Comparison of Electromagnetic Transient Models for Modular Multilevel Converters in High-Voltage Direct Current Applications

Inhalt:
Modular multilevel converters (MMC) for high-voltage direct current (HVDC) transmission systems can contain up to several thousand submodules per HVDC station. Modeling each submodule in electromagnetic transient type simulations poses a computational challenge as the runtime increases significantly. To tackle this issue, different modeling concepts were developed which can reduce the simulation runtime drastically. This paper focuses on the Detailed Equivalent Model (DEM), the Switching Function Model (SFM) and the Average Value Model (AVM), which are capable of modeling a full scale HVDC system efficiently. To compare them, simulations of the steady state operation as well as the operation during different transient conditions are conducted in PSCAD(TM)/EMTDC(TM) in conjunction with MATLAB(r) /Simulink(r) . Relevant quantities of the SFM and AVM are then validated against the DEM. The results show that the behavior of both, SFM and AVM, are very close to the DEM. However, the reaction of the AVM to sudden voltage or current changes, as in case of a fault event, differs greatly from the DEM. For the investigation of the DC pole-to-pole fault, the DEM block provided by PSCAD(TM) has proven to be not working as expected.