Determination of the numerical value for the strong coupling constant from tau decays in perturbative QCD

The determination of the numerical value for the strong coupling constant from tau decays in perturbative QCD is briefly described. Main emphasis is made on the use of the renormalization scheme invariance of the theory for reducing uncertainties related to truncation of the series in the strong coupling constant. The analysis of the convergence of the series is presented and the possibility of the asymptotic growth at the NNNLO is discussed.