**Preface XI**


Luís Fernando Corrêa Monteiro

Preface

power system equipment.

tages in the system.

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

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‐

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‐

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.

tems to mitigate the adverse harmonic distortion effects.
