University of Halabja (UoH) College of Science Physics Department Undergraduate’s Last year Project 2020-2021 ‘’Harmonics Cancellation from AC- DC Uncontrolled Rectifier by using Phase- Shifting Transformer.’’ Prepared by: Supervised by: Shilan Ali Faraj Mr .Farhad Muhsin Mahmood Bushra Ahmad Abdulla Nada Jaba Hassan 1 [‘’Harmonics Cancellation from AC- DC Uncontrolled Rectifier by using Phase-Shifting Transformer.’’] By Shilan Ali Faraj Bushra Ahmad Abdulla Nada Jaba Hassan A thesis submitted to the College of Science, University of Halabja In partial fulfillment of the requirements For the degree of Bachelor of Physics Graduate Program in Physics Written under the direction of [Mr. Farhad M. Mahmood] [May, 2021] 2 Contents Abstract ......................................................................................................................................................... 4 Chapter one (History and background) ........................................................................................................ 5 Background and history of Rectifier. ........................................................................................................ 5 1.1 Rectifier : ............................................................................................................................................. 5 1.2. Inverter :............................................................................................................................................. 7 Chapter two (introduction) ......................................................................................................................... 10 2.1 INTRODUCTION ................................................................................................................................. 10 2.2 Single Phase Rectification. ................................................................................................................ 11 2.2.1 AC Sinusoidal Waveform ................................................................................................................ 12 2.3 Single Phase Rectifier ........................................................................................................................ 13 2.3.1 Half-wave Rectification .................................................................................................................. 14 2.3.2 Sinusoids Average Value ................................................................................................................ 15 2.4 Full-wave Rectification ...................................................................................................................... 17 2.4.1 Single Phase Full-wave Bridge Rectifier ......................................................................................... 18 2.4.2 Full-wave Rectifier Output Waveform ........................................................................................... 19 Three Phase Rectification ....................................................................................................................... 25 Three-phase Waveform .......................................................................................................................... 26 Three-phase Rectification ....................................................................................................................... 27 2. The rectifiers load current. ................................................................................................................. 35 Chapter three (Literature Review). ............................................................................................................. 38 3.1 Harmonics ......................................................................................................................................... 38 3.2 Fundamental Frequency ................................................................................................................... 39 3.3 Complex Waveforms Due To Harmonics .......................................................................................... 41 3.4 Harmonics Summary ......................................................................................................................... 45 Chapter Four (Results and Discussion). ...................................................................................................... 46 4.1 Single phase rectifier ......................................................................................................................... 46 4.2 Three-phase bridge diode rectifier ................................................................................................... 47 4.3 12-pulse diode bridge harmonic cancellation................................................................................... 50 4.4 Harmonic Cancellation of 24-pulse Rectifier Using Phase-Shifting Transformers. ........................... 53 CONCLUSIONS ............................................................................................................................................ 56 List of references ......................................................................................................................................... 57 3 Abstract Harmonic distortion is a huge problem for the power systems. But harmonic distortion can be controlled using some unique methods with the utility systems. This paper discusses the impact of using 12- pulse and 24-pulse rectifier circuit. The 24-pulse topology is generally more expensive, but produces the least Input current harmonics. In this paper pulse multiplication technique is used to mitigate the harmonic distortion from the input line current. Phase-shifting transformers are used to produce 24-pulse from 12- pulse. A comparison between 12-pulse and 24- pulse rectifier also shown in this paper. Operation of the circuits is verified through computer simulations. 4 Chapter one (History and background) Background and history of Rectifier. 1.1 Rectifier : The term rectifier was in common use for more than two decades prior to 1925. It was understood to mean any stationary apparatus or rotating commutator for trans- forming alternating into direct current.(Rotary converters, later known as synchronous converters, were in use by 1892 to convert AC power into DC power [1]. Rotary converters were manufactured until the 1950s, when germanium diodes became available. When operated to convert DC power to AC power, rotaries were dubbed “inverted rotaries.” The distinction between rectifier and converter was sometimes vague, perhaps even arbitrary, but often based on use of static or non- rotating versus rotating parts). The term rectifier is often confused with similar or related terms and phrases It is sometimes used to denote rectifier element (device) or rectifier circuit when rectifier equipment is intended. Rectifier elements can be physical devices or circuit entities In either case, rectifier elements allow current to flow in only one direction, blocking its flow in the reverse direction (I e., diodes, thyristors ) The property of rectifier elements that permits only unidirectional current flow causes some persons to call them electric “valves,” being analogous to check valves in hydraulic circuits (In some places, they are still called valves ) Rectifier circuits are electrical circuits containing rectifier and other circuit elements (resistors, capacitors, etc.) interconnected into prescribed paths or current conduction, the whole assembly (or network) providing the function of rectification. Prince reviews prior art by first examining operation of a single-phase full-wave center-tap rectifier circuit. The DC output of the rectifier circuit includes both passive resistance and reactance. His figures provide ideal waveforms of most circuit variables, including potential and current at AC and DC terminals. Fig. 1 is depicted here, on the left side of the figure, and is identified as “rectifier circuit.” This figure 5 is identical in topology to Prince’s, except that modern symbols for rectifier circuit elements replace his archaic vacuum tube (diode) symbols. With this small change, his figure is identical to any modern single-phase full wave center-tap rectifier circuit. Rectifier devices available to Prince in1925 were of three basic types: mechanical rectifier, electrolytic “cells,” and high vacuum [2]. or gas-discharge “tubes.” Mechanical rectifiers consist of rotating commutators driven by synchronous motors and were in use prior to 1893. Electrolytic cells also originated prior to the turn of the century and were the second rectifier devices available. They evolved experimentally from electrochemical research before existence of the electron was discovered by J.J. Thomson in 1899. Similarly, the Edison effect (1883) was discovered before knowledge of the electron, but no immediate application was made of his discovery. It was the Cooper Hewitt patents on mercury-arc rectifiers (1901) and DeForest’s three-element valve (audion, 1907) that opened the way for gas-discharge tubes. 6 Fig.1. Prince’s rectifier circuit. 1.2. Inverter : By 1936, Prince’s inverter appearedn in literature from all corners of the world, Europe and Japan among them. It was in common use in English technical publications or its equivalent word was used in other languages. In 1925, Prince defined inverter as the inverse of rectifier. In so doing, he depended upon his audience having a clear mental abstraction of rectifier and built upon