Digital State Control with Preview for a Shunt Active Filter having the Function of Active Rectifier

This paper presents a novel discrete-time optimal state control for the 3-phase shunt active power filter (APF). The scheme utilizes a modified model for the converter derived in the synchronous reference frame. The model provides a means of controlling all the converter states by introducing an auxiliary input variable. The synthesized controller achieves simultaneous current control and regulation of the dc-link voltage, allowing extra functionality for the shunt APF as an active rectifier. The designed controller has good tracking performance and can cure the detrimental effects of the inevitable modeling errors and disturbances. Furthermore, a feedforward control loop is implemented to improve the transient response by compensating the dc-load current variations. Simulation studies are provided to confirm the effectiveness of the introduced control strategy.