Comparative study of three-phase grid connected inverter sharing unbalanced three-phase and/or single-phase systems

In a microgrid system, unbalance in the three-phase system is created due to single-phase loads and decentralized single-phase renewable energy sources. This unbalance can be compensated locally at the point of common coupling (PCC) using a three-phase four-wire grid tied inverter. This paper focuses on a comparative study of 3-phase, 4-wire inverter topologies to compensate for positive, negative and zero sequence components of the current injected into the grid. The function of this inverter is to inject power to the grid and additional active power compensation (APC) to support unbalance, load reactive power, and load neutral current. Performance analysis and control of these topologies are being compared to evaluate utilization of dc link, size, control, and ease of implementation. A qualitative comparison of the topologies is provided to illustrate the advantages and disadvantages of the analyzed systems. Simulation and experimental results are presented to support the analysis of 3-phase, 480V, 50kVA system. The experimental results validate the ability of the inverter to provide 4-quadrant control of each phase independently.