Three-phase current harmonics estimation for shunt active power filters

This paper deals with the on-line estimation of three-phase current harmonics on the base Luenberger observer technique. It is shown that standard observer for positive and negative sequences of each harmonic delivers strong selectivity properties, but has limited speed of convergence. A novel structure of estimator with filtered measured currents is proposed, it guarantees fast asymptotic convergence and simple in tuning. The important feature of the designed estimator is freedom in design of feedback coefficients matrix according to any optimization technique for linear systems, which are stable for any positive tuning gains. Simulation and experimental results proof the theoretical findings.