Nowadays, electric power quality (PQ) is an important concern in power supply industry due to widespread growth of digital economy and its dependence on sensitive equipments. Among various PQ attributes, voltage unbalance and harmonics distortion are probably the most degenerative conditions, due to their steady state nature. This book deals with harmonic pattern and performance of nonlinear loads in presence of voltage unbalance, through detailed logical investigations. Moreover, a thorough and systematic research review on the power system harmonics about its brief history, definitions, sources, effects, analysis and mitigation along with experimental survey of harmonics injected by various home appliances, equipments and devices is presented. A novel fuzzy-expert system based control strategy for harmonic mitigation is developed, resulting in almost sinusoidal, unity power factor, and balanced utility current operation of randomly & dynamically varying non-linear loads. In general, this book is addressed to post-graduate students, research scholars, university teachers along with engineers practicing in industries and electric utilities, having interest in power quality.