Preface

There is an upward trend that human activities involve more electric power nowadays and for years to come. And we will soon be facing shortage of electricity supply if we rely solely on non-renewable power generation from fossil fuels such as coals. Renewable energy generation has proven effective in meeting the demand. At the same time it has brought about a few issues to existing electricity infrastructure such as complex power flow due to distributed generations and unstable grid voltage and/or frequency profiles due to local generation and intermittent nature of renewable energy sources such as solar photovoltaic and wind power. Also the increasing penetration of power electronics converters associated with the adoption of renewable energies into the electricity networks has improved the functionality and flexibility in terms of control but meanwhile due to their switching nature the harmonics issue has to be dealt with. It is therefore important to investigate the causes of these power quality issues and explore feasible and cost-effective solutions to assist with the development of present and future electricity networks.

In the following chapters the reader will be introduced to power quality issues and solutions at different sections of the electricity networks, namely, power generation, transmission, distribution and end user stages. The book is divided into three sections: Power Quality Issues and Standards in Electricity Networks; Power Quality Improvements in Transmission and Distribution Systems; and Power Quality Improvement in End Users Stage. A brief discussion of each chapter is as follows.

Chapter 1 provides an overview of the causes, impacts, standards and solutions to voltage and current harmonics problems which are one of the key issues related to power quality. Chapter 2 investigates the challenges of increasing wind generation to the network. The chapter has identified and analyzed briefly several key issues including voltage variations, flickers, switching operation of wind generation, current harmonics and locations of wind turbine. Several solutions have been introduced such as low-voltage ride through capability and international standards. Lastly, but not the least, it describes the purposes of grid code to deal with power quality issues with renewable energy generation.

Flexible Alternating Current Transmission System (FACTS) controllers have been used in transmission and distribution systems to deal with power quality issues. Chapter 3 identifies the limitations in the transmission systems, i.e., angular stability, voltage magnitude, thermal limits, transient stability, and dynamic stability and presents a comparative study of three different series FACTS for power quality compensation of a single transmission line in Eastern Algerian transmissions networks. Chapter 4 applies particle swarm optimization technique to designing a shunt static var compensator (SVC) for a radial distribution feeder. The objective function of SVC placement is to reduce the power loss and keep bus voltages and total harmonic distortion within prescribed limits with minimum cost.

Chapter 5 proposes an electromechanical active power filter which uses a synchronous generator together with a unity power quality conditioner (UPQC). The idea originates from the fact that embedded generation is becoming a viable option in distributed generation and we should utilize this generator as a part of the power quality compensation solution. An algorithm of reference generation has been proposed to work with the two devices and simulation results are reported to verify the effectiveness of the approach. Chapter 6 continues with the previous study but the focus is on the speed to generate the references for UPQC. The general idea is that it uses an adaptive approach to designing the window's width for steady state and transient state operations and to adjusting the reference points for reactive power compensation. The proposed methods reduce the settling time to 1/12 of a cycle and have been verified under voltage sag, swell and load change conditions through MATLAB simulations.

In order to maintain the regulation of AC grid voltage, Chapter 7 investigates different types of AC regulators which include, Solid-state tap changer and steeples control by variac, Solid-tap changer using anti-parallel SCRs, voltage regulation using servo system, phase controlled AC voltage regulator, ferro-resonant AC voltage regulator and switch mode AC voltage regulator. A detailed design of a switch mode AC-AC voltage regulator is presented. Simulation results are reported to show the responsiveness and high power factor of the proposed method.

I hope this book will have been to you an enjoyable reading and a timely update of recent research and development in the field of Power Quality.

Lastly, I would like to thank all the researchers for their excellent works and studies in the different areas of Power Quality.

> **Dylan Dah-Chuan Lu** University of Sydney Australia

VIII Preface

MATLAB simulations.

identifies the limitations in the transmission systems, i.e., angular stability, voltage magnitude, thermal limits, transient stability, and dynamic stability and presents a comparative study of three different series FACTS for power quality compensation of a single transmission line in Eastern Algerian transmissions networks. Chapter 4 applies particle swarm optimization technique to designing a shunt static var compensator (SVC) for a radial distribution feeder. The objective function of SVC placement is to reduce the power loss and keep bus voltages and total harmonic

Chapter 5 proposes an electromechanical active power filter which uses a synchronous generator together with a unity power quality conditioner (UPQC). The idea originates from the fact that embedded generation is becoming a viable option in distributed generation and we should utilize this generator as a part of the power quality compensation solution. An algorithm of reference generation has been proposed to work with the two devices and simulation results are reported to verify the effectiveness of the approach. Chapter 6 continues with the previous study but the focus is on the speed to generate the references for UPQC. The general idea is that it uses an adaptive approach to designing the window's width for steady state and transient state operations and to adjusting the reference points for reactive power compensation. The proposed methods reduce the settling time to 1/12 of a cycle and have been verified under voltage sag, swell and load change conditions through

In order to maintain the regulation of AC grid voltage, Chapter 7 investigates different types of AC regulators which include, Solid-state tap changer and steeples control by variac, Solid-tap changer using anti-parallel SCRs, voltage regulation using servo system, phase controlled AC voltage regulator, ferro-resonant AC voltage regulator and switch mode AC voltage regulator. A detailed design of a switch mode AC-AC voltage regulator is presented. Simulation results are reported to show the

I hope this book will have been to you an enjoyable reading and a timely update of

Lastly, I would like to thank all the researchers for their excellent works and studies in

**Dylan Dah-Chuan Lu** University of Sydney

Australia

responsiveness and high power factor of the proposed method.

recent research and development in the field of Power Quality.

the different areas of Power Quality.

distortion within prescribed limits with minimum cost.

**Section 1** 

**Power Quality Issues and Standards** 

**in the Electricity Networks** 

**Power Quality Issues and Standards in the Electricity Networks** 

**Chapter 1** 

© 2013 Sher et al., 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.

and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Harmonics Generation, Propagation** 

Hadeed Ahmed Sher, Khaled E. Addoweesh and Yasin Khan

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/53422

**1. Introduction** 

harmonics control is

**and Purging Techniques in Non-Linear Loads** 

Industrial revolution has transformed the whole life with advanced technological improvements. The major contribution in the industrial revolution is due to the availability of electrical power that is distributed through electrical utilities around the world. The concept of power quality in this context is emerging as a "Basic Right" of user for safety as well as for uninterrupted working of their equipment. The electricity users whether domestic or industrial, need power, free from glitches, distortions, flicker, noise and outages. The utility desires that the users use good quality equipment so that they do not produce power quality threats for the system. The use of power electronic based devices in this industrial world has saved bounties in term of fuel and power savings, but on the other hand has created problems due to the generation of harmonics. Both commercial and domestic users use the devices with power electronics based switching that draw harmonic current. This current is a dominant factor in producing the harmonically polluted voltages. The "Basic Right" of the user is to have a clean power supply, whereas the demand of utility is to have good quality instrument/equipment. This makes power quality a point of common interest for both the users as well as the utility. Harmonics being a hot topic within power quality domain has been an area of discussion since decades and several design standards have been devised and published by various international organizations and institutions for maintaining a harmonically free power supply. In a wider scenario, the harmonically free environment means that the harmonics generated by the devices and its presence in the system is confined in the allowable limits so that they do not cause any damage to the power system components including the transformers, insulators, switch-gears etc. The deregulation of power systems is forcing the utilities to purge the harmonics at the very end of their generation before it comes to the main streamline and becomes a possible cause of system un-stability. The possible three stage scheme for
