Power quality issues under constant penetration rate of renewable energy into the electric network

This paper presents a comprehensive review of power quality challenges under high penetration rate, fluctuation and imprecise prediction of incoming energy provided from different types of renewable sources. Power electronics devices such as active and hybrid filters topologies as well as different harmonic extraction techniques, and advanced type of controllers are classified, evaluated and discussed. Integration of such devices at the distribution as well as at the transmission level to enhance power quality (harmonics, reactive power, unbalances, voltage stabilization, resonance etc.) and improvement of network stability is also presented. Results of different case studies are presented and discussed. It is demonstrated that power electronics devices are to play an important role in achieving smart grid operation of complex and dependent electric network.