International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 06 | June-2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 186 A REVIEW OF DESIGN DIGITAL FILTER FOR HARMONICS REDUCTION IN POWER SYSTEM Prashant Nagare 1 , Dr. Sachin Pable 2 , Dr. A.K. Kureshi 3 1 Electronics and Telecommunication, Matoshri College of Engineering and Research Center, India 2 Electronics and Telecommunication, Matoshri College of Engineering and Research Center, India 3 Electronics and Telecommunication, Vishwabharti Academy’s College of Engineering, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Harmonics that are created by non-linear devices connected to the power system. Power system harmonics are multiples integer of the fundamental power system frequency and these harmonic frequencies can create distorted voltages and currents. Distortion of voltages and currents can impact on the power system adversely causing power quality problems. Therefore, approximation of harmonics is of high importance for efficiency of the power system network to maintain the quality limits recommended by standards to protect the sensitive loads, it is necessary to enclosed some form of filtering device to the power system. filter is a device which passes specific frequencies while rejecting all other unwanted frequencies that fall outside range. Designing digital filter is one of the methods to control harmonic alleviation problems and improve power quality by delivering electrical power to the system. This paper presents the evaluation of digital filter design and harmonic analysis to the system. In order to achieve an adequate distortion, increase the power quality and to reduce the harmonics hence several digital filters are used. In this paper we have focused on digital filter such as FIR filter, IIR filter and their designing methods Key Words: Harmonics, non-linear devices, digital filter, power quality, FIR filter, IIR filter. 1.INTRODUCTION This paper provides overview of harmonics and designing digital filter with different types. Power transmission system are design for operation with sinusoidal voltage and current waveform in constant frequency. However, when non-linear device like thyristors drives, converters and arc furnace are connected to the system, excessive harmonic currents are created and this reason both current and voltage distortion. Also, some non- linear loads and electronics equipment’s are such that alternate of drawing current sinusoidally they tend to draw current in short pulses thus producing harmonics. Some of the examples of non-linear devices would be rectifiers, inverters, etc. The examples of electronics equipment’s would be PC, scanner, printer, etc. Some of the major issues involved with harmonics in non-linear devices are excessive heating, temperature increase in generators, etc. These effects may result into permanent damage of the devices. The filter plays a crucial role in analog and digital signal processing. Analog filters basically consist of resistor (R), capacitor (C) and inductor (L) which are also called passive components. The digital filter has two types such as IIR and FIR filter. Digital FIR filter constructed a linear phase digital filter which is convenient for data transmission and image processing applications. Whereas IIR filter is used in high speed and low-power communication transceivers system applications. As FIR requires large memory in order to store the previous input and forgoing output but FIR need less memory space to store present and past value of input. IIR contain following properties: the width of the pass-band, stop-band, limited ripple at pass-band and stop-band. The IIR filter types are Butterworth, Chebyshev, Elliptic. 2.POWER SYSTEM HARMONICS Harmonics nothing but the sinusoidal components of a repetitive waveform which consist of frequencies that are exact multiples or harmonic orders of fundamental frequency. A complete set of harmonics then makes up a Fourier series which together represent the original waveform. Harmonics are currents, usually in multiples of the supply fundamental frequency, generated by non-linear loads such as AC to DC power conversion circuits. For example, a 50Hz supply with 5 th harmonic is 250Hz, 7 th harmonic is 350Hz and other order harmonics. Fig -1: Fundamental wave 60Hz with harmonics distortion