Preface

Power quality is related to magnitude, frequency, and waveform of voltage and current. For good power quality level, supply voltages and line currents should be within their rated mag‐ nitudes, the frequency close to the prescribed supply frequency and sinusoidal waveform. There are many events disturbing power quality performance such as over-undervoltages, harmonic distortion, flickers, unbalance, sags, swells, transients, interruptions and frequency deviations. In addition, harmonic distortion is recognized as one of the most important power quality events in the literature since it has many adverse effects on operation and control of power system equipment.

Harmonic distortion occurs when voltage and currents deviate from the sinusoidal waveform. For the phasor analysis of these distorted waveforms, using Fourier transform, they are sepa‐ rated to the sinusoidal components, which have the frequencies of multiple integers of the supply frequency, called harmonics. In modern power systems, the main sources of current harmonic distortion are the loads and renewable energy generation units, which are all con‐ nected into a system via power electronic interfaces. At the same time, voltage drops on the line impedances caused by the distorted currents lead to harmonic distortion of the bus vol‐ tages in the system.

The most important impacts of harmonics on the power system equipment are the overheating and torque oscillations of the induction motors, overheating and decreased power transfer ca‐ pability of the transformers and supply lines and malfunctions of the protection/measurement devices. Thus, today, several international standards, such as IEEE Standard 519 and IEC 61000, present harmonic limitations for power systems. Accordingly, the harmonic mitigation has gained importance and passive, active or hybrid filters are widely employed in power sys‐ tems to mitigate the adverse harmonic distortion effects.

This book aims to present harmonic modeling, analysis and mitigation techniques for modern power systems. It is a tool for the planners, designers, operators and practicing engineers of electrical power systems involved in the power system harmonics. Likewise, it is a key re‐ source for advanced students, postgraduates, academics and researchers who have some back‐ ground in electrical power systems. The book is sorted out and organized in five chapters.

**Chapter 1:** This chapter summarizes the power quality events and their mitigation techniques.

**Chapter 2:** This chapter provides a discussion involving new trends on distribution power grids with active power filters to improve power quality, increase the reliability of the power grid and contribute to make feasible the implementation of decentralized microgrids.

**Chapter 3:** This chapter focuses on the sequential harmonic elimination method employed for multimodule multilevel converters. The principles of the sequential selective harmonic elimi‐ nation for MMC topology and amplitude control are described with examples.

**Chapter 4:** This chapter introduces a general model modified from the conventional control structure diagram for analysis of the harmonic generation process for photovoltaic (PV) instal‐ lations. Causes of the current harmonics and their relationships with output power levels are summarized and analyzed.

**Chapter 5:** This chapter presents a case study about harmonic measurements in high-voltage networks. The measurements are analyzed and temporal harmonic profiles are studied in detail.

> **Ahmed Zobaa** College of Engineering Design and Physical Sciences Brunel University London Uxbridge, United Kingdom

**Chapter 1**

**Provisional chapter**

**Introductory Chapter: Power System Harmonics—**

**Introductory Chapter: Power System Harmonics—**

**Quality Improvement**

**Quality Improvement**

Murat E. Balci

**1. Introduction**

his own perspective.

Murat E. Balci

Ahmed F. Zobaa, Shady H.E. Abdel Aleem and

Ahmed F. Zobaa, Shady H.E. Abdel Aleem and

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76628

**Analysis, Effects, and Mitigation Solutions for Power**

Nowadays, electrical utilities and consumers are paying much attention to enhance the quality of the generated and distributed electrical energy. The main aims are to produce clean electrical power and to distribute it to the end customers with acceptable power quality performance in a cost-effective manner. Nowadays, the importance of power quality aspects has increased due to the booming developments in power-electronic devices and renewable energy resources under the umbrella of smart grids. Besides, the deregulation of the electricity market resulted in a competitive market in which multiple utility companies try to deliver the best products (generated electrical energy) for the customers who have the chance to choose the utility company that provides them with electrical energy with the highest quality level. In consequence, power quality will play an essential role in modern electrical power systems. However, there are also difficulties before wider applicability is possible for the power quality performance limits. One difficulty is that, to date, there is no single commonly approved definition of power quality because of the various power quality perspectives and phenomena [1]. As well, power quality has dissimilar interpretations for people in various electric entities. Some express power quality as the voltage quality, others express it as the current quality, and some practice power quality as the system reliability. Furthermore, IEEE Std. 1100 [2] defines power quality as "the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment." One can say that everyone describes it from

**Analysis, Effects, and Mitigation Solutions for Power** 

© 2016 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, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. 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, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.76628

**Shady H. E. Abdel Aleem** 15th of May Higher Institute of Engineering Mathematical and Physical Sciences Cairo, Egypt

> **Murat Erhan Balci** Electrical and Electronics Engineering Balikesir University Balikesir, Turkey
