High performance repetitive control of an active filter under varying network frequency

Shunt active power filters are power electronics devices that are connected in parallel with nonlinear and reactive loads to compensate these characteristics in order to assure the quality of the electrical distribution network. This work proposes and designs a controller, based on combined feedforward and feedback actions, the last using repetitive control, to obtain a good closed-loop performance (power factor close to 1 and load current harmonics and reactive power compensation) in spite of the possible frequency variations that can occur in the electrical network. It is known that these variations clearly affect the performance of the usual discrete-time implementations of the repetitive based controllers. The paper analysis the effect of these variations and describes the architecture of the controller, its design, and the mechanism to compensate the network frequency variations. Some experimental results that show the good performance of the closed-loop system are also included.