Abstract
Because of the need to maintain an adequate margin against transient instability, long extra high voltage (EHV) AC lines cannot be filled to their thermal maximum. If the conductors are permitted to hold superimposed DC current along with AC current, EHV lines can be loaded to a very high value. There is no transient instability as a result of the additional DC power flow. Furthermore, it will provide the advantages of an AC-DC parallel system without the need for a separate DC thread. A modern solution is the simultaneous AC-DC method. Several works on this subject have been done, such as a stability and load capacity study of this system, and the development of an effective analytical model for this system. However, no cost analysis for this framework has yet been performed. The cost analysis of a simultaneous AC-DC power transmission system is the subject of this study. The cost variance related to various parameters has been extensively explored, and relationships between the parameters and cost have been developed. A detailed cost comparison has been made between the simultaneous AC-DC system and the current HVDC transmission line.