Repetitive control of an active filter under varying network frequency: Power factor correction

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 repetitive control and aimed at obtaining a good closed-loop performance in spite of the possible frequency variations that may occur in the electrical network. These changes affect the performance of the controller which, for the active filter application, can be seen as a degradation of the power factor in case of reactive loads. To overcome this problem a compensation technique consisting of adapting the sampling rate of the controller according to the network frequency variation is proposed. Experimental results indicate good performance of the closed-loop system preserving a unitary power factor for different network frequencies.