Methodology to define the arm inductance range in a Modular Multilevel Converter station for HVDC applications based on steady-state and DC pole-to-pole fault

Abstract

The arm inductance in modular multilevel converters (MMC) for high voltage direct current (HVDC) applications has a relevant impact in the performance of the converter in steady-state and during faults. This paper proposes the methodology to define a range of arm inductance values for a given MMC-HVDC station with fixed AC and DC voltage. The minimum value of arm inductance comes from protecting IGBTs, diodes and bypass thyristors in the submodules during a DC fault, while the maximum value comes from ensuring the steady-state PQ provision (ability to modulate the AC waveform with the DC voltage). A simplified MMC model is developed to calculate the converter fault currents. The sensitivity analysis shows that the constraints that define the minimum value of arm inductance depend on the case study, the most relevant being the IGBT turn-off capability, the maximum surge current of the diodes and the I^2 t of the bypass thyristors.

Joan Sau-Bassols, Florent MOREL, Konstantin VERSHININ.

Published in June 2024 – CIGRE science & engineering