Sliding DFT assisted instantaneous symmetrical components method for estimating reference current to Active Power Filter

The performance of Active Power Filter (APF) is decided by the reference current estimation technique. This estimation is not straightforward in practice due to the distorted and unbalanced supply; non-linear and unbalanced load. To address such practical situations, a new Sliding Discrete Fourier Transform (SDFT) based technique involving instantaneous symmetrical components and p-q theory is proposed. With this method, the harmonic, fundamental frequency unbalanced and reactive current components are determined. The feature that the SDFT could provide the 90-degree shifted signal together with the symmetrical components is utilized for the purpose of determining the unbalanced current component. Fundamental reactive current is obtained using the widely used instantaneous p-q theory. The effectiveness of the proposed technique is demonstrated through the simulation results pertaining to three phase system with distorted and unbalanced supply.