"Power systems are complex systems that evolve over years in response to economic growth and continuously increasing power demand. With growing populations and the industrialization of the developing world, more energy is required to satisfy the basic needs and to attain improved standards of human welfare. The power system construction has been actively developed. The distribution of power supply is uneven and the varying load demand will inevitably lead to the high capacity power delivery. However, the contradiction between the relative weak grid structure and the high capacity power delivery has become increasingly prominent. Massive integration of energy sources in electrical power systems is a subject of current interest. The increasing cost of fossil fuels, transport costs to isolated sites and environmental concerns constitute a serious drawback to the use of conventional fossil fuel plants. In a weak electrical grid, if a large amount of conventional generation is substituted by energy sources, power system safety and stability can be compromised, in the case of large grid disturbances. This book investigates power system reliability and efficiency, the possible impacts of power variability, power grid control strategy, energy penetration level. In order to maintain the stability of the power system, suitable stability analysis methods and techniques are presented. The chapters are contributed by prominent researchers in the field of energy and cover grid integration issues, modern control theories applied in power conversion system, and dynamic and transient stability studies. There are few topics studying the stability of power system when fault occurs on transmission lines with high capacity power sending."