Preface

More than a century long studies on power properties of systems with nonsinusoidal voltages, currents, and compensation in such a situation are faced with new challenges. An increase in the cost of energy, concern with the supply security, and the need of renewable sources of energy affect the power systems structure and operation. New concepts known as smart grids and micro-grids have emerged. Harmonic generating loads become more and more common not only on the customer side, but also on the side of electric energy providers. Development of micro-grids aimed at elevation of the supply security and self-sufficiency can lead to weak systems sensitive to harmonics, noise, and asymmetry.