Odd-harmonic Repetitive Control of an Active Filter under Varying Network Frequency: Practical Considerations

Abstract

This work deals with the design and analysis of a controller for a shunt active power filter. The design is based on combined feedforward and feedback actions, the last using oddharmonic repetitive control, and aims at obtaining good closedloop performance in spite of the possible frequency variations that may occur in the electrical network. As these changes affect the performance of the controller, the proposal includes a compensation technique consisting of an adaptive change of the sampling time of the digital controller according to the network frequency variation. However, this implies structural changes in the closed-loop system that may eventually destabilize it. Hence, this article is also concerned with closed-loop stability of the resulting system, which is analyzed using a robust control approach that takes advantage of the small gain theorem. Experimental results reporting good performance of the closedloop system are provided.