Harmonic analysis of a GTO controlled series capacitor operating under unbalanced currents

The GTO controlled series capacitor (GCSC), as a dual of the thyristor-controlled reactor (TCR), is supposed to be an excellent transmission line series compensator. Harmonic analysis of the GCSC is presented in this work. The characteristic harmonics are obtained through conventional Fourier analysis. Then, a generalized switching function model is derived. A method is developed to analyze the harmonic content of a GCSC fed by nonbalanced currents. Examples are given of the application of the method to analyze the harmonics of three-phase GCSCs, with individual and equidistant blocking of the GTOs, fed by unbalanced currents. The results show the adequacy of the method to analyze harmonics in the GCSC with phase imbalance.