Harmonic modelling of transmission systems containing synchronous machines and static convertors

This thesis describes the modelling of the major sources of harmonic distortion in electrical transmission systems, especially those of relevance to the New Zealand power system. The harmonics generated by the operation of a.c./d.c. convertors are modelled using an interactive algorithm. The algorithm is applied to a number of test systems and verified using a transient convertor simulation program. A harmonic admittance matrix model of a single phase traction system is derived and used to assess the effect of propossed harmonic filters. In this case the three phase iterative algorithm had to be modified to be able to model the locomotive's single phase convertors. Synchronous machines are modelled using a harmonic Norton equivalent, derived from the d-q axes differential equations. The case of this model yields harmonic impedances consistent with existing models and demonstrates the well known, but greatly ignored, phenomenon of harmonic conversion. The modelling of harmonic conversion is shown to significantly modify the harmonic flows under certain system conditions