Control techniques for three-phase four-leg voltage source inverters in autonomous microgrids: A review

The application of the four-leg inverter as an effective interface for renewable and sustainable distributed energy resources (DERs) is gaining more attention with the advances in power electronics technology. One of the key technologies in inverter-based distributed generation (DG) systems is the four-leg voltage source inverter (VSI) that is utilized to operate in autonomous four-wire microgrids. Four-leg VSIs are becoming increasingly popular in four-wire microgrid, because they can not only achieve a proper control scheme in autonomous mode but also cope with the prescribed power quality requirements. The aim of this paper is to provide an overview of the main characteristics of recently used control strategies for four-leg VSIs operating in autonomous microgrids. First, two commonly-used four-wire inverter configurations are discussed, and their advantages and disadvantages are compared. Afterwards, the most up to date control techniques for three-phase four-leg VSIs operating in islanded microgrid from the reference frame point of view are described. Lastly, a comparative analysis is carried out where the benefits and drawbacks of each strategy are assessed, and then some suggestions are put forward for the future research. (C) 2015 Elsevier Ltd. All rights reserved.