Thyristor controlled reactors as harmonic sources in HVDC convertor stations and AC systems

Thyristor controlled reactors (TCRs) are a relatively new source of harmonic distortion in power systems. The steady-state balanced (or characteristic) harmonics are easily calculated and are well known. Other noncharacteristic harmonics can, however, be generated by TCRs. A detailed representation is therefore necessary which will consider all types of imbalance, be it in the TCR or in other parts of the total system to which they are connected. It is also important to consider the effect of connecting TCRs to systems which do not have a high fault level (weak AC systems) and to consider the effect of control feedback on harmonic generation. The methods by which these factors can be included in calculations of nonideal systems are the subject of this paper. The methods are illustrated by example.