QCD Power Corrections from a Simple Model for the Running Coupling

A simple parametrization of the QCD running coupling at low scales is introduced and used to illustrate various schemes for the estimation of non-perturbative power corrections. The `infrared matching' scheme proposed earlier gives satisfactory results when combined with next-to-leading (or higher) order perturbative predictions. Estimates based on renormalons are shown to be inconsistent with universal behaviour of the running coupling.