1. Introduction

Deregulation of the electric power industry imposes requirements for more responsive economic dispatch for dynamic balance between energy generation and loads. Concern about environmental impacts and shortages of fossil fuels have increased interest in clean and renewable energy generation, including wind power, photovoltaic, hydroelectric power, fuel cells, and microturbines. Wind energy and photovoltaic are among the most promising renewable energy resources, yet these sources are intermittent and unpredictable and cannot be used for reliable economic dispatch; they have low inertias and cannot provide power quality support for the grid. Microgrids are small-scale power networks that are exploited to supply local loads in small geographical spans.