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

High order repetitive control has been introduced toovercomeperformance decay of repetitive control systems undervarying frequency of the signals to be tracked/rejected orimproving the interhamonic behavior. However, most highorder repetitive internal models used to improve frequencyuncertainty are unstable, as a consequence practicalimplementations are more difficult. In this work a stable,second order odd-harmonic repetitive control system ispresented and studied.The proposed internal model has been implemented andvalidated in a shunt active filter current controller. Thishigh order controller allows dealing with the gridfrequency variations without using adaptive schemes