International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 09 | Sep 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 118 Harmonic Mitigation for Power Quality Improvement using Active Power Filter with Current Control Strategy under Non-Linear Loads CH. SHANMUKHA RAO 1 , Dr. G.V. Siva Krishna Rao 2 1 PG Scholar, Dept. of Electrical Engineering, Andhra University College of Engineering, Visakhapatnam, A.P, India. 2 Professor, Dept. of Electrical Engineering, Andhra University College of Engineering, Visakhapatnam, A.P, India -------------------------------------------------------------------------***------------------------------------------------------------------------ Abstract : Application of nonlinear loads are increasing day by day with advancement of technology. Non-linear electrical devices has led to a distortion in the output sine waveforms of source current and voltage. It may lead equipment (connected to it) to overheat and sometimes cause damage. This paper concentrates on better design and application of three-phase shunt active power filter (SAPF) by using two different methods p-q theory and d-q theory to mitigate the harmonics which are created by nonlinear loads. To obtain result for this paper, the MATLAB / Simulink was used as a simulation tool. The achieved results are within the recommended IEEE-519 standard i.e. less than 5% and also the power factor (PF) of the system to almost unity. Index Terms: shunt active power filter, power quality, total harmonic distortion, power factor, UPS ,SMPS, Nonlinear Loads. INTRODUCTION In an electric power system, a harmonic is a voltage or current at a multiple of the fundamental frequency of the system, produced by the action of non- linear loads such as rectifiers, discharge lighting, or saturated magnetic devices. Harmonic frequencies in the power grid are a frequent cause of power quality problems. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors. Passive filters (combinations of capacitors and inductors) were used to mitigate the PQ problems. These approaches were extensively used in high voltage DC transmission (HVDC) for filtering the harmonics on the AC and DC sides. However, this approach is unsuitable at the distribution level as passive filters can only correct specific load conditions or a particular state of the PS. These filters are unable to follow the changing system conditions. Thus, the active power filter (APF) was introduced to compensate harmonics and reactive power. There are three types of APFs which are shunt APF, series APF, and hybrid APF (i.e. the combination of active and passive filters) (Badi, 2012), (Chaughule, Nehete, and Shinde, 2013). The purpose of an APF as a power line conditioner is to repay the utility line current waveform with the goal that it approximates a sine wave in phase with the line voltage when a nonlinear load is connected with the system. Classically, shunt power line conditioner (shunt passive filter) consists of tuned LC filters. OBJECTIVE The main objectives of this project are To give a brief overview about the cause and effect of harmonics in power system To study different types proposed filter used to eliminate harmonics from the power system .To study and implement different control strategies already proposed for modeling of 3 phase shunt active power filter. To model and simulate three phase shunt active power filter with different current control strategy in MATLAB/ SIMULINK environment To compare different control strategies based on FFT analysis (an important tool for harmonic behavioral analysis) for harmonic elimination in power system network. Passive Filter It is a combination of series/parallel connection of passive elements such as capacitors, inductors and/or resistor. They provide a low resistance path for the harmonic current to flow owing to the formation of resonance at that particular harmonic frequency. Hence harmonic current is diverted through passive filter network and system current becomes distortion free. Likewise distortion in voltage waveform is also removed. For bypassing the current effective means of connection is connecting the passive filter in parallel with the load. In order to improve power factor passive filters are designed as capacitive filter so that it correct the current displacement factor and provide reactive power to the load. Advantages of Passive Filters Although passive filters doesn’t eliminate harmonics to a greater extent yet it is used due to some prominent features which are described as under 1. They are simpler to configure and construct.