Current control implementation with deadbeat algorithm for three-phase current-source active power filter

An effective system control method is presented for applying a three-phase current-source PWM convertor with a deadbeat controller to active power filters (APFs). In the shunt-type configuration, the APF is controlled such that the current drown by the APF from the utility is equal to the current harmonics and reactive current required for the load. To attain the time-optimal response of the APF supply current, a two-dimensional deadbeat control scheme is applied to APF current control. To cancel both the delay in the two-dimensional deadbeat control scheme and the delay in DSP control strategy, an adaptive line enhancer (ALE) is introduced in order to predict the desired value of three sampling periods ahead. The ALE also brings robustness to the deadbeat control system. Owing to the ALE being in a transient state, the settling time is short. By comparison in a steady state, the total harmonic distortion ratio of source currents can be reduced as much as possible compared to the case that ideal identification of controlled system could be made. The experimental results obtained from a DSP-based APF are also reported. The compensating ability of this APF is very high in accuracy and responsiveness, although the modulation frequency is rather low.