**1. Introduction**

132 MATLAB – A Fundamental Tool for Scientific Computing and Engineering Applications – Volume 1

*IEEE Transaction on Power Delivery.* 11(1): 526 – 532, 1996.

Bollen MHJ (2000). Understanding Power quality problems voltage sags and interruption.

Bhavsar S, Shah VA, Gupta V. "Voltage dips and short interruption immunity test generator as per IEC 61000-4-11". *in Proc. of 15th National Power Systems Conference. Bombay, India*,

Collins ER, Morgan RL. "A Three-Phase Sag Generator for Testing Industrial Equipment".

Ma Y, Karady GG . "A single-phase voltage sag generator for testing electrical equipments". *in Proc. of Transmission and Distribution Conference and Exposition, Chicago IL,* pp 1 – 5,

Oranpiroj K, Premrudeepreechacharn S, Ngoudech M, Muangjai W, Yingkayun K, Boonsai T. "The 3-phase 4-wire voltage sag generator based on three dimensions space vector modulation in abc coordinates". *In Proc. of International Symposium on Industrial* 

Oranpiroj K, Premrudeepreechacharn S, Ngoudech M, Muangjai W, Yingkayun K, Boonsai T. "The 3-phase 4-wire voltage sag generator based on abc algorithm". *in Proc. of Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology* 

Oranpiroj K, Premrudeepreechacharn S, Higuchi K. "SagWave for the 3-phase 4-wire voltage sag generator prototype". *in Proc. of IEEE International conference on Control* 

Oranpiroj K, Premrudeepreechacharn S,Muangjai W, C.V. Nayar., "Development of the 3 phase 4-wire voltage sag generator". *Scientific Research and Eassys,* 6(23): 4960 – 4974,

Patrick Marchand, O.Thomas Holland, *Graphics and GUIs with MATLAB.* (CHAPMAD &

Rylande M, Grady WM, Arapostathis A. "Enhancement and application of a voltage sag station to test transient load response". *in Proc. of IEEE Electric Ship Technology* 

Takahashi R, Cortez JA, da Silva VF, Rezek AJJ. "A prototype implementation of a voltage sag generator". *VIII Conferencia Internacional de Aplicacoes Industriais, Poços de Caldas,* 

Teke A, Meral ME, and Tümay M. "Evaluation of available power quality disturbance generators for testing of power quality mitigation devices". *Int. J. of Sciences and Techniques* 

*of Automatic Control and Computer Engineering, (special issue)*, pp. 624 – 635, 2008

**8. References** 

2008.

2008.

2011.

*Brazil*, 2008

New York, IEEE Press. 193 – 196.

*Electronics ISIE2009*, 275 – 280, 2009.

*Applications CCA 2010*, 2209 – 2212, 2010.

*Symposium, Arlington VA.* pp. 428 – 433, 2007.

*ECTI-CON 2009*, 82 – 85, 2009.

HALL/CRC, LTD, 2003)

Advances in semiconductor technologies to produce high power devices have facilitated numerous applications where high power density is a key for practical and sophisticated solutions. Instead of being limited to the traditional low power electronics applications, high power devices opened a broad frontier for engineering design. These devices are now embedded in systems that span the full range from small electric motor drives to very high voltage transmission lines where hundreds of amperes are regulated while the devices are exposed to thousands of volts. Compared to the traditional rotating electric machine based (dynamic) energy conversion, these devices made static conversion from one form of electricity to another so seamless that employing a certain form of electric power (AC, DC, or a combination) has become an engineering design option rather than a forced solution. Application areas like in motor drives, fuel cells, solar panels, wind turbines, electric cars, and high speed transportation systems are only a few of the major beneficiaries of advances in power electronics. Emphases on energy conservation motivated the design for improved system efficiency where power electronics devices are utilized in their most desirable mode. These efforts resulted in increased portability of high power density systems and affected the design of the full range of power systems including those for small electronic equipment which are becoming more demanding on power for their ever increasing features and capabilities. Like all advanced engineering design applications, mathematical developments and supporting software tools for modeling, simulation and analysis are critical (Shaffer, 2007; Assi, 2011). In addition to introducing some of the fundamental concepts in power electronics and related applications, this chapter exploits the capabilities of Matlab and its associated SimPower and Simulink toolboxes as an effective relevant engineering tool.

When dealing with an alternating current, changing voltage levels, at the same frequency, is achieved simply by utilizing AC transformers where the principle of mutual induction

© 2012 Fagerstrom and Bengiamin, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Fagerstrom and Bengiamin, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

exists between two magnetic coils with the proper turns-ratio. Mutual induction is possible due to the rate at which the magnetic lines cut the wires of the transformer coils and the produced electromotive force that is capable of producing current in closed electric loops. This fundamental concept is not applicable to DC voltage and current due to the absence of the alternating nature of the produced magnetic fields. Therefore, changing DC voltage from one level to another must be achieved using different methodologies. One possible methodology is to modulate DC voltages by switching them on and off at proper rates and durations such that the average produced voltage is controlled. The key concept here is to store energy then release it at the proper time with the proper rate needed for the desired load. Energy storage elements like inductors and capacitors facilitate this methodology. Therefore, a combination of energy storage elements and switching schemes provide the basic ingredients for the design of DC-DC conversion devices. Such devices are referred to as power electronic DC-DC converters. The modes of operation of these devices are dependent on the shape of the produced voltage waveform which is manipulated by the switching scheme and the size of the energy storage elements. Compared to AC transformers which usually exhibit linear characteristics for its most modes of operation, DC transformers (DC-DC converters) possess highly non-linear characteristics which require more intensive analysis and design schemes.

Optimization of power electronics systems' design and operation is important to accommodate the growing need for energy efficiency in portable electronic devices to extend their battery life and respond to their increasing functionality and features. These features demand more electric power while the devices must reduce in size and weight; i.e. increased energy density. DC-DC converters are embedded in numerous electronic equipment and they have become an integral part of many commercial and industrial products. These converters are employed to lower (buck) or raise (boost) DC voltage levels as needed by the application. Buck and boost converters are emphasized in this chapter for their different topologies and modes of operation. The presented methodologies facilitate analysis, characterization, and design of efficient DC-DC converters. Sufficient background and theoretical development are provided for completeness.
