Cascaded Three-Phase H-Bridge Converter Applied as Series Active Compensator for DFIG-Based Wind Energy Conversion Systems

This paper presents the use of an active series compensator to improve the performance of wind energy conversion systems (WECS) using a grid-connected doubly-fed induction generator (DFIG) during grid disturbances. The series active compensator is based on a two-level three-phase inverter cascaded with three H-bridge inverters operating with floating capacitors and without using injection transformer. The converter operating principles and control strategies are discussed. Steady-state simulations were obtained for the DFIG with constant torque. Experimental results are also presented. It was verified that the proposed system is able to maintain sinusoidal and compensated voltages on the DFIG stator windings, even during a distorted grid voltage sag event.