ISSN: 2277-9655 [Vakula * et al., 7(8): August, 2018] Impact Factor: 5.164 IC™ Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com© International Journal of Engineering Sciences & Research Technology [284] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY MULTI-PULSE AC-DC CONVERTERS FOR POWER QUALITY IMPROVEMENT IN DC DRIVES Dr. V.S. Vakula* 1 , Ms. R. Sandhya Rani 2 & Mrs V.V. VijethaInti 3 *1 Assistant Professor & HOD, Department of EEE, UCEV, JNTUK, Vizianagaram, Andhra Pradesh, India 2 PG Student, Department of EEE, UCEV, JNTUK, Vizianagaram, Andhra Pradesh, India 3 Research Scholar, Department of EEE, JNTU Kakinada, Andhra Pradesh, India DOI: 10.5281/zenodo.1345617 ABSTRACT This article presents the design, modeling and simulation of three-phase multi-pulseAC–DC converters (MPC)for the improvement of power quality by the elimination of harmonics in ac mains and ripples in dc output.Multi pulse converters are operated with DC motors and run at different conditions to obtain output with less harmonic distortion.Total harmonic distortion is calculated by FFT analysis.With the help of MATLAB/Simulink modelling, simulation and digital implementation has been done for power quality improvement in DC drives using multi pulse converters. Keywords: AC–DC converters, DC motor, Multi pulse converter, Harmonic reduction, power quality, rectifiers. I. INRTODUCTION In converter circuits generally semiconductor switching devises are used which generates harmonics voltages and currents. Three phase ac-dc conversion of electric power are employed in the applications such as Adjustable speed drives (ASDs), Highvoltage dc (HVDC) transmission, Electro-chemical processes such as electroplating, Telecommunicationpower supplies, batterycharging, uninterruptible power supplies (UPS), High-capacitymagnet power supplies, high-power induction heatingequipment’sand converters for renewable energy conversion systems The major contributor to power system harmonics and consequences are diode bridge rectifiers. Generally converters are fed from three phase ac supply and have power quality problems like harmonics injection causes ac voltage distortion, rippled dc voltages and poor power factor. Various methods are used to minimize the problems in ac-dc converters. The DC motor drives are used in industries for converting electrical energy to mechanical energy. The advantage of choosing DC motors over AC components is because of their speed control.The main objective of the paper is to provide the power to consumer/industry load with proper sinusoidal wave of the voltage and current with fixed frequency and magnitude with minimized Total harmonic distortion,according to IEEE standards THD must be less than 5%. Power quality improvement can be achieved in 3-phase ac-dc converters by using multi-pulse converters. The converters are strong, simple, rough and efficient. The auto transformer based arrangement are more economical due to reduced magnetic losses. Different configurations from 12 pulse, controlled 24 pulse and controlled 48 pulse based ac-dc converters have been reported in literature.In literature several publications are reviewed and found on reduction on total harmonic distortion of power systems which are discussed in below section 2. This paper is divided into five sections. Starting with Section 1 gives introduction. Section gives detailed view of literature on reducing THD. Section 3 discussed about modeling of uncontrolled 12 pulseand controlled 12 pulse converter, controlled 24 pulse converter, controlled 48 pulse converter. Section 4 presents digital implementation, THD results and discussion. Section 5 concludes this paper. II. LITERATURE REVIEW The main objective of the research is to lessen harmonics in converters. Many methods are implemented and developed by the researches based on the needs and suitability. Selective harmonic elimination with pulse width modulation(SHEPWM) or programmed-PWM. This method calculates the switching instants of the devices in order to satisfy certain criteria. SHE method gives best outputs among PWM methods with low switching frequency to fundamental frequency ratios, direct control over output waveform harmonics.