Advanced current control implementation with robust deadbeat algorithm for shunt single-phase voltage-source type active power filter

A deadbeat current control implementation of shunt-type single-phase active power filter (APF) is considered. The deadbeat control technique is often proposed as an advanced current control method of APF, because the superiority of the digital control scheme to the analogue control one can be effectively utilised by adopting the dead beat-control strategy. Although the one-dimensional deadbeat control method can attain a time-optimal response for APF compensating current, one sampling period is actually required for its settling time. This delay is a serious drawback for this control technique. To cancel such a delay and one more delay caused by DSP execution time, the desired APF compensating current has to be predicted two sampling periods ahead. For the prediction value, the reference value of one source voltage period before is employed as a based value. At the same time, an adaptive line enhancer (ALE) is newly introduced to predict the control error of two sampling periods ahead. By adding the ALE output as an adjustment term to the based value, the settling time is made short in the transient state. On the other hand, in the steady state, the THD (total harmonic distortion) of the utility grid side AC source current can be reduced as much as possible compared to the case when an ideal identification of the controlled system can be made. The experimental results obtained from a DSP-based APF are also illustrated and evaluated. The compensating ability of this APF treated here is extremely high in accuracy and responsiveness.