Digital simulation of HVDC transmission and its correlation to simulator studies

In order to investigate the behaviour of HVDC transmission in a power system, suitable simulation models are required. A detailed commutation model with simulation of the thyristor bridges, while very precise, requires considerable time for calculation. Simplified models, on the other hand, do not always provide sufficiently accurate results. Simplified and detailed HVDC simulation models are described and compared. In order to provide a yardstick for comparison, the HVDC Benchmark model study of the FGH analog simulator at Mannheim-Rheinau was used as a reference. The NETOMAC digital simulation program which was employed for all calculations, is a powerful and flexible tool by means of which practically all problems of electrical energy transmission including control algorithms can be investigated. The variable time step of NETOMAC is of particular relevance for investigation of HVDC transmission and static VAr compensators thus ensuring that the continuity conditions are always satisfied while a thyristor is fired