Time-based and frequency-based fundamental grid current estimation for single-phase active power filters

This paper deals with two estimators designed for real-time fundamental component grid current extraction which is a critical task in control of single-phase active power filters (APF). An adaptive and predictive FIR filter and discrete Fourier transform have been employed in order to achieve proper APF operation, and thus, high-quality compensation of a distorted current drawn by a nonlinear load. Besides design and comparison of both implemented methods, the single-phase APF as well as its control algorithm based on direct current control are discussed in this paper. The compensation of both harmonic currents and reactive power, respectively, is presented by experimental results performed on designed laboratory APF prototype.