Internal model control of active power filter using resonance model

A new simple control method for an active power filter, which can realize the complete compensation of harmonics is proposed. In the proposed scheme, a model-based digital current control strategy is presented. The proposed control system is designed and implemented in a form referred to as internal model control structure. This method provides a convenient way for parameterizing the controller in terms of the nominal system model, including time-delays. As a result, the resulting controller parameters are directly set based on the power circuit parameters, which makes tuning of the controllers straightforward task. In the proposed control algorithm, overshoots and oscillations due to the computation time delay are prevented by explicit incorporation of the delay in the controller transfer function. In addition, a new compensating current reference generator employing resonance model implemented by a DSP (digital signal processor) is introduced. A resonance model has an infinite gain at resonant frequency, and it exhibits a band-pass filter. Consequently, the difference between the instantaneous load current and the output of this model is the current reference signal for the harmonic compensation