Time delay compensation for a current-source active power filter using state-feedback controller

The inevitable time delay in a digital signal processing (DSP) based controller can significantly degrade the performance of an active power filter. With a current-source active power filter (CS-APF) the problem can be more severe as this time delay can excite the filter resonance and cause oscillations in the compensation current. The paper derives the state space model for the CS-APF where the time delay is modeled properly into the state equations of the system. This makes the system dynamic model more accurate and the time delay can be compensated when a controller is designed for the system. State space control strategy is selected for the CS-APF controller. Experimental results from our prototype CS-APF system are presented to show the effect of the time delay on the CS-APF response and the validity of the proposed approach.