Modelling and nonlinear control of shunt active power filter

This article presents the modelling and nonlinear control of a three-phase voltage source shunt active filter. The modelling is based on the abc/dq transformation of the ac system variables. The currents injected by the active filter are controlled in the synchronous orthogonal dq frame using a decoupled nonlinear control strategy. The reference harmonic components are extracted from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase thyristor bridge rectifier with R-L load is taken as the nonlinear load. The voltage level of the dc side is regulated using a linearizing feedback control. The reference current needed to maintain a regulated dc voltage is added to the current loop reference. The transfer functions of the two loops are developed and synthesized to obtain the desired stability and dynamic response. Simulation results confirm the performance considered theoretically for the shunt active filter topology.