This book highlights the recent developments in the power systems that have led to the new challenges in the quality of power domain such as the large-scale renewable energy-based generation technologies, and the optimal utilisation of the existing power grid with the growing penetration of renewable-based generation technologies as a necessity for service operators and customers alike. In addition, the increased electricity demands and economic operation of power systems in a deregulated environment causes interconnected power grids to operate closer to their stability margins. Another challenge is the advance of nonlinear loads which may cause some problems such as power system harmonics distortion that may reduce the voltage quality and increase the transmission and distribution losses if they exceed their permissible levels. The book highlights this issue, causes and effects in detail whereas presenting the modern facilities of power conditioners that can solve the problem efficiently.