Voltage sag 2.2 Voltage Swells: A swell is defined as an increase in voltage between 1.1 and 1.8 pu at power frequency for duration from 0.5 cycle to 1 min. These voltage swells during fault is a function of fault location, grounding and impedance of the system. Fig 2. Voltage swell 2.3 Interruption: Interruption in a power system is one of the major problems that occurs when the system or supply voltage or load current decreases to less than 0.1 pu for a period of time