IJSRSET1623246 | Received : 25 June 2016 | Accepted : 30 June 2016 | May-June 2016 [(2)3: 947-950] © 2016 IJSRSET | Volume 2 | Issue 3 | Print ISSN : 2395-1990 | Online ISSN : 2394-4099 Themed Section: Engineering and Technology 947 Study of Power Quality Improvement Using UPQC Anupama Kulkarni, R. S. Desai Electrical Department, Bharati Vidyapeeth Deemed University College of Engineering, Pune, Maharashtra, India ABSTRACT This paper describes role of UPQC as applied to a 3P4W system to improve PQ. The Forth wire of 3P4W system is developed by means of neutral of series transformer. Neutral current which flows through neutral terminal of transformer is removed with the help of 4 leg voltage source inverter (VSI) topology for shunt part. The series transformer neutral will have 0 potential in all conditions of operation. Simulation is carried out by considering the major PQ issues like voltage, current, harmonic by connecting load which is nonlinear in nature to 3P4W scheme with UPQC. A novel control strategy of unit vector template is implemented here for designing series APF. By extending the principle of single phase PQ theory, series APF can be used for balancing the unbalanced voltage present at the load side. The PQ theory as applied to the 3 phase balanced system can even be independently used for unbalanced system. Keywords: UPQC, VSI, APF, PCC, FACTS, PQ, PF. I. INTRODUCTION Current harmonic causing PQ problem in distribution system are generated at the time of their switching. The devices build on power electronics are being employed to improve PQ. A 3P4W system of distribution could be formed by facilitating a neutral wire in conjunction to 3 power lines from generation location. Unbalance load circuits is a usual problem in 3P4W distribution system that should be taken into account. The PQ can be improving by employing series and shunt APF in the system. These are 2 classes of filter are Passive and Active filters. Passive filters are comprising of L and C component which provide simplicity as well as economy to system; but they have tendency to suffer from resonance problem and get filter for every frequency and bulky. On other hand active filters comprise of IGBTs, MOSFET, and devices of storage of energy like L and C. The privilege of active filter is that they filter a specific frequency range do not resonate with the system and provide fast response. But their cost is high. The serials APF basically draw out the harmonics in voltage by providing path of large impedance path to harmonic circuits. Non - linear loads highly produce distorted current resulting into third harmonic component. Power Quality Problems Both the electric utilities & end users of electric power are becoming aware of quality of power that they are getting from the grid. The definitions of the PQ may be different for various types of customers. For example an electrical utility may define PQ as reliability on other hand a manufacturer of load equipment can define PQ as characteristics of power supply that enables equipment work properly. The PQ problem is defined as “Any power-problem which results in voltage, current or frequency deviation which ultimately causes failure or mal-operation of the equipment of service users”. Following are the major problems related to power quality. Voltage Sag A voltage sag or dip is termed as a reduction to a low voltage (between 0.1 & 0.9 per unit RMS) at power frequency which may last from 0.5 cycles to 1 minute. Voltage Swell It is defined as increase in a voltage to a level (between 1.1 & 1.8 per unit RMS) at power frequency lasting from 0.5 cycles to 1minute.