Second-order odd-harmonic repetitive control and its application to active filter control

High order repetitive control has been introduced to overcome performance decay of repetitive control systems under varying frequency of the signals to be tracked/rejected or improving the interhamonic behavior. However, most high order repetitive internal models used to improve frequency uncertainty are unstable, as a consequence practical implementations are more difficult. In this work a stable, second order odd-harmonic repetitive control system is presented and studied. The proposed internal model has been implemented and validated in a shunt active filter current controller. This high order controller allows dealing with the grid frequency variations without using adaptive schemes.