On advanced control strategies for DFIG-based wind energy conversion systems during voltage unbalance

The penetration level of decentralized power generation plants based on renewable energy sources are continuously increasing with wind energy having a significant share. Considering present developments towards a purely renewable energy based electricity supply, Wind Energy Conversion Systems (WECS) play an important role in securing a stable, reliable and continuous supply of energy. Particularly in weak distribution grids with frequent power quality implications, WECS need to reliably operate and stable the grid. This paper presents advanced control strategies for DFIG-type WECS during unbalanced voltage conditions Applying resonant controllers, negative sequence components are well-controlled, contributing to an improved operation behavior particularly during less severe but persistent unbalanced grid voltages.