Comparative Study of the Three-Phase Grid-Connected Inverter Sharing Unbalanced Three-Phase and/or Single-Phase systems

摘要

Unbalance in a three-phase system is created due to single-phase loads and distributed single-phase renewable energy sources connected to the same system. This unbalance can be compensated locally at the point of common coupling using a three-phase four-wire grid-tied inverter. This paper presents a comparative study of three-phase four-wire inverter topologies to compensate for positive, negative, and zero sequence components of the current injected into the grid. The function of the 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 quantitative comparison of the topologies is provided to illustrate the advantages and disadvantages of the analyzed systems. The control algorithm has been presented to regulate the active and reactive power in each phase independently during both grid-connected and islanded modes. The analysis of three-phase 480-V 50-kV·A system based on three H-bridge converter is presented with simulation and experimental results. The experimental results validate the ability of the inverter to provide four-quadrant control of each phase independently.