Microgrid Power Quality Improvement by using Dual Output Four-Leg Inverter

Abstract

In this paper, a new system is proposed for connecting a microsource to a weak utility. The proposed system simultaneously conditions the quality of the power supplied to the microgrid loads. This system employs a recently introduced reduced switch count dual-output inverter in a so-called equal frequency mode which offers its best operation features such as maximum dc bus voltage utilization and minimum device ratings. Compared to the counterpart system, the proposed configuration enjoys an integrated structure and uses less number of semiconductor switches. Moreover, it retains the desirable features of the conventional system such as ability to compensate unbalanced/sagged utility and to supply three-phase unbalanced loads with balanced and ceaseless voltage. The proposed system is introduced and its carrier-based modulation scheme is elaborated. Subsequently, a detailed study on the maximum achievable modulation index under different working conditions is carried out. The report concludes with a discussion on control of the system and its controller design. The validity of operation of the proposed system is verified through simulation. Keywords —Distributed generation (DG), dual-output four leg inverter, microgrid.