Repetitive control and cascaded multilevel inverter with integrated hybrid active filter capability for wind energy conversion system

This manuscript presents a repetitive control (RC) method and 31-level reduced switch cascaded inverter topology (31-level RSCI) with an integrated hybrid active filter capability for a grid-connected doubly-fed induction generator (DFIG) based on wind energy conversion system (WECS). Repetitive control approach is considered for the inverter operation due to its better controllability and accuracy under periodic disturbance conditions. Further to enhance the system performance by supplying the desired reactive power to DFIG and harmonic reduction, a 31-level RSCI topology with a reduced number of unidirectional switch operations is proposed and implemented in the rotor side converter (RSC). This leads to benefit of highest power extraction and offer the required reactive power to DFIG. In addition to that an LC filter on the grid side converter (GSC) is added, to work as a hybrid active filter for harmonic cancellation produced by the nonlinear load and so behaves like a static compensator (STATCOM) even under shutdown condition of the wind turbine. Indirect current control and flux oriented reference frame control are implemented for grid and rotor side converter respectively. The proposed approach is validated with the simulated test results under both steady state and dynamic conditions.