Modeling of MMC-HVDC for grid integration applications

The large number of constitutive elements of modular multilevel converters requires a complex model for control and modulation simulation which usually requires a small step time in the range of microseconds. However, to study the interaction of the MMC-HVDC station with the electrical DC and AC systems, which dynamical response is in the range of seconds, requires a model more simple but without losing the main dynamical characteristics. This paper presents a simplified model which allows longer step time simulation retaining the main features of the modular multilevel converter. The complete model of MMC is introduced and sequentially simplified in order to achieve a given simulation step time. Simulation results of the different stages of simplification are given.