HARMONICS IN A PRACTICAL POWER SYSTEM EXHIBITING PARALLEL RESONANCE

AC/DC converters using thyristors and/or diodes are increasingly being used in industry, railway traction and power transmission applications. To preserve the quality of Electricity Supply in the presence of such large harmonic-producing loads it is essential to accurately predict the levels of harmonic waveform distortion produced, particularly in the event of parallel resonance conditions being anticipated. A research project jointed funded by the University of Sunderland and three Industrial Partners is currently being carried out with the aim of achieving good correlation between measured and computed results. System data for an existing network, together with measured results for distorted waveforms and harmonic content under parallel resonance conditions, have been provided by the Industrial Partners. The computer program CHAPS, developed by Dr. R H Kitchin, has been used to carry out a three-phase, time-domain simulation of the power system. The program computes the system voltage and current waveforms with corresponding harmonic levels. Reasonably good correlation is achieved between computed and measured results, indicating a parallel resonance condition. Three phase network models for system representation of up to 150 nodes and 200 branches have been studied.