Efficiency evaluation of offshore power systems with power electronics based on SiC technology

This contribution investigates the influence of SiC semiconductor devices for HVDC transmission technology on system level. Different SiC devices are recently in the focus of many scientific publications. However, for extra high power applications, the SiC-JFET exhibits promising properties. In order to assess the impact on system losses of such a new technology, a scenario of a large-scale meshed HVDC offshore power system using the CIGRE B4 DC Grid Test System is investigated. In contrast to classical approaches for power flow calculations, detailed representation of semi-conductor based power electronic converters is necessary if the impact of evolving module technologies is to be analyzed. Therefore, this contribution will introduce an efficient way to solve the load flow problem for hybrid AC/DC systems with a detailed and accurate loss representation for converter stations. First, the converter station loss model is derived based on power electronic device characteristics of the IGBT and associated data of standard modules for this application. Second, the hybrid power flow approach is described using a parallel solution of the AC and the DC system with a combined Jacobian. Third, synthetic SiC-JFET characteristics are used in order to compare the performance in terms of efficiency at different loadings of the converter stations. It is shown that SiC-JFETs can significantly reduce losses of the system and almost eliminate switching losses (no-load losses) of converters, which is especially relevant at low utilizations with high occurrence considering the fluctuating nature of offshore wind power.