Digital computer techniques for the analysis of HVDC transmission systems
The thesis reviews methods for the analysis of thyristor bridge circuits using a digital computer. Tensor techniques based on the work of Kron, and which deal efficiently and effectively with the varying topology of the bridge circuits, are then used to analyse both the 6-pulse and the l2-pulse fully-controlled circuits which are the most common convertor configurations in hvdc transmission systems. The work then extends to a more complete representation of such a system, with the transmission line being represented by a series of lumped T-section elements. Harmonic filtering is included in the later stages of the work, with consideration given to the most significant harmonics produced in the A.C. side of the invertors. The elements of a typical hvdc transmission system have been assembled in the laboratory, and the model system has been used as a check on the accuracy of results provided by the computer programs. A study has been made of the most common faults which occur in an hvdc system, including misfiring, backfire, faults in the transmission line, and the effects of a strike by lightning. Close agreement between computed and experimental results has been obtained over a wide range of normal and fault conditions.