In this book, Artificial Neural Network (ANN) controller based dynamic voltage restorer (DVR) is applied to mitigate voltage swell and voltage sag in Rumuola Distribution Network in Rivers State, Nigeria; the book: Discusses Power quality problems, their sources and effects, power quality indices, application of custom devices, and contributions of several authors to power quality improvement. Answers the question why Power quality is of great concern in recent times. Covers the design of DVR and ANN controller, Simulation of ANN controller based DVR in MATHLAB using a replicated network diagram of Rumuola Distribution Network of Rivers State Nigeria, and the analyses of results obtained.