G. Ashok et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.1040-1047 www.ijera.com 1040 | Page Closed Loop Operation of High Efficiency Ac-Dc Step-Up Converter Using Fuzzy Logic Controller G. Ashok 1 , K. B. Madhu Sahu 2 , Ch. Krishna Rao 3 1 P.G Student, Dept.of EEE, AITAM Engineering college, Andhra Pradesh 2 Professor, Dept.of EEE, AITAM Engineering College, Andhra Pradesh 3 Associate Professor, Dept.of EEE, AITAM Engineering College, Andhra Pradesh, ABSTRACT The conventional power electronic converters used in the micro generator based energy harvesting applications has two stages: a diode bridge rectifier and a dc-dc converter. But it is less efficient and can’t be used for electromagnetic micro generators, as the diode bridge rectification is not normally feasible due to extreme low output voltage of the micro generators. In this paper a direct ac-dc power electronic converter topology is proposed for efficient and maximum energy harvesting from low voltage micro generators. The single stage ac- to-dc power conversion is achieved by utilizing the bidirectional conduction capability of MOSFETs. This converter uses a boost converter and a buck-boost converter to process the positive and negative half cycles of the ac input voltage, respectively. The detailed analysis of this ac-dc step up converter is carried out to obtain the relations between power, circuit parameters, and duty cycle of the converter. The present model is proposed with the fuzzy logic controller for better performance. Furthermore, using this converter, maximum energy harvesting can be implemented effectively. The simulation results are obtained using MATLAB/SIMULINK software Keywords - AC-DC convertion ,boost converter, buck-boost converter, energy harvesting,Fuzzy logic controller, low voltage, low power. I. INTRODUCTION The recent development of compact and efficient semi conductor technologies has enabled the development of low-power wireless devices. Typical applications for such devices are wireless sensor nodes for structural monitoring, data transfer, biomedical implants etc. Batteries have been traditionally used as the energy source for such low-power wireless applications. However, they are inherently limited by capacity and size considerations. Therefore, they need to be recharged and replaced periodically. For low- power requirement of a few milli watts, harvesting energy from the environment has become feasible option. Vibration based energy harvesting is a popular way of extracting electrical energy from the environment. In particular, electromagnetic micro generators work on the principle of faraday’s law of electromagnetism. They utilize ambient vibrations to enable movement of a permanent magnet which induces an electromotive force in a stationary coil. The amount of harvested energy can be controlled by changing the load resistance connected to the coil. Unlike other popular vibration-based generators like piezo-electric micro generators, electromagnetic generators have to be specifically designed for a particular environment Many types of micro generators, used in the self-powered devices, are reported in the literature for harvesting different forms of ambient energies [1],[2]. The power level of the inertial -micro-generators is normally very low ranging from few microwatts to tens of mill watts. Based on the energy conversion principle, the inertial micro-generators can be classified mainly into three types: electromagnetic, piezoelectric, and electrostatic [5], [6], among them, the electromagnetic micro- generators have the highest energy density [7]. The electromagnetic generators are typically spring-mass damper- based resonance systems „as shown in Fig.1 in which the small amplitude ambient mechanical vibrations are amplified into larger amplitude translational movements and the mechanical energy of the motion is converted to electrical energy by electromagnetic coupling. An electromagnetic power generator consists of a copper coil, a permanent magnet (also acting as a mass), and a spring, the permanent magnet is attached to the coil through the spring. This generator works when there is a vibration input, the coil cuts through the magnetic flux formed by the permanent magnet due to the relative displacement between the permanent magnet and the coil. A sinusoidal electromotive force (EMF) in the coil can be generated and thus transfers mechanical energy into electrical energy. Since the output power of the power generator is very low, ranging from few micro-watts to tens of mill-watts, an energy harvesting interface circuit with high power transfer efficiency need to recharge and store the electrical power into the energy storage elements. RESEARCH ARTICLE OPEN ACCESS