The estimation of harmonic components of power voltage signals is one of the measurements prescribed by the power quality (PQ) standards (IEC 61000-4-30, 2008). In general, the harmonic components originate from non-linear elements connected to the power system such as non-linear loads (e.g., switched-mode power supplies) or transformers. An example of a distorted voltage measured in an office building is shown in Fig. 1. The negative effects associated with the presence of voltage harmonics include, for example, overheating and increased losses of transformers, malfunction of electronic instruments, additional losses in rotating machines or overheating of capacitor banks.