ISSN 2394-3777 (Print) ISSN 2394-3785 (Online) Available online at www.ijartet.com International Journal of Advanced Research Trends in Engineering and Technology (IJARTET) Vol. 2, Issue 4, April 2015 All Rights Reserved © 2015 IJARTET 80 Current Mode Control Techniques for the Reduction of THD using Fuzzy Logic J. Christina Rajakumari 1 , Mrs.A. Shiny Pradeepa 2 Final year ME-Power Electronics and Drives, SCAD college of engineering and technology, Cheranmahadevi, India 1 Assistant Professor (Phd), EEE Department, SCAD college of engineering and technology, Cheranmahadevi, India 2 Abstract: Typical electronic equipment requires dc power supply and an AC-DC power converter serves this purpose. These AC/DC power converters are connected to ac mains and they introduce harmonic current in the utility. The injection of harmonics in utility currents, caused by uncontrolled or phase-controlled rectifiers, distorts current and voltage waveforms thereby reducing power factor and produces negative effects in the neighbor loads and the power distribution network. This project is proposed to implement the current mode control techniques for the ac-dc converters to reduce the total harmonic distortion (THD). The performance of peak and average current mode controls are compared. Also ACMC is implemented in fuzzy logic because of its advantages over PCMC. Keywords: Peak current mode control (PCMC), Average current mode control (ACMC), Active power factor correction (APFC), Switched mode power supply (SMPS), Total harmonic distortion (THD). I. INTRODUCTION Regulations such as IEC-61000-3-2 demand some sort of input current shaping for single-phase equipment. Active current shaping is usually used in the power range around 2 kW in order to reduce the volume of the converter, and it usually consists of a conventional diode bridge followed by a dc–dc switch-mode converter, which shapes the current. Generally, the control strategies for DC-DC converters can be classified into two main categories, namely voltage-mode control (VMC) and current-mode control (CMC). In VMC the output voltage is sensed and subtracted from an external reference voltage in an error amplifier. The error amplifier produces a control signal which is compared to a constant amplitude saw-tooth waveform. The comparator produces a PWM signal which is fed to the drivers of the controllable switches of the converter. While in VMC only output voltage is sensed and compared to the reference value, in CMC both output voltage and inductor current are sensed and used for output voltage regulation. Actually, in a CMC scheme there are two control loops, namely voltage control loop (which is the outer loop) and current control loop (which is the inner loop). Inductor current feedback in CMC allows for fast response to variations in the input voltage. Furthermore, the current mode DC-DC converter shows superior dynamic characteristics than the voltage mode dc-dc converter. The current-mode control strategies are divided into peak current mode control (PCMC), average current-mode control (ACMC). Over the past decade, many approaches have been proposed for current-mode control in DC-DC converters. Most of these techniques rely on mathematical models of the power converters. However, the inherent nonlinearity and time varying characteristics of CMC power converters hinder the accurate mathematical modeling of the converters, which is a pre-requisite for control design. The fuzzy logic controller (FLC) is indeed capable of providing the high accuracy required by high performance drive system without the need of mathematical model.FLC accommodates non-linearity without utilization of mathematical model. The fuzzy logic controller uses fuzzy logic as a design methodology, which can be applied in developing nonlinear system for embedded control. Simplicity and less intensive mathematical design requirements are the most important features of the FLC. Fuzzy Logic controller is an attractive choice when precise mathematical formulations are not possible applications in many industries, in that ac–dc conversion of electric power is widely used in several applications such as adjustable- speed drives (ASDs), switch-mode power supplies (SMPSs), uninterrupted power supplies (UPSs), and battery energy storage. Traditionally, the diode bridge rectifier is used for AC-DC power conversion. This rectifier has the advantages of a simple circuit configuration and a low cost. Nevertheless, this rectifier results in some power pollutions, such as a high pulsating input current, a low power factor,