DESIGN OF A SINGLE PHASE AC-AC CONVERTER A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF BACHELOR OF SCIENCE IN ELECTRICAL AND ELECTRONIC ENGINEERING BY: Md. Imtiaz Khan- 10121103 Abdul Ahad- 09221087 Kamrul Islam- 09221151 Under the guidance of: Ms. Amina Hasan Abedin Assistant Professor Department of Electrical and Electronic Engineering BRAC University 1 DECLARATION This is to certify that the thesis entitled “Design of a single phase ac-ac converter”, submitted by Md. Imtiaz Khan (ID. 10121103), Abdul Ahad (ID. 09221087) and Kamrul Islam (ID. 09221151), in partial fulfillment of the award of Bachelor of Science (B.Sc.) in Electrical and Electronic Engineering in the Department of Electrical and Electronic Engineering at BRAC University is an authentic work carried out by them under my supervision and guidance. To the best of my knowledge, the matter embodied in the thesis has not been submitted to any other University / Institute for the award of any Degree or Diploma. Date: Md. Imtiaz Khan Abdul Ahad Ms. Amina Hasan Abedin Assistant Professor Department of Electrical and Electronic Engineering Kamrul Islam BRAC University 2 ACKNOWLEDGEMENT We would like to express our heartiest gratitude and sincere thanks to our mentor and project guide Ms. Amina Hasan Abedin, Assistant Professor, Department of Electrical and Electronic Engineering, BRAC University for providing us the necessary guidance to carry out our project work. We would like to take this opportunity to thank her for her constant support and encouragement and for guiding us throughout our work which would not have been possible without her guidance, support and motivation. Further, we would like to thank all the laboratory and administrative staff members of Department of Electrical and Electronic Engineering for their humble cooperation and support. We would also take this opportunity to give thanks to all our friends and others who have helped us throughout our project and study at our institute. Md. Imtiaz Khan ID. 10121103 Abdul Ahad ID. 09221087 Kamrul Islam ID. 09221151 3 ABSTRACT An AC-AC voltage controller is a converter which controls the voltage, current and average power delivered to an AC load from an AC source. They are used in practical circuits like light dimmer circuits, speed controls of induction motors, traction motors control etc. In our thesis we will analyze the performance of a single-phase AC-AC circuit with emphasis on the output harmonic content and utilization of input voltage. This converter can convert from a fixed AC input voltage into variable AC output voltage with desired frequency. 4 CONTENTS Topic Page 1. INTRODUCTION..……………………………………………………………6 1.1 TYPE OF AC VOLTAGE CONTROLLERS……………………………….8 1.2 AC-AC CONVERSION……………………………………………………….9 1.3 SINGLE PHASE FULL WAVE AC-AC VOLTAGE CONTROLLER…..11 2. APPLIED TECHNIQUES……………………………………………………13 2.1 4 TYPES OF SWITCHES THAT COULD BE USED IN AN AC-AC CONVERTER CIRCUIT………………………………………………….....14 2.2 REASONS OF USING MOSFET IN OUR CIRCUIT……………………..16 2.3 PULSE WIDTH MODULATOR…………………………………………….17 2.4 OPTO COUPLER…………………………………………………………….18 2.5 FILTER DESIGN……………………………………………………………..19 3 BUCK CIRCUIT………………………………………………………………21 3.1 BUCK CONVERTER………………………………………………………..22 3.2 BASIC OPERATION OF BUCK TOPOLOGY……………………………22 3.3 WAVE FORMS AND DATA SHEET OF BUCK TOPOLOGY………….24 3.4 BUCK TOPOLOGY WITH FILTER DESIGN……………………………26 3.5 CURRENT FLOW DIAGRAMS……………………………………………27 3.6 DATA ANALYSIS, WAVEFORMS AND CURVES ……………………...31 4 BOOST CONVERTER………………………………………………………51 4.1 BOOST CONVERTER………………………………………………………52 4.2 BASIC OPERATION OF BOOST TOPOLOGY…………………………..52 4.3 WAVE FORMS AND DATA SHEET OF BOOST TOPOLOGY………...53 4.4 BOOST TOPOLOGY WITH FILTER DESIGN…………………………..55 4.5 CURRENT FLOW DIAGRAMS …………………………………………...56 4.6 DATA ANALYSIS, WAVEFORMS AND CURVES ……………………..60 5 CONCLUSION………………………………………………………………..81 5 CHAPTER 1 INTRODUCTION 6 1.0 INTRODUCTION We will analyze the performance of a single-phase AC-AC circuit with emphasis on the output harmonic content and utilization of input voltage. The only disadvantage of the single-phase AC-AC converter is that the amplitudes of certain harmonic frequencies become abnormally high. This converter can convert from a fixed AC input voltage into variable AC output voltage. V 0(RMS) AC V AC Variable AC Input s Voltage RMS O/P Voltage Voltage f Controller s f s f S AC voltage controllers are working to vary the RMS value of the alternating voltage applied to a load circuit by introducing Thyristors, IGBT, BJT and MOSFET between the load and a constant voltage AC source. We have used MOSFET and design a single phase full wave AC voltage bi- directional controller. Our thesis is about AC-AC converter. An ac voltage controller is a converter which controls the voltage, current and average power delivered to an ac load from an ac source. The input voltage source is ac and the output voltage is also ac, so the circuit is an ac- ac converter. Voltage controllers use electronic switches to connect and disconnect a load to an ac source at regular intervals. This type of circuit is classified as an ac-ac converter. 7 1.1 TYPE OF AC VOLTAGE CONTROLLERS1 The ac voltage controllers are classified into two types based on the type of input ac supply applied to the circuit. They are:  Single Phase AC Controllers.  Three Phase AC Controller Each type of controller may be sub divided into;  Uni-directional or half wave ac controller.  Bi-directional or full wave ac controller. In brief different types of ac voltage controllers are:  Single phase half wave ac voltage controller (uni-directional controller).  Single phase full wave ac voltage controller (bi-directional controller).  Three phase half wave ac voltage controller (uni-directional controller).  Three phase full wave ac voltage controller (bi-directional controller). 1 Lecture notes on Power Electronics by Prof. Madhusudhan Rao 8 1.2 AC-AC CONVERSION Power electronics is the application of electronics for power conversion. A subcategory of power conversion is the AC to AC conversion. Converting an AC waveform to another AC waveform allows one to control the voltage, frequency, and phase of the waveform applied to a load from a supplied AC waveform. The two main categories that can be used to separate the types of converters are whether the frequency of the waveform is changed. The ones which don‟t allow the user to modify the frequencies are known as AC Voltage Controllers, or AC Regulators. AC converters are the ones which allow the user to change the frequency are simply referred to as frequency converters for AC to AC conversion. Under frequency converters there are three different types of converters that are typically used: cycloconverter, matrix converter, DC link converter (aka AC/DC/AC converter).2 The purpose of an AC Voltage Controller, or AC Regulator, is to vary the RMS voltage across the load at a constant frequency. Three control methods that are generally accepted are:  ON/OFF control  Phase-Angle Control  Pulse Width Modulation AC Chopper Control (PWM AC Chopper Control). All three of these methods can be implemented not only in single-phase circuits, but three-phase circuits as well. In our thesis we applied PWM AC Chopper Control method. 2 Power Electronics- Circuits, Devices and Applications by Muhammad Harunur Rashid 9 Applications: Understanding how each of the converters work is all good and well, but it is useless in a practical sense if one does not understand where each converter is applied in the real world. Below is a list of common applications that each converter is used in. 3  AC Voltage Controller: Lighting Control; Domestic and Industrial Heating; Speed Control of Fan, Pump or Hoist Drives, Soft Starting of Induction Motors, Static AC Switches (Temperature Control, Transformer Tap Changing, etc)  Cycloconverter: High-Power Low-Speed Reversible AC Motor Drives; Constant Frequency Power Supply with Variable Input Frequency; Controllable VAR Generators for Power Factor Correction; AC System Interties Linking Two Independent Power Systems.  Matrix Converter: Currently the application of Matrix converters are limited due to non-availability of bilateral monolithic switches capable of operating at high- frequency, complex control law implementation, commutation and other reasons.  DC Link: Can be used for individual or multiple load applications of machine building and construction. 3 http://en.wikipedia.org/wiki/Power_electronics reference 10