This book describes different aspects of distribution system in general and presents a critical survey of the research concerning economic load scheduling, economic emission load scheduling, loss minimization, and optimal distributed energy resources placement. It discusses detailed overview of proposed evolutionary based algorithms and implementation of it on economic load problem for getting optimal power allocation of thermal generators where emission, heat and cost is minimized. Population based evolutionary algorithms are also implemented in grid connected micro-grid for getting optimal sizing of distributed energy resources where power losses and fuel costs are minimized.